First svn commit of the experiment with layers. Preemptive backup (to shorten delay before drawing) is currently disabled. Basic Undo/Redo works, but not image resizing, the adjust tool, and saving (not even flattened)

git-svn-id: svn://pulkomandy.tk/GrafX2/branches/layers@1039 416bcca6-2ee7-4201-b75f-2eb2f807beb1

brush.c

@@ -728,8 +728,7 @@ void Capture_brush(short start_x,short start_y,short end_x,short end_y,short cle
       for (y_pos=start_y;y_pos<start_y+Brush_height;y_pos++)
         for (x_pos=start_x;x_pos<start_x+Brush_width;x_pos++)
         {
-          Pixel_in_current_screen(x_pos,y_pos,Back_color);
+          Pixel_in_current_screen(x_pos,y_pos,Back_color,1);
-          Pixel_preview           (x_pos,y_pos,Back_color);
         }
       Update_part_of_screen(start_x,start_y,Brush_width,Brush_height);
     }
@@ -1154,10 +1153,10 @@ void Capture_brush_with_lasso(int vertices, short * points,short clear)
       for (x_pos=start_x;x_pos<=end_x;x_pos++)
         if (Read_pixel_from_brush(x_pos-start_x,y_pos-start_y)!=Back_color)
         {
-          Pixel_in_brush(x_pos-start_x,y_pos-start_y,Read_pixel_from_current_screen(x_pos,y_pos));
+          Pixel_in_brush(x_pos-start_x,y_pos-start_y,Read_pixel_from_current_layer(x_pos,y_pos));
           // On regarde s'il faut effacer quelque chose:
           if (clear)
-            Pixel_in_current_screen(x_pos,y_pos,Back_color);
+            Pixel_in_current_screen(x_pos,y_pos,Back_color,0);
         }
 
     // On centre la prise sur la brosse

buttons.c

@@ -1351,13 +1351,15 @@ void Button_Page(void)
   SWAP_BYTES (Main_image_is_modified,Spare_image_is_modified)
 
   // Swap des infos sur les fileselects
-  strcpy(Temp_buffer             ,Spare_current_directory);
+  strcpy(Temp_buffer            ,Spare_current_directory);
   strcpy(Spare_current_directory,Main_current_directory);
   strcpy(Main_current_directory,Temp_buffer             );
 
   SWAP_BYTES (Main_format,Spare_format)
   SWAP_WORDS (Main_fileselector_position,Spare_fileselector_position)
   SWAP_WORDS (Main_fileselector_offset,Spare_fileselector_offset)
+  SWAP_SHORTS(Main_current_layer,Spare_current_layer)
+  SWAP_BYTES (Main_layers_visible,Spare_layers_visible)
 
   // A la fin, on affiche l'écran
   for (factor_index=0; ZOOM_FACTOR[factor_index]!=Main_magnifier_factor; factor_index++);
@@ -1503,10 +1505,10 @@ void Button_Copy_page(void)
 // -- Suppression d'une page -------------------------------------------------
 void Button_Kill(void)
 {
-  if ( (Main_backups->Nb_pages_allocated==1)
+  if ( (Main_backups->List_size==1)
     || (!Confirmation_box("Delete the current page?")) )
   {
-    if (Main_backups->Nb_pages_allocated==1)
+    if (Main_backups->List_size==1)
       Warning_message("You can't delete the last page.");
     Hide_cursor();
     Unselect_button(BUTTON_KILL);
@@ -2540,14 +2542,14 @@ void Button_Paintbrush_menu(void)
         Hide_cursor();
         Display_stored_brush_in_window(x_pos+2, y_pos+2, index);
         Display_cursor();
-      }
+  }
       else
       {
         // Restore and exit
 
