Ticket #1530

[pantumic.git] / src / help.c

/* Hypertext file browser.
   Copyright (C) 1994, 1995, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   2005, 2006, 2007 Free Software Foundation, Inc.
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/


/** \file help.c
 *  \brief Source: hypertext file browser
 *
 *  Implements the hypertext file viewer.
 *  The hypertext file is a file that may have one or more nodes.  Each
 *  node ends with a ^D character and starts with a bracket, then the
 *  name of the node and then a closing bracket. Right after the closing
 *  bracket a newline is placed. This newline is not to be displayed by
 *  the help viewer and must be skipped - its sole purpose is to faciliate
 *  the work of the people managing the help file template (xnc.hlp) .
 *
 *  Links in the hypertext file are specified like this: the text that
 *  will be highlighted should have a leading ^A, then it comes the
 *  text, then a ^B indicating that highlighting is done, then the name
 *  of the node you want to link to and then a ^C.
 *
 *  The file must contain a ^D at the beginning and at the end of the
 *  file or the program will not be able to detect the end of file.
 *
 *  Lazyness/widgeting attack: This file does use the dialog manager
 *  and uses mainly the dialog to achieve the help work.  there is only
 *  one specialized widget and it's only used to forward the mouse messages
 *  to the appropiate routine.
 */


#include <config.h>

#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "global.h"

#include "../src/tty/tty.h"
#include "../src/tty/color.h"
#include "../src/tty/mouse.h"
#include "../src/tty/key.h"

#include "help.h"
#include "dialog.h"             /* For Dlg_head */
#include "widget.h"             /* For Widget */
#include "wtools.h"             /* For common_dialog_repaint() */
#include "strutil.h"

#define MAXLINKNAME 80
#define HISTORY_SIZE 20
#define HELP_WINDOW_WIDTH (HELP_TEXT_WIDTH + 4)

#define STRING_LINK_START       "\01"
#define STRING_LINK_POINTER     "\02"
#define STRING_LINK_END         "\03"
#define STRING_NODE_END         "\04"

static char *data = NULL;       /* Pointer to the loaded data file */
static int help_lines;          /* Lines in help viewer */
static int  history_ptr;        /* For the history queue */
static const char *main_node;   /* The main node */
static const char *last_shown = NULL;   /* Last byte shown in a screen */
static int end_of_node = 0;     /* Flag: the last character of the node shown? */
static const char *currentpoint;
static const char *selected_item;

/* The widget variables */
static Dlg_head *whelp;

static struct {
    const char *page;           /* Pointer to the selected page */
    const char *link;           /* Pointer to the selected link */
} history [HISTORY_SIZE];

/* Link areas for the mouse */
typedef struct Link_Area {
    int x1, y1, x2, y2;
    const char *link_name;
    struct Link_Area *next;
} Link_Area;

static Link_Area *link_area = NULL;
static int inside_link_area = 0;

static cb_ret_t help_callback (struct Dlg_head *h, dlg_msg_t, int parm);

/* returns the position where text was found in the start buffer */
/* or 0 if not found */
static const char *
search_string (const char *start, const char *text)
{
    const char *result = NULL;
    char *local_text = g_strdup (text);
    char *d = local_text;
    const char *e = start;

    /* fmt sometimes replaces a space with a newline in the help file */
    /* Replace the newlines in the link name with spaces to correct the situation */
    while (*d){
        if (*d == '\n')
            *d = ' ';
        str_next_char (&d);
    }
    /* Do search */
    for (d = local_text; *e; e++){
        if (*d == *e)
            d++;
        else
            d = local_text;
        if (!*d) {
            result = e + 1;
            goto cleanup;
        }
    }
cleanup:
    g_free (local_text);
    return result;
}

/* Searches text in the buffer pointed by start.  Search ends */
/* if the CHAR_NODE_END is found in the text.  Returns 0 on failure */
static const char *search_string_node (const char *start, const char *text)
{
    const char *d = text;
    const char *e = start;

    if (!start)
        return 0;
    
    for (; *e && *e != CHAR_NODE_END; e++){
        if (*d == *e)
            d++;
        else
            d = text;
        if (!*d)
            return e+1;
    }
    return 0;
}

