Updated italian translation

[midnight-commander.git] / slang / slsmg.c

/* SLang Screen management routines */
/* Copyright (c) 1992, 1999, 2001, 2002, 2003 John E. Davis
 * This file is part of the S-Lang library.
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Perl Artistic License.
 */

#include "slinclud.h"

#include "slang.h"
#include "_slang.h"

typedef struct Screen_Type
  {
     int n;                    /* number of chars written last time */
     int flags;                /* line untouched, etc... */
     SLsmg_Char_Type *old, *neew;
#ifndef IBMPC_SYSTEM
     unsigned long old_hash, new_hash;
#endif
  }
Screen_Type;

#define TOUCHED 0x1
#define TRASHED 0x2
static int Screen_Trashed;

Screen_Type SL_Screen[SLTT_MAX_SCREEN_ROWS];
static int Start_Col, Start_Row;
static int Screen_Cols, Screen_Rows;
static int This_Row, This_Col;
static int This_Color;                 /* only the first 8 bits of this
                                        * are used.  The highest bit is used
                                        * to indicate an alternate character
                                        * set.  This leaves 127 userdefineable
                                        * color combination.
                                        */

#ifndef IBMPC_SYSTEM
#define ALT_CHAR_FLAG 0x80
#else
#define ALT_CHAR_FLAG 0x00
#endif

#if SLTT_HAS_NON_BCE_SUPPORT && !defined(IBMPC_SYSTEM)
#define REQUIRES_NON_BCE_SUPPORT 1
static int Bce_Color_Offset;
#endif

int SLsmg_Newline_Behavior = 0;
int SLsmg_Backspace_Moves = 0;
/* Backward compatibility. Not used. */
/* int SLsmg_Newline_Moves; */

static void (*tt_normal_video)(void) = SLtt_normal_video;
static void (*tt_goto_rc)(int, int) = SLtt_goto_rc;
static void (*tt_cls) (void) = SLtt_cls;
static void (*tt_del_eol) (void) = SLtt_del_eol;
static void (*tt_smart_puts) (SLsmg_Char_Type *, SLsmg_Char_Type *, int, int) = SLtt_smart_puts;
static int (*tt_flush_output) (void) = SLtt_flush_output;
static int (*tt_reset_video) (void) = SLtt_reset_video;
static int (*tt_init_video) (void) = SLtt_init_video;
static int *tt_Screen_Rows = &SLtt_Screen_Rows;
static int *tt_Screen_Cols = &SLtt_Screen_Cols;

#ifndef IBMPC_SYSTEM
static void (*tt_set_scroll_region)(int, int) = SLtt_set_scroll_region;
static void (*tt_reverse_index)(int) = SLtt_reverse_index;
static void (*tt_reset_scroll_region)(void) = SLtt_reset_scroll_region;
static void (*tt_delete_nlines)(int) = SLtt_delete_nlines;
#endif

#ifndef IBMPC_SYSTEM
static int *tt_Term_Cannot_Scroll = &SLtt_Term_Cannot_Scroll;
static int *tt_Has_Alt_Charset = &SLtt_Has_Alt_Charset;
static char **tt_Graphics_Char_Pairs = &SLtt_Graphics_Char_Pairs;
static int *tt_Use_Blink_For_ACS = &SLtt_Use_Blink_For_ACS;
#endif

static int Smg_Inited;

static void blank_line (SLsmg_Char_Type *p, int n, unsigned char ch)
{
   register SLsmg_Char_Type *pmax = p + n;
   register SLsmg_Char_Type color_ch;

   color_ch = SLSMG_BUILD_CHAR(ch,This_Color);

   while (p < pmax)
     {
        *p++ = color_ch;
     }
}

static void clear_region (int row, int n, unsigned char ch)
{
   int i;
   int imax = row + n;

   if (imax > Screen_Rows) imax = Screen_Rows;
   for (i = row; i < imax; i++)
     {
        if (i >= 0)
          {
             blank_line (SL_Screen[i].neew, Screen_Cols, ch);
             SL_Screen[i].flags |= TOUCHED;
          }
     }
}

void SLsmg_erase_eol (void)
{
   int r, c;

   if (Smg_Inited == 0) return;

   c = This_Col - Start_Col;
   r = This_Row - Start_Row;

   if ((r < 0) || (r >= Screen_Rows)) return;
   if (c < 0) c = 0; else if (c >= Screen_Cols) return;
   blank_line (SL_Screen[This_Row].neew + c , Screen_Cols - c, ' ');
   SL_Screen[This_Row].flags |= TOUCHED;
}

static void scroll_up (void)
{
   unsigned int i, imax;
   SLsmg_Char_Type *neew;

   neew = SL_Screen[0].neew;
   imax = Screen_Rows - 1;
   for (i = 0; i < imax; i++)
     {
        SL_Screen[i].neew = SL_Screen[i + 1].neew;
        SL_Screen[i].flags |= TOUCHED;
     }
   SL_Screen[i].neew = neew;
   SL_Screen[i].flags |= TOUCHED;
   blank_line (neew, Screen_Cols, ' ');
   This_Row--;
}

void SLsmg_gotorc (int r, int c)
{
   This_Row = r;
   This_Col = c;
}

int SLsmg_get_row (void)
{
   return This_Row;
}

int SLsmg_get_column (void)
{
   return This_Col;
}

void SLsmg_erase_eos (void)
{
   if (Smg_Inited == 0) return;

