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 const global_keymap_t *help_map;
  71
  72 #define MAXLINKNAME 80
  73 #define HISTORY_SIZE 20
  74 #define HELP_WINDOW_WIDTH (COLS - 16)
  75
  76 #define STRING_LINK_START       "\01"
  77 #define STRING_LINK_POINTER     "\02"
  78 #define STRING_LINK_END         "\03"
  79 #define STRING_NODE_END         "\04"
  80
  81
  82 static char *fdata = NULL;      /* Pointer to the loaded data file */
  83 static int help_lines;          /* Lines in help viewer */
  84 static int history_ptr;         /* For the history queue */
  85 static const char *main_node;   /* The main node */
  86 static const char *last_shown = NULL;   /* Last byte shown in a screen */
  87 static gboolean end_of_node = FALSE;    /* Flag: the last character of the node shown? */
  88 static const char *currentpoint;
  89 static const char *selected_item;
  90
  91 /* The widget variables */
  92 static Dlg_head *whelp;
  93
  94 static struct
  95 {
  96     const char *page;           /* Pointer to the selected page */
  97     const char *link;           /* Pointer to the selected link */
  98 } history[HISTORY_SIZE];
  99
 100 /* Link areas for the mouse */
 101 typedef struct Link_Area
 102 {
 103     int x1, y1, x2, y2;
 104     const char *link_name;
 105 } Link_Area;
 106
 107 static GSList *link_area = NULL;
 108 static gboolean inside_link_area = FALSE;
 109
 110 static cb_ret_t help_callback (Dlg_head * h, Widget * sender, dlg_msg_t msg, int parm, void *data);
 111
 112 /* returns the position where text was found in the start buffer */
 113 /* or 0 if not found */
 114 static const char *
 115 search_string (const char *start, const char *text)
 116 {
 117     const char *result = NULL;
 118     char *local_text = g_strdup (text);
 119     char *d = local_text;
 120     const char *e = start;
 121
 122     /* fmt sometimes replaces a space with a newline in the help file */
 123     /* Replace the newlines in the link name with spaces to correct the situation */
 124     while (*d != '\0')
 125     {
 126         if (*d == '\n')
 127             *d = ' ';
 128         str_next_char (&d);
 129     }
 130
 131     /* Do search */
 132     for (d = local_text; *e; e++)
 133     {
 134         if (*d == *e)
 135             d++;
 136         else
 137             d = local_text;
 138         if (*d == '\0')
 139         {
 140             result = e + 1;
 141             break;
 142         }
 143     }
 144
 145     g_free (local_text);
 146     return result;
 147 }
 148
 149 /* Searches text in the buffer pointed by start.  Search ends */
 150 /* if the CHAR_NODE_END is found in the text.  Returns 0 on failure */
 151 static const char *
 152 search_string_node (const char *start, const char *text)
 153 {
 154     const char *d = text;
 155     const char *e = start;
 156
 157     if (start != NULL)
 158         for (; *e && *e != CHAR_NODE_END; e++)
 159         {
 160             if (*d == *e)
 161                 d++;
 162             else
 163                 d = text;
 164             if (*d == '\0')
 165                 return e + 1;
 166         }
 167
 168     return NULL;
 169 }
 170
 171 /* Searches the_char in the buffer pointer by start and searches */
 172 /* it can search forward (direction = 1) or backward (direction = -1) */
 173 static const char *
 174 search_char_node (const char *start, char the_char, int direction)
 175 {
 176     const char *e;
 177
 178     for (e = start; (*e != '\0') && (*e != CHAR_NODE_END); e += direction)
 179         if (*e == the_char)
 180             return e;
 181
 182     return NULL;
 183 }
 184
 185 /* Returns the new current pointer when moved lines lines */
 186 static const char *
 187 move_forward2 (const char *c, int lines)
 188 {
 189     const char *p;
 190     int line;
 191
 192     currentpoint = c;