         if (Restore_brush(index))
         {
-          Close_window();
+  Close_window();
           break;
         }
       }
@@ -2555,18 +2557,18 @@ void Button_Paintbrush_menu(void)
     }
     else if (clicked_button>1 && Window_attribute1==LEFT_SIDE)
     // Standard paintbrushes
-    {
+  {
       Close_window();
-      index=clicked_button-2;
+    index=clicked_button-2;
-      Paintbrush_shape=Gfx->Paintbrush_type[index];
+    Paintbrush_shape=Gfx->Paintbrush_type[index];
-      Paintbrush_width=Gfx->Preset_paintbrush_width[index];
+    Paintbrush_width=Gfx->Preset_paintbrush_width[index];
-      Paintbrush_height=Gfx->Preset_paintbrush_height[index];
+    Paintbrush_height=Gfx->Preset_paintbrush_height[index];
-      Paintbrush_offset_X=Gfx->Preset_paintbrush_offset_X[index];
+    Paintbrush_offset_X=Gfx->Preset_paintbrush_offset_X[index];
-      Paintbrush_offset_Y=Gfx->Preset_paintbrush_offset_Y[index];
+    Paintbrush_offset_Y=Gfx->Preset_paintbrush_offset_Y[index];
-      for (y_pos=0; y_pos<Paintbrush_height; y_pos++)
+    for (y_pos=0; y_pos<Paintbrush_height; y_pos++)
-        for (x_pos=0; x_pos<Paintbrush_width; x_pos++)
+      for (x_pos=0; x_pos<Paintbrush_width; x_pos++)
-          Paintbrush_sprite[(y_pos*MAX_PAINTBRUSH_SIZE)+x_pos]=Gfx->Paintbrush_sprite[index][y_pos][x_pos];
+        Paintbrush_sprite[(y_pos*MAX_PAINTBRUSH_SIZE)+x_pos]=Gfx->Paintbrush_sprite[index][y_pos][x_pos];
-      Change_paintbrush_shape(Gfx->Paintbrush_type[index]);
+    Change_paintbrush_shape(Gfx->Paintbrush_type[index]);
       
       break;
     }
@@ -4254,6 +4256,45 @@ void Transparency_set(byte amount)
   Compute_colorize_table();
 }
 
+void Layer_activate(short layer, short side)
+{
+  if (side == RIGHT_SIDE)
+  {
+    // Right-click on current layer
+    if (Main_current_layer == layer)
+    {
+      if (Main_layers_visible == (1<<layer))
+      {
+        // Set all layers visible
+        Main_layers_visible = 0xFF;
+      }
+      else
+      {
+        // Set only this one visible
+        Main_layers_visible = 1<<layer;
+      }
+    }
+    else
+    {
+      // Right-click on an other layer : toggle its visibility
+      Main_layers_visible ^= 1<<layer;
+    }
+  }
+  else
+  {
+    // Left-click on any layer
+    Main_current_layer = layer;
+    Main_layers_visible |= 1<<layer;
+  }
+
+  Hide_cursor();
+  Redraw_layered_image();
+  //Download_infos_page_main(Main_backups->Pages);
+  //Download_infos_backup(Main_backups);
+  Display_all_screen();
+  Display_cursor();
+}
+
 //---------------------------- Courbes de Bézier ----------------------------
 
 void Button_Curves(void)
@@ -5442,9 +5483,11 @@ void Button_Effects(void)
         break;
       case 13 : // Feedback (pour Colorize et Shade)
         if ((Config.FX_Feedback=!Config.FX_Feedback)) //!!!
-          FX_feedback_screen=Main_screen;
+          FX_feedback_screen=Main_backups->Pages->Image[Main_current_layer];
+          // Main_screen
         else
-          FX_feedback_screen=Screen_backup;
+          FX_feedback_screen=Main_backups->Pages->Next->Image[Main_current_layer];
+          // Screen_backup
         Hide_cursor();
         Display_feedback_state();
         Display_cursor();

buttons.h

@@ -441,6 +441,8 @@ void Effects_off(void);
 */
 void Transparency_set(byte amount);
 
+void Layer_activate(short layer, short side);
+
 // Menu des effets
 
 /*!