   SLsmg_erase_eol ();
   clear_region (This_Row + 1, Screen_Rows, ' ');
}

static int This_Alt_Char;

void SLsmg_set_char_set (int i)
{
#ifdef IBMPC_SYSTEM
   (void) i;
#else
   if ((tt_Use_Blink_For_ACS != NULL)
       && (*tt_Use_Blink_For_ACS != 0))
     return;/* alt chars not used and the alt bit
             * is used to indicate a blink.
             */

   if (i) This_Alt_Char = ALT_CHAR_FLAG;
   else This_Alt_Char = 0;

   This_Color &= 0x7F;
   This_Color |= This_Alt_Char;
#endif
}

void SLsmg_set_color (int color)
{
   if (color < 0) return;
#ifdef REQUIRES_NON_BCE_SUPPORT
   color += Bce_Color_Offset;
#endif
   This_Color = color | This_Alt_Char;
}

void SLsmg_reverse_video (void)
{
   SLsmg_set_color (1);
}

void SLsmg_normal_video (void)
{
   SLsmg_set_color (0);
}

static int point_visible (int col_too)
{
   return ((This_Row >= Start_Row) && (This_Row < Start_Row + Screen_Rows)
           && ((col_too == 0)
               || ((This_Col >= Start_Col)
                   && (This_Col < Start_Col + Screen_Cols))));
}

void SLsmg_write_string (char *str)
{
   SLsmg_write_nchars (str, strlen (str));
}

void SLsmg_write_nstring (char *str, unsigned int n)
{
   unsigned int width;
   char blank = ' ';

   /* Avoid a problem if a user accidently passes a negative value */
   if ((int) n < 0)
     return;

   if (str == NULL) width = 0;
   else
     {
        width = strlen (str);
        if (width > n) width = n;
        SLsmg_write_nchars (str, width);
     }
   while (width++ < n) SLsmg_write_nchars (&blank, 1);
}

void SLsmg_write_wrapped_string (char *s, int r, int c,
                                 unsigned int dr, unsigned int dc,
                                 int fill)
{
   register char ch, *p;
   int maxc = (int) dc;

   if ((dr == 0) || (dc == 0)) return;
   p = s;
   dc = 0;
   while (1)
     {
        ch = *p++;
        if ((ch == 0) || (ch == '\n'))
          {
             int diff;

             diff = maxc - (int) dc;

             SLsmg_gotorc (r, c);
             SLsmg_write_nchars (s, dc);
             if (fill && (diff > 0))
               {
                  while (diff--) SLsmg_write_char (' ');
               }
             if ((ch == 0) || (dr == 1)) break;

             r++;
             dc = 0;
             dr--;
             s = p;
          }
        else if ((int) dc == maxc)
          {
             SLsmg_gotorc (r, c);
             SLsmg_write_nchars (s, dc + 1);
             if (dr == 1) break;

             r++;
             dc = 0;
             dr--;
             s = p;
          }
        else dc++;
     }
}

int SLsmg_Tab_Width = 8;

/* Minimum value for which eight bit char is displayed as is. */

#ifndef IBMPC_SYSTEM
int SLsmg_Display_Eight_Bit = 160;
static unsigned char Alt_Char_Set[129];/* 129th is used as a flag */
#else
int SLsmg_Display_Eight_Bit = 128;
#endif

void SLsmg_write_nchars (char *str, unsigned int n)
{
   register SLsmg_Char_Type *p, old, neew, color;
   unsigned char ch;
   unsigned int flags;
   int len, start_len, max_len;
   char *str_max;
   int newline_flag;
#ifndef IBMPC_SYSTEM
   int alt_char_set_flag;

   alt_char_set_flag = ((This_Color & ALT_CHAR_FLAG)
                        && ((tt_Use_Blink_For_ACS == NULL)
                            || (*tt_Use_Blink_For_ACS == 0)));
#endif

   if (Smg_Inited == 0) return;

   str_max = str + n;
   color = This_Color;

   top:                                /* get here only on newline */

   newline_flag = 0;
   start_len = Start_Col;

   if (point_visible (0) == 0) return;

   len = This_Col;
   max_len = start_len + Screen_Cols;

   p = SL_Screen[This_Row - Start_Row].neew;
   if (len > start_len) p += (len - start_len);

   flags = SL_Screen[This_Row - Start_Row].flags;
   while ((len < max_len) && (str < str_max))
     {
        ch = (unsigned char) *str++;

#ifndef IBMPC_SYSTEM
        if (alt_char_set_flag)
          ch = Alt_Char_Set [ch & 0x7F];
#endif
        if (((ch >= ' ') && (ch < 127))
            || (ch >= (unsigned char) SLsmg_Display_Eight_Bit)
#ifndef IBMPC_SYSTEM
            || alt_char_set_flag
#endif
            )
          {
             len += 1;
             if (len > start_len)
               {
                  old = *p;
                  neew = SLSMG_BUILD_CHAR(ch,color);
                  if (old != neew)
                    {
                       flags |= TOUCHED;
                       *p = neew;
                    }
                  p++;
               }
          }

        else if ((ch == '\t') && (SLsmg_Tab_Width > 0))
          {
             n = len;
             n += SLsmg_Tab_Width;
             n = SLsmg_Tab_Width - (n % SLsmg_Tab_Width);
             if ((unsigned int) len + n > (unsigned int) max_len)
               n = (unsigned int) (max_len - len);
             neew = SLSMG_BUILD_CHAR(' ',color);
             while (n--)
               {
                  len += 1;
                  if (len > start_len)
                    {
                       if (*p != neew)
                         {
                            flags |= TOUCHED;
                            *p = neew;
                         }
                       p++;
                    }
               }
          }
        else if ((ch == '\n')
                 && (SLsmg_Newline_Behavior != SLSMG_NEWLINE_PRINTABLE))
          {
             newline_flag = 1;
             break;
          }
        else if ((ch == 0x8) && SLsmg_Backspace_Moves)
          {
             if (len != 0) len--;
          }
        else
          {
             if (ch & 0x80)
               {
                  neew = SLSMG_BUILD_CHAR('~',color);
                  len += 1;
                  if (len > start_len)
                    {
                       if (*p != neew)
                         {
                            *p = neew;
                            flags |= TOUCHED;
                         }
                       p++;
                       if (len == max_len) break;
                       ch &= 0x7F;
                    }
               }