 193     for (line = 0, p = currentpoint; (*p != '\0') && (*p != CHAR_NODE_END); str_cnext_char (&p))
 194     {
 195         if (line == lines)
 196             return currentpoint = p;
 197
 198         if (*p == '\n')
 199             line++;
 200     }
 201     return currentpoint = c;
 202 }
 203
 204 static const char *
 205 move_backward2 (const char *c, int lines)
 206 {
 207     const char *p;
 208     int line;
 209
 210     currentpoint = c;
 211     for (line = 0, p = currentpoint; (*p != '\0') && ((int) (p - fdata) >= 0); str_cprev_char (&p))
 212     {
 213         if (*p == CHAR_NODE_END)
 214         {
 215             /* We reached the beginning of the node */
 216             /* Skip the node headers */
 217             while (*p != ']')
 218                 str_cnext_char (&p);
 219             return currentpoint = p + 2;        /* Skip the newline following the start of the node */
 220         }
 221
 222         if (*(p - 1) == '\n')
 223             line++;
 224         if (line == lines)
 225             return currentpoint = p;
 226     }
 227     return currentpoint = c;
 228 }
 229
 230 static void
 231 move_forward (int i)
 232 {
 233     if (!end_of_node)
 234         currentpoint = move_forward2 (currentpoint, i);
 235 }
 236
 237 static void
 238 move_backward (int i)
 239 {
 240     currentpoint = move_backward2 (currentpoint, ++i);
 241 }
 242
 243 static void
 244 move_to_top (void)
 245 {
 246     while (((int) (currentpoint > fdata) > 0) && (*currentpoint != CHAR_NODE_END))
 247         currentpoint--;
 248
 249     while (*currentpoint != ']')
 250         currentpoint++;
 251     currentpoint = currentpoint + 2;    /* Skip the newline following the start of the node */
 252     selected_item = NULL;
 253 }
 254
 255 static void
 256 move_to_bottom (void)
 257 {
 258     while ((*currentpoint != '\0') && (*currentpoint != CHAR_NODE_END))
 259         currentpoint++;
 260     currentpoint--;
 261     move_backward (1);
 262 }
 263
 264 static const char *
 265 help_follow_link (const char *start, const char *lc_selected_item)
 266 {
 267     char link_name[MAXLINKNAME];
 268     const char *p;
 269     int i = 0;
 270
 271     if (lc_selected_item == NULL)
 272         return start;
 273
 274     for (p = lc_selected_item; *p && *p != CHAR_NODE_END && *p != CHAR_LINK_POINTER; p++)
 275         ;
 276     if (*p == CHAR_LINK_POINTER)
 277     {
 278         link_name[0] = '[';
 279         for (i = 1; *p != CHAR_LINK_END && *p && *p != CHAR_NODE_END && i < MAXLINKNAME - 3;)
 280             link_name[i++] = *++p;
 281         link_name[i - 1] = ']';
 282         link_name[i] = '\0';
 283         p = search_string (fdata, link_name);
 284         if (p != NULL)
 285         {
 286             p += 1;             /* Skip the newline following the start of the node */
 287             return p;
 288         }
 289     }
 290
 291     /* Create a replacement page with the error message */
 292     return _(" Help file format error\n");
 293 }
 294
 295 static const char *
 296 select_next_link (const char *current_link)
 297 {
 298     const char *p;
 299
 300     if (current_link == NULL)
 301         return NULL;
 302
 303     p = search_string_node (current_link, STRING_LINK_END);
 304     if (p == NULL)
 305         return NULL;
 306     p = search_string_node (p, STRING_LINK_START);
 307     if (p == NULL)
 308         return NULL;
 309     return p - 1;
 310 }
 311
 312 static const char *
 313 select_prev_link (const char *current_link)
 314 {
 315     return current_link == NULL ? NULL : search_char_node (current_link - 1, CHAR_LINK_START, -1);
 316 }
 317
 318 static void
 319 start_link_area (int x, int y, const char *link_name)
 320 {
 321     Link_Area *la;
 322
 323     if (inside_link_area)
 324         message (D_NORMAL, _("Warning"), _(" Internal bug: Double start of link area "));
 325
