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[AROS.git] / arch / all-pc / boot / grub2-aros / docs / grub-dev.info

This is /home/phcoder/grub2/bzr/mainline/docs/grub-dev.info, produced
by makeinfo version 4.13 from
/home/phcoder/grub2/bzr/mainline/docs/grub-dev.texi.

This developer manual is for GNU GRUB (version 2.00, 22 May 2012).

   Copyright (C) 1999,2000,2001,2002,2004,2005,2006,2008,2009,2010,2011
Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.2 or any later version published by the Free Software
     Foundation; with no Invariant Sections.

INFO-DIR-SECTION Kernel
START-INFO-DIR-ENTRY
* grub-dev: (grub-dev).                 The GRand Unified Bootloader Dev
END-INFO-DIR-ENTRY

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File: grub-dev.info,  Node: Top,  Next: Getting the source code,  Up: (dir)

GNU GRUB developer manual
*************************

This is the developer documentation of GNU GRUB, the GRand Unified
Bootloader, a flexible and powerful boot loader program for a wide
range of architectures.

   This edition documents version 2.00.

   This developer manual is for GNU GRUB (version 2.00, 22 May 2012).

   Copyright (C) 1999,2000,2001,2002,2004,2005,2006,2008,2009,2010,2011
Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.2 or any later version published by the Free Software
     Foundation; with no Invariant Sections.

* Menu:

* Getting the source code::
* Finding your way around::
* Coding style::
* Contributing Changes::
* Porting::
* Error Handling::
* CIA::
* BIOS port memory map::
* Video Subsystem::
* PFF2 Font File Format::
* Graphical Menu Software Design::
* Copying This Manual::         Copying This Manual
* Index::

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File: grub-dev.info,  Node: Getting the source code,  Next: Finding your way around,  Prev: Top,  Up: Top

1 Getting the source code
*************************

GRUB is maintained using the Bazaar revision control system
(http://bazaar-vcs.org/).  To fetch the primary development branch:

     bzr get http://bzr.savannah.gnu.org/r/grub/trunk/grub

   The GRUB developers maintain several other branches with work in
progress.  Of these, the most interesting is the experimental branch,
which is a staging area for new code which we expect to eventually
merge into trunk but which is not yet ready:

     bzr get http://bzr.savannah.gnu.org/r/grub/branches/experimental

   Once you have used `bzr get' to fetch an initial copy of a branch,
you can use `bzr pull' to keep it up to date.  If you have modified your
local version, you may need to resolve conflicts when pulling.

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File: grub-dev.info,  Node: Coding style,  Next: Contributing Changes,  Prev: Finding your way around,  Up: Top

2 Coding style
**************

Basically we follow the GNU Coding Standards
(http://www.gnu.org/prep/standards_toc.html). We define additional
conventions for GRUB here.

* Menu:

* Naming Conventions::
* Functions::
* Variables::
* Types::
* Macros::
* Comments::
* Multi-Line Comments::

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2.1 Naming Conventions
======================

All global symbols (i.e. functions, variables, types, and macros) must
have the prefix grub_ or GRUB_. The all capital form is used only by
macros.

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2.2 Functions
=============

If a function is global, its name must be prefixed with grub_ and must
consist of only small letters. If the function belongs to a specific
function module, the name must also be prefixed with the module name.
For example, if a function is for file systems, its name is prefixed
with grub_fs_. If a function is for FAT file system but not for all
file systems, its name is prefixed with grub_fs_fat_. The hierarchy is
noted this way.

   After a prefix, a function name must start with a verb (such as get
or is). It must not be a noun. Some kind of abbreviation is permitted,
as long as it wouldn't make code less readable (e.g. init).

   If a function is local, its name may not start with any prefix. It
must start with a verb.

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File: grub-dev.info,  Node: Variables,  Next: Types,  Prev: Functions,  Up: Coding style

2.3 Variables
=============

The rule is mostly the same as functions, as noted above. If a variable
is global, its name must be prefixed with grub_ and must consist of
only small letters. If the variable belongs to a specific function
module, the name must also be prefixed with the module name. For
example, if a function is for dynamic loading, its name is prefixed
with grub_dl_. If a variable is for ELF but not for all dynamic loading
systems, its name is prefixed with grub_dl_elf_.

   After a prefix, a variable name must start with a noun or an
adjective (such as name or long) and it should end with a noun. Some
kind of abbreviation is permitted, as long as it wouldn't make code
less readable (e.g. i18n).

   If a variable is global in the scope of a single file (i.e. it is
declared with static), its name may not start with any prefix. It must
start with a noun or an adjective.

   If a variable is local, you may choose any shorter name, as long as
it wouldn't make code less readable (e.g. i).

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File: grub-dev.info,  Node: Types,  Next: Macros,  Prev: Variables,  Up: Coding style

2.4 Types
=========

The name of a type must be prefixed with grub_ and must consist of only
small letters. If the type belongs to a specific function module, the
name must also be prefixed with the module name. For example, if a type
is for OS loaders, its name is prefixed with grub_loader_. If a type is
for Multiboot but not for all OS loaders, its name is prefixed with
grub_loader_linux_.

   The name must be suffixed with _t, to emphasize the fact that it is
a type but not a variable or a function.

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2.5 Macros
==========

If a macro is global, its name must be prefixed with GRUB_ and must
consist of only large letters. Other rules are the same as functions or
variables, depending on whether a macro is used like a function or a
variable.

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File: grub-dev.info,  Node: Comments,  Next: Multi-Line Comments,  Prev: Macros,  Up: Coding style

2.6 Comments
============

All comments shall be C-style comments, of the form `/* ... */'.

   Comments shall be placed only on a line by themselves.  They shall
not be placed together with code, variable declarations, or other
non-comment entities.  A comment should be placed immediately preceding
the entity it describes.

   Acceptable:
     /* The page # that is the front buffer.  */
     int displayed_page;
     /* The page # that is the back buffer.  */
     int render_page;

   Unacceptable:
     int displayed_page;           /* The page # that is the front buffer. */
     int render_page;              /* The page # that is the back buffer. */

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2.7 Multi-Line Comments
=======================

Comments spanning multiple lines shall be formatted with all lines
after the first aligned with the first line.

   Asterisk characters should not be repeated a the start of each
subsequent line.

   Acceptable:
     /* This is a comment
        which spans multiple lines.
        It is long.  */

   Unacceptable:
     /*
      * This is a comment
      * which spans multiple lines.
      * It is long. */

   The opening `/*' and closing `*/' should be placed together on a
line with text.

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File: grub-dev.info,  Node: Finding your way around,  Next: Coding style,  Prev: Getting the source code,  Up: Top

3 Finding your way around
*************************

Here is a brief map of the GRUB code base.

   GRUB uses Autoconf and Automake, with most of the Automake input
generated by AutoGen.  The top-level build rules are in `configure.ac',
`grub-core/Makefile.core.def', and `Makefile.util.def'.  Each block in
a `*.def' file represents a build target, and specifies the source
files used to build it on various platforms.  The `*.def' files are
processed into AutoGen input by `gentpl.py' (which you only need to
look at if you are extending the build system).  If you are adding a new
module which follows an existing pattern, such as a new command or a new
filesystem implementation, it is usually easiest to grep
`grub-core/Makefile.core.def' and `Makefile.util.def' for an existing
example of that pattern to find out where it should be added.

   In general, code that may be run at boot time is in a subdirectory of
`grub-core', while code that is only run from within a full operating
system is in a subdirectory of the top level.

   Low-level boot code, such as the MBR implementation on PC BIOS
systems, is in the `grub-core/boot/' directory.

   The GRUB kernel is in `grub-core/kern/'.  This contains core
facilities such as the device, disk, and file frameworks, environment
variable handling, list processing, and so on.  The kernel should
contain enough to get up to a rescue prompt.  Header files for kernel
facilities, among others, are in `include/'.

   Terminal implementations are in `grub-core/term/'.

   Disk access code is spread across `grub-core/disk/' (for accessing
the disk devices themselves), `grub-core/partmap/' (for interpreting
partition table data), and `grub-core/fs/' (for accessing filesystems).
Note that, with the odd specialised exception, GRUB only contains code
to _read_ from filesystems and tries to avoid containing any code to
_write_ to filesystems; this lets us confidently assure users that GRUB
cannot be responsible for filesystem corruption.

   PCI and USB bus handling is in `grub-core/bus/'.

   Video handling code is in `grub-core/video/'.  The graphical menu
system uses this heavily, but is in a separate directory,
`grub-core/gfxmenu/'.