const.h

@@ -64,7 +64,7 @@
 #define LEFT_TRIANGLE_CHARACTER   17
 /// Character to display in menus for an ellipsis.
 #define ELLIPSIS_CHARACTER       '…'
-
+#define NB_LAYERS                 8
 #define BRUSH_CONTAINER_PREVIEW_WIDTH    16  ///< Size for preview of a brush in Brush container
 #define BRUSH_CONTAINER_PREVIEW_HEIGHT   16  ///< Size for preview of a brush in Brush container
 #define BRUSH_CONTAINER_COLUMNS          4  ///< Number of columns in the Brush container

engine.c

@@ -870,35 +870,43 @@ void Main_handler(void)
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_1 :
-          Transparency_set(1);
+          Layer_activate(0, LEFT_SIDE);
+          //Transparency_set(1);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_2 :
-          Transparency_set(2);
+          Layer_activate(1, LEFT_SIDE);
+          //Transparency_set(2);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_3 :
-          Transparency_set(3);
+          Layer_activate(2, LEFT_SIDE);
+          //Transparency_set(3);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_4 :
-          Transparency_set(4);
+          Layer_activate(3, LEFT_SIDE);
+          //Transparency_set(4);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_5 :
-          Transparency_set(5);
+          Layer_activate(0, RIGHT_SIDE);
+          //Transparency_set(5);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_6 :
-          Transparency_set(6);
+          Layer_activate(1, RIGHT_SIDE);
+          //Transparency_set(6);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_7 :
-          Transparency_set(7);
+          Layer_activate(2, RIGHT_SIDE);
+          //Transparency_set(7);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_8 :
-          Transparency_set(8);
+          Layer_activate(3, RIGHT_SIDE);
+          //Transparency_set(8);
           Key=0;
           break;
         case SPECIAL_TRANSPARENCY_9 :

global.h

@@ -345,6 +345,10 @@ GFX2_GLOBAL word  Main_magnifier_width;
 GFX2_GLOBAL short Main_magnifier_offset_X;
 /// Y position (in image space) of the pixel to display in the top left corner of the magnified view.
 GFX2_GLOBAL short Main_magnifier_offset_Y;
+/// Index of layer currently being edited
+GFX2_GLOBAL int Main_current_layer;
+/// Bitfield that records which layers are visible. 2^0 for 0, 2^1 for 1, 2^2 for 2, etc.
+GFX2_GLOBAL byte Main_layers_visible;
 
 // -- Spare page data
 
@@ -405,7 +409,10 @@ GFX2_GLOBAL word  Spare_magnifier_width;
 GFX2_GLOBAL short Spare_magnifier_offset_X;
 /// Y position (in image space) of the pixel to display in the top left corner of the magnified view.
 GFX2_GLOBAL short Spare_magnifier_offset_Y;
-
+/// Index of layer currently being edited
+GFX2_GLOBAL short Spare_current_layer;
+/// Bitfield that records which layers are visible. 2^0 for 0, 2^1 for 1, 2^2 for 2, etc.
+GFX2_GLOBAL byte Spare_layers_visible;
 // -- Image backups
 
 /// Backup of the current screen, used during drawing when FX feedback is OFF.
@@ -415,6 +422,15 @@ GFX2_GLOBAL T_List_of_pages * Main_backups;
 /// List of backup pages for the spare page.
 GFX2_GLOBAL T_List_of_pages * Spare_backups;
 
+
+// -- Layers data
+
+/// Array of two images, that contains the "flattened" version of the visible layers.
+GFX2_GLOBAL T_Image Visible_image[2];
+GFX2_GLOBAL T_Image Visible_image_depth_buffer;
+/// Index that is 0 or 1, it ways which of the two ::Visible_image[] contains the current image (the other contains the data from last backup)
+GFX2_GLOBAL int Visible_image_index;
+
 // -- Brush data
 
 /// Pixel data of the current brush.