/* Searches the_char in the buffer pointer by start and searches */
/* it can search forward (direction = 1) or backward (direction = -1) */
static const char *search_char_node (const char *start, char the_char, int direction)
{
    const char *e;

    e = start;
    
    for (; *e && (*e != CHAR_NODE_END); e += direction){
        if (*e == the_char)
            return e;
    }
    return 0;
}

/* Returns the new current pointer when moved lines lines */
static const char *move_forward2 (const char *c, int lines)
{
    const char *p;
    int  line;

    currentpoint = c;
    for (line = 0, p = currentpoint; *p && *p != CHAR_NODE_END; 
         str_cnext_char (&p)){
             
        if (line == lines)
            return currentpoint = p;
        if (*p == '\n')
            line++;
    }
    return currentpoint = c;
}

static const char *move_backward2 (const char *c, int lines)
{
    const char *p;
    int line;

    currentpoint = c;
    for (line = 0, p = currentpoint; *p && p >= data; 
         str_cprev_char (&p)) {
             
        if (*p == CHAR_NODE_END)
        {
            /* We reached the beginning of the node */
            /* Skip the node headers */
            while (*p != ']') str_cnext_char (&p);
            return currentpoint = p + 2; /* Skip the newline following the start of the node */
        }
        if (*(p - 1) == '\n')
            line++;
        if (line == lines)
            return currentpoint = p;
    }
    return currentpoint = c;
}

static void move_forward (int i)
{
    if (end_of_node)
        return;
    currentpoint = move_forward2 (currentpoint, i);
}

static void move_backward (int i)
{
    currentpoint = move_backward2 (currentpoint, ++i);
}

static void move_to_top (void)
{
    while (currentpoint > data && *currentpoint != CHAR_NODE_END)
        currentpoint--;
    while (*currentpoint != ']')
        currentpoint++;
    currentpoint = currentpoint + 2; /* Skip the newline following the start of the node */
    selected_item = NULL;
}

static void move_to_bottom (void)
{
    while (*currentpoint && *currentpoint != CHAR_NODE_END)
        currentpoint++;
    currentpoint--;
    move_backward (help_lines - 1);
}

static const char *help_follow_link (const char *start, const char *selected_item)
{
    char link_name [MAXLINKNAME];
    const char *p;
    int  i = 0;

    if (!selected_item)
        return start;
    
    for (p = selected_item; *p && *p != CHAR_NODE_END && *p != CHAR_LINK_POINTER; p++)
        ;
    if (*p == CHAR_LINK_POINTER){
        link_name [0] = '[';
        for (i = 1; *p != CHAR_LINK_END && *p && *p != CHAR_NODE_END && i < MAXLINKNAME-3; )
            link_name [i++] = *++p;
        link_name [i-1] = ']';
        link_name [i] = 0;
        p = search_string (data, link_name);
        if (p) {
            p += 1; /* Skip the newline following the start of the node */
            return p;
        }
    }

    /* Create a replacement page with the error message */
    return _(" Help file format error\n");
}

static const char *select_next_link (const char *current_link)
{
    const char *p;

    if (!current_link)
        return 0;

    p = search_string_node (current_link, STRING_LINK_END);
    if (!p)
        return NULL;
    p = search_string_node (p, STRING_LINK_START);
    if (!p)
        return NULL;
    return p - 1;
}

static const char *select_prev_link (const char *current_link)
{
    if (!current_link)
        return 0;

    return search_char_node (current_link - 1, CHAR_LINK_START, -1);
}

static void start_link_area (int x, int y, const char *link_name)
{
    Link_Area *new;

    if (inside_link_area)
        message (D_NORMAL, _("Warning"), _(" Internal bug: Double start of link area "));

    /* Allocate memory for a new link area */
    new = g_new (Link_Area, 1);
    new->next = link_area;
    link_area = new;