   Most commands are implemented by files in `grub-core/commands/', with
the following exceptions:

   * A few core commands live in `grub-core/kern/corecmd.c'.

   * Commands related to normal mode live under `grub-core/normal/'.

   * Commands that load and boot kernels live under `grub-core/loader/'.

   * The `loopback' command is really a disk device, and so lives in
     `grub-core/disk/loopback.c'.

   * The `gettext' command lives under `grub-core/gettext/'.

   * The `loadfont' and `lsfonts' commands live under `grub-core/font/'.

   * The `serial', `terminfo', and `background_image' commands live
     under `grub-core/term/'.

   * The `efiemu_*' commands live under `grub-core/efiemu/'.

   There are a few other special-purpose exceptions; grep for them if
they matter to you.

   Utility programs meant to be run from a full operating system are in
`util/'.

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File: grub-dev.info,  Node: Contributing Changes,  Next: Porting,  Prev: Coding style,  Up: Top

4 Contributing changes
**********************

Contributing changes to GRUB 2 is welcomed activity. However we have a
bit of control what kind of changes will be accepted to GRUB 2.
Therefore it is important to discuss your changes on grub-devel mailing
list (see MailingLists). On this page there are some basic details on
the development process and activities.

   First of all you should come up with the idea yourself what you want
to contribute. If you do not have that beforehand you are advised to
study this manual and try GRUB 2 out to see what you think is missing
from there.

   Here are additional pointers:
   * `https://savannah.gnu.org/task/?group=grub GRUB's Task Tracker'

   * `https://savannah.gnu.org/bugs/?group=grub GRUB's Bug Tracker'

   If you intended to make changes to GRUB Legacy (<=0.97) those are
not accepted anymore.

* Menu:

* Getting started::
* Typical Developer Experience::
* When you are approved for write access to project's files::

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File: grub-dev.info,  Node: Getting started,  Next: Typical Developer Experience,  Up: Contributing Changes

4.1 Getting started
===================

   * Always use latest GRUB 2 source code. So get that first.

     For developers it is recommended always to use the newest
     development version of GRUB 2. If development takes a long period
     of time, please remember to keep in sync with newest developments
     regularly so it is much easier to integrate your change in the
     future. GRUB 2 is being developed in a Bazaar (bzr) repository.

     Please check Savannah's GRUB project page for details how to get
     newest bzr: GRUB 2 bzr Repository
     (http://savannah.gnu.org/bzr/?group=grub)

   * Compile it and try it out.

     It is always good idea to first see that things work somehow and
     after that to start to implement new features or develop fixes to
     bugs.

   * Study the code.

     There are sometimes odd ways to do things in GRUB 2 code base.
     This is mainly related to limited environment where GRUB 2 is
     being executed.  You usually do not need to understand it all so
     it is better to only try to look at places that relates to your
     work. Please do not hesitate to ask for help if there is something
     that you do not understand.

   * Develop a new feature.

     Now that you know what to do and how it should work in GRUB 2 code
     base, please be free to develop it. If you have not so far
     announced your idea on grub-devel mailing list, please do it now.
     This is to make sure you are not wasting your time working on the
     solution that will not be integrated to GRUB 2 code base.

     You might want to study our coding style before starting
     development so you do not need to change much of the code when
     your patch is being reviewed.  (see *note Coding style::)

     For every accepted patch there has to exist a ChangeLog entry. Our
     ChangeLog consist of changes within source code and are not
     describing about what the change logically does. Please see
     examples from previous entries.

     Also remember that GRUB 2 is licensed under GPLv3 license and that
     usually means that you are not allowed to copy pieces of code from
     other projects.  Even if the source project's license would be
     compatible with GPLv3, please discuss it beforehand on grub-devel
     mailing list.

   * Test your change.

     Test that your change works properly. Try it out a couple of
     times, preferably on different systems, and try to find problems
     with it.

   * Publish your change.

     When you are happy with your change, first make sure it is
     compilable with latest development version of GRUB 2. After that
     please send a patch to grub-devel for review. Please describe in
     your email why you made the change, what it changes and so on.
     Please be prepared to receive even discouraging comments about
     your patch. There is usually at least something that needs to be
     improved in every patch.

     Please use unified diff to make your patch (good match of
     arguments for diff is `-pruN').

   * Respond to received feedback.

     If you are asked to modify your patch, please do that and resubmit
     it for review. If your change is large you are required to submit
     a copyright agreement to FSF. Please keep in mind that if you are
     asked to submit for copyright agreement, process can take some
     time and is mandatory in order to get your changes integrated.

     If you are not on grub-devel to respond to questions, most likely
     your patch will not be accepted. Also if problems arise from your
     changes later on, it would be preferable that you also fix the
     problem. So stay around for a while.

   * Your patch is accepted.

     Good job! Your patch will now be integrated into GRUB 2 mainline,
     and if it didn't break anything it will be publicly available in
     the next release.

     Now you are welcome to do further improvements :)

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File: grub-dev.info,  Node: Typical Developer Experience,  Next: When you are approved for write access to project's files,  Prev: Getting started,  Up: Contributing Changes

4.2 Typical Developer Experience
================================

The typical experience for a developer in this project is the following:

  1. You find yourself wanting to do something (e.g. fixing a bug).

  2. You show some result in the mailing list or the IRC.

  3. You are getting to be known to other developers.

  4. You accumulate significant amount of contribution, so copyright
     assignment is processed.

  5. You are free to check in your changes on your own, legally
     speaking.

   At this point, it is rather annoying that you ought to ask somebody
else every change to be checked in. For efficiency, it is far better,
if you can commit it yourself. Therefore, our policy is to give you the
write permission to our official repository, once you have shown your
skill and will, and the FSF clerks have dealt with your copyright
assignment.

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4.3 When you are approved for write access to project's files
=============================================================

As you might know, GRUB is hosted on
`https://savannah.gnu.org/projects/grub Savannah', thus the membership
is managed by Savannah. This means that, if you want to be a member of
this project:

  1. You need to create your own account on Savannah.

  2. You can submit "Request for Inclusion" from "My Groups" on
     Savannah.

   Then, one of the admins can approve your request, and you will be a
member.  If you don't want to use the Savannah interface to submit a
request, you can simply notify the admins by email or something else,
alternatively. But you still need to create an account beforehand.

   NOTE: we sometimes receive a "Request for Inclusion" from an unknown
person.  In this case, the request would be just discarded, since it is
too dangerous to allow a stranger to be a member, which automatically
gives him a commit right to the repository, both for a legal reason and
for a technical reason.

   If your intention is to just get started, please do not submit a
inclusion request. Instead, please subscribe to the mailing list, and
communicate first (e.g. sending a patch, asking a question, commenting
on another message...).

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File: grub-dev.info,  Node: Porting,  Next: Error Handling,  Prev: Contributing Changes,  Up: Top

5 Porting
*********

GRUB2 is designed to be easily portable accross platforms. But because
of the nature of bootloader every new port must be done separately.
Here is how I did MIPS (loongson and ARC) and Xen ports. Note than this
is more of suggestions, not absolute truth.

   First of all grab any architecture specifications you can find in
public (please avoid NDA).

   First stage is "Hello world". I've done it outside of GRUB for
simplicity.  Your task is to have a small program which is loadable as
bootloader and clearly shows its presence to you. If you have easily
accessible console you can just print a message. If you have a mapped
framebuffer you know address of, you can draw a square. If you have a
debug facility, just hanging without crashing might be enough. For the
first stage you can choose to load the bootloader across the network
since format for network image is often easier than for local boot and
it skips the need of small intermediary stages and nvram handling.
Additionally you can often have a good idea of the needed format by
running "file" on any netbootable executable for given platform.

   This program should probably have 2 parts: an assembler and C one.
Assembler one handles BSS cleaning and other needed setup (on some
platforms you may need to switch modes or copy the executable to its
definitive position). So your code may look like (x86 assembly for
illustration purposes)

             .globl _start
     _start:
        movl    $_bss_start, %edi
        movl    $_end, %ecx
        subl    %edi, %ecx
        xorl    %eax, %eax
        cld
        rep
        stosb
             call main


     static const char msg[] = "Hello, world";

     void
     putchar (int c)
     {
       ...
     }

     void
     main (void)
     {
       const char *ptr = msg;
       while (*ptr)
         putchar (*ptr++);
       while (1);
     }

   Sometimes you need a third file: assembly stubs for
ABI-compatibility.