             len += 1;
             if (len > start_len)
               {
                  neew = SLSMG_BUILD_CHAR('^',color);
                  if (*p != neew)
                    {
                       *p = neew;
                       flags |= TOUCHED;
                    }
                  p++;
                  if (len == max_len) break;
               }

             if (ch == 127) ch = '?'; else ch = ch + '@';
             len++;
             if (len > start_len)
               {
                  neew = SLSMG_BUILD_CHAR(ch,color);
                  if (*p != neew)
                    {
                       *p = neew;
                       flags |= TOUCHED;
                    }
                  p++;
               }
          }
     }

   SL_Screen[This_Row - Start_Row].flags = flags;
   This_Col = len;

   if (SLsmg_Newline_Behavior == 0)
     return;

   if (newline_flag == 0)
     {
        while (str < str_max)
          {
             if (*str == '\n') break;
             str++;
          }
        if (str == str_max) return;
        str++;
     }

   This_Row++;
   This_Col = 0;
   if (This_Row == Start_Row + Screen_Rows)
     {
        if (SLsmg_Newline_Behavior == SLSMG_NEWLINE_SCROLLS) scroll_up ();
     }
   goto top;
}

void SLsmg_write_char (char ch)
{
   SLsmg_write_nchars (&ch, 1);
}

static int Cls_Flag;

void SLsmg_cls (void)
{
   int tac;
   if (Smg_Inited == 0) return;

   tac = This_Alt_Char; This_Alt_Char = 0;
   SLsmg_set_color (0);
   clear_region (0, Screen_Rows, ' ');
   This_Alt_Char = tac;
   SLsmg_set_color (0);
   Cls_Flag = 1;
}
#if 0
static void do_copy (SLsmg_Char_Type *a, SLsmg_Char_Type *b)
{
   SLsmg_Char_Type *amax = a + Screen_Cols;

   while (a < amax) *a++ = *b++;
}
#endif

#ifndef IBMPC_SYSTEM
int SLsmg_Scroll_Hash_Border = 0;
static unsigned long compute_hash (SLsmg_Char_Type *s, int n)
{
   register unsigned long h = 0, g;
   register unsigned long sum = 0;
   register SLsmg_Char_Type *smax, ch;
   int is_blank = 2;

   s += SLsmg_Scroll_Hash_Border;
   smax = s + (n - SLsmg_Scroll_Hash_Border);
   while (s < smax)
     {
        ch = *s++;
        if (is_blank && (SLSMG_EXTRACT_CHAR(ch) != 32)) is_blank--;

        sum += ch;

        h = sum + (h << 3);
        if ((g = h & 0xE0000000UL) != 0)
          {
             h = h ^ (g >> 24);
             h = h ^ g;
          }
     }
   if (is_blank) return 0;
   return h;
}

static unsigned long Blank_Hash;

static int try_scroll_down (int rmin, int rmax)
{
   int i, r1, r2, di, j;
   unsigned long hash;
   int did_scroll;
   int color;
   SLsmg_Char_Type *tmp;
   int ignore;

   did_scroll = 0;
   for (i = rmax; i > rmin; i--)
     {
        hash = SL_Screen[i].new_hash;
        if (hash == Blank_Hash) continue;

        if ((hash == SL_Screen[i].old_hash)
#if 0
            || ((i + 1 < Screen_Rows) && (hash == SL_Screen[i + 1].old_hash))
            || ((i - 1 > rmin) && (SL_Screen[i].old_hash == SL_Screen[i - 1].new_hash))
#endif
            )
          continue;

        for (j = i - 1; j >= rmin; j--)
          {
             if (hash == SL_Screen[j].old_hash) break;
          }
        if (j < rmin) continue;

        r2 = i;                        /* end scroll region */

        di = i - j;
        j--;
        ignore = 0;
        while ((j >= rmin) && (SL_Screen[j].old_hash == SL_Screen[j + di].new_hash))
          {
             if (SL_Screen[j].old_hash == Blank_Hash) ignore++;
             j--;
          }
        r1 = j + 1;

        /* If this scroll only scrolls this line into place, don't do it.
         */
        if ((di > 1) && (r1 + di + ignore == r2)) continue;

        /* If there is anything in the scrolling region that is ok, abort the
         * scroll.
         */

        for (j = r1; j <= r2; j++)
          {
             if ((SL_Screen[j].old_hash != Blank_Hash)
                 && (SL_Screen[j].old_hash == SL_Screen[j].new_hash))
               {
                  /* See if the scroll is happens to scroll this one into place. */
                  if ((j + di > r2) || (SL_Screen[j].old_hash != SL_Screen[j + di].new_hash))
                    break;
               }
          }
        if (j <= r2) continue;

        color = This_Color;  This_Color = 0;
        did_scroll = 1;
        (*tt_normal_video) ();
        (*tt_set_scroll_region) (r1, r2);
        (*tt_goto_rc) (0, 0);
        (*tt_reverse_index) (di);
        (*tt_reset_scroll_region) ();
        /* Now we have a hole in the screen.
         * Make the virtual screen look like it.
         * 
         * Note that if the terminal does not support BCE, then we have
         * no idea what color the hole is.  So, for this case, we do not
         * want to add Bce_Color_Offset to This_Color since if Bce_Color_Offset
         * is non-zero, then This_Color = 0 does not match any valid color
         * obtained by adding Bce_Color_Offset.
         */
        for (j = r1; j <= r2; j++) SL_Screen[j].flags = TOUCHED;