 326     /* Allocate memory for a new link area */
 327     la = g_new (Link_Area, 1);
 328     /* Save the beginning coordinates of the link area */
 329     la->x1 = x;
 330     la->y1 = y;
 331     /* Save the name of the destination anchor */
 332     la->link_name = link_name;
 333     link_area = g_slist_prepend (link_area, la);
 334
 335     inside_link_area = TRUE;
 336 }
 337
 338 static void
 339 end_link_area (int x, int y)
 340 {
 341     if (inside_link_area)
 342     {
 343         Link_Area *la = (Link_Area *) link_area->data;
 344         /* Save the end coordinates of the link area */
 345         la->x2 = x;
 346         la->y2 = y;
 347         inside_link_area = FALSE;
 348     }
 349 }
 350
 351 static void
 352 clear_link_areas (void)
 353 {
 354     g_slist_foreach (link_area, (GFunc) g_free, NULL);
 355     g_slist_free (link_area);
 356     link_area = NULL;
 357     inside_link_area = FALSE;
 358 }
 359
 360 static void
 361 help_print_word (Dlg_head * h, GString * word, int *col, int *line, gboolean add_space)
 362 {
 363     if (*line >= help_lines)
 364         g_string_set_size (word, 0);
 365     else
 366     {
 367         int w;
 368
 369         w = str_term_width1 (word->str);
 370         if (*col + w >= HELP_WINDOW_WIDTH)
 371         {
 372             *col = 0;
 373             (*line)++;
 374         }
 375
 376         if (*line >= help_lines)
 377             g_string_set_size (word, 0);
 378         else
 379         {
 380             dlg_move (h, *line + 2, *col + 2);
 381             tty_print_string (word->str);
 382             g_string_set_size (word, 0);
 383             *col += w;
 384         }
 385     }
 386
 387     if (add_space)
 388     {
 389         if (*col < HELP_WINDOW_WIDTH - 1)
 390         {
 391             tty_print_char (' ');
 392             (*col)++;
 393         }
 394         else
 395         {
 396             *col = 0;
 397             (*line)++;
 398         }
 399     }
 400 }
 401
 402 static void
 403 help_show (Dlg_head * h, const char *paint_start)
 404 {
 405     const char *p, *n;
 406     int col, line, c;
 407     gboolean painting = TRUE;
 408     gboolean acs;               /* Flag: Alternate character set active? */
 409     gboolean repeat_paint;
 410     int active_col, active_line;        /* Active link position */
 411     char buff[MB_LEN_MAX + 1];
 412     GString *word;
 413
 414     word = g_string_sized_new (32);
 415
 416     tty_setcolor (HELP_NORMAL_COLOR);
 417     do
 418     {
 419         line = col = active_col = active_line = 0;
 420         repeat_paint = FALSE;
 421         acs = FALSE;
 422
 423         clear_link_areas ();
 424         if ((int) (selected_item - paint_start) < 0)
 425             selected_item = NULL;
 426
 427         p = paint_start;
 428         n = paint_start;
 429         while ((n[0] != '\0') && (n[0] != CHAR_NODE_END) && (line < help_lines))
 430         {
 431             p = n;
 432             n = str_cget_next_char (p);
 433             memcpy (buff, p, n - p);
 434             buff[n - p] = '\0';
 435
 436             c = (unsigned char) buff[0];
 437             switch (c)
 438             {
 439             case CHAR_LINK_START:
 440                 if (selected_item == NULL)
 441                     selected_item = p;
 442                 if (p != selected_item)
 443                     tty_setcolor (HELP_LINK_COLOR);
 444                 else
 445                 {
 446                     tty_setcolor (HELP_SLINK_COLOR);
 447
 448                     /* Store the coordinates of the link */
 449                     active_col = col + 2;
 450                     active_line = line + 2;
 451                 }
 452                 start_link_area (col, line, p);
 453                 break;
 454             case CHAR_LINK_POINTER:
 455                 painting = FALSE;
