display.c

/* display.c: Routines for printing the Spectrum screen
   Copyright (c) 1999-2006 Philip Kendall, Thomas Harte, Witold Filipczyk
                           and Fredrick Meunier

   $Id: display.c 3482 2008-01-07 12:32:26Z pak21 $

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

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

   Author contact information:

   E-mail: philip-fuse@shadowmagic.org.uk

*/

#include <config.h>

#include <assert.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

#include "display.h"
#include "event.h"
#include "fuse.h"
#include "machine.h"
#include "screenshot.h"
#include "settings.h"
#include "spectrum.h"
#include "ui/ui.h"
#include "ui/uidisplay.h"
#include "scld.h"

/* Set once we have initialised the UI */
int display_ui_initialised = 0;

/* The current border colour */
libspectrum_byte display_lores_border;
libspectrum_byte display_hires_border;
libspectrum_byte display_last_border;

/* Stores the pixel, attribute and SCLD screen mode information used to
   draw each 8x1 group of pixels (including border) last frame */
static libspectrum_dword
display_last_screen[ DISPLAY_SCREEN_WIDTH_COLS * DISPLAY_SCREEN_HEIGHT ];

/* Offsets as to where the data and the attributes for each pixel
   line start */
libspectrum_word display_line_start[ DISPLAY_HEIGHT ];
libspectrum_word display_attr_start[ DISPLAY_HEIGHT ];

/* If you write to the byte at display_dirty_?table[n+0x4000], then
   the eight pixels starting at (8*xtable[n],ytable[n]) must be
   replotted */
static libspectrum_word
  display_dirty_ytable[ DISPLAY_WIDTH_COLS * DISPLAY_HEIGHT ];
static libspectrum_word
  display_dirty_xtable[ DISPLAY_WIDTH_COLS * DISPLAY_HEIGHT ];

/* If you write to the byte at display_dirty_?table2[n+0x5800], then
   the 64 pixels starting at (8*xtable2[n],ytable2[n]) must be
   replotted */
static libspectrum_word
  display_dirty_ytable2[ DISPLAY_WIDTH_COLS * DISPLAY_HEIGHT_ROWS ];
static libspectrum_word
  display_dirty_xtable2[ DISPLAY_WIDTH_COLS * DISPLAY_HEIGHT_ROWS ];

/* The number of frames mod 32 that have elapsed.
    0<=d_f_c<16 => Flashing characters are normal
   16<=d_f_c<32 => Flashing characters are reversed
*/
static int display_frame_count;
static int display_flash_reversed;

/* Which eight-pixel chunks on each line (including border) need to
   be redisplayed. Bit 0 corresponds to pixels 0-7, bit 39 to
   pixels 311-319. */
static libspectrum_qword display_is_dirty[ DISPLAY_SCREEN_HEIGHT ];

/* Which eight-pixel chunks on each line may need to be redisplayed. Bit 0
   corresponds to pixels 0-7, bit 31 to pixels 248-255. */
static libspectrum_dword display_maybe_dirty[ DISPLAY_HEIGHT ];

/* This value signifies that the entire line must be redisplayed */
static libspectrum_qword display_all_dirty;

/* Used to signify that we're redrawing the entire screen */
static int display_redraw_all;

/* Value used to signify a border line has more than one colour on it. */
static const int display_border_mixed = 0xff;

/* Used for grouping screen writes together */
struct rectangle { int x,y; int w,h; };

/* Those rectangles which were modified on the last line to be displayed */
struct rectangle *active_rectangle = NULL;
size_t active_rectangle_count = 0, active_rectangle_allocated = 0;

/* Those rectangles which weren't */
struct rectangle *inactive_rectangle = NULL;
size_t inactive_rectangle_count = 0, inactive_rectangle_allocated = 0;

/* The last point at which we updated the screen display */
int critical_region_x = 0, critical_region_y = 0;

/* The border colour changes which have occurred in this frame */
struct border_change_t {
  int x, y;
  int colour;
};

static struct border_change_t border_change_end_sentinel =
  { DISPLAY_SCREEN_WIDTH_COLS, DISPLAY_SCREEN_HEIGHT - 1, 0 };