        while (di--)
          {
             tmp = SL_Screen[r2].old;
             for (j = r2; j > r1; j--)
               {
                  SL_Screen[j].old = SL_Screen[j - 1].old;
                  SL_Screen[j].old_hash = SL_Screen[j - 1].old_hash;
               }
             SL_Screen[r1].old = tmp;
             blank_line (SL_Screen[r1].old, Screen_Cols, ' ');
             SL_Screen[r1].old_hash = Blank_Hash;
             r1++;
          }
        This_Color = color;
     }

   return did_scroll;
}

static int try_scroll_up (int rmin, int rmax)
{
   int i, r1, r2, di, j;
   unsigned long hash;
   int did_scroll;
   int color;
   SLsmg_Char_Type *tmp;
   int ignore;

   did_scroll = 0;
   for (i = rmin; i < rmax; i++)
     {
        hash = SL_Screen[i].new_hash;
        if (hash == Blank_Hash) continue;
        if (hash == SL_Screen[i].old_hash)
          continue;
        /* find a match further down screen */
        for (j = i + 1; j <= rmax; j++)
          {
             if (hash == SL_Screen[j].old_hash) break;
          }
        if (j > rmax) continue;

        r1 = i;                        /* beg scroll region */
        di = j - i;                    /* number of lines to scroll */
        j++;                           /* since we know this is a match */

        /* find end of scroll region */
        ignore = 0;
        while ((j <= rmax) && (SL_Screen[j].old_hash == SL_Screen[j - di].new_hash))
          {
             if (SL_Screen[j].old_hash == Blank_Hash) ignore++;
             j++;
          }
        r2 = j - 1;                    /* end of scroll region */

        /* If this scroll only scrolls this line into place, don't do it.
         */
        if ((di > 1) && (r1 + di + ignore == r2)) continue;

        /* If there is anything in the scrolling region that is ok, abort the
         * scroll.
         */

        for (j = r1; j <= r2; j++)
          {
             if ((SL_Screen[j].old_hash != Blank_Hash)
                 && (SL_Screen[j].old_hash == SL_Screen[j].new_hash))
               {
                  if ((j - di < r1) || (SL_Screen[j].old_hash != SL_Screen[j - di].new_hash))
                    break;
               }

          }
        if (j <= r2) continue;

        did_scroll = 1;

        /* See the above comments about BCE */
        color = This_Color;  This_Color = 0;
        (*tt_normal_video) ();
        (*tt_set_scroll_region) (r1, r2);
        (*tt_goto_rc) (0, 0);          /* relative to scroll region */
        (*tt_delete_nlines) (di);
        (*tt_reset_scroll_region) ();
        /* Now we have a hole in the screen.  Make the virtual screen look
         * like it.
         */
        for (j = r1; j <= r2; j++) SL_Screen[j].flags = TOUCHED;

        while (di--)
          {
             tmp = SL_Screen[r1].old;
             for (j = r1; j < r2; j++)
               {
                  SL_Screen[j].old = SL_Screen[j + 1].old;
                  SL_Screen[j].old_hash = SL_Screen[j + 1].old_hash;
               }
             SL_Screen[r2].old = tmp;
             blank_line (SL_Screen[r2].old, Screen_Cols, ' ');
             SL_Screen[r2].old_hash = Blank_Hash;
             r2--;
          }
        This_Color = color;
     }
   return did_scroll;
}

static void try_scroll (void)
{
   int r1, rmin, rmax;
   int num_up, num_down;
   /* find region limits. */

   for (rmax = Screen_Rows - 1; rmax > 0; rmax--)
     {
        if (SL_Screen[rmax].new_hash != SL_Screen[rmax].old_hash)
          {
             r1 = rmax - 1;
             if ((r1 == 0)
                 || (SL_Screen[r1].new_hash != SL_Screen[r1].old_hash))
               break;

             rmax = r1;
          }
     }

   for (rmin = 0; rmin < rmax; rmin++)
     {
        if (SL_Screen[rmin].new_hash != SL_Screen[rmin].old_hash)
          {
             r1 = rmin + 1;
             if ((r1 == rmax)
                 || (SL_Screen[r1].new_hash != SL_Screen[r1].old_hash))
               break;

             rmin = r1;
          }
     }

   /* Below, we have two scrolling algorithms.  The first has the effect of
    * scrolling lines down.  This is usually appropriate when one moves
    * up the display, e.g., with the UP arrow.  The second algorithm is
    * appropriate for going the other way.  It is important to choose the
    * correct one.
    */

   num_up = 0;
   for (r1 = rmin; r1 < rmax; r1++)
     {
        if (SL_Screen[r1].new_hash == SL_Screen[r1 + 1].old_hash)
          num_up++;
     }

   num_down = 0;
   for (r1 = rmax; r1 > rmin; r1--)
     {
        if (SL_Screen[r1 - 1].old_hash == SL_Screen[r1].new_hash)
          num_down++;
     }

   if (num_up > num_down)
     {
        if (try_scroll_up (rmin, rmax))
          return;

        (void) try_scroll_down (rmin, rmax);
     }
   else
     {
        if (try_scroll_down (rmin, rmax))
          return;