   Once this file is functional it's time to move it into GRUB2. The
startup assembly file goes to grub-core/kern/$cpu/$platform/startup.S.
You should also include grub/symbol.h and replace call to entry point
with call to EXT_C(grub_main). The C file goes to
grub-core/kern/$cpu/$platform/init.c and its entry point is renamed to
void grub_machine_init (void). Keep final infinite loop for now. Stubs
file if any goes to grub-core/kern/$cpu/$platform/callwrap.S. Sometimes
either $cpu or $platform is dropped if file is used on several cpus
respectivelyplatforms.  Check those locations if they already have what
you're looking for.

   Then modify in configure.ac the following parts:

   CPU names:

     case "$target_cpu" in
       i[[3456]]86)     target_cpu=i386 ;;
       amd64)   target_cpu=x86_64 ;;
       sparc)   target_cpu=sparc64 ;;
       s390x)   target_cpu=s390 ;;
       ...
     esac

   Sometimes CPU have additional architecture names which don't
influence booting.  You might want to have some canonical name to avoid
having bunch of identical platforms with different names.

   NOTE: it doesn't influence compile optimisations which depend solely
on chosen compiler and compile options.

     if test "x$with_platform" = x; then
       case "$target_cpu"-"$target_vendor" in
         i386-apple) platform=efi ;;
         i386-*) platform=pc ;;
         x86_64-apple) platform=efi ;;
         x86_64-*) platform=pc ;;
         powerpc-*) platform=ieee1275 ;;
         ...
       esac
     else
       ...
     fi

   This part deals with guessing the platform from CPU and vendor.
Sometimes you need to use 32-bit mode for booting even if OS runs in
64-bit one. If so add your platform to:

     case "$target_cpu"-"$platform" in
       x86_64-efi) ;;
       x86_64-emu) ;;
       x86_64-*) target_cpu=i386 ;;
       powerpc64-ieee1275) target_cpu=powerpc ;;
     esac

   Add your platform to the list of supported ones:

     case "$target_cpu"-"$platform" in
       i386-efi) ;;
       x86_64-efi) ;;
       i386-pc) ;;
       i386-multiboot) ;;
       i386-coreboot) ;;
       ...
     esac

   If explicit -m32 or -m64 is needed add it to:

     case "$target_cpu" in
       i386 | powerpc) target_m32=1 ;;
       x86_64 | sparc64) target_m64=1 ;;
     esac

   Finally you need to add a conditional to the following block:

     AM_CONDITIONAL([COND_mips_arc], [test x$target_cpu = xmips -a x$platform = xarc])
     AM_CONDITIONAL([COND_sparc64_ieee1275], [test x$target_cpu = xsparc64 -a x$platform = xieee1275])
     AM_CONDITIONAL([COND_powerpc_ieee1275], [test x$target_cpu = xpowerpc -a x$platform = xieee1275])

   Next stop is gentpl.py. You need to add your platform to the list of
supported ones (sorry that this list is duplicated):

     GRUB_PLATFORMS = [ "emu", "i386_pc", "i386_efi", "i386_qemu", "i386_coreboot",
                        "i386_multiboot", "i386_ieee1275", "x86_64_efi",
                        "mips_loongson", "sparc64_ieee1275",
                        "powerpc_ieee1275", "mips_arc", "ia64_efi",
                        "mips_qemu_mips", "s390_mainframe" ]

   You may also want already to add new platform to one or several of
available groups. In particular we always have a group for each CPU
even when only one platform for given CPU is available.

   Then comes grub-core/Makefile.core.def. In the block "kernel" you'll
need to define ldflags for your platform ($cpu_$platform_ldflags). You
also need to declare startup asm file ($cpu_$platform_startup) as well
as any other files (e.g. init.c and callwrap.S) (e.g. $cpu_$platform =
kern/$cpu/$platform/init.c).  At this stage you will also need to add
dummy dl.c and cache.S with functions grub_err_t
grub_arch_dl_check_header (void *ehdr), grub_err_t
grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr) (dl.c) and
void grub_arch_sync_caches (void *address, grub_size_t len) (cache.S).
They won't be used for now.

   You will need to create directory include/$cpu/$platform and a file
include/$cpu/types.h. The later folowing this template:

     #ifndef GRUB_TYPES_CPU_HEADER
     #define GRUB_TYPES_CPU_HEADER      1

     /* The size of void *.  */
     #define GRUB_TARGET_SIZEOF_VOID_P  4

     /* The size of long.  */
     #define GRUB_TARGET_SIZEOF_LONG            4

     /* mycpu is big-endian.  */
     #define GRUB_TARGET_WORDS_BIGENDIAN        1
     /* Alternatively: mycpu is little-endian.  */
     #undef GRUB_TARGET_WORDS_BIGENDIAN

     #endif /* ! GRUB_TYPES_CPU_HEADER */

   You will also need to add a dummy file to datetime and setjmp
modules to avoid any of it having no files. It can be just completely
empty at this stage.

   You'll need to make grub-mkimage.c (util/grub_mkimage.c) aware of
the needed format. For most commonly used formats like ELF, PE, aout or
raw the support is already present and you'll need to make it follow
the existant code paths for your platform adding adjustments if
necessary. When done compile:

     ./autogen.sh
     ./configure --target=$cpu --with-platform=$platform TARGET_CC=.. OBJCOPY=... STRIP=...
     make > /dev/null

   And create image

     ./grub-mkimage -d grub-core -O $format_id -o test.img

   And it's time to test your test.img.

   If it works next stage is to have heap, console and timer.

   To have the heap working you need to determine which regions are
suitable for heap usage, allocate them from firmware and map (if
applicable). Then call grub_mm_init_region (vois *start, grub_size_t s)
for every of this region.  As a shortcut for early port you can
allocate right after _end or have a big static array for heap. If you
do you'll probably need to come back to this later. As for output
console you should distinguish between an array of text, terminfo or
graphics-based console. Many of real-world examples don't fit perfectly
into any of these categories but one of the models is easier to be used
as base. In second and third case you should add your platform to
terminfokernel respectively videoinkernel group. A good example of
array of text is i386-pc (kern/i386/pc/init.c and
term/i386/pc/console.c).  Of terminfo is ieee1275 (kern/ieee1275/init.c
and term/ieee1275/console.c).  Of video is loongson
(kern/mips/loongson/init.c). Note that terminfo has to be inited in 2
stages: one before (to get at least rudimentary console as early as
possible) and another after the heap (to get full-featured console).
For the input there are string of keys, terminfo and direct hardware.
For string of keys look at i386-pc (same files), for termino ieee1275
(same files) and for hardware loongson (kern/mips/loongson/init.c and
term/at_keyboard.c).

   For the timer you'll need to call grub_install_get_time_ms (...)
with as sole argument a function returning a grub_uint64_t of a number
of milliseconds elapsed since arbitrary point in the past.

   Once these steps accomplished you can remove the inifinite loop and
you should be able to get to the minimal console. Next step is to have
module loading working. For this you'll need to fill kern/$cpu/dl.c and
kern/$cpu/cache.S with real handling of relocations and respectively
the real sync of I and D caches. Also you'll need to decide where in
the image to store the modules.  Usual way is to have it concatenated
at the end. In this case you'll need to modify startup.S to copy
modules out of bss to let's say ALIGN_UP (_end, 8) before cleaning out
bss. You'll probably find useful to add total_module_size field to
startup.S. In init.c you need to set grub_modbase to the address where
modules can be found. You may need grub_modules_get_end () to avoid
declaring the space occupied by modules as usable for heap. You can
test modules with:

     ./grub-mkimage -d grub-core -O $format_id -o test.img hello

   and then running "hello" in the shell.

   Once this works, you should think of implementing disk access. Look
around disk/ for examples.

   Then, very importantly, you probably need to implement the actual
loader (examples available in loader/)

   Last step to have minimally usable port is to add support to
grub-install to put GRUB in a place where firmware or platform will
pick it up.

   Next steps are: filling datetime.c, setjmp.S, network (net/drivers),
video (video/), halt (lib/), reboot (lib/).

   Please add your platform to Platform limitations and Supported
kernels chapter in user documentation and mention any steps you skipped
which result in reduced features or performance. Here is the quick
checklist of features. Some of them are less important than others and
skipping them is completely ok, just needs to be mentioned in user
documentation.

   Checklist:
   * Is heap big enough?

   * Which charset is supported by console?

   * Does platform have disk driver?

   * Do you have network card support?

   * Are you able to retrieve datetime (with date)?

   * Are you able to set datetime (with date)?

   * Is serial supported?

   * Do you have direct disk support?

   * Do you have direct keyboard support?

   * Do you have USB support?