 456                 end_link_area (col - 1, line);
 457                 break;
 458             case CHAR_LINK_END:
 459                 painting = TRUE;
 460                 help_print_word (h, word, &col, &line, FALSE);
 461                 tty_setcolor (HELP_NORMAL_COLOR);
 462                 break;
 463             case CHAR_ALTERNATE:
 464                 acs = TRUE;
 465                 break;
 466             case CHAR_NORMAL:
 467                 acs = FALSE;
 468                 break;
 469             case CHAR_VERSION:
 470                 dlg_move (h, line + 2, col + 2);
 471                 tty_print_string (VERSION);
 472                 col += str_term_width1 (VERSION);
 473                 break;
 474             case CHAR_FONT_BOLD:
 475                 tty_setcolor (HELP_BOLD_COLOR);
 476                 break;
 477             case CHAR_FONT_ITALIC:
 478                 tty_setcolor (HELP_ITALIC_COLOR);
 479                 break;
 480             case CHAR_FONT_NORMAL:
 481                 help_print_word (h, word, &col, &line, FALSE);
 482                 tty_setcolor (HELP_NORMAL_COLOR);
 483                 break;
 484             case '\n':
 485                 if (painting)
 486                     help_print_word (h, word, &col, &line, FALSE);
 487                 line++;
 488                 col = 0;
 489                 break;
 490             case '\t':
 491                 col = (col / 8 + 1) * 8;
 492                 if (col >= HELP_WINDOW_WIDTH)
 493                 {
 494                     line++;
 495                     col = 8;
 496                 }
 497                 break;
 498             case ' ':
 499                 /* word delimeter */
 500                 if (painting)
 501                     help_print_word (h, word, &col, &line, TRUE);
 502                 break;
 503             default:
 504                 if (painting && (line < help_lines))
 505                 {
 506                     if (!acs)
 507                         /* accumulate symbols in a word */
 508                         g_string_append (word, buff);
 509                     else if (col < HELP_WINDOW_WIDTH)
 510                     {
 511                         dlg_move (h, line + 2, col + 2);
 512
 513                         if ((c == ' ') || (c == '.'))
 514                             tty_print_char (c);
 515                         else
 516 #ifndef HAVE_SLANG
 517                             tty_print_char (acs_map[c]);
 518 #else
 519                             SLsmg_draw_object (h->y + line + 2, h->x + col + 2, c);
 520 #endif
 521                         col++;
 522                     }
 523                 }
 524             }
 525         }
 526
 527         /* print last word */
 528         if (n[0] == CHAR_NODE_END)
 529             help_print_word (h, word, &col, &line, FALSE);
 530
 531         last_shown = p;
 532         end_of_node = line < help_lines;
 533         tty_setcolor (HELP_NORMAL_COLOR);
 534         if ((int) (selected_item - last_shown) >= 0)
 535         {
 536             if ((link_area == NULL) || (link_area->data == NULL))
 537                 selected_item = NULL;
 538             else
 539             {
 540                 selected_item = ((Link_Area *) link_area->data)->link_name;
 541                 repeat_paint = TRUE;
 542             }
 543         }
 544     }
 545     while (repeat_paint);
 546
 547     g_string_free (word, TRUE);
 548
 549     /* Position the cursor over a nice link */
 550     if (active_col)
 551         dlg_move (h, active_line, active_col);
 552 }
 553
 554 static int
 555 help_event (Gpm_Event * event, void *vp)
 556 {
 557     Widget *w = vp;
 558     GSList *current_area;
 559
 560     if ((event->type & GPM_UP) == 0)
 561         return 0;
 562
 563     /* The event is relative to the dialog window, adjust it: */
 564     event->x -= 2;