        (void) try_scroll_up (rmin, rmax);
     }
}
#endif   /* NOT IBMPC_SYSTEM */


#ifdef REQUIRES_NON_BCE_SUPPORT
static void adjust_colors (void)
{
   int bce;
   int i;

   bce = Bce_Color_Offset;
   Bce_Color_Offset = _SLtt_get_bce_color_offset ();
   if (bce == Bce_Color_Offset)
     return;
   
  if ((tt_Use_Blink_For_ACS != NULL)
       && (*tt_Use_Blink_For_ACS != 0))
     return;                           /* this mode does not support non-BCE
                                        * terminals.
                                        */

   for (i = 0; i < Screen_Rows; i++)
     {
        SLsmg_Char_Type *s, *smax;

        SL_Screen[i].flags |= TRASHED;
        s = SL_Screen[i].neew;
        smax = s + Screen_Cols;
        
        while (s < smax)
          {
             int color = (int) SLSMG_EXTRACT_COLOR(*s);
             int acs;

             if (color < 0)
               {
                  s++;
                  continue;
               }
             
             acs = color & 0x80;
             color = (color & 0x7F) - bce;
             color += Bce_Color_Offset;
             if (color >= 0)
               {
                  unsigned char ch = SLSMG_EXTRACT_CHAR(*s);
                  *s = SLSMG_BUILD_CHAR(ch, ((color&0x7F)|acs));
               }
             s++;
          }
     }
}
#endif

void SLsmg_refresh (void)
{
   int i;
#ifndef IBMPC_SYSTEM
   int trashed = 0;
#endif

   if (Smg_Inited == 0) return;
   
   if (Screen_Trashed)
     {
        Cls_Flag = 1;
        for (i = 0; i < Screen_Rows; i++)
          SL_Screen[i].flags |= TRASHED;
#ifdef REQUIRES_NON_BCE_SUPPORT
        adjust_colors ();
#endif
     }

#ifndef IBMPC_SYSTEM
   for (i = 0; i < Screen_Rows; i++)
     {
        if (SL_Screen[i].flags == 0) continue;
        SL_Screen[i].new_hash = compute_hash (SL_Screen[i].neew, Screen_Cols);
        trashed = 1;
     }
#endif

   if (Cls_Flag)
     {
        (*tt_normal_video) ();  (*tt_cls) ();
     }
#ifndef IBMPC_SYSTEM
   else if (trashed && (*tt_Term_Cannot_Scroll == 0)) try_scroll ();
#endif

   for (i = 0; i < Screen_Rows; i++)
     {
        if (SL_Screen[i].flags == 0) continue;

        if (Cls_Flag || SL_Screen[i].flags & TRASHED)
          {
             int color = This_Color;

             if (Cls_Flag == 0) 
               {
                  (*tt_goto_rc) (i, 0);
                  (*tt_del_eol) ();
               }
             This_Color = 0;
             blank_line (SL_Screen[i].old, Screen_Cols, ' ');
             This_Color = color;
          }

        SL_Screen[i].old[Screen_Cols] = 0;
        SL_Screen[i].neew[Screen_Cols] = 0;

        (*tt_smart_puts) (SL_Screen[i].neew, SL_Screen[i].old, Screen_Cols, i);

        SLMEMCPY ((char *) SL_Screen[i].old, (char *) SL_Screen[i].neew,
                  Screen_Cols * sizeof (SLsmg_Char_Type));

        SL_Screen[i].flags = 0;
#ifndef IBMPC_SYSTEM
        SL_Screen[i].old_hash = SL_Screen[i].new_hash;
#endif
     }

   if (point_visible (1)) (*tt_goto_rc) (This_Row - Start_Row, This_Col - Start_Col);
   (*tt_flush_output) ();
   Cls_Flag = 0;
   Screen_Trashed = 0;
}

static int compute_clip (int row, int n, int box_start, int box_end,
                         int *rmin, int *rmax)
{
   int row_max;

   if (n < 0) return 0;
   if (row >= box_end) return 0;
   row_max = row + n;
   if (row_max <= box_start) return 0;

   if (row < box_start) row = box_start;
   if (row_max >= box_end) row_max = box_end;
   *rmin = row;
   *rmax = row_max;
   return 1;
}

void SLsmg_touch_lines (int row, unsigned int n)
{
   int i;
   int r1, r2;

   /* Allow this function to be called even when we are not initialied.
    * Calling this function is useful after calling SLtt_set_color
    * to force the display to be redrawn
    */

   if (Smg_Inited == 0)
     return;

   if (0 == compute_clip (row, (int) n, Start_Row, Start_Row + Screen_Rows, &r1, &r2))
     return;

   r1 -= Start_Row;
   r2 -= Start_Row;
   for (i = r1; i < r2; i++)
     {
        SL_Screen[i].flags |= TRASHED;
     }
}

void SLsmg_touch_screen (void)
{
   Screen_Trashed = 1;
}

                          
#ifndef IBMPC_SYSTEM
static const char Fake_Alt_Char_Pairs [] = "a:j+k+l+m+q-t+u+v+w+x|n+`+f\\g#~o,<+>.v-^h#0#";

static void init_alt_char_set (void)
{
   int i;
   unsigned const char *p, *pmax;
   unsigned char ch;

   if (Alt_Char_Set[128] == 128) return;

   i = 32;
   memset ((char *)Alt_Char_Set, ' ', i);
   while (i <= 128)
     {
        Alt_Char_Set [i] = i;
        i++;
     }

   /* Map to VT100 */
   if (*tt_Has_Alt_Charset)
     {
        if (tt_Graphics_Char_Pairs == NULL) p = NULL;
        else p = (unsigned char *) *tt_Graphics_Char_Pairs;
        if (p == NULL) return;
     }
   else p = (unsigned const char *) Fake_Alt_Char_Pairs;
   pmax = p + strlen ((const char *) p);