   * Do you support loading through network?

   * Do you support loading from disk?

   * Do you support chainloading?

   * Do you support network chainloading?

   * Does cpuid command supports checking all CPU features that the
     user might want conditionalise on (64-bit mode, hypervisor,...)

   * Do you support hints? How reliable are they?

   * Does platform have ACPI? If so do "acpi" and "lsacpi" modules work?

   * Do any of platform-specific operations mentioned in the relevant
     section of user manual makes sense on your platform?

   * Does your platform support PCI? If so is there an appropriate
     driver for GRUB?

   * Do you support badram?

\x1f
File: grub-dev.info,  Node: Error Handling,  Next: CIA,  Prev: Porting,  Up: Top

6 Error Handling
****************

Error handling in GRUB 2 is based on exception handling model. As C
language doesn't directly support exceptions, exception handling
behavior is emulated in software.

   When exception is raised, function must return to calling function.
If calling function does not provide handling of the exception it must
return back to its calling function and so on, until exception is
handled. If exception is not handled before prompt is displayed, error
message will be shown to user.

   Exception information is stored on `grub_errno' global variable. If
`grub_errno' variable contains value `GRUB_ERR_NONE', there is no active
exception and application can continue normal processing. When
`grub_errno' has other value, it is required that application code
either handles this error or returns instantly to caller. If function
is with return type `grub_err_t' is about to return `GRUB_ERR_NONE', it
should not set `grub_errno' to that value. Only set `grub_errno' in
cases where there is error situation.

   Simple exception forwarder.
     grub_err_t
     forwarding_example (void)
     {
       /* Call function that might cause exception.  */
       foobar ();

       /* No special exception handler, just forward possible exceptions.  */
       if (grub_errno != GRUB_ERR_NONE)
         {
           return grub_errno;
         }

       /* All is OK, do more processing.  */

       /* Return OK signal, to caller.  */
       return GRUB_ERR_NONE;
     }

   Error reporting has two components, the actual error code (of type
`grub_err_t') and textual message that will be displayed to user. List
of valid error codes is listed in header file `include/grub/err.h'.
Textual error message can contain any textual data. At time of writing,
error message can contain up to 256 characters (including terminating
NUL). To ease error reporting there is a helper function `grub_error'
that allows easier formatting of error messages and should be used
instead of writing directly to global variables.

   Example of error reporting.
     grub_err_t
     failing_example ()
     {
       return grub_error (GRUB_ERR_FILE_NOT_FOUND,
                          "Failed to read %s, tried %d times.",
                          "test.txt",
                          10);
     }

   If there is a special reason that error code does not need to be
taken account, `grub_errno' can be zeroed back to `GRUB_ERR_NONE'. In
cases like this all previous error codes should have been handled
correctly. This makes sure that there are no unhandled exceptions.

   Example of zeroing `grub_errno'.
     grub_err_t
     probe_example ()
     {
       /* Try to probe device type 1.  */
       probe_for_device ();
       if (grub_errno == GRUB_ERR_NONE)
         {
           /* Device type 1 was found on system.  */
           register_device ();
           return GRUB_ERR_NONE;
         }
       /* Zero out error code.  */
       grub_errno = GRUB_ERR_NONE;

       /* No device type 1 found, try to probe device type 2.  */
       probe_for_device2 ();
       if (grub_errno == GRUB_ERR_NONE)
         {
           /* Device type 2 was found on system.  */
           register_device2 ();
           return GRUB_ERR_NONE;
         }
       /* Zero out error code.  */
       grub_errno = GRUB_ERR_NONE;

       /* Return custom error message.  */
       return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "No device type 1 or 2 found.");
     }

   Some times there is a need to continue processing even if there is a
error state in application. In situations like this, there is a needed
to save old error state and then call other functions that might fail.
To aid in this, there is a error stack implemented. Error state can be
pushed to error stack by calling function `grub_error_push ()'. When
processing has been completed, `grub_error_pop ()' can be used to pop
error state from stack. Error stack contains predefined amount of error
stack items. Error stack is protected for overflow and marks these
situations so overflow error does not get unseen.  If there is no space
available to store error message, it is simply discarded and overflow
will be marked as happened. When overflow happens, it most likely will
corrupt error stack consistency as for pushed error there is no matching
pop, but overflow message will be shown to inform user about the
situation.  Overflow message will be shown at time when prompt is about
to be drawn.

   Example usage of error stack.
     /* Save possible old error message.  */
     grub_error_push ();

     /* Do your stuff here.  */
     call_possibly_failing_function ();

     if (grub_errno != GRUB_ERR_NONE)
       {
         /* Inform rest of the code that there is error (grub_errno
            is set). There is no pop here as we want both error states
            to be displayed.  */
         return;
       }

     /* Restore old error state by popping previous item from stack. */
     grub_error_pop ();

\x1f
File: grub-dev.info,  Node: CIA,  Next: BIOS port memory map,  Prev: Error Handling,  Up: Top

7 CIA
*****

If you have commit access, please setup CIA in your Bazaar config so
those in IRC receive notification of your commits.

   In `~/.bazaar/bazaar.conf', add "cia_send_revno = true".
Optionally, you can also add "cia_user = myusername" if you'd like CIA
service to use a specific account (for statistical purpose).

   In the `.bzr/branch/branch.conf' of your checkout branch, "set
nickname = /path_to_this_branch" and "cia_project = GNU GRUB".

   Additionally, please set cia_send_revno in the [DEFAULT] section of
your `~/.bazaar/bazaar.conf'. E.g.:

     [DEFAULT]
     cia_send_revno = true

   Remember to install cia-clients (Debian/Ubuntu package) to be able
to use CIA.

   Keep in mind Bazaar sends notifications for all commits to branches
that have this setting, regardless of whether they're bound branches
(checkouts) or not.  So if you make local commits in a non-bound branch
and it bothers you that others can read them, do not use this setting.

\x1f
File: grub-dev.info,  Node: BIOS port memory map,  Next: Video Subsystem,  Prev: CIA,  Up: Top

8 BIOS port memory map
**********************

Start       End                Usage
-------------------------------------------------------------------- 
0           0x1000 - 1         BIOS and real mode interrupts
0x07BE      0x07FF             Partition table passed to another
                               boot loader
?           0x2000 - 1         Real mode stack
0x7C00      0x7D00 - 1         Boot sector
0x8000      ?                  GRUB kernel
0x68000     0x78000 - 1        Disk buffer
?           0x80000 - 1        Protected mode stack
0x80000     ?                  Heap
?           0xA0000 - 1        Extended BIOS Data Area
0xA0000     0xC0000 - 1        Video RAM
0xC0000     0x100000 - 1       BIOS
0x100000    ?                  Heap and module code

\x1f
File: grub-dev.info,  Node: Video Subsystem,  Next: PFF2 Font File Format,  Prev: BIOS port memory map,  Up: Top

9 Video Subsystem
*****************

This document contains specification for Video Subsystem for GRUB2.
Currently only the usage interface is described in this document.
Internal structure of how video drivers are registering and how video
driver manager works are not included here.

* Menu:

* Video API::
* Bitmap API::
* Example usage of Video API::

\x1f
File: grub-dev.info,  Node: Video API,  Next: Bitmap API,  Up: Video Subsystem

9.1 Video API
=============

9.1.1 grub_video_setup
----------------------

   * Prototype:
          grub_err_t
          grub_video_setup (unsigned int width, unsigned int height, unsigned int mode_type);

   * Description:

     Driver will use information provided to it to select best possible
     video mode and switch to it. Supported values for `mode_type' are
     `GRUB_VIDEO_MODE_TYPE_INDEX_COLOR' for index color modes,
     `GRUB_VIDEO_MODE_TYPE_RGB' for direct RGB color modes and
     `GRUB_VIDEO_MODE_TYPE_DOUBLE_BUFFERED' for double buffering. When
     requesting RGB mode, highest bits per pixel mode will be selected.
     When requesting Index color mode, mode with highest number of
     colors will be selected. If all parameters are specified as zero,
     video adapter will try to figure out best possible mode and
     initialize it, platform specific differences are allowed here. If
     there is no mode matching request, error X will be returned. If
     there are no problems, function returns `GRUB_ERR_NONE'.

     This function also performs following task upon succesful mode
     switch. Active rendering target is changed to screen and viewport
     is maximized to allow whole screen to be used when performing
     graphics operations. In RGB modes, emulated palette gets 16
     entries containing default values for VGA palette, other colors
     are defined as black. When switching to Indexed Color mode, driver
     may set default VGA palette to screen if the video card allows the
     operation.


