src/help.c

   1 /* Hypertext file browser.
   2    Copyright (C) 1994, 1995, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   3    2005, 2006, 2007 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  */
  19
  20
  21 /** \file help.c
  22  *  \brief Source: hypertext file browser
  23  *
  24  *  Implements the hypertext file viewer.
  25  *  The hypertext file is a file that may have one or more nodes.  Each
  26  *  node ends with a ^D character and starts with a bracket, then the
  27  *  name of the node and then a closing bracket. Right after the closing
  28  *  bracket a newline is placed. This newline is not to be displayed by
  29  *  the help viewer and must be skipped - its sole purpose is to faciliate
  30  *  the work of the people managing the help file template (xnc.hlp) .
  31  *
  32  *  Links in the hypertext file are specified like this: the text that
  33  *  will be highlighted should have a leading ^A, then it comes the
  34  *  text, then a ^B indicating that highlighting is done, then the name
  35  *  of the node you want to link to and then a ^C.
  36  *
  37  *  The file must contain a ^D at the beginning and at the end of the
  38  *  file or the program will not be able to detect the end of file.
  39  *
  40  *  Lazyness/widgeting attack: This file does use the dialog manager
  41  *  and uses mainly the dialog to achieve the help work.  there is only
  42  *  one specialized widget and it's only used to forward the mouse messages
  43  *  to the appropiate routine.
  44  */
  45
  46
  47 #include <config.h>
  48
  49 #include <errno.h>
  50 #include <stdio.h>
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53
  54 #include "lib/global.h"
  55
  56 #include "lib/tty/tty.h"
  57 #include "lib/skin.h"
  58 #include "lib/tty/mouse.h"
  59 #include "lib/tty/key.h"
  60 #include "lib/strutil.h"
  61
  62 #include "dialog.h"             /* For Dlg_head */
  63 #include "widget.h"             /* For Widget */
  64 #include "wtools.h"             /* For common_dialog_repaint() */
  65 #include "cmddef.h"
  66 #include "keybind.h"
  67 #include "help.h"
  68 #include "main.h"
  69
  70 #define MAXLINKNAME 80
  71 #define HISTORY_SIZE 20
  72 #define HELP_WINDOW_WIDTH min(80, COLS - 16)
  73
  74 #define STRING_LINK_START       "\01"
  75 #define STRING_LINK_POINTER     "\02"
  76 #define STRING_LINK_END         "\03"
  77 #define STRING_NODE_END         "\04"
  78
  79
  80 static char *fdata = NULL;      /* Pointer to the loaded data file */
  81 static int help_lines;          /* Lines in help viewer */
  82 static int history_ptr;         /* For the history queue */
  83 static const char *main_node;   /* The main node */
  84 static const char *last_shown = NULL;   /* Last byte shown in a screen */
  85 static gboolean end_of_node = FALSE;    /* Flag: the last character of the node shown? */
  86 static const char *currentpoint;
  87 static const char *selected_item;
  88
  89 /* The widget variables */
  90 static Dlg_head *whelp;
  91
  92 static struct
  93 {
  94     const char *page;           /* Pointer to the selected page */
  95     const char *link;           /* Pointer to the selected link */
  96 } history[HISTORY_SIZE];
  97
  98 /* Link areas for the mouse */
  99 typedef struct Link_Area
 100 {
 101     int x1, y1, x2, y2;
 102     const char *link_name;
 103 } Link_Area;
 104
 105 static GSList *link_area = NULL;
 106 static gboolean inside_link_area = FALSE;
 107
 108 static cb_ret_t help_callback (Dlg_head * h, Widget * sender, dlg_msg_t msg, int parm, void *data);
 109
 110 /* returns the position where text was found in the start buffer */
 111 /* or 0 if not found */
 112 static const char *
 113 search_string (const char *start, const char *text)
 114 {
 115     const char *result = NULL;
 116     char *local_text = g_strdup (text);
 117     char *d = local_text;
 118     const char *e = start;
 119
 120     /* fmt sometimes replaces a space with a newline in the help file */
