Fix compiler warnings about uninitialised variables.

[geany-mirror.git] / HACKING

=============
Hacking Geany
=============
.. contents::

General
=======

About this file
---------------
This file contains information for anyone wanting to work on the Geany
codebase. You should be aware of the open source licenses used - see
the README file or the documentation. It is reStructuredText; the
source file is HACKING. You can generate hacking.html by running ``make
hacking-doc`` from the doc/ subdirectory.

Writing plugins
---------------
* src/plugindata.h contains the plugin API data types.
* See plugins/demoplugin.c for a very basic example plugin.
* src/plugins.c loads and unloads plugins (you shouldn't need to read
  this really).
* The API documentation contains a few basic guidelines and hints to
  write plugins.

You should generate and read the plugin API documentation, see below.

Plugin API documentation
^^^^^^^^^^^^^^^^^^^^^^^^
You can generate documentation for the plugin API using the doxygen
tool. Run ``make api-doc`` in the doc subdirectory. The documentation
will be output to doc/reference/index.html.
Alternatively you can view the API documentation online at
http://www.geany.org/manual/reference/.

Patches
-------
We are happy to receive patches, but it's best to check with us by email
or mailing list whether a new feature is appropriate, and whether someone
is already working on similar code.

In general it's best to work from the current SVN, but we accept patches
against other releases::

    $ svn diff > fix-some-bug.patch

If you're not using SVN, you can use the diff command::

    $ diff -u originalpath modifiedpath > new-feature.patch

.. note::
    Please make sure patches follow the style of existing code - In
    particular, use tabs for indentation. See `Coding`_.

Windows tools
-------------
* Subversion (SVN): http://subversion.tigris.org/
* diff, grep, etc: http://mingw.org/ or http://unxutils.sourceforge.net/

See also the 'Building on Windows' document on the website.

File organization
-----------------
callbacks.c is just for Glade callbacks.
Avoid adding code to geany.h if it will fit better elsewhere.
See the top of each ``src/*.c`` file for a brief description of what
it's for.

Keeping the plugin ABI stable
-----------------------------
Please be aware that anything with a doc-comment (a comment with an
extra asterix: ``/**``) is something in the plugin API. Things like
enums and structs can usually still be appended to, ensuring that all
the existing elements stay in place - this will keep the ABI stable.

.. warning::

    Some structs like GeanyKeyGroupInfo and GeanyCallback cannot be
    appended to without breaking the ABI because they are used to declare
    structs by plugins, not just for accessing struct members through
    a pointer.

Before the 1.0 release series, the ABI can change when necessary, and
even the API can change. An ABI change just means that all plugins will
not load and they must be rebuilt. An API change means that some plugins
might not build correctly.

If you're reordering or changing existing elements of structs that are
used as part of the plugin API, you should increment GEANY_ABI_VERSION
in plugindata.h. This is usually not needed if you're just appending
fields to structs. The GEANY_API_VERSION value should be incremented
for any changes to the plugin API, including appending elements.

If you're in any doubt when making changes to plugin API code, just ask us.

Plugin API/ABI design
^^^^^^^^^^^^^^^^^^^^^
You should not make plugins rely on the size of a struct. This means:

* Don't let plugins allocate any structs (stack or heap).
* Don't let plugins index any arrays of structs.
* Don't add any array fields to structs in case we want to change the
  array size later.

Glade
-----
Use the code generation features of Glade instead of editing interface.c
or support.c. Glade 2.12 is recommended as long as we support GTK+ 2.8,
because later versions of Glade are not 100% compatible with GTK+ 2.8
(e.g. they may use functions added in GTK+ 2.10).

You can build Glade 2.12 and run the binary in place, without installing
it - this should work fine even if you have another version of Glade
installed on the system.

GTK API documentation
---------------------
The official GTK 2.8 API documentation is not available online anymore,
so we put them on http://www.geany.org/manual/gtk/.
There is also a tarball with all available files for download and use
with devhelp.

Using the 2.8 API documentation of the GTK libs (including GLib, GDK and
Pango) has the advantages that you don't get confused by any newer API
additions and you don't have to take care about whether you can use
them or not.
This is because Geany depends on GTK 2.8. API symbols from newer
GTK/GLib versions should be avoided to keep the source code building
against GTK 2.8.

Coding
------
* Don't write long functions with a lot of variables and/or scopes - break
  them down into smaller static functions where possible. This makes code
  much easier to read and maintain.
* Use GLib types and functions - gint not int, g_free() not free().
* Your code should build against GLib 2.8 and GTK 2.8. At least for the
  moment, we want to keep the minimum requirement for GTK at 2.8 (of
  course, you can use the GTK_CHECK_VERSION macro to protect code using
  later versions).
* Variables should be declared before statements. You can use
  gcc's -Wdeclaration-after-statement to warn about this.
* Don't let variable names shadow outer variables - use gcc's -Wshadow
  option.