9.1.2 grub_video_restore
------------------------

   * Prototype:

          grub_err_t
          grub_video_restore (void);

   * Description:

     Video subsystem will deinitialize activated video driver to
     restore old state of video device. This can be used to switch back
     to text mode.

9.1.3 grub_video_get_info
-------------------------

   * Prototype:

          grub_err_t
          grub_video_get_info (struct grub_video_mode_info *mode_info);

          struct grub_video_mode_info
          {
            /* Width of the screen.  */
            unsigned int width;
            /* Height of the screen.  */
            unsigned int height;
            /* Mode type bitmask.  Contains information like is it Index color or
               RGB mode.  */
            unsigned int mode_type;
            /* Bits per pixel.  */
            unsigned int bpp;
            /* Bytes per pixel.  */
            unsigned int bytes_per_pixel;
            /* Pitch of one scanline.  How many bytes there are for scanline.  */
            unsigned int pitch;
            /* In index color mode, number of colors.  In RGB mode this is 256.  */
            unsigned int number_of_colors;
            /* Optimization hint how binary data is coded.  */
            enum grub_video_blit_format blit_format;
            /* How many bits are reserved for red color.  */
            unsigned int red_mask_size;
            /* What is location of red color bits.  In Index Color mode, this is 0.  */
            unsigned int red_field_pos;
            /* How many bits are reserved for green color.  */
            unsigned int green_mask_size;
            /* What is location of green color bits.  In Index Color mode, this is 0.  */
            unsigned int green_field_pos;
            /* How many bits are reserved for blue color.  */
            unsigned int blue_mask_size;
            /* What is location of blue color bits.  In Index Color mode, this is 0.  */
            unsigned int blue_field_pos;
            /* How many bits are reserved in color.  */
            unsigned int reserved_mask_size;
            /* What is location of reserved color bits.  In Index Color mode,
               this is 0.  */
            unsigned int reserved_field_pos;
          };

   * Description:

     Software developer can use this function to query properties of
     active rendering taget. Information provided here can be used by
     other parts of GRUB, like image loaders to convert loaded images
     to correct screen format to allow more optimized blitters to be
     used. If there there is no configured video driver with active
     screen, error `GRUB_ERR_BAD_DEVICE' is returned, otherwise
     `mode_info' is filled with valid information and `GRUB_ERR_NONE'
     is returned.

9.1.4 grub_video_get_blit_format
--------------------------------

   * Prototype:

          enum grub_video_blit_format
          grub_video_get_blit_format (struct grub_video_mode_info *mode_info);

          enum grub_video_blit_format
            {
              /* Follow exactly field & mask information.  */
              GRUB_VIDEO_BLIT_FORMAT_RGBA,
              /* Make optimization assumption.  */
              GRUB_VIDEO_BLIT_FORMAT_R8G8B8A8,
              /* Follow exactly field & mask information.  */
              GRUB_VIDEO_BLIT_FORMAT_RGB,
              /* Make optimization assumption.  */
              GRUB_VIDEO_BLIT_FORMAT_R8G8B8,
              /* When needed, decode color or just use value as is.  */
              GRUB_VIDEO_BLIT_FORMAT_INDEXCOLOR
            };

   * Description:

     Used to query how data could be optimized to suit specified video
     mode. Returns exact video format type, or a generic one if there
     is no definition for the type. For generic formats, use
     `grub_video_get_info' to query video color coding settings.

9.1.5 grub_video_set_palette
----------------------------

   * Prototype:

          grub_err_t
          grub_video_set_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);

          struct grub_video_palette_data
          {
              grub_uint8_t r; /* Red color value (0-255). */
              grub_uint8_t g; /* Green color value (0-255). */
              grub_uint8_t b; /* Blue color value (0-255). */
              grub_uint8_t a; /* Reserved bits value (0-255). */
          };

   * Description:

     Used to setup indexed color palettes. If mode is RGB mode, colors
     will be set to emulated palette data. In Indexed Color modes,
     palettes will be set to hardware. Color values will be converted
     to suit requirements of the video mode. `start' will tell what
     hardware color index (or emulated color index) will be set to
     according information in first indice of `palette_data', after
     that both hardware color index and `palette_data' index will be
     incremented until `count' number of colors have been set.

9.1.6 grub_video_get_palette
----------------------------

   * Prototype:

          grub_err_t
          grub_video_get_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);

          struct grub_video_palette_data
          {
              grub_uint8_t r; /* Red color value (0-255). */
              grub_uint8_t g; /* Green color value (0-255). */
              grub_uint8_t b; /* Blue color value (0-255). */
              grub_uint8_t a; /* Reserved bits value (0-255). */
          };

   * Description:

     Used to query indexed color palettes. If mode is RGB mode, colors
     will be copied from emulated palette data. In Indexed Color modes,
     palettes will be read from hardware. Color values will be
     converted to suit structure format. `start' will tell what
     hardware color index (or emulated color index) will be used as a
     source for first indice of `palette_data', after that both
     hardware color index and `palette_data' index will be incremented
     until `count' number of colors have been read.

9.1.7 grub_video_set_viewport
-----------------------------

   * Prototype:

          grub_err_t
          grub_video_set_viewport (unsigned int x, unsigned int y, unsigned int width, unsigned int height);

   * Description:

     Used to specify viewport where draw commands are performed. When
     viewport is set, all draw commands coordinates relate to those
     specified by `x' and `y'. If draw commands try to draw over
     viewport, they are clipped. If developer requests larger than
     possible viewport, width and height will be clamped to fit screen.
     If `x' and `y' are out of bounds, all functions drawing to screen
     will not be displayed. In order to maximize viewport, use
     `grub_video_get_info' to query actual screen dimensions and
     provide that information to this function.

9.1.8 grub_video_get_viewport
-----------------------------

   * Prototype:

          grub_err_t
          grub_video_get_viewport (unsigned int *x, unsigned int *y, unsigned int *width, unsigned int *height);

   * Description:

     Used to query current viewport dimensions. Software developer can
     use this to choose best way to render contents of the viewport.

9.1.9 grub_video_map_color
--------------------------

   * Prototype:

          grub_video_color_t
          grub_video_map_color (grub_uint32_t color_name);

   * Description:

     Map color can be used to support color themes in GRUB. There will
     be collection of color names that can be used to query actual
     screen mapped color data. Examples could be
     `GRUB_COLOR_CONSOLE_BACKGROUND', `GRUB_COLOR_CONSOLE_TEXT'. The
     actual color defines are not specified at this point.

9.1.10 grub_video_map_rgb
-------------------------

   * Prototype:

          grub_video_color_t
          grub_video_map_rgb (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue);

   * Description:

     Map RGB values to compatible screen color data. Values are
     expected to be in range 0-255 and in RGB modes they will be
     converted to screen color data. In index color modes, index color
     palette will be searched for specified color and then index is
     returned.

9.1.11 grub_video_map_rgba
--------------------------

   * Prototype:

          grub_video_color_t
          grub_video_map_rgba (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue, grub_uint8_t alpha);

   * Description:

     Map RGBA values to compatible screen color data. Values are
     expected to be in range 0-255. In RGBA modes they will be
     converted to screen color data. In index color modes, index color
     palette will be searched for best matching color and its index is
     returned.

9.1.12 grub_video_unmap_color
-----------------------------

   * Prototype:

          grub_err_t
          grub_video_unmap_color (grub_video_color_t color, grub_uint8_t *red, grub_uint8_t *green, grub_uint8_t *blue, grub_uint8_t *alpha);

   * Description:

     Unmap color value from `color' to color channels in `red',
     `green', `blue' and `alpha'. Values will be in range 0-255. Active
     rendering target will be used for color domain. In case alpha
     information is not available in rendering target, it is assumed to
     be opaque (having value 255).

9.1.13 grub_video_fill_rect
---------------------------

   * Prototype:

          grub_err_t
          grub_video_fill_rect (grub_video_color_t color, int x, int y, unsigned int width, unsigned int height);

   * Description:

     Fill specified area limited by given coordinates within specified
     viewport. Negative coordinates are accepted in order to allow easy
     moving of rectangle within viewport. If coordinates are negative,
     area of the rectangle will be shrinken to follow size limits of
     the viewport.

     Software developer should use either `grub_video_map_color',
     `grub_video_map_rgb' or `grub_video_map_rgba' to map requested
     color to `color' parameter.