 121     /* Replace the newlines in the link name with spaces to correct the situation */
 122     while (*d != '\0')
 123     {
 124         if (*d == '\n')
 125             *d = ' ';
 126         str_next_char (&d);
 127     }
 128
 129     /* Do search */
 130     for (d = local_text; *e; e++)
 131     {
 132         if (*d == *e)
 133             d++;
 134         else
 135             d = local_text;
 136         if (*d == '\0')
 137         {
 138             result = e + 1;
 139             break;
 140         }
 141     }
 142
 143     g_free (local_text);
 144     return result;
 145 }
 146
 147 /* Searches text in the buffer pointed by start.  Search ends */
 148 /* if the CHAR_NODE_END is found in the text.  Returns 0 on failure */
 149 static const char *
 150 search_string_node (const char *start, const char *text)
 151 {
 152     const char *d = text;
 153     const char *e = start;
 154
 155     if (start != NULL)
 156         for (; *e && *e != CHAR_NODE_END; e++)
 157         {
 158             if (*d == *e)
 159                 d++;
 160             else
 161                 d = text;
 162             if (*d == '\0')
 163                 return e + 1;
 164         }
 165
 166     return NULL;
 167 }
 168
 169 /* Searches the_char in the buffer pointer by start and searches */
 170 /* it can search forward (direction = 1) or backward (direction = -1) */
 171 static const char *
 172 search_char_node (const char *start, char the_char, int direction)
 173 {
 174     const char *e;
 175
 176     for (e = start; (*e != '\0') && (*e != CHAR_NODE_END); e += direction)
 177         if (*e == the_char)
 178             return e;
 179
 180     return NULL;
 181 }
 182
 183 /* Returns the new current pointer when moved lines lines */
 184 static const char *
 185 move_forward2 (const char *c, int lines)
 186 {
 187     const char *p;
 188     int line;
 189
 190     currentpoint = c;
 191     for (line = 0, p = currentpoint; (*p != '\0') && (*p != CHAR_NODE_END); str_cnext_char (&p))
 192     {
 193         if (line == lines)
 194             return currentpoint = p;
 195
 196         if (*p == '\n')
 197             line++;
 198     }
 199     return currentpoint = c;
 200 }
 201
 202 static const char *
 203 move_backward2 (const char *c, int lines)
 204 {
 205     const char *p;
 206     int line;
 207
 208     currentpoint = c;
 209     for (line = 0, p = currentpoint; (*p != '\0') && ((int) (p - fdata) >= 0); str_cprev_char (&p))
 210     {
 211         if (*p == CHAR_NODE_END)
 212         {
 213             /* We reached the beginning of the node */
 214             /* Skip the node headers */
 215             while (*p != ']')
 216                 str_cnext_char (&p);
 217             return currentpoint = p + 2;        /* Skip the newline following the start of the node */
 218         }
 219
 220         if (*(p - 1) == '\n')
 221             line++;
 222         if (line == lines)
 223             return currentpoint = p;
 224     }
 225     return currentpoint = c;
 226 }
 227
 228 static void
 229 move_forward (int i)
 230 {
 231     if (!end_of_node)
 232         currentpoint = move_forward2 (currentpoint, i);
 233 }
 234
 235 static void
 236 move_backward (int i)
 237 {
 238     currentpoint = move_backward2 (currentpoint, ++i);
 239 }
 240
 241 static void
 242 move_to_top (void)
 243 {
 244     while (((int) (currentpoint > fdata) > 0) && (*currentpoint != CHAR_NODE_END))
 245         currentpoint--;
 246
 247     while (*currentpoint != ']')
 248         currentpoint++;
 249     currentpoint = currentpoint + 2;    /* Skip the newline following the start of the node */
 250     selected_item = NULL;
 251 }
 252
 253 static void
 254 move_to_bottom (void)
 255 {
 256     while ((*currentpoint != '\0') && (*currentpoint != CHAR_NODE_END))
 257         currentpoint++;
 258     currentpoint--;
 259     move_backward (1);
 260 }
 261
 262 static const char *
 263 help_follow_link (const char *start, const char *lc_selected_item)