    /* Save the beginning coordinates of the link area */
    link_area->x1 = x;
    link_area->y1 = y;

    /* Save the name of the destination anchor */
    link_area->link_name = link_name;

    inside_link_area = 1;
}

static void end_link_area (int x, int y)
{
    if (inside_link_area){
        /* Save the end coordinates of the link area */
        link_area->x2 = x;
        link_area->y2 = y;

        inside_link_area = 0;
    }
}

static void clear_link_areas (void)
{
    Link_Area *current;

    while (link_area){
        current = link_area;
        link_area = current -> next;
        g_free (current);
    }
    inside_link_area = 0;
}

static void help_show (Dlg_head *h, const char *paint_start)
{
    const char *p, *n;
    int  col, line, c, w;
    int  painting = 1;
    int acs;                    /* Flag: Alternate character set active? */
    int repeat_paint;
    int active_col, active_line;/* Active link position */
    static char buff[MB_LEN_MAX + 1];

    tty_setcolor (HELP_NORMAL_COLOR);
    do {
        
        line = col = acs = active_col = active_line = repeat_paint = 0;
    
        clear_link_areas ();
        if (selected_item < paint_start)
            selected_item = NULL;
        
        p = paint_start;
        n = paint_start;
        while (n[0] != '\0' && n[0] != CHAR_NODE_END && line < help_lines) {
            p = n;
            n = str_cget_next_char (p);
            memcpy (buff, p, n - p);
            buff[n - p] = '\0';
            c = (unsigned char) buff[0];
                
            switch (c){
            case CHAR_LINK_START:
                if (selected_item == NULL)
                    selected_item = p;
                if (p == selected_item){
                    tty_setcolor (HELP_SLINK_COLOR);

                    /* Store the coordinates of the link */
                    active_col = col + 2;
                    active_line = line + 2;
                }
                else
                    tty_setcolor (HELP_LINK_COLOR);
                start_link_area (col, line, p);
                break;
            case CHAR_LINK_POINTER:
                painting = 0;
                end_link_area (col - 1, line);
                break;
            case CHAR_LINK_END:
                painting = 1;
                tty_setcolor (HELP_NORMAL_COLOR);
                break;
            case CHAR_ALTERNATE:
                acs = 1;
                break;
            case CHAR_NORMAL:
                acs = 0;
                break;
            case CHAR_VERSION:
                dlg_move (h, line+2, col+2);
                tty_print_string (VERSION);
                col += str_term_width1 (VERSION);
                break;
            case CHAR_FONT_BOLD:
                tty_setcolor (HELP_BOLD_COLOR);
                break;
            case CHAR_FONT_ITALIC:
                tty_setcolor (HELP_ITALIC_COLOR);
                break;
            case CHAR_FONT_NORMAL:
                tty_setcolor (HELP_NORMAL_COLOR);
                break;
            case '\n':
                line++;
                col = 0;
                break;
            case '\t':
                col = (col / 8 + 1) * 8;
                break;
            default:
                if (!painting)
                    continue;
                w = str_term_width1 (buff);
                if (col + w > HELP_WINDOW_WIDTH)
                    continue;
                
                dlg_move (h, line+2, col+2);
                if (acs){
                    if (c == ' ' || c == '.')
                        tty_print_char (c);
                    else
#ifndef HAVE_SLANG
                        tty_print_char (acs_map [c]);
#else
                        SLsmg_draw_object (h->y + line + 2, h->x + col + 2, c);
#endif
                } else {
                    tty_print_string (buff);
                }
                col+= w;
                break;
            }
        }
        last_shown = p;
        end_of_node = line < help_lines;
        tty_setcolor (HELP_NORMAL_COLOR);
        if (selected_item >= last_shown){
            if (link_area != NULL){
                selected_item = link_area->link_name;
                repeat_paint = 1;
            }
            else
                selected_item = NULL;
        }
    } while (repeat_paint);