Compiler options & warnings
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Use ``CFLAGS='-Wfoo' ./configure`` or ``CFLAGS='-Wfoo' ./autogen.sh``
to set warning options (as well as anything else e.g. -g -O2).

* Enable warnings - for gcc use '-Wall -W' (and optionally
  -Wno-unused-parameter to avoid unused parameter warnings in Glade
  callbacks).
* You should try to write ISO C90 code for portability, so always
  use C ``/* */`` comments and function_name(void) instead of
  function_name(). This is for compatibility with various Unix-like
  compilers. You should use -ansi to help check this.

Style
^^^^^
* We use a tab width of 4 and indent completely with tabs not spaces.
  Note the documentation files use (4) spaces instead, so you may want
  to use the 'Detect from file' indent pref.
* Use the multiline comment ``/* */`` to comment small blocks of code,
  functions descriptions or longer explanations of code, etc. C++ single
  line comments will cause portability issues. The more comments are in
  your code the better. (See also ``scripts/fix-cxx-comments.pl`` in SVN).
* Lines should not be longer than about 100 characters and after 100
  characters the lines should be wrapped and indented once more to
  show that the line is continued.
* We don't put spaces between function names and the opening brace for
  argument lists.
* Variable declarations come first after an opening brace, then one
  newline to separate declarations and code.
* 2-operand operators should have a space each side.
* Function bodies should have 2 blank newlines after them.
* Align braces together on separate lines.
* Don't put assignments in 'if/while/etc' expressions.
* if statements without brace bodies should have the code on a separate
  line, then a blank line afterwards.
* Use braces after if/while statements if the body uses another
  if/while statement.
* Try to fit in with the existing code style.

.. note::
    A few of the above can be done with the SVN
    ``scripts/fix-alignment.pl``, but it is quite dumb and it's much better
    to write it correctly in the first place.

.. below tabs should be used, but spaces are required for reST.

Example::

    gint some_func(void);


    gint function_long_name(gchar arg1, <too many args to fit on this line>,
            gchar argN)
    {
        gint foo, bar;  /* variables can go on the same line */
        gchar *ptr;     /* pointer symbol must go next to variable name, not type */
        gchar *another; /* pointers should normally go on separate lines */

        if (foo)
        {
            gint dir = -1;    /* -1 to search backwards */

            bar = foo;
            if ((bar & (guint)dir) != 7)
                some_code(arg1, <too many args to fit on this line>,
                    argN - 1, argN);

            some_func();
        }
    }


    gint another_function(void)
    {
        ...


Libraries
---------
We prefer to use an unmodified version of Scintilla - any changes should
be passed on to the maintainers at http://scintilla.org.

Tagmanager was originally taken from Anjuta 1.2.2, and parts of it
(notably c.c) have been merged from later versions of Anjuta and
CTags. The independent Tagmanager library itself ceased development
before Geany was started. It's source code parsing is mostly taken from
Exuberant CTags (see http://ctags.sf.net).


Notes
=====
Some of these notes below are brief (or maybe incomplete) - please
contact the geany-devel mailing list for more information.

Using pre-defined autotools values
----------------------------------
When you are use macros supplied by the autotools like GEANY_PREFIX,
GEANY_LIBDIR, GEANY_DATADIR and GEANY_LOCALEDIR be aware that these
might not be static strings when Geany is configured with
--enable-binreloc. Then these macros will be replaced by function calls
(in src/prefix.h). So, don't use anything like
printf("Prefix: " GEANY_PREFIX); but instead use
printf("Prefix: %s", GEANY_PREFIX);

Adding a source file foo.[hc] in src/ or plugins/
-------------------------------------------------
* Add foo.c, foo.h to SRCS in path/Makefile.am.
* Add foo.o to OBJS in path/makefile.win32.
* Add path/foo.c to po/POTFILES.in (for string translation).

Adding a filetype
-----------------
You can add a filetype without syntax highlighting or tag parsing, but
check to see if those features have been written in other projects first.

* Add GEANY_FILETYPES_FOO to filetypes.h.
* Initialize GEANY_FILETYPES_FOO in init_builtin_filetypes() of
  filetypes.c. You should use filetype_make_title() to avoid a
  translation whenever possible.
* Update data/filetype_extensions.conf.

filetypes.* configuration file
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
All languages need a data/filetypes.foo configuration file. See
the "Filetype definition files" section in the manual and/or
data/filetypes.c for an example.

Programming languages should have:

* [keywords] if the lexer supports it.
* [settings] mostly for comment settings.
* [build_settings] for commands to run.

For languages with a Scintilla lexer, there should be a [styling] section,
to correspond to the styles used in styleset_foo() in highlighting.c -
see below.

Syntax highlighting
^^^^^^^^^^^^^^^^^^^
It may be possible to use an existing Scintilla lexer in the scintilla/
subdirectory - if not, you will need to find (or write) one,
LexFoo.cxx. Try the official Scintilla project first.