 264 {
 265     char link_name[MAXLINKNAME];
 266     const char *p;
 267     int i = 0;
 268
 269     if (lc_selected_item == NULL)
 270         return start;
 271
 272     for (p = lc_selected_item; *p && *p != CHAR_NODE_END && *p != CHAR_LINK_POINTER; p++)
 273         ;
 274     if (*p == CHAR_LINK_POINTER)
 275     {
 276         link_name[0] = '[';
 277         for (i = 1; *p != CHAR_LINK_END && *p && *p != CHAR_NODE_END && i < MAXLINKNAME - 3;)
 278             link_name[i++] = *++p;
 279         link_name[i - 1] = ']';
 280         link_name[i] = '\0';
 281         p = search_string (fdata, link_name);
 282         if (p != NULL)
 283         {
 284             p += 1;             /* Skip the newline following the start of the node */
 285             return p;
 286         }
 287     }
 288
 289     /* Create a replacement page with the error message */
 290     return _(" Help file format error\n");
 291 }
 292
 293 static const char *
 294 select_next_link (const char *current_link)
 295 {
 296     const char *p;
 297
 298     if (current_link == NULL)
 299         return NULL;
 300
 301     p = search_string_node (current_link, STRING_LINK_END);
 302     if (p == NULL)
 303         return NULL;
 304     p = search_string_node (p, STRING_LINK_START);
 305     if (p == NULL)
 306         return NULL;
 307     return p - 1;
 308 }
 309
 310 static const char *
 311 select_prev_link (const char *current_link)
 312 {
 313     return current_link == NULL ? NULL : search_char_node (current_link - 1, CHAR_LINK_START, -1);
 314 }
 315
 316 static void
 317 start_link_area (int x, int y, const char *link_name)
 318 {
 319     Link_Area *la;
 320
 321     if (inside_link_area)
 322         message (D_NORMAL, _("Warning"), _(" Internal bug: Double start of link area "));
 323
 324     /* Allocate memory for a new link area */
 325     la = g_new (Link_Area, 1);
 326     /* Save the beginning coordinates of the link area */
 327     la->x1 = x;
 328     la->y1 = y;
 329     /* Save the name of the destination anchor */
 330     la->link_name = link_name;
 331     link_area = g_slist_prepend (link_area, la);
 332
 333     inside_link_area = TRUE;
 334 }
 335
 336 static void
 337 end_link_area (int x, int y)
 338 {
 339     if (inside_link_area)
 340     {
 341         Link_Area *la = (Link_Area *) link_area->data;
 342         /* Save the end coordinates of the link area */
 343         la->x2 = x;
 344         la->y2 = y;
 345         inside_link_area = FALSE;
 346     }
 347 }
 348
 349 static void
 350 clear_link_areas (void)
 351 {
 352     g_slist_foreach (link_area, (GFunc) g_free, NULL);
 353     g_slist_free (link_area);
 354     link_area = NULL;
 355     inside_link_area = FALSE;
 356 }
 357
 358 static void
 359 help_print_word (Dlg_head * h, GString * word, int *col, int *line, gboolean add_space)
 360 {
 361     if (*line >= help_lines)
 362         g_string_set_size (word, 0);
 363     else
 364     {
 365         int w;
 366
 367         w = str_term_width1 (word->str);
 368         if (*col + w >= HELP_WINDOW_WIDTH)
 369         {
 370             *col = 0;
 371             (*line)++;
 372         }
 373
 374         if (*line >= help_lines)
 375             g_string_set_size (word, 0);
 376         else
 377         {
 378             dlg_move (h, *line + 2, *col + 2);
 379             tty_print_string (word->str);
 380             g_string_set_size (word, 0);
 381             *col += w;
 382         }
 383     }
 384
 385     if (add_space)
 386     {
 387         if (*col < HELP_WINDOW_WIDTH - 1)
 388         {
 389             tty_print_char (' ');
 390             (*col)++;
 391         }
 392         else
 393         {
 394             *col = 0;
 395             (*line)++;
 396         }
 397     }
 398 }
 399
 400 static void
 401 help_show (Dlg_head * h, const char *paint_start)
 402 {
 403     const char *p, *n;
 404     int col, line, c;
 405     gboolean painting = TRUE;