 565     event->y -= 2;
 566
 567     if (event->buttons & GPM_B_RIGHT)
 568     {
 569         currentpoint = history[history_ptr].page;
 570         selected_item = history[history_ptr].link;
 571         history_ptr--;
 572         if (history_ptr < 0)
 573             history_ptr = HISTORY_SIZE - 1;
 574
 575         help_callback (w->parent, NULL, DLG_DRAW, 0, NULL);
 576         return 0;
 577     }
 578
 579     /* Test whether the mouse click is inside one of the link areas */
 580     for (current_area = link_area; current_area != NULL; current_area = g_slist_next (current_area))
 581     {
 582         Link_Area *la = (Link_Area *) current_area->data;
 583         /* Test one line link area */
 584         if (event->y == la->y1 && event->x >= la->x1 && event->y == la->y2 && event->x <= la->x2)
 585             break;
 586         /* Test two line link area */
 587         if (la->y1 + 1 == la->y2)
 588         {
 589             /* The first line */
 590             if (event->y == la->y1 && event->x >= la->x1)
 591                 break;
 592             /* The second line */
 593             if (event->y == la->y2 && event->x <= la->x2)
 594                 break;
 595         }
 596         /* Mouse will not work with link areas of more than two lines */
 597     }
 598
 599     /* Test whether a link area was found */
 600     if (current_area != NULL)
 601     {
 602         Link_Area *la = (Link_Area *) current_area->data;
 603
 604         /* The click was inside a link area -> follow the link */
 605         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 606         history[history_ptr].page = currentpoint;
 607         history[history_ptr].link = la->link_name;
 608         currentpoint = help_follow_link (currentpoint, la->link_name);
 609         selected_item = NULL;
 610     }
 611     else if (event->y < 0)
 612         move_backward (help_lines - 1);
 613     else if (event->y >= help_lines)
 614         move_forward (help_lines - 1);
 615     else if (event->y < help_lines / 2)
 616         move_backward (1);
 617     else
 618         move_forward (1);
 619
 620     /* Show the new node */
 621     help_callback (w->parent, NULL, DLG_DRAW, 0, NULL);
 622
 623     return 0;
 624 }
 625
 626 /* show help */
 627 static void
 628 help_help (Dlg_head * h)
 629 {
 630     const char *p;
 631
 632     history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 633     history[history_ptr].page = currentpoint;
 634     history[history_ptr].link = selected_item;
 635
 636     p = search_string (fdata, "[How to use help]");
 637     if (p != NULL)
 638     {
 639         currentpoint = p + 1;   /* Skip the newline following the start of the node */
 640         selected_item = NULL;
 641         help_callback (h, NULL, DLG_DRAW, 0, NULL);
 642     }
 643 }
 644
 645 static void
 646 help_index (Dlg_head * h)
 647 {
 648     const char *new_item;
 649
 650     new_item = search_string (fdata, "[Contents]");
 651
 652     if (new_item == NULL)
 653         message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "), "[Contents]");
 654     else
 655     {
 656         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 657         history[history_ptr].page = currentpoint;
 658         history[history_ptr].link = selected_item;
 659
 660         currentpoint = new_item + 1;    /* Skip the newline following the start of the node */
 661         selected_item = NULL;
 662         help_callback (h, NULL, DLG_DRAW, 0, NULL);
 663     }
 664 }
 665
 666 static void
 667 help_back (Dlg_head * h)
 668 {
 669     currentpoint = history[history_ptr].page;
 670     selected_item = history[history_ptr].link;
 671     history_ptr--;
 672     if (history_ptr < 0)
 673         history_ptr = HISTORY_SIZE - 1;
 674
 675     help_callback (h, NULL, DLG_DRAW, 0, NULL); /* FIXME: unneeded? */
 676 }
 677