graph.c

@@ -725,7 +725,7 @@ void Fill(short * top_reached  , short * bottom_reached,
   current_limit_bottom =Min(Paintbrush_Y+1,Limit_bottom);
   *left_reached=Paintbrush_X;
   *right_reached=Paintbrush_X+1;
-  Pixel_in_current_screen(Paintbrush_X,Paintbrush_Y,2);
+  Pixel_in_current_screen(Paintbrush_X,Paintbrush_Y,2,0);
 
   while (changes_made)
   {
@@ -786,7 +786,7 @@ void Fill(short * top_reached  , short * bottom_reached,
               *right_reached=end_x;
             // On remplit le segment de start_x à end_x-1.
             for (x_pos=start_x;x_pos<end_x;x_pos++)
-              Pixel_in_current_screen(x_pos,line,2);
+              Pixel_in_current_screen(x_pos,line,2,0);
             // On vient d'effectuer des modifications.
             changes_made=1;
             line_is_modified=1;
@@ -865,7 +865,7 @@ void Fill(short * top_reached  , short * bottom_reached,
               *right_reached=end_x;
             // On remplit le segment de start_x à end_x-1.
             for (x_pos=start_x;x_pos<end_x;x_pos++)
-              Pixel_in_current_screen(x_pos,line,2);
+              Pixel_in_current_screen(x_pos,line,2,0);
             // On vient d'effectuer des modifications.
             changes_made=1;
             line_is_modified=1;
@@ -933,7 +933,7 @@ void Fill_general(byte fill_color)
     Replace_colors_within_limits(replace_table);
 
     // On fait maintenant un remplissage classique de la couleur 1 avec la 2
-   Fill(&top_reached  ,&bottom_reached,
+    Fill(&top_reached  ,&bottom_reached,
          &left_reached,&right_reached);
 
     //  On s'apprête à faire des opérations qui nécessitent un affichage. Il
@@ -985,14 +985,14 @@ void Fill_general(byte fill_color)
           //  Ceci se fait en commençant par restaurer la couleur qu'il y avait
           // précédemment (c'est important pour que les effets ne s'emmèlent
           // pas le pinceaux)
-          Pixel_in_current_screen(x_pos,y_pos,Read_pixel_from_backup_screen(x_pos,y_pos));
+          Pixel_in_current_screen(x_pos,y_pos,Read_pixel_from_backup_screen(x_pos,y_pos),0);
 
           //  Enfin, on peut afficher le pixel, en le soumettant aux effets en
           // cours:
           Display_pixel(x_pos,y_pos,fill_color);
         }
         else
-          Pixel_in_current_screen(x_pos,y_pos,Read_pixel_from_backup_screen(x_pos,y_pos));
+          Pixel_in_current_screen(x_pos,y_pos,Read_pixel_from_backup_screen(x_pos,y_pos),0);
 
     FX_feedback_screen=old_fx_feedback_screen;
 
@@ -1001,7 +1001,6 @@ void Fill_general(byte fill_color)
     // puisque les seuls points qui ont changé dans l'image ont été raffichés
     // par l'utilisation de "Display_pixel()", et que les autres... eh bein
     // on n'y a jamais touché à l'écran les autres: ils sont donc corrects.
-
     if(Main_magnifier_mode)
     {
       short w,h;
@@ -2642,8 +2641,7 @@ void Display_pixel(word x,word y,byte color)
     && (!((Mask_mode)    && (Mask_table[Read_pixel_from_spare_screen(x,y)]))) )
   {
     color=Effect_function(x,y,color);
-    Pixel_in_current_screen(x,y,color);
+    Pixel_in_current_screen(x,y,color,1);
-    Pixel_preview(x,y,color);
   }
 }
 

loadsave.c

@@ -154,7 +154,7 @@ void Pixel_load_in_current_screen(word x_pos,word y_pos,byte color)
 {
   //if ((x_pos>=0) && (y_pos>=0)) //Toujours vrai ?
   if ((x_pos<Main_image_width) && (y_pos<Main_image_height))
-    Pixel_in_current_screen(x_pos,y_pos,color);
+    Pixel_in_current_screen(x_pos,y_pos,color,0);
 }
 
 
@@ -343,7 +343,7 @@ void Init_preview_24b(short width,short height,long size,int format)
 