 406     gboolean acs;               /* Flag: Alternate character set active? */
 407     gboolean repeat_paint;
 408     int active_col, active_line;        /* Active link position */
 409     char buff[MB_LEN_MAX + 1];
 410     GString *word;
 411
 412     word = g_string_sized_new (32);
 413
 414     tty_setcolor (HELP_NORMAL_COLOR);
 415     do
 416     {
 417         line = col = active_col = active_line = 0;
 418         repeat_paint = FALSE;
 419         acs = FALSE;
 420
 421         clear_link_areas ();
 422         if ((int) (selected_item - paint_start) < 0)
 423             selected_item = NULL;
 424
 425         p = paint_start;
 426         n = paint_start;
 427         while ((n[0] != '\0') && (n[0] != CHAR_NODE_END) && (line < help_lines))
 428         {
 429             p = n;
 430             n = str_cget_next_char (p);
 431             memcpy (buff, p, n - p);
 432             buff[n - p] = '\0';
 433
 434             c = (unsigned char) buff[0];
 435             switch (c)
 436             {
 437             case CHAR_LINK_START:
 438                 if (selected_item == NULL)
 439                     selected_item = p;
 440                 if (p != selected_item)
 441                     tty_setcolor (HELP_LINK_COLOR);
 442                 else
 443                 {
 444                     tty_setcolor (HELP_SLINK_COLOR);
 445
 446                     /* Store the coordinates of the link */
 447                     active_col = col + 2;
 448                     active_line = line + 2;
 449                 }
 450                 start_link_area (col, line, p);
 451                 break;
 452             case CHAR_LINK_POINTER:
 453                 painting = FALSE;
 454                 end_link_area (col - 1, line);
 455                 break;
 456             case CHAR_LINK_END:
 457                 painting = TRUE;
 458                 help_print_word (h, word, &col, &line, FALSE);
 459                 tty_setcolor (HELP_NORMAL_COLOR);
 460                 break;
 461             case CHAR_ALTERNATE:
 462                 acs = TRUE;
 463                 break;
 464             case CHAR_NORMAL:
 465                 acs = FALSE;
 466                 break;
 467             case CHAR_VERSION:
 468                 dlg_move (h, line + 2, col + 2);
 469                 tty_print_string (VERSION);
 470                 col += str_term_width1 (VERSION);
 471                 break;
 472             case CHAR_FONT_BOLD:
 473                 tty_setcolor (HELP_BOLD_COLOR);
 474                 break;
 475             case CHAR_FONT_ITALIC:
 476                 tty_setcolor (HELP_ITALIC_COLOR);
 477                 break;
 478             case CHAR_FONT_NORMAL:
 479                 help_print_word (h, word, &col, &line, FALSE);
 480                 tty_setcolor (HELP_NORMAL_COLOR);
 481                 break;
 482             case '\n':
 483                 if (painting)
 484                     help_print_word (h, word, &col, &line, FALSE);
 485                 line++;
 486                 col = 0;
 487                 break;
 488             case '\t':
 489                 col = (col / 8 + 1) * 8;
 490                 if (col >= HELP_WINDOW_WIDTH)
 491                 {
 492                     line++;
 493                     col = 8;
 494                 }
 495                 break;
 496             case ' ':
 497                 /* word delimeter */
 498                 if (painting)
 499                     help_print_word (h, word, &col, &line, TRUE);
 500                 break;
 501             default:
 502                 if (painting && (line < help_lines))
 503                 {
 504                     if (!acs)
 505                         /* accumulate symbols in a word */
 506                         g_string_append (word, buff);
 507                     else if (col < HELP_WINDOW_WIDTH)
 508                     {
 509                         dlg_move (h, line + 2, col + 2);
 510
 511                         if ((c == ' ') || (c == '.'))