 678 static void
 679 help_cmk_move_backward (void *vp, int lines)
 680 {
 681     (void) &vp;
 682     move_backward (lines);
 683 }
 684
 685 static void
 686 help_cmk_move_forward (void *vp, int lines)
 687 {
 688     (void) &vp;
 689     move_forward (lines);
 690 }
 691
 692 static void
 693 help_cmk_moveto_top (void *vp, int lines)
 694 {
 695     (void) &vp;
 696     (void) &lines;
 697     move_to_top ();
 698 }
 699
 700 static void
 701 help_cmk_moveto_bottom (void *vp, int lines)
 702 {
 703     (void) &vp;
 704     (void) &lines;
 705     move_to_bottom ();
 706 }
 707
 708 static void
 709 help_next_link (gboolean move_down)
 710 {
 711     const char *new_item;
 712
 713     new_item = select_next_link (selected_item);
 714     if (new_item != NULL)
 715     {
 716         selected_item = new_item;
 717         if ((int) (selected_item - last_shown) >= 0)
 718         {
 719             if (move_down)
 720                 move_forward (1);
 721             else
 722                 selected_item = NULL;
 723         }
 724     }
 725     else if (move_down)
 726         move_forward (1);
 727     else
 728         selected_item = NULL;
 729 }
 730
 731 static void
 732 help_prev_link (gboolean move_up)
 733 {
 734     const char *new_item;
 735
 736     new_item = select_prev_link (selected_item);
 737     selected_item = new_item;
 738     if ((selected_item == NULL) || (selected_item < currentpoint))
 739     {
 740         if (move_up)
 741             move_backward (1);
 742         else if ((link_area != NULL) && (link_area->data != NULL))
 743             selected_item = ((Link_Area *) link_area->data)->link_name;
 744         else
 745             selected_item = NULL;
 746     }
 747 }
 748
 749 static void
 750 help_next_node (void)
 751 {
 752     const char *new_item;
 753
 754     new_item = currentpoint;
 755     while ((*new_item != '\0') && (*new_item != CHAR_NODE_END))
 756         new_item++;
 757
 758     if (*++new_item == '[')
 759         while (*++new_item != '\0')
 760             if ((*new_item == ']') && (*++new_item != '\0') && (*++new_item != '\0'))
 761             {
 762                 currentpoint = new_item;
 763                 selected_item = NULL;
 764                 break;
 765             }
 766 }
 767
 768 static void
 769 help_prev_node (void)
 770 {
 771     const char *new_item;
 772
 773     new_item = currentpoint;
 774     while (((int) (new_item - fdata) > 1) && (*new_item != CHAR_NODE_END))
 775         new_item--;
 776     new_item--;
 777     while (((int) (new_item - fdata) > 0) && (*new_item != CHAR_NODE_END))
 778         new_item--;
 779     while (*new_item != ']')
 780         new_item++;
 781     currentpoint = new_item + 2;
 782     selected_item = NULL;
 783 }
 784
 785 static void
 786 help_select_link (void)
 787 {
 788     /* follow link */
 789     if (selected_item == NULL)
 790     {
 791 #ifdef WE_WANT_TO_GO_BACKWARD_ON_KEY_RIGHT
 792         /* Is there any reason why the right key would take us
 793          * backward if there are no links selected?, I agree
 794          * with Torben than doing nothing in this case is better
 795          */
 796         /* If there are no links, go backward in history */
 797         history_ptr--;
 798         if (history_ptr < 0)
 799             history_ptr = HISTORY_SIZE - 1;
 800
 801         currentpoint = history[history_ptr].page;
 802         selected_item = history[history_ptr].link;
 803 #endif
 804     }
 805     else
 806     {
 807         history_ptr = (history_ptr + 1) % HISTORY_SIZE;
 808         history[history_ptr].page = currentpoint;
 809         history[history_ptr].link = selected_item;
 810         currentpoint = help_follow_link (currentpoint, selected_item);
 811     }
 812
 813     selected_item = NULL;
 814 }
 815
 816 static cb_ret_t
 817 help_execute_cmd (unsigned long command)