/* The current border colour */
int current_border[ DISPLAY_SCREEN_HEIGHT ][ DISPLAY_SCREEN_WIDTH_COLS ];

static void display_dirty8( libspectrum_word address );
static void display_dirty64( libspectrum_word address );

static void display_get_attr( int x, int y,
			      libspectrum_byte *ink, libspectrum_byte *paper);

static int add_rectangle( int y, int x, int w );
static int end_line( int y );

static void display_dirty_flashing(void);

static int border_changes_last = 0;
static struct border_change_t *border_changes = NULL;

static struct border_change_t *
alloc_change(void)
{
  static int border_changes_size = 0;

  if( border_changes_size == border_changes_last ) {
    border_changes_size += 10;
    border_changes = realloc( border_changes,
                              border_changes_size*
                                sizeof( struct border_change_t )
                            );
    if( !border_changes ) {
      ui_error( UI_ERROR_ERROR, "out of memory at %s:%d", __FILE__, __LINE__ );
      fuse_abort();
    }
  }
  return border_changes + border_changes_last++; 
}

static int
add_border_sentinel( void )
{
  struct border_change_t *sentinel = alloc_change();

  sentinel->x = sentinel->y = 0;
  sentinel->colour = scld_last_dec.name.hires ?
                            display_hires_border : display_lores_border;

  return 0;
}

int
display_init( int *argc, char ***argv )
{
  int i, j, k, x, y;
  int error;

  if(ui_init(argc, argv))
    return 1;

  /* Set up the 'all pixels must be refreshed' marker */
  display_all_dirty = 0;
  for( i = 0; i < DISPLAY_SCREEN_WIDTH_COLS; i++ )
    display_all_dirty = ( display_all_dirty << 1 ) | 0x01;

  for(i=0;i<3;i++)
    for(j=0;j<8;j++)
      for(k=0;k<8;k++)
	display_line_start[ (64*i) + (8*j) + k ] =
	  32 * ( (64*i) + j + (k*8) );

  for(y=0;y<DISPLAY_HEIGHT;y++) {
    display_attr_start[y]=6144 + (32*(y/8));
  }

  for(y=0;y<DISPLAY_HEIGHT;y++)
    for(x=0;x<DISPLAY_WIDTH_COLS;x++) {
      display_dirty_ytable[ display_line_start[y]+x ] = y;
      display_dirty_xtable[ display_line_start[y]+x ] = x;
    }

  for(y=0;y<DISPLAY_HEIGHT_ROWS;y++)
    for(x=0;x<DISPLAY_WIDTH_COLS;x++) {
      display_dirty_ytable2[ (32*y) + x ] = y * 8;
      display_dirty_xtable2[ (32*y) + x ] = x;
    }

  display_frame_count=0; display_flash_reversed=0;

  display_refresh_all();

  border_changes_last = 0;
  if( border_changes ) {
    free( border_changes );
  }
  border_changes = NULL;
  error = add_border_sentinel(); if( error ) return error;
  display_last_border = scld_last_dec.name.hires ?
                            display_hires_border : display_lores_border;

  return 0;
}

/* Add the rectangle { x, line, w, 1 } to the list of rectangles to be
   redrawn, either by extending an existing rectangle or creating a
   new one */
static int
add_rectangle( int y, int x, int w )
{
  size_t i;
  struct rectangle *ptr;

  /* Check through all 'active' rectangles (those which were modified
     on the previous line) and see if we can use this new rectangle
     to extend them */
  for( i = 0; i < active_rectangle_count; i++ ) {

    if( active_rectangle[i].x == x &&
	active_rectangle[i].w == w    ) {
      active_rectangle[i].h++;
      return 0;
    }
  }

  /* We couldn't find a rectangle to extend, so create a new one */
  if( ++active_rectangle_count > active_rectangle_allocated ) {

    size_t new_alloc;

    new_alloc = active_rectangle_allocated     ?
                2 * active_rectangle_allocated :
                8;

    ptr = realloc( active_rectangle, new_alloc * sizeof( struct rectangle ) );
    if( !ptr ) {
      ui_error( UI_ERROR_ERROR, "Out of memory at %s:%d", __FILE__, __LINE__ );
      return 1;
    }

    active_rectangle_allocated = new_alloc; active_rectangle = ptr;
  }

  ptr = &active_rectangle[ active_rectangle_count - 1 ];

  ptr->x = x; ptr->y = y;
  ptr->w = w; ptr->h = 1;

  return 0;
}

#ifndef MAX
#define MAX(a,b)    (((a) > (b)) ? (a) : (b))
#define MIN(a,b)    (((a) < (b)) ? (a) : (b))
#endif

inline static int
compare_and_merge_rectangles( struct rectangle *source )
{
  size_t z;