 512                             tty_print_char (c);
 513                         else
 514 #ifndef HAVE_SLANG
 515                             tty_print_char (acs_map[c]);
 516 #else
 517                             SLsmg_draw_object (h->y + line + 2, h->x + col + 2, c);
 518 #endif
 519                         col++;
 520                     }
 521                 }
 522             }
 523         }
 524
 525         /* print last word */
 526         if (n[0] == CHAR_NODE_END)
 527             help_print_word (h, word, &col, &line, FALSE);
 528
 529         last_shown = p;
 530         end_of_node = line < help_lines;
 531         tty_setcolor (HELP_NORMAL_COLOR);
 532         if ((int) (selected_item - last_shown) >= 0)
 533         {
 534             if ((link_area == NULL) || (link_area->data == NULL))
 535                 selected_item = NULL;
 536             else
 537             {
 538                 selected_item = ((Link_Area *) link_area->data)->link_name;
 539                 repeat_paint = TRUE;
 540             }
 541         }
 542     }
 543     while (repeat_paint);
 544
 545     g_string_free (word, TRUE);
 546
 547     /* Position the cursor over a nice link */
 548     if (active_col)
 549         dlg_move (h, active_line, active_col);
 550 }
 551
 552 static int
 553 help_event (Gpm_Event * event, void *vp)
 554 {
 555     Widget *w = vp;
 556     GSList *current_area;
 557
 558     if ((event->type & GPM_UP) == 0)
 559         return 0;
 560
 561     /* The event is relative to the dialog window, adjust it: */
 562     event->x -= 2;
 563     event->y -= 2;
 564
 565     if (event->buttons & GPM_B_RIGHT)
 566     {
 567         currentpoint = history[history_ptr].page;
 568         selected_item = history[history_ptr].link;
 569         history_ptr--;
 570         if (history_ptr < 0)
 571             history_ptr = HISTORY_SIZE - 1;
 572
 573         help_callback (w->parent, NULL, DLG_DRAW, 0, NULL);
 574         return 0;
 575     }
 576
 577     /* Test whether the mouse click is inside one of the link areas */
 578     for (current_area = link_area; current_area != NULL; current_area = g_slist_next (current_area))
 579     {
 580         Link_Area *la = (Link_Area *) current_area->data;
 581         /* Test one line link area */
 582         if (event->y == la->y1 && event->x >= la->x1 && event->y == la->y2 && event->x <= la->x2)
 583             break;
 584         /* Test two line link area */
 585         if (la->y1 + 1 == la->y2)
 586         {
 587             /* The first line */
 588             if (event->y == la->y1 && event->x >= la->x1)
 589                 break;
 590             /* The second line */
 591             if (event->y == la->y2 && event->x <= la->x2)
 592                 break;
 593         }
 594         /* Mouse will not work with link areas of more than two lines */
 595     }
 596
 597     /* Test whether a link area was found */
 598     if (current_area != NULL)
 599     {
 600         Link_Area *la = (Link_Area *) current_area->data;
 601
 602         /* The click was inside a link area -> follow the link */
 603         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 604         history[history_ptr].page = currentpoint;
 605         history[history_ptr].link = la->link_name;
 606         currentpoint = help_follow_link (currentpoint, la->link_name);
 607         selected_item = NULL;
 608     }
 609     else if (event->y < 0)
 610         move_backward (help_lines - 1);
 611     else if (event->y >= help_lines)
 612         move_forward (help_lines - 1);
 613     else if (event->y < help_lines / 2)
 614         move_backward (1);
 615     else
 616         move_forward (1);
 617
 618     /* Show the new node */
 619     help_callback (w->parent, NULL, DLG_DRAW, 0, NULL);
 620
 621     return 0;
 622 }
 623
 624 /* show help */
 625 static void
 626 help_help (Dlg_head * h)
 627 {
 628     const char *p;
 629
 630     history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 631     history[history_ptr].page = currentpoint;
 632     history[history_ptr].link = selected_item;
 633
 634     p = search_string (fdata, "[How to use help]");
 635     if (p != NULL)
 636     {
 637         currentpoint = p + 1;   /* Skip the newline following the start of the node */