9.1.14 grub_video_blit_glyph
----------------------------

   * Prototype:

          grub_err_t
          grub_video_blit_glyph (struct grub_font_glyph *glyph, grub_video_color_t color, int x, int y);

          struct grub_font_glyph {
              /* TBD. */
          };

   * Description:

     Used to blit glyph to viewport in specified coodinates. If glyph
     is at edge of viewport, pixels outside of viewport will be clipped
     out. Software developer should use either `grub_video_map_rgb' or
     `grub_video_map_rgba' to map requested color to `color' parameter.

9.1.15 grub_video_blit_bitmap
-----------------------------

   * Prototype:

          grub_err_t
          grub_video_blit_bitmap (struct grub_video_bitmap *bitmap, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);

          struct grub_video_bitmap
          {
              /* TBD. */
          };

          enum grub_video_blit_operators
            {
              GRUB_VIDEO_BLIT_REPLACE,
              GRUB_VIDEO_BLIT_BLEND
            };

   * Description:

     Used to blit bitmap to viewport in specified coordinates. If part
     of bitmap is outside of viewport region, it will be clipped out.
     Offsets affect bitmap position where data will be copied from.
     Negative values for both viewport coordinates and bitmap offset
     coordinates are allowed. If data is looked out of bounds of
     bitmap, color value will be assumed to be transparent. If viewport
     coordinates are negative, area of the blitted rectangle will be
     shrinken to follow size limits of the viewport and bitmap.
     Blitting operator `oper' specifies should source pixel replace
     data in screen or blend with pixel alpha value.

     Software developer should use `grub_video_bitmap_create' or
     `grub_video_bitmap_load' to create or load bitmap data.

9.1.16 grub_video_blit_render_target
------------------------------------

   * Prototype:

          grub_err_t
          grub_video_blit_render_target (struct grub_video_render_target *source, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);

          struct grub_video_render_target {
              /* This is private data for video driver. Should not be accessed from elsewhere directly.  */
          };

          enum grub_video_blit_operators
            {
              GRUB_VIDEO_BLIT_REPLACE,
              GRUB_VIDEO_BLIT_BLEND
            };

   * Description:

     Used to blit source render target to viewport in specified
     coordinates. If part of source render target is outside of
     viewport region, it will be clipped out. If blitting operator is
     specified and source contains alpha values, resulting pixel color
     components will be calculated using formula ((src_color *
     src_alpha) + (dst_color * (255 - src_alpha)) / 255, if target
     buffer has alpha, it will be set to src_alpha. Offsets affect
     render target position where data will be copied from. If data is
     looked out of bounds of render target, color value will be assumed
     to be transparent. Blitting operator `oper' specifies should
     source pixel replace data in screen or blend with pixel alpha
     value.

9.1.17 grub_video_scroll
------------------------

   * Prototype:

          grub_err_t
          grub_video_scroll (grub_video_color_t color, int dx, int dy);

   * Description:

     Used to scroll viewport to specified direction. New areas are
     filled with specified color. This function is used when screen is
     scroller up in video terminal.

9.1.18 grub_video_swap_buffers
------------------------------

   * Prototype:

          grub_err_t
          grub_video_swap_buffers (void);

   * Description:

     If double buffering is enabled, this swaps frontbuffer and
     backbuffer, in order to show values drawn to back buffer. Video
     driver is free to choose how this operation is techincally done.

9.1.19 grub_video_create_render_target
--------------------------------------

   * Prototype:

          grub_err_t
          grub_video_create_render_target (struct grub_video_render_target **result, unsigned int width, unsigned int height, unsigned int mode_type);

          struct grub_video_render_target {
              /* This is private data for video driver. Should not be accessed from elsewhere directly.  */
          };

   * Description:

     Driver will use information provided to it to create best fitting
     render target. `mode_type' will be used to guide on selecting what
     features are wanted for render target. Supported values for
     `mode_type' are `GRUB_VIDEO_MODE_TYPE_INDEX_COLOR' for index color
     modes, `GRUB_VIDEO_MODE_TYPE_RGB' for direct RGB color modes and
     `GRUB_VIDEO_MODE_TYPE_ALPHA' for alpha component.

9.1.20 grub_video_delete_render_target
--------------------------------------

   * Prototype:

          grub_err_t
          grub_video_delete_render_target (struct grub_video_render_target *target);

   * Description:

     Used to delete previously created render target. If `target'
     contains `NULL' pointer, nothing will be done. If render target is
     correctly destroyed, GRUB_ERR_NONE is returned.

9.1.21 grub_video_set_active_render_target
------------------------------------------

   * Prototype:

          grub_err_t
          grub_video_set_active_render_target (struct grub_video_render_target *target);

   * Description:

     Sets active render target. If this comand is successful all
     drawing commands will be done to specified `target'. There is also
     special values for target, `GRUB_VIDEO_RENDER_TARGET_DISPLAY' used
     to reference screen's front buffer,
     `GRUB_VIDEO_RENDER_TARGET_FRONT_BUFFER' used to reference screen's
     front buffer (alias for `GRUB_VIDEO_RENDER_TARGET_DISPLAY') and
     `GRUB_VIDEO_RENDER_TARGET_BACK_BUFFER' used to reference back
     buffer (if double buffering is enabled). If render target is
     correclty switched GRUB_ERR_NONE is returned. In no any event
     shall there be non drawable active render target.


9.1.22 grub_video_get_active_render_target
------------------------------------------

   * Prototype:

          grub_err_t
          grub_video_get_active_render_target (struct grub_video_render_target **target);

   * Description:

     Returns currently active render target. It returns value in
     `target' that can be subsequently issued back to
     `grub_video_set_active_render_target'.

\x1f
File: grub-dev.info,  Node: Example usage of Video API,  Prev: Bitmap API,  Up: Video Subsystem

9.2 Example usage of Video API
==============================

9.2.1 Example of screen setup
-----------------------------

     grub_err_t rc;
     /* Try to initialize video mode 1024 x 768 with direct RGB.  */
     rc = grub_video_setup (1024, 768, GRUB_VIDEO_MODE_TYPE_RGB);
     if (rc != GRUB_ERR_NONE)
     {
       /* Fall back to standard VGA Index Color mode.  */
       rc = grub_video_setup (640, 480, GRUB_VIDEO_MODE_TYPE_INDEX);
       if (rc != GRUB_ERR_NONE)
       {
       /* Handle error.  */
       }
     }

9.2.2 Example of setting up console viewport
--------------------------------------------

     grub_uint32_t x, y, width, height;
     grub_video_color_t color;
     struct grub_font_glyph glyph;
     grub_err_t rc;
     /* Query existing viewport.  */
     grub_video_get_viewport (&x, &y, &width, &height);
     /* Fill background.  */
     color = grub_video_map_color (GRUB_COLOR_BACKGROUND);
     grub_video_fill_rect (color, 0, 0, width, height);
     /* Setup console viewport.  */
     grub_video_set_viewport (x + 10, y + 10, width - 20, height - 20);
     grub_video_get_viewport (&x, &y, &width, &height);
     color = grub_video_map_color (GRUB_COLOR_CONSOLE_BACKGROUND);
     grub_video_fill_rect (color, 0, 0, width, height);
     /* Draw text to viewport.  */
     color = grub_video_map_color (GRUB_COLOR_CONSOLE_TEXT);
     grub_font_get_glyph ('X', &glyph);
     grub_video_blit_glyph (&glyph, color, 0, 0);

\x1f
File: grub-dev.info,  Node: Bitmap API,  Next: Example usage of Video API,  Prev: Video API,  Up: Video Subsystem

9.3 Bitmap API
==============

9.3.1 grub_video_bitmap_create
------------------------------

   * Prototype:
          grub_err_t grub_video_bitmap_create (struct grub_video_bitmap **bitmap, unsigned int width, unsigned int height, enum grub_video_blit_format blit_format)

   * Description:

     Creates a new bitmap with given dimensions and blitting format.
     Allocated bitmap data can then be modified freely and finally
     blitted with `grub_video_blit_bitmap' to rendering target.

9.3.2 grub_video_bitmap_destroy
-------------------------------

   * Prototype:
          grub_err_t grub_video_bitmap_destroy (struct grub_video_bitmap *bitmap);

   * Description:

     When bitmap is no longer needed, it can be freed from memory using
     this command. `bitmap' is previously allocated bitmap with
     `grub_video_bitmap_create' or loaded with `grub_video_bitmap_load'.

9.3.3 grub_video_bitmap_load
----------------------------

   * Prototype:
          grub_err_t grub_video_bitmap_load (struct grub_video_bitmap **bitmap, const char *filename);

   * Description:

     Tries to load given bitmap (`filename') using registered bitmap
     loaders. In case bitmap format is not recognized or supported
     error `GRUB_ERR_BAD_FILE_TYPE' is returned.