  /* Now look to see if there is an overlapping rectangle in the inactive
     list.  These occur when frame skip is on and the same lines are
     covered more than once... */
  for( z = 0; z < inactive_rectangle_count; z++ ) {
    if( inactive_rectangle[z].x == source->x &&
          inactive_rectangle[z].w == source->w ) {
      if( inactive_rectangle[z].y == source->y &&
            inactive_rectangle[z].h == source->h )
        return 1;

      if( ( inactive_rectangle[z].y < source->y && 
          ( source->y < ( inactive_rectangle[z].y +
            inactive_rectangle[z].h + 1 ) ) ) ||
          ( source->y < inactive_rectangle[z].y && 
          ( inactive_rectangle[z].y < ( source->y + source->h + 1 ) ) ) ) {
        /* rects overlap or touch in the y dimension, merge */
        inactive_rectangle[z].h = MAX( inactive_rectangle[z].y +
                                    inactive_rectangle[z].h,
                                    source->y + source->h ) -
                                  MIN( inactive_rectangle[z].y, source->y );
        inactive_rectangle[z].y = MIN( inactive_rectangle[z].y, source->y );

        return 1;
      }
    }
    if( inactive_rectangle[z].y == source->y &&
          inactive_rectangle[z].h == source->h ) {

      if( (inactive_rectangle[z].x < source->x && 
          ( source->x < ( inactive_rectangle[z].x +
            inactive_rectangle[z].w + 1 ) ) ) ||
          ( source->x < inactive_rectangle[z].x && 
          ( inactive_rectangle[z].x < ( source->x + source->w + 1 ) ) ) ) {
        /* rects overlap or touch in the x dimension, merge */
        inactive_rectangle[z].w = MAX( inactive_rectangle[z].x +
          inactive_rectangle[z].w, source->x +
          source->w ) - MIN( inactive_rectangle[z].x, source->x );
        inactive_rectangle[z].x = MIN( inactive_rectangle[z].x, source->x );
        return 1;
      }
    }
     /* Handle overlaps offset by both x and y? how much overlap and hence 
        overdraw can be tolerated? */
  }
  return 0;
}

/* Move all rectangles not updated on this line to the inactive list */
static int
end_line( int y )
{
  size_t i;
  struct rectangle *ptr;

  for( i = 0; i < active_rectangle_count; i++ ) {

    /* Skip if this rectangle was updated this line */
    if( active_rectangle[i].y + active_rectangle[i].h == y + 1 ) continue;

    if ( settings_current.frame_rate > 1 &&
	 compare_and_merge_rectangles( &active_rectangle[i] ) ) {

      /* Mark the active rectangle as done */
      active_rectangle[i].h = 0;
      continue;
    }

    /* We couldn't find a rectangle to extend, so create a new one */
    if( ++inactive_rectangle_count > inactive_rectangle_allocated ) {

      size_t new_alloc;

      new_alloc = inactive_rectangle_allocated     ?
	          2 * inactive_rectangle_allocated :
	          8;

      ptr = realloc( inactive_rectangle,
		     new_alloc * sizeof( struct rectangle ) );
      if( !ptr ) {
	ui_error( UI_ERROR_ERROR, "Out of memory at %s:%d",
		  __FILE__, __LINE__ );
	return 1;
      }

      inactive_rectangle_allocated = new_alloc; inactive_rectangle = ptr;
    }

    inactive_rectangle[ inactive_rectangle_count - 1 ] = active_rectangle[i];