   /* Some systems have messed up entries for this */
   while (p < pmax)
     {
        ch = *p++;
        ch &= 0x7F;                    /* should be unnecessary */
        Alt_Char_Set [ch] = *p;
        p++;
     }
}
#endif

#ifndef IBMPC_SYSTEM
# define BLOCK_SIGNALS SLsig_block_signals ()
# define UNBLOCK_SIGNALS SLsig_unblock_signals ()
#else
# define BLOCK_SIGNALS (void)0
# define UNBLOCK_SIGNALS (void)0
#endif

static int Smg_Suspended;
int SLsmg_suspend_smg (void)
{
   BLOCK_SIGNALS;

   if (Smg_Suspended == 0)
     {
        (*tt_reset_video) ();
        Smg_Suspended = 1;
     }

   UNBLOCK_SIGNALS;
   return 0;
}

int SLsmg_resume_smg (void)
{
   BLOCK_SIGNALS;

   if (Smg_Suspended == 0)
     {
        UNBLOCK_SIGNALS;
        return 0;
     }

   Smg_Suspended = 0;

   if (-1 == (*tt_init_video) ())
     {
        UNBLOCK_SIGNALS;
        return -1;
     }

   Cls_Flag = 1;
   SLsmg_touch_screen ();
   SLsmg_refresh ();

   UNBLOCK_SIGNALS;
   return 0;
}

   
static void reset_smg (void)
{
   int i;
   if (Smg_Inited == 0)
     return;

   for (i = 0; i < Screen_Rows; i++)
     {
        SLfree ((char *)SL_Screen[i].old);
        SLfree ((char *)SL_Screen[i].neew);
        SL_Screen[i].old = SL_Screen[i].neew = NULL;
     }
   This_Alt_Char = This_Color = 0;
   Smg_Inited = 0;
}


static int init_smg (void)
{
   int i, len;
   SLsmg_Char_Type *old, *neew;

   Smg_Inited = 0;

#ifdef REQUIRES_NON_BCE_SUPPORT
   Bce_Color_Offset = _SLtt_get_bce_color_offset ();
#endif

   Screen_Rows = *tt_Screen_Rows;
   if (Screen_Rows > SLTT_MAX_SCREEN_ROWS)
     Screen_Rows = SLTT_MAX_SCREEN_ROWS;

   Screen_Cols = *tt_Screen_Cols;

   This_Col = This_Row = Start_Col = Start_Row = 0;

   This_Alt_Char = 0;
   SLsmg_set_color (0);
   Cls_Flag = 1;
#ifndef IBMPC_SYSTEM
   init_alt_char_set ();
#endif
   len = Screen_Cols + 3;
   for (i = 0; i < Screen_Rows; i++)
     {
        if ((NULL == (old = (SLsmg_Char_Type *) SLmalloc (sizeof(SLsmg_Char_Type) * len)))
            || ((NULL == (neew = (SLsmg_Char_Type *) SLmalloc (sizeof(SLsmg_Char_Type) * len)))))
          {
             SLfree ((char *) old);
             return -1;
          }
        blank_line (old, len, ' ');
        blank_line (neew, len, ' ');
        SL_Screen[i].old = old;
        SL_Screen[i].neew = neew;
        SL_Screen[i].flags = 0;
#ifndef IBMPC_SYSTEM
        Blank_Hash = compute_hash (old, Screen_Cols);
        SL_Screen[i].new_hash = SL_Screen[i].old_hash =  Blank_Hash;
#endif
     }
   
   _SLtt_color_changed_hook = SLsmg_touch_screen;
   Screen_Trashed = 1;
   Smg_Inited = 1;
   return 0;
}


int SLsmg_init_smg (void)
{
   int ret;

   BLOCK_SIGNALS;

   if (Smg_Inited)
     SLsmg_reset_smg ();

   if (-1 == (*tt_init_video) ())
     {
        UNBLOCK_SIGNALS;
        return -1;
     }
   
   if (-1 == (ret = init_smg ()))
     (void) (*tt_reset_video)();

   UNBLOCK_SIGNALS;
   return ret;
}

int SLsmg_reinit_smg (void)
{
   int ret;

   if (Smg_Inited == 0)
     return SLsmg_init_smg ();

   BLOCK_SIGNALS;
   reset_smg ();
   ret = init_smg ();
   UNBLOCK_SIGNALS;
   return ret;
}

void SLsmg_reset_smg (void)
{   
   if (Smg_Inited == 0)
     return;
   
   BLOCK_SIGNALS;

   reset_smg ();
   (*tt_reset_video)();

   UNBLOCK_SIGNALS;
}

SLsmg_Char_Type SLsmg_char_at (void)
{
   if (Smg_Inited == 0) return 0;

   if (point_visible (1))
     {
        return SL_Screen[This_Row - Start_Row].neew[This_Col - Start_Col];
     }
   return 0;
}

void SLsmg_vprintf (char *fmt, va_list ap)
{
   char buf[1024];

   if (Smg_Inited == 0) return;