 638         selected_item = NULL;
 639         help_callback (h, NULL, DLG_DRAW, 0, NULL);
 640     }
 641 }
 642
 643 static void
 644 help_index (Dlg_head * h)
 645 {
 646     const char *new_item;
 647
 648     new_item = search_string (fdata, "[Contents]");
 649
 650     if (new_item == NULL)
 651         message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "), "[Contents]");
 652     else
 653     {
 654         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 655         history[history_ptr].page = currentpoint;
 656         history[history_ptr].link = selected_item;
 657
 658         currentpoint = new_item + 1;    /* Skip the newline following the start of the node */
 659         selected_item = NULL;
 660         help_callback (h, NULL, DLG_DRAW, 0, NULL);
 661     }
 662 }
 663
 664 static void
 665 help_back (Dlg_head * h)
 666 {
 667     currentpoint = history[history_ptr].page;
 668     selected_item = history[history_ptr].link;
 669     history_ptr--;
 670     if (history_ptr < 0)
 671         history_ptr = HISTORY_SIZE - 1;
 672
 673     help_callback (h, NULL, DLG_DRAW, 0, NULL); /* FIXME: unneeded? */
 674 }
 675
 676 static void
 677 help_cmk_move_backward (void *vp, int lines)
 678 {
 679     (void) &vp;
 680     move_backward (lines);
 681 }
 682
 683 static void
 684 help_cmk_move_forward (void *vp, int lines)
 685 {
 686     (void) &vp;
 687     move_forward (lines);
 688 }
 689
 690 static void
 691 help_cmk_moveto_top (void *vp, int lines)
 692 {
 693     (void) &vp;
 694     (void) &lines;
 695     move_to_top ();
 696 }
 697
 698 static void
 699 help_cmk_moveto_bottom (void *vp, int lines)
 700 {
 701     (void) &vp;
 702     (void) &lines;
 703     move_to_bottom ();
 704 }
 705
 706 static void
 707 help_next_link (gboolean move_down)
 708 {
 709     const char *new_item;
 710
 711     new_item = select_next_link (selected_item);
 712     if (new_item != NULL)
 713     {
 714         selected_item = new_item;
 715         if ((int) (selected_item - last_shown) >= 0)
 716         {
 717             if (move_down)
 718                 move_forward (1);
 719             else
 720                 selected_item = NULL;
 721         }
 722     }
 723     else if (move_down)
 724         move_forward (1);
 725     else
 726         selected_item = NULL;
 727 }
 728
 729 static void
 730 help_prev_link (gboolean move_up)
 731 {
 732     const char *new_item;
 733
 734     new_item = select_prev_link (selected_item);
 735     selected_item = new_item;
 736     if ((selected_item == NULL) || (selected_item < currentpoint))
 737     {
 738         if (move_up)
 739             move_backward (1);
 740         else if ((link_area != NULL) && (link_area->data != NULL))
 741             selected_item = ((Link_Area *) link_area->data)->link_name;
 742         else
 743             selected_item = NULL;
 744     }
 745 }
 746
 747 static void
 748 help_next_node (void)
 749 {
 750     const char *new_item;
 751
 752     new_item = currentpoint;
 753     while ((*new_item != '\0') && (*new_item != CHAR_NODE_END))
 754         new_item++;
 755
 756     if (*++new_item == '[')
 757         while (*++new_item != '\0')
 758             if ((*new_item == ']') && (*++new_item != '\0') && (*++new_item != '\0'))
 759             {
 760                 currentpoint = new_item;
 761                 selected_item = NULL;
 762                 break;
 763             }
 764 }
 765
 766 static void
 767 help_prev_node (void)
 768 {
 769     const char *new_item;
 770
 771     new_item = currentpoint;
 772     while (((int) (new_item - fdata) > 1) && (*new_item != CHAR_NODE_END))
 773         new_item--;
 774     new_item--;
 775     while (((int) (new_item - fdata) > 0) && (*new_item != CHAR_NODE_END))
 776         new_item--;
 777     while (*new_item != ']')
 778         new_item++;
 779     currentpoint = new_item + 2;
 780     selected_item = NULL;
 781 }
 782
 783 static void
 784 help_select_link (void)
 785 {
 786     /* follow link */
 787     if (selected_item == NULL)
 788     {
 789 #ifdef WE_WANT_TO_GO_BACKWARD_ON_KEY_RIGHT
 790         /* Is there any reason why the right key would take us
 791          * backward if there are no links selected?, I agree