 818 {
 819     cb_ret_t ret = MSG_HANDLED;
 820
 821     switch (command)
 822     {
 823     case CK_HelpHelp:
 824         help_help (whelp);
 825         break;
 826     case CK_HelpIndex:
 827         help_index (whelp);
 828         break;
 829     case CK_HelpBack:
 830         help_back (whelp);
 831         break;
 832     case CK_HelpMoveUp:
 833         help_prev_link (TRUE);
 834         break;
 835     case CK_HelpMoveDown:
 836         help_next_link (TRUE);
 837         break;
 838     case CK_HelpSelectLink:
 839         help_select_link ();
 840         break;
 841     case CK_HelpNextLink:
 842         help_next_link (FALSE);
 843         break;
 844     case CK_HelpPrevLink:
 845         help_prev_link (FALSE);
 846         break;
 847     case CK_HelpNextNode:
 848         help_next_node ();
 849         break;
 850     case CK_HelpPrevNode:
 851         help_prev_node ();
 852         break;
 853     case CK_HelpQuit:
 854         dlg_stop (whelp);
 855         break;
 856     default:
 857         ret = MSG_NOT_HANDLED;
 858     }
 859
 860     return ret;
 861 }
 862
 863 static cb_ret_t
 864 help_handle_key (Dlg_head * h, int c)
 865 {
 866     if (c != KEY_UP && c != KEY_DOWN &&
 867         check_movement_keys (c, help_lines, NULL,
 868                              help_cmk_move_backward,
 869                              help_cmk_move_forward,
 870                              help_cmk_moveto_top, help_cmk_moveto_bottom) == MSG_HANDLED)
 871     {
 872         /* Nothing */ ;
 873     }
 874     else
 875     {
 876         unsigned long command;
 877
 878         command = lookup_keymap_command (help_map, c);
 879         if ((command == CK_Ignore_Key) || (help_execute_cmd (command) == MSG_NOT_HANDLED))
 880             return MSG_NOT_HANDLED;
 881     }
 882
 883     help_callback (h, NULL, DLG_DRAW, 0, NULL);
 884     return MSG_HANDLED;
 885 }
 886
 887 static cb_ret_t
 888 help_callback (Dlg_head * h, Widget * sender, dlg_msg_t msg, int parm, void *data)
 889 {
 890     WButtonBar *bb;
 891
 892     switch (msg)
 893     {
 894     case DLG_RESIZE:
 895         help_lines = min (LINES - 4, max (2 * LINES / 3, 18));
 896         dlg_set_size (h, help_lines + 4, HELP_WINDOW_WIDTH + 4);
 897         bb = find_buttonbar (h);
 898         widget_set_size (&bb->widget, LINES - 1, 0, 1, COLS);
 899         return MSG_HANDLED;
 900
 901     case DLG_DRAW:
 902         common_dialog_repaint (h);
 903         help_show (h, currentpoint);
 904         return MSG_HANDLED;
 905
 906     case DLG_KEY:
 907         return help_handle_key (h, parm);
 908
 909     case DLG_ACTION:
 910         /* command from buttonbar */
 911         return help_execute_cmd (parm);
 912
 913     default:
 914         return default_dlg_callback (h, sender, msg, parm, data);
 915     }
 916 }
 917
 918 static void
 919 interactive_display_finish (void)
 920 {
 921     clear_link_areas ();
 922 }
 923
 924 /* translate help file into terminal encoding */
 925 static void
 926 translate_file (char *filedata)
 927 {
 928     GIConv conv;
 929     GString *translated_data;
 930
 931     /* initial allocation for largest whole help file */
 932     translated_data = g_string_sized_new (32 * 1024);
 933
 934     conv = str_crt_conv_from ("UTF-8");
 935
 936     if (conv == INVALID_CONV)
 937         g_string_free (translated_data, TRUE);
 938     else
 939     {
 940         g_free (fdata);
 941
 942         if (str_convert (conv, filedata, translated_data) != ESTR_FAILURE)
 943             fdata = g_string_free (translated_data, FALSE);
 944         else
 945         {
 946             fdata = NULL;
 947             g_string_free (translated_data, TRUE);
 948         }
 949         str_close_conv (conv);
 950     }
 951 }
 952
 953 static cb_ret_t
 954 md_callback (Widget * w, widget_msg_t msg, int parm)
 955 {
 956     switch (msg)