9.3.4 grub_video_bitmap_get_width
---------------------------------

   * Prototype:
          unsigned int grub_video_bitmap_get_width (struct grub_video_bitmap *bitmap);

   * Description:

     Returns bitmap width.

9.3.5 grub_video_bitmap_get_height
----------------------------------

   * Prototype:
          unsigned int grub_video_bitmap_get_height (struct grub_video_bitmap *bitmap);

   * Description:

     Return bitmap height.

9.3.6 grub_video_bitmap_get_mode_info
-------------------------------------

   * Prototype:
          void grub_video_bitmap_get_mode_info (struct grub_video_bitmap *bitmap, struct grub_video_mode_info *mode_info);

   * Description:

     Returns bitmap format details in form of `grub_video_mode_info'.

9.3.7 grub_video_bitmap_get_data
--------------------------------

   * Prototype:
          void *grub_video_bitmap_get_data (struct grub_video_bitmap *bitmap);

   * Description:

     Return pointer to bitmap data. Contents of the pointed data can be
     freely modified. There is no extra protection against going off
     the bounds so you have to be carefull how to access the data.

\x1f
File: grub-dev.info,  Node: PFF2 Font File Format,  Next: Graphical Menu Software Design,  Prev: Video Subsystem,  Up: Top

10 PFF2 Font File Format
************************

* Menu:

* Introduction::
* File Structure::
* Font Metrics::

\x1f
File: grub-dev.info,  Node: Introduction,  Next: File Structure,  Up: PFF2 Font File Format

10.1 Introduction
=================

The goal of this format is to provide a bitmap font format that is
simple to use, compact, and cleanly supports Unicode.

10.1.1 Goals of the GRUB Font Format
------------------------------------

   * Simple to read and use.  Since GRUB will only be reading the font
     files, we are more concerned with making the code to read the font
     simple than we are with writing the font.

   * Compact storage.  The fonts will generally be stored in a small
     boot partition where GRUB is located, and this may be on a
     removable storage device such as a CD or USB flash drive where
     space is more limited than it is on most hard drives.

   * Unicode.  GRUB should not have to deal with multiple character
     encodings.  The font should always use Unicode character codes for
     simple internationalization.

10.1.2 Why Another Font Format?
-------------------------------

There are many existing bitmap font formats that GRUB could use.
However, there are aspects of these formats that may make them less
than suitable for use in GRUB at this time:

`BDF'
     Inefficient storage; uses ASCII to describe properties and
     hexadecimal numbers in ASCII for the bitmap rows.

`PCF'
     Many format variations such as byte order and bitmap padding (rows
     padded to byte, word, etc.) would result in more complex code to
     handle the font format.

\x1f
File: grub-dev.info,  Node: File Structure,  Next: Font Metrics,  Prev: Introduction,  Up: PFF2 Font File Format

10.2 File Structure
===================

A file *section* consists of a 4-byte name, a 32-bit big-endian length
(not including the name or length), and then LENGTH more
section-type-specific bytes.

   The standard file extension for PFF2 font files is `.pf2'.

10.2.1 Section Types
--------------------

`FILE'
     *File type ID* (ASCII string).  This must be the first section in
     the file.  It has length 4 and the contents are the four bytes of
     the ASCII string `PFF2'.

`NAME'
     *Font name* (ASCII string).  This is the full font name including
     family, weight, style, and point size.  For instance, "Helvetica
     Bold Italic 14".

`FAMI'
     *Font family name* (ASCII string).  For instance, "Helvetica".
     This should be included so that intelligent font substitution can
     take place.

`WEIG'
     *Font weight* (ASCII string).  Valid values are `bold' and
     `normal'.  This should be included so that intelligent font
     substitution can take place.

`SLAN'
     *Font slant* (ASCII string).  Valid values are `italic' and
     `normal'.  This should be included so that intelligent font
     substitution can take place.

`PTSZ'
     *Font point size* (uint16be).

`MAXW'
     *Maximum character width in pixels* (uint16be).

`MAXH'
     *Maximum character height in pixels* (uint16be).

`ASCE'
     *Ascent in pixels* (uint16be).  *Note Font Metrics::, for details.

`DESC'
     *Descent in pixels* (uint16be).  *Note Font Metrics::, for details.

`CHIX'
     *Character index.* The character index begins with a 32-bit
     big-endian unsigned integer indicating the total size of the
     section, not including this size value.  For each character, there
     is an instance of the following entry structure:

        * *Unicode code point.* (32-bit big-endian integer.)

        * *Storage flags.* (byte.)

             * Bits 2..0:

               If equal to 000 binary, then the character data is stored
               uncompressed beginning at the offset indicated by the
               character's *offset* value.

               If equal to 001 binary, then the character data is
               stored within a compressed character definition block
               that begins at the offset within the file indicated by
               the character's *offset* value.

        * *Offset.* (32-bit big-endian integer.)

          A marker that indicates the remainder of the file is data
          accessed via the character index (CHIX) section.  When
          reading this font file, the rest of the file can be ignored
          when scanning the sections.  The length should be set to -1
          (0xFFFFFFFF).

          Supported data structures:

          Character definition Each character definition consists of:

             * *Width.* Width of the bitmap in pixels.  The bitmap's
               extents represent the glyph's bounding box.  `uint16be'.

             * *Height.* Height of the bitmap in pixels.  The bitmap's
               extents represent the glyph's bounding box.  `uint16be'.

             * *X offset.* The number of pixels to shift the bitmap by
               horizontally before drawing the character. `int16be'.

             * *Y offset.* The number of pixels to shift the bitmap by
               vertically before drawing the character. `int16be'.

             * *Device width.* The number of pixels to advance
               horizontally from this character's origin to the origin
               of the next character.  `int16be'.

             * *Bitmap data.* This is encoded as a string of bits.  It
               is organized as a row-major, top-down, left-to-right
               bitmap.  The most significant bit of each byte is taken
               to be the leftmost or uppermost bit in the byte.  For
               the sake of compact storage, rows are not padded to byte
               boundaries (i.e., a single byte may contain bits
               belonging to multiple rows).  The last byte of the
               bitmap *is* padded with zero bits in the bits positions
               to the right of the last used bit if the bitmap data
               does not fill the last byte.

               The length of the *bitmap data* field is (WIDTH * HEIGHT
               + 7) / 8 using integer arithmetic, which is equivalent
               to ceil(WIDTH * HEIGHT / 8) using real number arithmetic.

               It remains to be determined whether bitmap fonts usually
               make all glyph bitmaps the same height, or if smaller
               glyphs are stored with bitmaps having a lesser height.
               In the latter case, the baseline would have to be used
               to calculate the location the bitmap should be anchored
               at on screen.


\x1f
File: grub-dev.info,  Node: Font Metrics,  Prev: File Structure,  Up: PFF2 Font File Format

10.3 Font Metrics
=================

   * Ascent.  The distance from the baseline to the top of most
     characters.  Note that in some cases characters may extend above
     the ascent.

   * Descent.  The distance from the baseline to the bottom of most
     characters.  Note that in some cases characters may extend below
     the descent.

   * Leading.  The amount of space, in pixels, to leave between the
     descent of one line of text and the ascent of the next line.  This
     metrics is not specified in the current file format; instead, the
     font rendering engine calculates a reasonable leading value based
     on the other font metrics.

   * Horizonal leading.  The amount of space, in pixels, to leave
     horizontally between the left and right edges of two adjacent
     glyphs.  The *device width* field determines the effective leading
     value that is used to render the font.

[Please fill this in.
]

   An illustration of how the various font metrics apply to characters.

\x1f
File: grub-dev.info,  Node: Graphical Menu Software Design,  Next: Copying This Manual,  Prev: PFF2 Font File Format,  Up: Top

11 Graphical Menu Software Design
*********************************

* Menu:

* Introduction_2::
* Startup Sequence::
* GUI Components::
* Command Line Window::

\x1f
File: grub-dev.info,  Node: Introduction_2,  Next: Startup Sequence,  Up: Graphical Menu Software Design

11.1 Introduction
=================

The `gfxmenu' module provides a graphical menu interface for GRUB 2.  It
functions as an alternative to the menu interface provided by the
`normal' module, which uses the grub terminal interface to display a
menu on a character-oriented terminal.

   The graphical menu uses the GRUB video API, which is currently for
the VESA BIOS extensions (VBE) 2.0+.  This is supported on the i386-pc
platform.  However, the graphical menu itself does not depend on using
VBE, so if another GRUB video driver were implemented, the `gfxmenu'
graphical menu would work on the new video driver as well.