    /* Mark the active rectangle as done */
    active_rectangle[i].h = 0;
  }

  /* Compress the list of active rectangles */
  for( i = 0, ptr = active_rectangle; i < active_rectangle_count; i++ ) {
    if( active_rectangle[i].h == 0 ) continue;
    *ptr = active_rectangle[i]; ptr++;
  }

  active_rectangle_count = ptr - active_rectangle;

  return 0;
}

/* Mark as 'dirty' the pixels which have been changed by a write to
   'offset' within the RAM page containing the screen */
void
display_dirty( libspectrum_word offset )
{
  switch ( scld_last_dec.mask.scrnmode ) {

    case STANDARD: /* standard Speccy screen */
    case HIRESATTR: /* strange mode */
      if( offset >= 0x1b00 ) break;
      if( offset <  0x1800 ) {		/* 0x1800 = first attributes byte */
        display_dirty8( offset );
      } else {
        display_dirty64( offset );
      }
      break;

    case ALTDFILE: /* second screen */
    case HIRESATTRALTD: /* strange mode using second screen */      
      if( offset < 0x2000 || offset >= 0x3b00 ) break;
      if( offset < 0x3800 ) {		/* 0x3800 = first attributes byte */
        display_dirty8( offset - ALTDFILE_OFFSET );
      } else {
        display_dirty64( offset - ALTDFILE_OFFSET );
      }
      break;

    case EXTCOLOUR: /* extended colours */
    case HIRES: /* hires mode */
      if( offset >= 0x3800 ) break;
      if( offset >= 0x1800 && offset < 0x2000 ) break;
      if( offset >= 0x2000 ) offset -= ALTDFILE_OFFSET;
      display_dirty8( offset );
      break;

    default:
    /* case EXTCOLALTD: extended colours, but attributes and data
       taken from second screen */
    /* case HIRESDOUBLECOL: hires mode, but data taken only from
       second screen */
      if( offset >= 0x2000 && offset < 0x3800 )
	display_dirty8( offset - ALTDFILE_OFFSET );
      break;
  }
}

/* Get the attribute byte or equivalent for the eight pixels starting at
   ( (8*x) , y ) */
static inline libspectrum_byte
display_get_attr_byte( int x, int y )
{
  libspectrum_byte attr;

  if ( scld_last_dec.name.hires ) {
    attr = hires_get_attr();
  } else {

    libspectrum_word offset;

    if( scld_last_dec.name.b1 ) {
      offset = display_line_start[y] + x + ALTDFILE_OFFSET;
    } else if( scld_last_dec.name.altdfile ) {
      offset = display_attr_start[y] + x + ALTDFILE_OFFSET;
    } else {
      offset = display_attr_start[y] + x;
    }

    attr = RAM[ memory_current_screen ][ offset ];
  }

  return attr;
}

static void
update_dirty_rects( void )
{
  int start, y, error;

  for( y=0; y<DISPLAY_SCREEN_HEIGHT; y++ ) {
    int x = 0;
    while( display_is_dirty[y] ) {

      /* Find the first dirty chunk on this row */
      while( !( display_is_dirty[y] & 0x01 ) ) {
        display_is_dirty[y] >>= 1;
        x++;
      }

      start = x;

      /* Walk to the end of the dirty region */
      do {
        display_is_dirty[y] >>= 1;
        x++;
      } while( display_is_dirty[y] & 0x01 );

      error = add_rectangle( y, start, x - start );
      if( error ) return;
    }

    /* compress the active rectangles list */
    error = end_line( y ); if( error ) return;
  }

  /* Force all rectangles into the inactive list */
  error = end_line( DISPLAY_SCREEN_HEIGHT ); if( error ) return;
}

static void
write_if_dirty( int x, int y )
{
  int beam_x, beam_y;
  int index;
  libspectrum_word offset;
  libspectrum_byte *screen;
  libspectrum_dword data, data2;
  libspectrum_dword mode_data;
  libspectrum_dword last_chunk_detail;

  beam_x = x + DISPLAY_BORDER_WIDTH_COLS;
  beam_y = y + DISPLAY_BORDER_HEIGHT;
  offset = display_get_addr( x, y );