   (void) _SLvsnprintf (buf, sizeof (buf), fmt, ap);
   SLsmg_write_string (buf);
}

void SLsmg_printf (char *fmt, ...)
{
   va_list ap;
   unsigned int len;
   char *f;

   if (Smg_Inited == 0) return;

   va_start(ap, fmt);

   f = fmt;
   while (*f && (*f != '%'))
     f++;
   len = (unsigned int) (f - fmt);
   if (len) SLsmg_write_nchars (fmt, len);

   if (*f != 0)
     SLsmg_vprintf (f, ap);

   va_end (ap);
}

void SLsmg_set_screen_start (int *r, int *c)
{
   int orow = Start_Row, oc = Start_Col;

   if (Smg_Inited == 0) return;

   if (c == NULL) Start_Col = 0;
   else
     {
        Start_Col = *c;
        *c = oc;
     }
   if (r == NULL) Start_Row = 0;
   else
     {
        Start_Row = *r;
        *r = orow;
     }
}

void SLsmg_draw_object (int r, int c, unsigned char object)
{
   This_Row = r;  This_Col = c;

   if (Smg_Inited == 0) return;

   if (point_visible (1))
     {
        int color = This_Color;
        This_Color |= ALT_CHAR_FLAG;
        SLsmg_write_char (object);
        This_Color = color;
     }

   This_Col = c + 1;
}

void SLsmg_draw_hline (unsigned int n)
{
   static unsigned char hbuf[16];
   int count;
   int cmin, cmax;
   int final_col = This_Col + (int) n;
   int save_color;

   if (Smg_Inited == 0) return;

   if ((This_Row < Start_Row) || (This_Row >= Start_Row + Screen_Rows)
       || (0 == compute_clip (This_Col, n, Start_Col, Start_Col + Screen_Cols,
                              &cmin, &cmax)))
     {
        This_Col = final_col;
        return;
     }

   if (hbuf[0] == 0)
     {
        SLMEMSET ((char *) hbuf, SLSMG_HLINE_CHAR, 16);
     }

   n = (unsigned int)(cmax - cmin);
   count = n / 16;

   save_color = This_Color;
   This_Color |= ALT_CHAR_FLAG;
   This_Col = cmin;

   SLsmg_write_nchars ((char *) hbuf, n % 16);
   while (count-- > 0)
     {
        SLsmg_write_nchars ((char *) hbuf, 16);
     }

   This_Color = save_color;
   This_Col = final_col;
}

void SLsmg_draw_vline (int n)
{
   unsigned char ch = SLSMG_VLINE_CHAR;
   int c = This_Col, rmin, rmax;
   int final_row = This_Row + n;
   int save_color;

   if (Smg_Inited == 0) return;

   if (((c < Start_Col) || (c >= Start_Col + Screen_Cols)) ||
       (0 == compute_clip (This_Row, n, Start_Row, Start_Row + Screen_Rows,
                          &rmin, &rmax)))
     {
        This_Row = final_row;
        return;
     }

   save_color = This_Color;
   This_Color |= ALT_CHAR_FLAG;

   for (This_Row = rmin; This_Row < rmax; This_Row++)
     {
        This_Col = c;
        SLsmg_write_nchars ((char *) &ch, 1);
     }

   This_Col = c;  This_Row = final_row;
   This_Color = save_color;
}

void SLsmg_draw_box (int r, int c, unsigned int dr, unsigned int dc)
{
   if (Smg_Inited == 0) return;

   if (!dr || !dc) return;
   This_Row = r;  This_Col = c;
   dr--; dc--;
   SLsmg_draw_hline (dc);
   SLsmg_draw_vline (dr);
   This_Row = r;  This_Col = c;
   SLsmg_draw_vline (dr);
   SLsmg_draw_hline (dc);
   SLsmg_draw_object (r, c, SLSMG_ULCORN_CHAR);
   SLsmg_draw_object (r, c + (int) dc, SLSMG_URCORN_CHAR);
   SLsmg_draw_object (r + (int) dr, c, SLSMG_LLCORN_CHAR);
   SLsmg_draw_object (r + (int) dr, c + (int) dc, SLSMG_LRCORN_CHAR);
   This_Row = r; This_Col = c;
}

void SLsmg_fill_region (int r, int c, unsigned int dr, unsigned int dc, unsigned char ch)
{
   static unsigned char hbuf[16];
   int count;
   int dcmax, rmax;

   if (Smg_Inited == 0) return;

   SLsmg_gotorc (r, c);
   r = This_Row; c = This_Col;

   dcmax = Screen_Cols - This_Col;
   if (dcmax < 0)
     return;

   if (dc > (unsigned int) dcmax) dc = (unsigned int) dcmax;

   rmax = This_Row + dr;
   if (rmax > Screen_Rows) rmax = Screen_Rows;

#if 0
   ch = Alt_Char_Set[ch];
#endif
   if (ch != hbuf[0]) SLMEMSET ((char *) hbuf, (char) ch, 16);

   for (This_Row = r; This_Row < rmax; This_Row++)
     {
        This_Col = c;
        count = dc / 16;
        SLsmg_write_nchars ((char *) hbuf, dc % 16);
        while (count-- > 0)
          {
             SLsmg_write_nchars ((char *) hbuf, 16);
          }
     }

   This_Row = r;
}

void SLsmg_forward (int n)
{
   This_Col += n;
}

void SLsmg_write_color_chars (SLsmg_Char_Type *s, unsigned int len)
{
   SLsmg_Char_Type *smax, sh;
   char buf[32], *b, *bmax;
   int color, save_color;

   if (Smg_Inited == 0) return;

   smax = s + len;
   b = buf;
   bmax = b + sizeof (buf);

   save_color = This_Color;

   while (s < smax)
     {
        sh = *s++;

        color = SLSMG_EXTRACT_COLOR(sh);

#if REQUIRES_NON_BCE_SUPPORT
        if (Bce_Color_Offset)
          {
             if (color & 0x80)
               color = ((color & 0x7F) + Bce_Color_Offset) | 0x80;
             else
               color = ((color & 0x7F) + Bce_Color_Offset) & 0x7F;
          }
#endif

        if ((color != This_Color) || (b == bmax))
          {
             if (b != buf)
               {
                  SLsmg_write_nchars (buf, (int) (b - buf));
                  b = buf;
               }
             This_Color = color;
          }
        *b++ = (char) SLSMG_EXTRACT_CHAR(sh);
     }

   if (b != buf)
     SLsmg_write_nchars (buf, (unsigned int) (b - buf));