.. warning::
    We won't accept adding a lexer that conflicts with one in
    Scintilla. All new lexers should be submitted back to the Scintilla
    project to save duplication of work.

When adding a lexer, update:

* scintilla/Makefile.am
* scintilla/makefile.win32
* scintilla/KeyWords.cxx - add a LINK_LEXER command *manually*

For syntax highlighting, you will need to edit highlighting.c and add
the following things:

1. Write styleset_foo_init() to setup default styles and load style
   settings from the filetypes.foo configuration file. You should probably
   start by copying and adapting another filetype's initialization, such
   as styleset_tcl_init(). Another way is to use load_style_entries()
   to make style initialization simpler - see styleset_c_like_init().

.. note::
    Please try to make your styles fit in with the other filetypes' default
    colors, and to use named styles where possible. Filetypes that share a
    lexer should have the same colors. Normally, styles should leave the
    background color empty to match the default color.

2. Write styleset_foo() to apply styles when a new scintilla widget
   is created. Again you could copy and adapt a function like
   styleset_tcl().
3. In highlighting_init_styles(), add
   ``init_styleset_case(GEANY_FILETYPES_FOO, styleset_foo_init);``.
4. In highlighting_set_styles(), add
   ``styleset_case(GEANY_FILETYPES_FOO, styleset_foo);``.

Error message parsing
^^^^^^^^^^^^^^^^^^^^^
New-style error message parsing is done with an extended GNU-style regex
stored in the filetypes.foo file - see the [build_settings] information
in the manual for details.

Old-style error message parsing is done in
msgwin_parse_compiler_error_line() of msgwindow.c - see the ParseData
typedef for more information.

Other features
^^^^^^^^^^^^^^
For brace indentation, update lexer_has_braces() in editor.c;
indentation after ':' is done from on_new_line_added().

If the lexer has comment styles, you should add them in is_comment_style()
in editor.c. You should also update is_string_style() for string/character
styles. For now, this prevents calltips and autocompletion when typing
in a comment (but it can still be forced by the user).

If the Scintilla lexer supports user type keyword highlighting (e.g.
SCLEX_CPP), update editor_lexer_get_type_keyword_idx() in editor.c.

Adding a TagManager parser
^^^^^^^^^^^^^^^^^^^^^^^^^^
This assumes the filetype for Geany already exists.

First write or find a CTags compatible parser, foo.c. Note that there
are some language patches for CTags at:
http://sf.net/projects/ctags - see the tracker.

(You can also try the Anjuta project's tagmanager codebase.)

* Add foo.c to SRCS in Makefile.am.
* Add foo.o to OBJS in makefile.win32.
* Add Foo to parsers.h & fill in comment with parser number for foo.

In foo.c:
Edit FooKinds 3rd column to match a s_tag_type_names string in tm_tag.c.

In filetypes.c, init_builtin_filetypes():
Set filetypes[GEANY_FILETYPES_FOO].lang = foo's parser number.

In symbols.c:
If your parser doesn't use C-like tag type names, update
add_top_level_items() for foo, calling tag_list_add_groups().


GDB
---

Stop on warnings
^^^^^^^^^^^^^^^^
When a GLib or GTK warning is printed, often you want to get a
backtrace to find out what code caused them. You can do that with the
``--g-fatal-warnings`` argument, which will abort Geany on the first
warning it receives.

But for ordinary testing, you don't always want your editor to abort
just because of a warning - use::

    (gdb) b handler_log if level <= G_LOG_LEVEL_WARNING


Running with batch commands
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Use::

    $ gdb src/geany -x gdb-commands

Where ``gdb-commands`` is a file with the following lines::

    set pagination off
    b handler_log if level <= G_LOG_LEVEL_WARNING
    r -v


Loading a plugin
^^^^^^^^^^^^^^^^
This is useful so you can load plugins without installing them first.
Alternatively you can use a symlink in ~/.config/geany/plugins or
$prefix/lib/geany (where $prefix is /usr/local by default).

The gdb session below was run from the toplevel Geany source directory.
Start normally with e.g. "gdb src/geany".
Type 'r' to run.
Press Ctrl-C from the gdb window to interrupt program execution.

Example::

    Program received signal SIGINT, Interrupt.
    0x00d16402 in __kernel_vsyscall ()
    (gdb) call plugin_new("./plugins/.libs/demoplugin.so")
    ** INFO: Loaded:   ./plugins/.libs/demoplugin.so (Demo)
    $1 = (Plugin *) 0x905a890
    (gdb) c
    Continuing.

    Program received signal SIGINT, Interrupt.
    0x00d16402 in __kernel_vsyscall ()
    (gdb) call plugin_free(0x905a890)
    ** INFO: Unloaded: ./plugins/.libs/demoplugin.so
    (gdb) c
    Continuing.