  /* Read byte, atrr/byte, and screen mode */
  screen = RAM[ memory_current_screen ];
  data = screen[ offset ];
  mode_data = scld_last_dec.byte;

  if( scld_last_dec.name.hires ) {
    switch( scld_last_dec.mask.scrnmode ) {

    case HIRESATTRALTD:
      offset = display_attr_start[ y ] + x + ALTDFILE_OFFSET;
      data2 = screen[ offset ];
      break;

    case HIRES:
      data2 = screen[ offset + ALTDFILE_OFFSET ];
      break;

    case HIRESDOUBLECOL:
      data2 = data;
      break;

    default: /* case HIRESATTR: */
      offset = display_attr_start[ y ] + x;
      data2 = screen[ offset ];
      break;

    }
  } else {
    data2 = display_get_attr_byte( x, y );
  }

  last_chunk_detail = (display_flash_reversed << 24) | (mode_data << 16) |
                      (data2 << 8) | data;
  /* And draw it if it is different to what was there last time */
  index = beam_x + beam_y * DISPLAY_SCREEN_WIDTH_COLS;
  if( display_last_screen[ index ] != last_chunk_detail ) {
    libspectrum_byte ink, paper;
    display_get_attr( x, y, &ink, &paper );
    if( scld_last_dec.name.hires ) {
      libspectrum_word hires_data = (data << 8) + data2;
      uidisplay_plot16( beam_x, beam_y, hires_data, ink, paper );
    } else {
      uidisplay_plot8( beam_x, beam_y, data, ink, paper );
    }

    /* Update last display record */
    display_last_screen[ index ] = last_chunk_detail;

    /* And now mark it dirty */
    display_is_dirty[ beam_y ] |= ( (libspectrum_qword)1 << beam_x );
  }
}

/* Plot any dirty data from ( x, y ) to ( end, y ) of the critical
   region to the drawing region */
static void
copy_critical_region_line( int y, int x, int end )
{
  int start;
  libspectrum_dword bit_mask, dirty;

  if( x < DISPLAY_WIDTH_COLS ) {

    /* Build a mask for the bits we're interested in */
    bit_mask = display_all_dirty;

    bit_mask >>= x;
    bit_mask <<= x + ( 32 - end );
    bit_mask >>= ( 32 - end );

    /* Get the bits we're interested in */
    dirty = ( display_maybe_dirty[y] & bit_mask ) >> x;

    /* And remove those bits from the dirty mask */
    display_maybe_dirty[y] &= ~bit_mask;

  } else {

    dirty = 0;

  }

  while( dirty ) {

    /* Find the first dirty chunk on this row */
    while( !( dirty & 0x01 ) ) {

      dirty >>= 1;
      x++;

    }

    start = x;

    /* Walk to the end of the dirty region, writing the bytes to the
       drawing area along the way */
    do {

      write_if_dirty( x, y );

      dirty >>= 1;
      x++;

    } while( dirty & 0x01 );

  }
  
}

/* Copy any dirty data from the critical region to the drawing region */
static void
copy_critical_region( int beam_x, int beam_y )
{
  if( critical_region_y == beam_y ) {

    copy_critical_region_line( critical_region_y, critical_region_x, beam_x );

  } else {

    copy_critical_region_line( critical_region_y++, critical_region_x,
			       DISPLAY_WIDTH_COLS );
  
    for( ; critical_region_y < beam_y; critical_region_y++ )
      copy_critical_region_line( critical_region_y, 0,
				 DISPLAY_WIDTH_COLS );

    copy_critical_region_line( critical_region_y, 0, beam_x );
  }

  critical_region_x = beam_x;
}

inline static void
get_beam_position( int *x, int *y )
{
  if( tstates < machine_current->line_times[ 0 ] ) {
    *x = *y = -1;
    return;
  }

  *y = ( tstates - machine_current->line_times[ 0 ] ) /
    machine_current->timings.tstates_per_line;

  if( *y >= 0 && *y <= DISPLAY_SCREEN_HEIGHT )
    *x = ( tstates - machine_current->line_times[ *y ] ) / 4;
  else *x = 0;
}

void
display_update_critical( int x, int y )
{
  int beam_x, beam_y;

  get_beam_position( &beam_x, &beam_y );

  beam_x -= DISPLAY_BORDER_WIDTH_COLS;
  beam_y -= DISPLAY_BORDER_HEIGHT;

  if( beam_y < 0 ) {
    beam_x = beam_y = 0;
  } else if( beam_y >= DISPLAY_HEIGHT ) {
    beam_x = DISPLAY_WIDTH_COLS;
    beam_y = DISPLAY_HEIGHT - 1;
  }

  if( beam_x < 0 ) {
    beam_x = 0;
  } else if( beam_x > DISPLAY_WIDTH_COLS ) {
    beam_x = DISPLAY_WIDTH_COLS;
  }

  if(   y <  beam_y                 ||
      ( y == beam_y && x < beam_x )    )
    copy_critical_region( beam_x, beam_y );
}