\x1f
File: grub-dev.info,  Node: Startup Sequence,  Next: GUI Components,  Prev: Introduction_2,  Up: Graphical Menu Software Design

11.2 Startup Sequence
=====================

   * grub_enter_normal_mode [normal/main.c]

   * grub_normal_execute [normal/main.c]

   * read_config_file [normal/main.c]

   * (When `gfxmenu.mod' is loaded with `insmod', it will call
     `grub_menu_viewer_register()' to register itself.)

   * GRUB_MOD_INIT (gfxmenu) [gfxmenu/gfxmenu.c]

   * grub_menu_viewer_register [kern/menu_viewer.c]

   * grub_menu_viewer_show_menu [kern/menu_viewer.c]

   * get_current_menu_viewer() [kern/menu_viewer.c]

   * show_menu() [gfxmenu/gfxmenu.c]

   * grub_gfxmenu_model_new [gfxmenu/model.c]

   * grub_gfxmenu_view_new [gfxmenu/view.c]

   * set_graphics_mode [gfxmenu/view.c]

   * grub_gfxmenu_view_load_theme [gfxmenu/theme_loader.c]

\x1f
File: grub-dev.info,  Node: GUI Components,  Next: Command Line Window,  Prev: Startup Sequence,  Up: Graphical Menu Software Design

11.3 GUI Components
===================

The graphical menu implements a GUI component system that supports a
container-based layout system.  Components can be added to containers,
and containers (which are a type of component) can then be added to
other containers, to form a tree of components.  Currently, the root
component of this tree is a `canvas' component, which allows manual
layout of its child components.

   Components (non-container):

   * label

   * image

   * progress_bar

   * circular_progress

   * list (currently hard coded to be a boot menu list)

   Containers:

   * canvas

   * hbox

   * vbox

   The GUI component instances are created by the theme loader in
`gfxmenu/theme_loader.c' when a theme is loaded.  Theme files specify
statements such as `+vbox{ +label { text="Hello" } +label{ text="World"
} }' to add components to the component tree root.  By nesting the
component creation statements in the theme file, the instantiated
components are nested the same way.

   When a component is added to a container, that new child is
considered *owned* by the container.  Great care should be taken if the
caller retains a reference to the child component, since it will be
destroyed if its parent container is destroyed.  A better choice
instead of storing a pointer to the child component is to use the
component ID to find the desired component.  Component IDs do not have
to be unique (it is often useful to have multiple components with an ID
of "__timeout__", for instance).

   In order to access and use components in the component tree, there
are two functions (defined in `gfxmenu/gui_util.c') that are
particularly useful:

   * `grub_gui_find_by_id (root, id, callback, userdata)':

     This function ecursively traverses the component tree rooted at
     ROOT, and for every component that has an ID equal to ID, calls
     the function pointed to by CALLBACK with the matching component
     and the void pointer USERDATA as arguments.  The callback function
     can do whatever is desired to use the component passed in.

   * `grub_gui_iterate_recursively (root, callback, userdata)':

     This function calls the function pointed to by CALLBACK for every
     component that is a descendant of ROOT in the component tree.
     When the callback function is called, the component and the void
     pointer USERDATA as arguments.  The callback function can do
     whatever is desired to use the component passed in.

\x1f
File: grub-dev.info,  Node: Command Line Window,  Prev: GUI Components,  Up: Graphical Menu Software Design

11.4 Command Line Window
========================

The terminal window used to provide command line access within the
graphical menu is managed by `gfxmenu/view.c'.  The `gfxterm' terminal
is used, and it has been modified to allow rendering to an offscreen
render target to allow it to be composed into the double buffering
system that the graphical menu view uses.  This is bad for performance,
however, so it would probably be a good idea to make it possible to
temporarily disable double buffering as long as the terminal window is
visible.  There are still unresolved problems that occur when commands
are executed from the terminal window that change the graphics mode.
It's possible that making `grub_video_restore()' return to the graphics
mode that was in use before `grub_video_setup()' was called might fix
some of the problems.

\x1f
File: grub-dev.info,  Node: Copying This Manual,  Next: Index,  Prev: Graphical Menu Software Design,  Up: Top

Appendix A Copying This Manual
******************************

* Menu:

* GNU Free Documentation License::  License for copying this manual.

\x1f
File: grub-dev.info,  Node: GNU Free Documentation License,  Up: Copying This Manual

A.1 GNU Free Documentation License
==================================

                      Version 1.2, November 2002

     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
     51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

  0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other
     functional and useful document "free" in the sense of freedom: to
     assure everyone the effective freedom to copy and redistribute it,
     with or without modifying it, either commercially or
     noncommercially.  Secondarily, this License preserves for the
     author and publisher a way to get credit for their work, while not
     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative
     works of the document must themselves be free in the same sense.
     It complements the GNU General Public License, which is a copyleft
     license designed for free software.

     We have designed this License in order to use it for manuals for
     free software, because free software needs free documentation: a
     free program should come with manuals providing the same freedoms
     that the software does.  But this License is not limited to
     software manuals; it can be used for any textual work, regardless
     of subject matter or whether it is published as a printed book.
     We recommend this License principally for works whose purpose is
     instruction or reference.

  1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium,
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     A "Modified Version" of the Document means any work containing the
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  2. VERBATIM COPYING

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     If the Modified Version includes new front-matter sections or
     appendices that qualify as Secondary Sections and contain no
     material copied from the Document, you may at your option
     designate some or all of these sections as invariant.  To do this,
     add their titles to the list of Invariant Sections in the Modified
     Version's license notice.  These titles must be distinct from any
     other section titles.

     You may add a section Entitled "Endorsements", provided it contains
     nothing but endorsements of your Modified Version by various
     parties--for example, statements of peer review or that the text
     has been approved by an organization as the authoritative
     definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text,
     and a passage of up to 25 words as a Back-Cover Text, to the end
     of the list of Cover Texts in the Modified Version.  Only one
     passage of Front-Cover Text and one of Back-Cover Text may be
     added by (or through arrangements made by) any one entity.  If the
     Document already includes a cover text for the same cover,
     previously added by you or by arrangement made by the same entity
     you are acting on behalf of, you may not add another; but you may
     replace the old one, on explicit permission from the previous
     publisher that added the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination
     all of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the
     documents in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow
     this License in all other respects regarding verbatim copying of
     that document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of
     a storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included in an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warranty Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document
     except as expressly provided for under this License.  Any other
     attempt to copy, modify, sublicense or distribute the Document is
     void, and will automatically terminate your rights under this
     License.  However, parties who have received copies, or rights,
     from you under this License will not have their licenses
     terminated so long as such parties remain in full compliance.

 10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     `http://www.gnu.org/copyleft/'.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If
     the Document does not specify a version number of this License,
     you may choose any version ever published (not as a draft) by the
     Free Software Foundation.

A.1.1 ADDENDUM: How to use this License for your documents
----------------------------------------------------------

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.2
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.

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* FDL, GNU Free Documentation License:   GNU Free Documentation License.
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Tag Table:
Node: Top\x7f714
Node: Getting the source code\x7f1786
Node: Coding style\x7f2666
Node: Naming Conventions\x7f3071
Node: Functions\x7f3354
Node: Variables\x7f4221
Node: Types\x7f5327
Node: Macros\x7f5925
Node: Comments\x7f6256
Node: Multi-Line Comments\x7f7018
Node: Finding your way around\x7f7649
Node: Contributing Changes\x7f10846
Node: Getting started\x7f11923
Node: Typical Developer Experience\x7f15969
Node: When you are approved for write access to project's files\x7f17012
Node: Porting\x7f18442
Node: Error Handling\x7f30182
Node: CIA\x7f35242
Node: BIOS port memory map\x7f36314
Node: Video Subsystem\x7f37184
Node: Video API\x7f37656
Node: Example usage of Video API\x7f55910
Node: Bitmap API\x7f57466
Node: PFF2 Font File Format\x7f59997
Node: Introduction\x7f60237
Node: File Structure\x7f61740
Node: Font Metrics\x7f66647
Node: Graphical Menu Software Design\x7f67751
Node: Introduction_2\x7f68043
Node: Startup Sequence\x7f68777
Node: GUI Components\x7f69640
Node: Command Line Window\x7f72245
Node: Copying This Manual\x7f73197
Node: GNU Free Documentation License\x7f73453
Node: Index\x7f95865
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End Tag Table