 792          * with Torben than doing nothing in this case is better
 793          */
 794         /* If there are no links, go backward in history */
 795         history_ptr--;
 796         if (history_ptr < 0)
 797             history_ptr = HISTORY_SIZE - 1;
 798
 799         currentpoint = history[history_ptr].page;
 800         selected_item = history[history_ptr].link;
 801 #endif
 802     }
 803     else
 804     {
 805         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 806         history[history_ptr].page = currentpoint;
 807         history[history_ptr].link = selected_item;
 808         currentpoint = help_follow_link (currentpoint, selected_item);
 809     }
 810
 811     selected_item = NULL;
 812 }
 813
 814 static cb_ret_t
 815 help_execute_cmd (unsigned long command)
 816 {
 817     cb_ret_t ret = MSG_HANDLED;
 818
 819     switch (command)
 820     {
 821     case CK_HelpHelp:
 822         help_help (whelp);
 823         break;
 824     case CK_HelpIndex:
 825         help_index (whelp);
 826         break;
 827     case CK_HelpBack:
 828         help_back (whelp);
 829         break;
 830     case CK_HelpMoveUp:
 831         help_prev_link (TRUE);
 832         break;
 833     case CK_HelpMoveDown:
 834         help_next_link (TRUE);
 835         break;
 836     case CK_HelpSelectLink:
 837         help_select_link ();
 838         break;
 839     case CK_HelpNextLink:
 840         help_next_link (FALSE);
 841         break;
 842     case CK_HelpPrevLink:
 843         help_prev_link (FALSE);
 844         break;
 845     case CK_HelpNextNode:
 846         help_next_node ();
 847         break;
 848     case CK_HelpPrevNode:
 849         help_prev_node ();
 850         break;
 851     case CK_HelpQuit:
 852         dlg_stop (whelp);
 853         break;
 854     default:
 855         ret = MSG_NOT_HANDLED;
 856     }
 857
 858     return ret;
 859 }
 860
 861 static cb_ret_t
 862 help_handle_key (Dlg_head * h, int c)
 863 {
 864     if (c != KEY_UP && c != KEY_DOWN &&
 865         check_movement_keys (c, help_lines, NULL,
 866                              help_cmk_move_backward,
 867                              help_cmk_move_forward,
 868                              help_cmk_moveto_top, help_cmk_moveto_bottom) == MSG_HANDLED)
 869     {
 870         /* Nothing */ ;
 871     }
 872     else
 873     {
 874         unsigned long command;
 875
 876         command = lookup_keymap_command (help_map, c);
 877         if ((command == CK_Ignore_Key) || (help_execute_cmd (command) == MSG_NOT_HANDLED))
 878             return MSG_NOT_HANDLED;
 879     }
 880
 881     help_callback (h, NULL, DLG_DRAW, 0, NULL);
 882     return MSG_HANDLED;
 883 }
 884
 885 static cb_ret_t
 886 help_callback (Dlg_head * h, Widget * sender, dlg_msg_t msg, int parm, void *data)
 887 {
 888     WButtonBar *bb;
 889
 890     switch (msg)
 891     {
 892     case DLG_RESIZE:
 893         help_lines = min (LINES - 4, max (2 * LINES / 3, 18));
 894         dlg_set_size (h, help_lines + 4, HELP_WINDOW_WIDTH + 4);
 895         bb = find_buttonbar (h);
 896         widget_set_size (&bb->widget, LINES - 1, 0, 1, COLS);
 897         return MSG_HANDLED;
 898
 899     case DLG_DRAW:
 900         common_dialog_repaint (h);
 901         help_show (h, currentpoint);
 902         return MSG_HANDLED;
 903
 904     case DLG_KEY:
 905         return help_handle_key (h, parm);
 906
 907     case DLG_ACTION:
 908         /* command from buttonbar */
 909         return help_execute_cmd (parm);
 910
 911     default:
 912         return default_dlg_callback (h, sender, msg, parm, data);
 913     }
 914 }
 915
 916 static void
 917 interactive_display_finish (void)
 918 {
 919     clear_link_areas ();
 920 }
 921
 922 /* translate help file into terminal encoding */
 923 static void
 924 translate_file (char *filedata)
 925 {
 926     GIConv conv;
 927     GString *translated_data;
 928
 929     /* initial allocation for largest whole help file */
 930     translated_data = g_string_sized_new (32 * 1024);
 931
 932     conv = str_crt_conv_from ("UTF-8");
 933
 934     if (conv == INVALID_CONV)
 935         g_string_free (translated_data, TRUE);
 936     else
 937     {
 938         g_free (fdata);
 939
 940         if (str_convert (conv, filedata, translated_data) != ESTR_FAILURE)