/* Mark the 8-pixel chunk at (x,y) as maybe dirty and update the critical
   region as appropriate */
inline static void
display_dirty_chunk( int x, int y )
{
  /* If the write is between the start of the critical region and the
     current beam position, then we must copy the critical region now */
  if(   y >  critical_region_y                             ||
      ( y == critical_region_y && x >= critical_region_x )    ) {

    display_update_critical( x, y );
  }

  display_maybe_dirty[y] |= ( (libspectrum_dword)1 << x );
}

static void
display_dirty8( libspectrum_word offset )
{
  int x, y;

  x=display_dirty_xtable[ offset ];
  y=display_dirty_ytable[ offset ];

  display_dirty_chunk( x, y );
}

static void
display_dirty64( libspectrum_word offset )
{
  int i, x, y;

  x=display_dirty_xtable2[ offset - 0x1800 ];
  y=display_dirty_ytable2[ offset - 0x1800 ];

  for( i = 0; i < 8; i++ ) display_dirty_chunk( x, y + i );
}

/* Get the attributes for the eight pixels starting at
   ( (8*x) , y ) */
static void
display_get_attr( int x, int y,
                  libspectrum_byte *ink, libspectrum_byte *paper )
{
  display_parse_attr( display_get_attr_byte( x, y ), ink, paper );
}

void
display_parse_attr( libspectrum_byte attr,
		    libspectrum_byte *ink, libspectrum_byte *paper )
{
  if( (attr & 0x80) && display_flash_reversed ) {
    *ink  = (attr & ( 0x0f << 3 ) ) >> 3;
    *paper= (attr & 0x07) + ( (attr & 0x40) >> 3 );
  } else {
    *ink= (attr & 0x07) + ( (attr & 0x40) >> 3 );
    *paper= (attr & ( 0x0f << 3 ) ) >> 3;
  }
}

static void
push_border_change( int colour )
{
  int beam_x, beam_y;
  struct border_change_t *change;

  get_beam_position( &beam_x, &beam_y );

  if( beam_y >= DISPLAY_SCREEN_HEIGHT ) return;

  if( beam_x < 0 ) beam_x = 0;
  if( beam_x > DISPLAY_SCREEN_WIDTH_COLS ) beam_x = DISPLAY_SCREEN_WIDTH_COLS;
  if( beam_y < 0 ) beam_y = 0;

  change = alloc_change();

  change->x = beam_x;
  change->y = beam_y;
  change->colour = colour;
}

/* Change border colour if the colour in use changes */
static void
check_border_change( void )
{
  if( scld_last_dec.name.hires &&
      display_hires_border != display_last_border ) {
    push_border_change( display_hires_border );
    display_last_border = display_hires_border;
  } else if( !scld_last_dec.name.hires &&
             display_lores_border != display_last_border ) {
    push_border_change( display_lores_border );
    display_last_border = display_lores_border;
  }
}

void
display_set_lores_border( int colour )
{
  if( display_lores_border != colour ) {
    display_lores_border = colour;
  }
  check_border_change();
}

void
display_set_hires_border( int colour )
{
  if( display_hires_border != colour ) {
    display_hires_border = colour;
  }
  check_border_change();
}

static void
set_border( int y, int start, int end, int colour )
{
  libspectrum_dword chunk_detail = 0x000000ff | colour << 8;
  int index = start + y * DISPLAY_SCREEN_WIDTH_COLS;

  for( ; start < end; start++ ) {
    /* Draw it if it is different to what was there last time - we know that
    data and mode will have been the same */
    if( display_last_screen[ index ] != chunk_detail ) {
      uidisplay_plot8( start, y, 0xff, colour, 0 );