    /* Position the cursor over a nice link */
    if (active_col)
        dlg_move (h, active_line, active_col);
}

static int
help_event (Gpm_Event *event, void *vp)
{
    Widget *w = vp;
    Link_Area *current_area;

    if (! (event->type & GPM_UP))
        return 0;

    /* The event is relative to the dialog window, adjust it: */
    event->x -= 2;
    event->y -= 2;

    if (event->buttons & GPM_B_RIGHT){
        currentpoint = history [history_ptr].page;
        selected_item = history [history_ptr].link;
        history_ptr--;
        if (history_ptr < 0)
            history_ptr = HISTORY_SIZE-1;
        
        help_callback (w->parent, DLG_DRAW, 0);
        return 0;
    }

    /* Test whether the mouse click is inside one of the link areas */
    current_area = link_area;
    while (current_area)
    {
        /* Test one line link area */
        if (event->y == current_area->y1 && event->x >= current_area->x1 &&
            event->y == current_area->y2 && event->x <= current_area->x2)
            break;
        /* Test two line link area */
        if (current_area->y1 + 1 == current_area->y2){
            /* The first line */
            if (event->y == current_area->y1 && event->x >= current_area->x1)
                break;
            /* The second line */
            if (event->y == current_area->y2 && event->x <= current_area->x2)
                break;
        }
        /* Mouse will not work with link areas of more than two lines */

        current_area = current_area -> next;
    }

    /* Test whether a link area was found */
    if (current_area){
        /* The click was inside a link area -> follow the link */
        history_ptr = (history_ptr+1) % HISTORY_SIZE;
        history [history_ptr].page = currentpoint;
        history [history_ptr].link = current_area->link_name;
        currentpoint = help_follow_link (currentpoint, current_area->link_name);
        selected_item = NULL;
    } else{
        if (event->y < 0)
            move_backward (help_lines - 1);
        else if (event->y >= help_lines)
            move_forward (help_lines - 1);
        else if (event->y < help_lines/2)
            move_backward (1);
        else
            move_forward (1);
    }

    /* Show the new node */
    help_callback (w->parent, DLG_DRAW, 0);

    return 0;
}

/* show help */
static void
help_help_cmd (void *vp)
{
    Dlg_head *h = vp;
    const char *p;

    history_ptr = (history_ptr+1) % HISTORY_SIZE;
    history [history_ptr].page = currentpoint;
    history [history_ptr].link = selected_item;

    p = search_string(data, "[How to use help]");
    if (p == NULL)
        return;

    currentpoint = p + 1; /* Skip the newline following the start of the node */
    selected_item = NULL;
    help_callback (h, DLG_DRAW, 0);
}

static void
help_index_cmd (void *vp)
{
    Dlg_head *h = vp;
    const char *new_item;

    if (!(new_item = search_string (data, "[Contents]"))) {
        message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "),
                 "[Contents]");
        return;
    }

    history_ptr = (history_ptr + 1) % HISTORY_SIZE;
    history[history_ptr].page = currentpoint;
    history[history_ptr].link = selected_item;

    currentpoint = new_item + 1; /* Skip the newline following the start of the node */
    selected_item = NULL;
    help_callback (h, DLG_DRAW, 0);
}

static void help_quit_cmd (void *vp)
{
    dlg_stop ((Dlg_head *) vp);
}

static void prev_node_cmd (void *vp)
{
    Dlg_head *h = vp;
    currentpoint = history [history_ptr].page;
    selected_item = history [history_ptr].link;
    history_ptr--;
    if (history_ptr < 0)
        history_ptr = HISTORY_SIZE-1;

    help_callback (h, DLG_DRAW, 0);
}

static cb_ret_t
md_callback (Widget *w, widget_msg_t msg, int parm)
{
    switch (msg) {
    case WIDGET_RESIZED:
        w->lines = help_lines;
        return MSG_HANDLED;

    default:
        return default_proc (msg, parm);
    }
}

static Widget *
mousedispatch_new (int y, int x, int yl, int xl)
{
    Widget *w = g_new (Widget, 1);

    init_widget (w, y, x, yl, xl, md_callback, help_event);

