Implement a more generic "rasters" mode for CPC

This is similar to mode 5, but with less constraints:
- All inks can have split rasters
- Split rasters have a min width of 32 pixels

Note that this is nowhere near enough to make sure the image will be
renderable (number of colors should be limited, unless there is a span
without rasters allowing to reload registers with new colors, and
moving from one pen to another also has a cost). The goal is to offer no
over-restriction (everything that can be shown on the real machine is
drawable). Additional constraints may be checked from a lua script that
will generate the code and data for displaying the picture.

src/brush.c

@@ -120,7 +120,8 @@ void Display_paintbrush(short x,short y,byte color)
   if (Mouse_K) // pas de curseur si on est en preview et 
     return;                  // en train de cliquer
     
-  if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5 && Main.current_layer < 4)
+  if ((Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5
+  	|| Main.backups->Pages->Image_mode == IMAGE_MODE_RASTER) && Main.current_layer < 4)
   {
     goto single_pixel;
   }
@@ -284,7 +285,8 @@ void Draw_paintbrush(short x,short y,byte color)
   int position;
   byte old_color;
 
-  if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5 && Main.current_layer < 4)
+  if ((Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5
+  	|| Main.backups->Pages->Image_mode == IMAGE_MODE_RASTER) && Main.current_layer < 4)
   {
     // Flood-fill the enclosing area
     if (x<Main.image_width && y<Main.image_height && x>= 0 && y >= 0
@@ -296,6 +298,8 @@ void Draw_paintbrush(short x,short y,byte color)
       short min_x,width,min_y,height;
       short xx,yy;
 
+  	  if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5)
+	  {
 		  // determine area
 		  switch(Main.current_layer)
 		  {
@@ -322,13 +326,80 @@ void Draw_paintbrush(short x,short y,byte color)
 				  width=48;
 				  height=1;
 				  break;
-        //case 4:
+		  }
-        //  // 8x8
+	  } else {
-        //  min_x=x / 8 * 8;
+		int prev_x;
-        //  min_y=y / 8 * 8;
+		// Raster mode
-        //  width=8;
+		// No matter what, you can always edit only 1 line at a time here, and you will always
-        //  height=8;
+		// draw on "nops" boundaries (8 pixels in mode 1)
-        //  break;
+		height=1;
+		min_y=y;
+		min_x=x / 8 * 8;
+		width = 8;
+
+		// ????????
+		//     ^
+		//     A
+
+		// First look for the previous span to see if it is the same color
+		prev_x = min_x - 8;
+
+		old_color = Read_pixel_from_current_screen(prev_x, y);
+
+		if (old_color == color) {
+			// aaaA????
+			//     ^
+			//     A
+			// We are just making the previous span larger
+			width = 8;
+			while ((min_x >= 0) && (width < 32)
+				&& (Read_pixel_from_current_screen(min_x, y) == color))
+			{
+				min_x -= 8;
+				width += 8;
+			}
+		} else {
+			// ???B????
+			//     ^
+			//     A
+			// We are creating a new span. We need to check if the previous span is still large
+			// enough to be allowed. If it is less than 32 pixels, there is no way to render it
+			// on the real hardware (this is the time the OUT instruction to change the palette
+			// needs)
+			while ((min_x - prev_x < 48)
+				&& (prev_x <= 0 || old_color == Read_pixel_from_current_screen(prev_x, y)))
+			{
+				prev_x -= 8;
+			}
+			prev_x += 8;
+
+			// CBBB????
+			//  p  ^
+			//     A
+			// The previous span is too small, so eat it
+			if (min_x - prev_x < 32) {
+				width += min_x - prev_x;
+				min_x = prev_x;
+			}
+
+			if (width < 32)
+				width = 32;
+		}
+		// Now, we also need to check if the next span is still large enough, as we are going to
+		// remove 8 pixels from it. If it is not, we just replace it with the current color and
+		// let the user figure out how to reinsert it without breaking everything.
+		prev_x = min_x + width;
+		old_color = Read_pixel_from_current_screen(prev_x, y);
+		if (old_color != color) {
+			while ((prev_x - (min_x + width) < 40)
+				&& (prev_x > Main.image_width || old_color == Read_pixel_from_current_screen(prev_x, y)))
+			{
+				prev_x += 8;
+			}
+
+			if (prev_x - (min_x + width) < 32)
+				width = prev_x - min_x;
+		}
 	  }
       // Clip the bottom edge.
       // (Necessary if image height is not a multiple)

src/buttons_effects.c

@@ -180,19 +180,26 @@ void Button_Constraint_mode(void)
   if (Selected_Constraint_Mode <= IMAGE_MODE_ANIMATION)
     Selected_Constraint_Mode = IMAGE_MODE_EGX;
 