      /* Update last display record */
      display_last_screen[ index ] = chunk_detail;

      /* And now mark it dirty */
      display_is_dirty[y] |= ( (libspectrum_qword)1 << start );
    }
    index++;
  }
}

static void
border_change_write( int y, int start, int end, int colour )
{
  if(   y <  DISPLAY_BORDER_HEIGHT                    ||
      ( y >= DISPLAY_BORDER_HEIGHT + DISPLAY_HEIGHT )    ) {

    /* Top and bottom borders */
    set_border( y, start, end, colour );

    return;
  }

  /* Left border */
  if( start < DISPLAY_BORDER_WIDTH_COLS ) {

    int left_end =
      end > DISPLAY_BORDER_WIDTH_COLS ? DISPLAY_BORDER_WIDTH_COLS : end;

    set_border( y, start, left_end, colour );
  }

  /* Right border */
  if( end > DISPLAY_BORDER_WIDTH_COLS + DISPLAY_WIDTH_COLS ) {

    if( start < DISPLAY_BORDER_WIDTH_COLS + DISPLAY_WIDTH_COLS )
      start = DISPLAY_BORDER_WIDTH_COLS + DISPLAY_WIDTH_COLS;

    set_border( y, start, end, colour );
  }
}

static void
border_change_line_part( int y, int start, int end, int colour )
{
  border_change_write( y, start, end, colour );
}

static void
border_change_line( int y, int colour )
{
  border_change_write( y, 0, DISPLAY_SCREEN_WIDTH_COLS, colour );
}

static void
do_border_change( struct border_change_t *first,
		  struct border_change_t *second )
{
  if( first->x ) {
    if( first->x != DISPLAY_SCREEN_WIDTH_COLS )
      border_change_line_part( first->y, first->x, DISPLAY_SCREEN_WIDTH_COLS,
			       first->colour );
    /* Don't extend region past the end of the screen */
    if( first->y < DISPLAY_SCREEN_HEIGHT - 1 ) first->y++;
  }

  for( ; first->y < second->y; first->y++ ) {
    border_change_line( first->y, first->colour );
  }

  if( second->x ) {
    if( second->x == DISPLAY_SCREEN_WIDTH_COLS ) {
      border_change_line( first->y, first->colour );
    } else {
      border_change_line_part( first->y, 0, second->x, first->colour );
    }
  }
}

/* Take account of all the border colour changes which happened in this
   frame */
static void
update_border( void )
{
  int pos;
  int error;

  /* Put the final sentinel onto the list */
  struct border_change_t *end_sentinel = alloc_change();

  memcpy( end_sentinel, &border_change_end_sentinel,
          sizeof( struct border_change_t ) );

  for( pos = 0; pos < border_changes_last-1; pos++ ) {
    do_border_change( border_changes+pos, border_changes+pos+1 );
  }

  border_changes_last = 0;

  error = add_border_sentinel(); if( error ) return;
}

/* Send the updated screen to the UI-specific code */
static void
update_ui_screen( void )
{
  static int frame_count = 0;
  int scale = machine_current->timex ? 2 : 1;
  size_t i;
  struct rectangle *ptr;

  if( settings_current.frame_rate <= ++frame_count ) {
    frame_count = 0;

    if( display_redraw_all ) {
      uidisplay_area( 0, 0,
		      scale * DISPLAY_ASPECT_WIDTH,
		      scale * DISPLAY_SCREEN_HEIGHT );
      display_redraw_all = 0;
    } else {
      for( i = 0, ptr = inactive_rectangle;
	   i < inactive_rectangle_count;
	   i++, ptr++ ) {
            uidisplay_area( 8 * scale * ptr->x, scale * ptr->y,
			8 * scale * ptr->w, scale * ptr->h );
      }
    }

    inactive_rectangle_count = 0;
    
    uidisplay_frame_end();
  }
}

int
display_frame( void )
{
  /* Copy all the critical region to the display */
  copy_critical_region( DISPLAY_WIDTH_COLS, DISPLAY_HEIGHT - 1 );
  critical_region_x = critical_region_y = 0;

  update_border();
  update_dirty_rects();
  update_ui_screen();

  if( screenshot_movie_record == 1 ) {

    snprintf( screenshot_movie_name, SCREENSHOT_MOVIE_FILE_MAX,
              "%s-frame-%09ld.scr", screenshot_movie_file,
              screenshot_movie_frame++ );
    screenshot_scr_write( screenshot_movie_name );