    return w;
}

static void help_cmk_move_backward(void *vp, int lines) {
    (void) &vp;
    move_backward(lines);
}
static void help_cmk_move_forward(void *vp, int lines) {
    (void) &vp;
    move_forward(lines);
}
static void help_cmk_moveto_top(void *vp, int lines) {
    (void) &vp;
    (void) &lines;
    move_to_top();
}
static void help_cmk_moveto_bottom(void *vp, int lines) {
    (void) &vp;
    (void) &lines;
    move_to_bottom();
}

static cb_ret_t
help_handle_key (struct Dlg_head *h, int c)
{
    const char *new_item;

    if (c != KEY_UP && c != KEY_DOWN &&
        check_movement_keys (c, help_lines, NULL,
                             help_cmk_move_backward,
                             help_cmk_move_forward,
                             help_cmk_moveto_top,
                             help_cmk_moveto_bottom)) {
        /* Nothing */;
    } else switch (c){
    case 'l':
    case KEY_LEFT:
        prev_node_cmd (h);
        break;

    case '\n':
    case KEY_RIGHT:
        /* follow link */
        if (!selected_item){
#ifdef WE_WANT_TO_GO_BACKWARD_ON_KEY_RIGHT
            /* Is there any reason why the right key would take us
             * backward if there are no links selected?, I agree
             * with Torben than doing nothing in this case is better
             */
            /* If there are no links, go backward in history */
            history_ptr--;
            if (history_ptr < 0)
                history_ptr = HISTORY_SIZE-1;

            currentpoint = history [history_ptr].page;
            selected_item   = history [history_ptr].link;
#endif
        } else {
            history_ptr = (history_ptr+1) % HISTORY_SIZE;
            history [history_ptr].page = currentpoint;
            history [history_ptr].link = selected_item;
            currentpoint = help_follow_link (currentpoint, selected_item);
        }
        selected_item = NULL;
        break;

    case KEY_DOWN:
    case '\t':
        new_item = select_next_link (selected_item);
        if (new_item){
            selected_item = new_item;
            if (selected_item >= last_shown){
                if (c == KEY_DOWN)
                    move_forward (1);
                else
                    selected_item = NULL;
            }
        } else if (c == KEY_DOWN)
            move_forward (1);
        else
            selected_item = NULL;
        break;

    case KEY_UP:
    case ALT ('\t'):
        /* select previous link */
        new_item = select_prev_link (selected_item);
        selected_item = new_item;
        if (selected_item == NULL || selected_item < currentpoint) {
            if (c == KEY_UP)
                move_backward (1);
            else{
                if (link_area != NULL)
                    selected_item = link_area->link_name;
                else
                    selected_item = NULL;
            }
        }
        break;

    case 'n':
        /* Next node */
        new_item = currentpoint;
        while (*new_item && *new_item != CHAR_NODE_END)
            new_item++;
        if (*++new_item == '['){
            while (*++new_item) {
                if (*new_item == ']' && *++new_item && *++new_item) {
                    currentpoint = new_item;
                    selected_item = NULL;
                    break;
                }
            }
        }
        break;

    case 'p':
        /* Previous node */
        new_item = currentpoint;
        while (new_item > data + 1 && *new_item != CHAR_NODE_END)
            new_item--;
        new_item--;
        while (new_item > data && *new_item != CHAR_NODE_END)
            new_item--;
        while (*new_item != ']')
            new_item++;
        currentpoint = new_item + 2;
        selected_item = NULL;
        break;

    case 'c':
        help_index_cmd (h);
        break;

    case ESC_CHAR:
    case XCTRL('g'):
        dlg_stop (h);
        break;

    default:
        return MSG_NOT_HANDLED;
    }
    help_callback (h, DLG_DRAW, 0);
    return MSG_HANDLED;
}

static cb_ret_t
help_callback (Dlg_head *h, dlg_msg_t msg, int parm)
{
    WButtonBar *bb;