 941             fdata = g_string_free (translated_data, FALSE);
 942         else
 943         {
 944             fdata = NULL;
 945             g_string_free (translated_data, TRUE);
 946         }
 947         str_close_conv (conv);
 948     }
 949 }
 950
 951 static cb_ret_t
 952 md_callback (Widget * w, widget_msg_t msg, int parm)
 953 {
 954     switch (msg)
 955     {
 956     case WIDGET_RESIZED:
 957         w->lines = help_lines;
 958         return MSG_HANDLED;
 959
 960     default:
 961         return default_proc (msg, parm);
 962     }
 963 }
 964
 965 static Widget *
 966 mousedispatch_new (int y, int x, int yl, int xl)
 967 {
 968     Widget *w = g_new (Widget, 1);
 969     init_widget (w, y, x, yl, xl, md_callback, help_event);
 970     return w;
 971 }
 972
 973 void
 974 interactive_display (const char *filename, const char *node)
 975 {
 976     const int help_colors[DLG_COLOR_NUM] = {
 977         HELP_NORMAL_COLOR,      /* common text color */
 978         0,                      /* unused in help */
 979         HELP_BOLD_COLOR,        /* title color */
 980         0                       /* unused in help */
 981     };
 982
 983     WButtonBar *help_bar;
 984     Widget *md;
 985     char *hlpfile = NULL;
 986     char *filedata;
 987
 988     if (filename != NULL)
 989         filedata = load_file (filename);
 990     else
 991         filedata = load_mc_home_file (mc_home, mc_home_alt, "mc.hlp", &hlpfile);
 992
 993     if (filedata == NULL)
 994         message (D_ERROR, MSG_ERROR, _(" Cannot open file %s \n %s "),
 995                  filename ? filename : hlpfile, unix_error_string (errno));
 996
 997     g_free (hlpfile);
 998
 999     if (filedata == NULL)
1000         return;
1001
1002     translate_file (filedata);
1003
1004     g_free (filedata);
1005
1006     if (fdata == NULL)
1007         return;
1008
1009     if ((node == NULL) || (*node == '\0'))
1010         node = "[main]";
1011
1012     main_node = search_string (fdata, node);
1013
1014     if (main_node == NULL)
1015     {
1016         message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "), node);
1017
1018         /* Fallback to [main], return if it also cannot be found */
1019         main_node = search_string (fdata, "[main]");
1020         if (main_node == NULL)
1021         {
1022             interactive_display_finish ();
1023             return;
1024         }
1025     }
1026
1027     help_lines = min (LINES - 4, max (2 * LINES / 3, 18));
1028
1029     whelp =
1030         create_dlg (0, 0, help_lines + 4, HELP_WINDOW_WIDTH + 4,
1031                     help_colors, help_callback, "[Help]", _("Help"),
1032                     DLG_TRYUP | DLG_CENTER | DLG_WANT_TAB);
1033
1034     selected_item = search_string_node (main_node, STRING_LINK_START) - 1;
1035     currentpoint = main_node + 1;       /* Skip the newline following the start of the node */
1036
1037     for (history_ptr = HISTORY_SIZE; history_ptr;)
1038     {
1039         history_ptr--;
1040         history[history_ptr].page = currentpoint;
1041         history[history_ptr].link = selected_item;
1042     }
1043
1044     help_bar = buttonbar_new (TRUE);
1045     help_bar->widget.y -= whelp->y;
1046     help_bar->widget.x -= whelp->x;
1047
1048     md = mousedispatch_new (1, 1, help_lines, HELP_WINDOW_WIDTH - 2);
1049
1050     add_widget (whelp, md);
1051     add_widget (whelp, help_bar);
1052
1053     buttonbar_set_label (help_bar, 1, Q_ ("ButtonBar|Help"), help_map, NULL);
1054     buttonbar_set_label (help_bar, 2, Q_ ("ButtonBar|Index"), help_map, NULL);
1055     buttonbar_set_label (help_bar, 3, Q_ ("ButtonBar|Prev"), help_map, NULL);
1056     buttonbar_set_label (help_bar, 4, "", help_map, NULL);
1057     buttonbar_set_label (help_bar, 5, "", help_map, NULL);
1058     buttonbar_set_label (help_bar, 6, "", help_map, NULL);
1059     buttonbar_set_label (help_bar, 7, "", help_map, NULL);
1060     buttonbar_set_label (help_bar, 8, "", help_map, NULL);
1061     buttonbar_set_label (help_bar, 9, "", help_map, NULL);
1062     buttonbar_set_label (help_bar, 10, Q_ ("ButtonBar|Quit"), help_map, NULL);
1063
1064     run_dlg (whelp);
1065     interactive_display_finish ();
1066     destroy_dlg (whelp);
1067 }