-  if (Selected_Constraint_Mode == IMAGE_MODE_MODE5)
+  if (Selected_Constraint_Mode == IMAGE_MODE_MODE5 && (Main.image_width%48))
   {
+	  Verbose_message("Error!", "Emulation of Amstrad CPC's Mode5 can only be used on an image whose width is a multiple of 48.");
+      return;
+  }
+
+  if (Selected_Constraint_Mode == IMAGE_MODE_MODE5 || Selected_Constraint_Mode == IMAGE_MODE_RASTER)
+  {
+	/* TODO it would be great to auto-create extra layers */
     if (Main.backups->Pages->Image_mode != IMAGE_MODE_LAYERED ||
-        Main.backups->Pages->Nb_layers!=5 || (Main.image_width%48))
+        Main.backups->Pages->Nb_layers!=5)
     {
-      Verbose_message("Error!", "This emulation of Amstrad CPC's Mode5 can only be used on a 5-layer image whose width is a multiple of 48.");
+      Verbose_message("Error!", "Emulation of Amstrad CPC's rasters requires a 5-layer image.");
       return;
     }
     for (pixel=0; pixel < Main.image_width*Main.image_height; pixel++)
     {
       if (Main.backups->Pages->Image[4].Pixels[pixel]>3)
       {
-        Verbose_message("Error!", "This emulation of Amstrad CPC's Mode5 needs all pixels of layer 5 to use colors 0-3.");
+        Verbose_message("Error!", "Emulation of Amstrad CPC's rasters needs all pixels of layer 5 to use colors 0-3.");
         return;
       }
     }
@@ -220,6 +227,7 @@ void Button_Constraint_menu(void)
     {IMAGE_MODE_EGX,     "EGX (CPC)"},
     {IMAGE_MODE_EGX2,    "EGX2 (CPC)"},
     {IMAGE_MODE_MODE5,   "Mode 5 (CPC)"},
+    {IMAGE_MODE_RASTER,  "Rasters (CPC)"},
   };
 
   Open_window(154,79,"8-bit constraints");

src/const.h

@@ -614,6 +614,7 @@ enum IMAGE_MODES
   IMAGE_MODE_EGX,       ///< CPC EGX
   IMAGE_MODE_EGX2,      ///< CPC EGX2
   IMAGE_MODE_MODE5,     ///< CPC mode 5
+  IMAGE_MODE_RASTER,    ///< CPC generic rasters
 };
 
 /// Circle / Ellipse Modes

src/graph.c

@@ -3213,7 +3213,8 @@ byte Read_pixel_from_current_screen  (word x,word y)
     return *((y)*Main.image_width+(x)+Main.backups->Pages->Image[Main.current_layer].Pixels);
   }
 
-  if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5)
+  if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5
+  	|| Main.backups->Pages->Image_mode == IMAGE_MODE_RASTER)
     if (Main.current_layer==4)
       return *(Main.backups->Pages->Image[Main.current_layer].Pixels + x+y*Main.image_width);
 
@@ -3632,7 +3633,7 @@ void Update_pixel_renderer(void)
     Pixel_in_current_screen = Pixel_in_screen_zx;
     Pixel_in_current_screen_with_preview = Pixel_in_screen_zx_with_preview;
   }
-  // Implicit else : Image_mode must be IMAGE_MODE_MODE5
+  // Implicit else : Image_mode must be IMAGE_MODE_MODE5 or IMAGE_MODE_RASTER
   else if ( Main.current_layer == 4)
   {
     // overlay
@@ -3647,7 +3648,7 @@ void Update_pixel_renderer(void)
   }
   else
   {
-    // layered (again, for layers > 4 in MODE5)
+    // layered (again, for layers > 4 in MODE5 and RASTER)
     Pixel_in_current_screen = Pixel_in_screen_layered;
     Pixel_in_current_screen_with_preview = Pixel_in_screen_layered_with_preview;
   }

src/pages.c

@@ -203,7 +203,8 @@ void Redraw_layered_image(void)
     // Re-construct the image with the visible layers
     byte layer=0;  
     // First layer
-    if (Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5 && Main.layers_visible & (1<<4))
+    if ((Main.backups->Pages->Image_mode == IMAGE_MODE_MODE5
+		|| Main.backups->Pages->Image_mode == IMAGE_MODE_RASTER) && Main.layers_visible & (1<<4))
     {
       // The raster result layer is visible: start there
       // Copy it in Main_visible_image
@@ -1466,6 +1467,7 @@ byte Delete_layer(T_List_of_pages *list, int layer)
   return 0;
 }
 
+
 /// Merges the current layer onto the one below it.
 byte Merge_layer()
 {
@@ -1479,6 +1481,7 @@ byte Merge_layer()
   return Delete_layer(Main.backups,Main.current_layer);
 }
 
+
 void Switch_layer_mode(enum IMAGE_MODES new_mode)
 {
   if (new_mode == Main.backups->Pages->Image_mode)
@@ -1486,18 +1489,12 @@ void Switch_layer_mode(enum IMAGE_MODES new_mode)
 
   Main.backups->Pages->Image_mode = new_mode;
 
-  switch (new_mode)
+  if (new_mode != IMAGE_MODE_ANIMATION)
   {
-    case IMAGE_MODE_MODE5:
-    case IMAGE_MODE_LAYERED:
-    default:
       Update_buffers(Main.image_width, Main.image_height);
       Redraw_layered_image();
-      break;
-    case IMAGE_MODE_ANIMATION:
-      // nothing to do.
-      // Eventually, we may clear the buffers to save a bit of memory...
-      break;
   }
+  // TODO Eventually, in animation mode we may clear the buffers to save a bit of memory...
+
   Update_pixel_renderer();
 }

src/palette.c

@@ -345,7 +345,8 @@ void Remap_image_highlevel(byte * conversion_table)
 
   // Remap the flatenned image view
   if (Main.backups->Pages->Image_mode != IMAGE_MODE_ANIMATION
-      && Main.backups->Pages->Image_mode != IMAGE_MODE_MODE5)
+      && Main.backups->Pages->Image_mode != IMAGE_MODE_MODE5
+      && Main.backups->Pages->Image_mode != IMAGE_MODE_RASTER)
   {
     Remap_general_lowlevel(conversion_table,Main.visible_image.Image,Main.visible_image.Image,
                          Main.image_width,Main.image_height,Main.image_width);