   This_Color = save_color;
}

unsigned int SLsmg_read_raw (SLsmg_Char_Type *buf, unsigned int len)
{
   unsigned int r, c;

   if (Smg_Inited == 0) return 0;

   if (0 == point_visible (1)) return 0;

   r = (unsigned int) (This_Row - Start_Row);
   c = (unsigned int) (This_Col - Start_Col);

   if (c + len > (unsigned int) Screen_Cols)
     len = (unsigned int) Screen_Cols - c;

   memcpy ((char *) buf, (char *) (SL_Screen[r].neew + c), len * sizeof (SLsmg_Char_Type));
   return len;
}

unsigned int SLsmg_write_raw (SLsmg_Char_Type *buf, unsigned int len)
{
   unsigned int r, c;
   SLsmg_Char_Type *dest;

   if (Smg_Inited == 0) return 0;

   if (0 == point_visible (1)) return 0;

   r = (unsigned int) (This_Row - Start_Row);
   c = (unsigned int) (This_Col - Start_Col);

   if (c + len > (unsigned int) Screen_Cols)
     len = (unsigned int) Screen_Cols - c;

   dest = SL_Screen[r].neew + c;

   if (0 != memcmp ((char *) dest, (char *) buf, len * sizeof (SLsmg_Char_Type)))
     {
        memcpy ((char *) dest, (char *) buf, len * sizeof (SLsmg_Char_Type));
        SL_Screen[r].flags |= TOUCHED;
     }
   return len;
}

void
SLsmg_set_color_in_region (int color, int r, int c, unsigned int dr, unsigned int dc)
{
   int cmax, rmax;
   SLsmg_Char_Type char_mask;

   if (Smg_Inited == 0) return;

   c -= Start_Col;
   r -= Start_Row;

   cmax = c + (int) dc;
   rmax = r + (int) dr;

   if (cmax > Screen_Cols) cmax = Screen_Cols;
   if (rmax > Screen_Rows) rmax = Screen_Rows;

   if (c < 0) c = 0;
   if (r < 0) r = 0;

#if REQUIRES_NON_BCE_SUPPORT
   if (Bce_Color_Offset)
     {
        if (color & 0x80)
          color = ((color & 0x7F) + Bce_Color_Offset) | 0x80;
        else
          color = ((color & 0x7F) + Bce_Color_Offset) & 0x7F;
     }
#endif
   color = color << 8;

   char_mask = 0xFF;

#ifndef IBMPC_SYSTEM
   if ((tt_Use_Blink_For_ACS == NULL)
       || (0 == *tt_Use_Blink_For_ACS))
     char_mask = 0x80FF;
#endif

   while (r < rmax)
     {
        SLsmg_Char_Type *s, *smax;

        SL_Screen[r].flags |= TOUCHED;
        s = SL_Screen[r].neew;
        smax = s + cmax;
        s += c;

        while (s < smax)
          {
             *s = (*s & char_mask) | color;
             s++;
          }
        r++;
     }
}

void SLsmg_set_terminal_info (SLsmg_Term_Type *tt)
{
   if (tt == NULL)                     /* use default */
     return;

   if ((tt->tt_normal_video == NULL)
       || (tt->tt_goto_rc == NULL)
       || (tt->tt_cls == NULL)
       || (tt->tt_del_eol == NULL)
       || (tt->tt_smart_puts == NULL)
       || (tt->tt_flush_output == NULL)
       || (tt->tt_reset_video == NULL)
       || (tt->tt_init_video == NULL)
#ifndef IBMPC_SYSTEM
       || (tt->tt_set_scroll_region == NULL)
       || (tt->tt_reverse_index == NULL)
       || (tt->tt_reset_scroll_region == NULL)
       || (tt->tt_delete_nlines == NULL)
       /* Variables */
       || (tt->tt_term_cannot_scroll == NULL)
       || (tt->tt_has_alt_charset == NULL)
#if 0 /* These can be NULL */
       || (tt->tt_use_blink_for_acs == NULL)
       || (tt->tt_graphic_char_pairs == NULL)
#endif
       || (tt->tt_screen_cols == NULL)
       || (tt->tt_screen_rows == NULL)
#endif
       )
     SLang_exit_error ("Terminal not powerful enough for SLsmg");

   tt_normal_video = tt->tt_normal_video;
   tt_goto_rc = tt->tt_goto_rc;
   tt_cls = tt->tt_cls;
   tt_del_eol = tt->tt_del_eol;
   tt_smart_puts = tt->tt_smart_puts;
   tt_flush_output = tt->tt_flush_output;
   tt_reset_video = tt->tt_reset_video;
   tt_init_video = tt->tt_init_video;

#ifndef IBMPC_SYSTEM
   tt_set_scroll_region = tt->tt_set_scroll_region;
   tt_reverse_index = tt->tt_reverse_index;
   tt_reset_scroll_region = tt->tt_reset_scroll_region;
   tt_delete_nlines = tt->tt_delete_nlines;

   tt_Term_Cannot_Scroll = tt->tt_term_cannot_scroll;
   tt_Has_Alt_Charset = tt->tt_has_alt_charset;
   tt_Use_Blink_For_ACS = tt->tt_use_blink_for_acs;
   tt_Graphics_Char_Pairs = tt->tt_graphic_char_pairs;
#endif

   tt_Screen_Cols = tt->tt_screen_cols;
   tt_Screen_Rows = tt->tt_screen_rows;
}