    switch (msg) {
    case DLG_RESIZE:
        help_lines = min (LINES - 4, max (2 * LINES / 3, 18));
        dlg_set_size (h, help_lines + 4, HELP_WINDOW_WIDTH + 4);
        bb = find_buttonbar (h);
        widget_set_size (&bb->widget, LINES - 1, 0, 1, COLS);
        return MSG_HANDLED;

    case DLG_DRAW:
        common_dialog_repaint (h);
        help_show (h, currentpoint);
        return MSG_HANDLED;

    case DLG_KEY:
        return help_handle_key (h, parm);

    default:
        return default_dlg_callback (h, msg, parm);
    }
}

static void
interactive_display_finish (void)
{
    clear_link_areas ();
}

/* translate help file into terminal encoding */
static void 
translate_file (char *filedata)
{
    GIConv conv;
    GString *translated_data;

    translated_data = g_string_new ("");

    conv = str_crt_conv_from ("UTF-8");

    if (conv != INVALID_CONV) {
        g_free (data);

        if (str_convert (conv, filedata, translated_data) != ESTR_FAILURE) {
            data = translated_data->str;
            g_string_free (translated_data, FALSE);
        } else {
            data = NULL;
            g_string_free (translated_data, TRUE);
        }
        str_close_conv (conv);
    } else
        g_string_free (translated_data, TRUE);
}

void
interactive_display (const char *filename, const char *node)
{
    WButtonBar *help_bar;
    Widget *md;
    char *hlpfile = NULL;
    char *filedata;

    if (filename)
        filedata = load_file (filename);
    else
        filedata = load_mc_home_file ("mc.hlp", &hlpfile);

    if (filedata == NULL) {
        message (D_ERROR, MSG_ERROR, _(" Cannot open file %s \n %s "), filename ? filename : hlpfile,
                 unix_error_string (errno));
    }

    if (!filename)
        g_free (hlpfile);

    if (filedata == NULL)
        return;

    translate_file (filedata);

    g_free (filedata);

    if (!data)
        return;

    if (!node || !*node)
        node = "[main]";

    if (!(main_node = search_string (data, node))) {
        message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "),
                 node);

        /* Fallback to [main], return if it also cannot be found */
        main_node = search_string (data, "[main]");
        if (!main_node) {
            interactive_display_finish ();
            return;
        }
    }

    help_lines = min (LINES - 4, max (2 * LINES / 3, 18));

    whelp =
        create_dlg (0, 0, help_lines + 4, HELP_WINDOW_WIDTH + 4,
                    dialog_colors, help_callback, "[Help]", _("Help"),
                    DLG_TRYUP | DLG_CENTER | DLG_WANT_TAB);

    selected_item = search_string_node (main_node, STRING_LINK_START) - 1;
    currentpoint = main_node + 1; /* Skip the newline following the start of the node */

    for (history_ptr = HISTORY_SIZE; history_ptr;) {
        history_ptr--;
        history[history_ptr].page = currentpoint;
        history[history_ptr].link = selected_item;
    }

    help_bar = buttonbar_new (1);
    help_bar->widget.y -= whelp->y;
    help_bar->widget.x -= whelp->x;

    md = mousedispatch_new (1, 1, help_lines, HELP_WINDOW_WIDTH - 2);

    add_widget (whelp, md);
    add_widget (whelp, help_bar);

    buttonbar_set_label_data (whelp, 1, _("Help"), help_help_cmd, whelp);
    buttonbar_set_label_data (whelp, 2, _("Index"), help_index_cmd, whelp);
    buttonbar_set_label_data (whelp, 3, _("Prev"), prev_node_cmd, whelp);
    buttonbar_clear_label (whelp, 4);
    buttonbar_clear_label (whelp, 5);
    buttonbar_clear_label (whelp, 6);
    buttonbar_clear_label (whelp, 7);
    buttonbar_clear_label (whelp, 8);
    buttonbar_clear_label (whelp, 9);
    buttonbar_set_label_data (whelp, 10, _("Quit"), help_quit_cmd, whelp);

    run_dlg (whelp);
    interactive_display_finish ();
    destroy_dlg (whelp);
}