#ifdef USE_LIBPNG

  } else if( screenshot_movie_record == 2 ) {

    snprintf( screenshot_movie_name, SCREENSHOT_MOVIE_FILE_MAX,
              "%s-frame-%09ld.png", screenshot_movie_file,
              screenshot_movie_frame++ );
    screenshot_write_fast( screenshot_movie_name, screenshot_movie_scaler );

#endif                          /* #ifdef USE_LIBPNG */

  }

  display_frame_count++;
  if(display_frame_count==16) {
    display_flash_reversed=1;
    display_dirty_flashing();
  } else if(display_frame_count==32) {
    display_flash_reversed=0;
    display_dirty_flashing();
    display_frame_count=0;
  }
  
  return 0;
}

static void display_dirty_flashing(void)
{
  libspectrum_word offset;
  libspectrum_byte *screen, attr;

  screen = RAM[ memory_current_screen ];
  
  if( !scld_last_dec.name.hires ) {
    if( scld_last_dec.name.b1 ) {

      for( offset = ALTDFILE_OFFSET; offset < 0x3800; offset++ ) {
        attr = screen[ offset ];
        if( attr & 0x80 ) display_dirty8( offset - ALTDFILE_OFFSET );
      }

    } else if( scld_last_dec.name.altdfile ) {

      for( offset= 0x3800; offset < 0x3b00; offset++ ) {
        attr = screen[ offset ];
        if( attr & 0x80 ) display_dirty64( offset - ALTDFILE_OFFSET );
      }

    } else { /* Standard Speccy screen */

      for( offset = 0x1800; offset < 0x1b00; offset++ ) {
        attr = screen[ offset ];
        if( attr & 0x80 ) display_dirty64( offset );
      }

    }
  }
}

void display_refresh_main_screen(void)
{
  size_t i;

  for( i = 0; i < DISPLAY_HEIGHT; i++ )
    display_maybe_dirty[i] = display_all_dirty;
}

void display_refresh_all(void)
{
  size_t i;

  display_redraw_all = 1;

  display_refresh_main_screen();

  for( i = 0; i < DISPLAY_SCREEN_HEIGHT; i++ )
    display_is_dirty[i] = display_all_dirty;

  memset( display_last_screen, 0xff,
          DISPLAY_SCREEN_WIDTH_COLS * DISPLAY_SCREEN_HEIGHT 
          * sizeof(libspectrum_dword) );
}

/* Fetch pixel (x, y). On a Timex this will be a point on a 640x480 canvas,
   on a Sinclair/Amstrad/Russian clone this will be a point on a 320x240
   canvas */
int
display_getpixel( int x, int y )
{
  libspectrum_byte ink, paper;
  libspectrum_byte data, data2;
  int mask = 1 << (7 - (x % 8));
  int index;

  if( machine_current->timex ) {
    int column = x >> 4;
    scld mode_data;

    y >>= 1;
    index = column + y * DISPLAY_SCREEN_WIDTH_COLS;

    data = display_last_screen[ index ] & 0xff;
    data2 = (display_last_screen[ index ] & 0xff00)>>8;
    mode_data.byte = (display_last_screen[ index ] & 0xff0000)>>16;

    if( mode_data.name.hires ) {
      if( x % 16 > 7 ) data = data2;
      display_parse_attr( hires_convert_dec( mode_data.byte ), &ink, &paper );
    } else {
      /* divide x by two to get the same value for adjacent pixels */
      mask = 1 << (7 - ((x>>1) % 8));
      display_parse_attr( data2, &ink, &paper );
    }
  } else {
    int column = x >> 3;

    index = column + y * DISPLAY_SCREEN_WIDTH_COLS;

    data = display_last_screen[ index ] & 0xff;
    data2 = (display_last_screen[ index ] & 0xff00)>>8;

    display_parse_attr( data2, &ink, &paper );
  }

  if( data & mask ) return ink;

  return paper;
}