 957     {
 958     case WIDGET_RESIZED:
 959         w->lines = help_lines;
 960         return MSG_HANDLED;
 961
 962     default:
 963         return default_proc (msg, parm);
 964     }
 965 }
 966
 967 static Widget *
 968 mousedispatch_new (int y, int x, int yl, int xl)
 969 {
 970     Widget *w = g_new (Widget, 1);
 971     init_widget (w, y, x, yl, xl, md_callback, help_event);
 972     return w;
 973 }
 974
 975 void
 976 interactive_display (const char *filename, const char *node)
 977 {
 978     const int help_colors[DLG_COLOR_NUM] = {
 979         HELP_NORMAL_COLOR,      /* common text color */
 980         0,                      /* unused in help */
 981         HELP_BOLD_COLOR,        /* title color */
 982         0                       /* unused in help */
 983     };
 984
 985     WButtonBar *help_bar;
 986     Widget *md;
 987     char *hlpfile = NULL;
 988     char *filedata;
 989
 990     if (filename != NULL)
 991         filedata = load_file (filename);
 992     else
 993         filedata = load_mc_home_file (mc_home, mc_home_alt, "mc.hlp", &hlpfile);
 994
 995     if (filedata == NULL)
 996         message (D_ERROR, MSG_ERROR, _(" Cannot open file %s \n %s "),
 997                  filename ? filename : hlpfile, unix_error_string (errno));
 998
 999     g_free (hlpfile);
1000
1001     if (filedata == NULL)
1002         return;
1003
1004     translate_file (filedata);
1005
1006     g_free (filedata);
1007
1008     if (fdata == NULL)
1009         return;
1010
1011     if ((node == NULL) || (*node == '\0'))
1012         node = "[main]";
1013
1014     main_node = search_string (fdata, node);
1015
1016     if (main_node == NULL)
1017     {
1018         message (D_ERROR, MSG_ERROR, _(" Cannot find node %s in help file "), node);
1019
1020         /* Fallback to [main], return if it also cannot be found */
1021         main_node = search_string (fdata, "[main]");
1022         if (main_node == NULL)
1023         {
1024             interactive_display_finish ();
1025             return;
1026         }
1027     }
1028
1029     help_lines = min (LINES - 4, max (2 * LINES / 3, 18));
1030
1031     whelp =
1032         create_dlg (0, 0, help_lines + 4, HELP_WINDOW_WIDTH + 4,
1033                     help_colors, help_callback, "[Help]", _("Help"),
1034                     DLG_TRYUP | DLG_CENTER | DLG_WANT_TAB);
1035
1036     selected_item = search_string_node (main_node, STRING_LINK_START) - 1;
1037     currentpoint = main_node + 1;       /* Skip the newline following the start of the node */
1038
1039     for (history_ptr = HISTORY_SIZE; history_ptr;)
1040     {
1041         history_ptr--;
1042         history[history_ptr].page = currentpoint;
1043         history[history_ptr].link = selected_item;
1044     }
1045
1046     help_bar = buttonbar_new (TRUE);
1047     help_bar->widget.y -= whelp->y;
1048     help_bar->widget.x -= whelp->x;
1049
1050     md = mousedispatch_new (1, 1, help_lines, HELP_WINDOW_WIDTH - 2);
1051
1052     add_widget (whelp, md);
1053     add_widget (whelp, help_bar);
1054
1055     buttonbar_set_label (help_bar, 1, Q_ ("ButtonBar|Help"), help_map, NULL);
1056     buttonbar_set_label (help_bar, 2, Q_ ("ButtonBar|Index"), help_map, NULL);
1057     buttonbar_set_label (help_bar, 3, Q_ ("ButtonBar|Prev"), help_map, NULL);
1058     buttonbar_set_label (help_bar, 4, "", help_map, NULL);
1059     buttonbar_set_label (help_bar, 5, "", help_map, NULL);
1060     buttonbar_set_label (help_bar, 6, "", help_map, NULL);
1061     buttonbar_set_label (help_bar, 7, "", help_map, NULL);
1062     buttonbar_set_label (help_bar, 8, "", help_map, NULL);
1063     buttonbar_set_label (help_bar, 9, "", help_map, NULL);
1064     buttonbar_set_label (help_bar, 10, Q_ ("ButtonBar|Quit"), help_map, NULL);
1065
1066     run_dlg (whelp);
1067     interactive_display_finish ();
1068     destroy_dlg (whelp);
1069 }