     // Allocate 24bit buffer
     Buffer_image_24b=
-      (T_Components *)Borrow_memory_from_page(width*height*sizeof(T_Components));
+      (T_Components *)malloc(width*height*sizeof(T_Components));
     if (!Buffer_image_24b)
     {
       // Print an error message

main.c

@@ -360,6 +360,11 @@ int Init_program(int argc,char * argv[])
   Main_fileselector_position=0; // Au début, le fileselect est en haut de la liste des fichiers
   Main_fileselector_offset=0; // Au début, le fileselect est en haut de la liste des fichiers
   Main_format=0;
+  Main_current_layer=0;
+  Main_layers_visible=0xFF;
+  Spare_current_layer=0;
+  Spare_layers_visible=0xFF;
+  
   Spare_fileselector_position=0;
   Spare_fileselector_offset=0;
   Spare_format=0;
@@ -616,8 +621,19 @@ int Init_program(int argc,char * argv[])
   Main_image_height=Screen_height/Pixel_height;
   Spare_image_width=Screen_width/Pixel_width;
   Spare_image_height=Screen_height/Pixel_height;
+  
+  Visible_image[0].Width = 0;
+  Visible_image[0].Height = 0;
+  Visible_image[0].Image = NULL;
+  Visible_image[1].Width = 0;
+  Visible_image[1].Height = 0;
+  Visible_image[1].Image = NULL;
+  Visible_image_depth_buffer.Width = 0;
+  Visible_image_depth_buffer.Height = 0;
+  Visible_image_depth_buffer.Image = NULL;
+  
   // Allocation de mémoire pour les différents écrans virtuels (et brosse)
-  if (Init_all_backup_lists(Config.Max_undo_pages+1,Screen_width,Screen_height)==0)
+  if (Init_all_backup_lists(Screen_width,Screen_height)==0)
     Error(ERROR_MEMORY);
   // On remet le nom par défaut pour la page de brouillon car il été modifié
   // par le passage d'un fichier en paramètre lors du traitement précédent.

misc.c

@@ -219,13 +219,37 @@ byte Read_pixel_from_brush         (word x,word y)
 
 byte Read_pixel_from_current_screen  (word x,word y)
 {
-	return *(Main_screen+y*Main_image_width+x);
+  byte depth;
+  byte color;
+  color = *(Main_screen+y*Main_image_width+x);
+  if (color != 0) // transparent
+    return color;
+  
+  depth = *(Visible_image_depth_buffer.Image+x+y*Main_image_width);
+  return *(Main_backups->Pages->Image[depth] + x+y*Main_image_width);
+  // return *(Main_screen+y*Main_image_width+x);
 }
 
-void Pixel_in_current_screen      (word x,word y,byte color)
+void Pixel_in_current_screen      (word x,word y,byte color,int with_preview)
 {
-	byte* dest=(x+y*Main_image_width+Main_screen);
+    byte depth = *(Visible_image_depth_buffer.Image+x+y*Main_image_width);
-	*dest=color;
+    *(Main_backups->Pages->Image[Main_current_layer] + x+y*Main_image_width)=color;
+    if ( depth <= Main_current_layer)
+    {
+      if (color == 0) // transparent
+        // fetch pixel color from the topmost visible layer
+        color=*(Main_backups->Pages->Image[depth] + x+y*Main_image_width);
+      
+      *(x+y*Main_image_width+Main_screen)=color;
+      
+      if (with_preview)
+        Pixel_preview(x,y,color);
+    }
+}
+
+byte Read_pixel_from_current_layer(word x,word y)
+{
+  return *((y)*Main_image_width+(x)+Main_backups->Pages->Image[Main_current_layer]);
 }
 
 void Replace_a_color(byte old_color, byte New_color)
@@ -346,9 +370,9 @@ void Remap_general_lowlevel(byte * conversion_table,byte * buffer,short width,sh
 
 void Copy_image_to_brush(short start_x,short start_y,short Brush_width,short Brush_height,word image_width)
 {
-	byte* src=start_y*image_width+start_x+Main_screen; //Adr départ image (ESI)
+    byte* src=start_y*image_width+start_x+Main_backups->Pages->Image[Main_current_layer]; //Adr départ image (ESI)
-	byte* dest=Brush; //Adr dest brosse (EDI)
+    byte* dest=Brush; //Adr dest brosse (EDI)
-	int dx;
+    int dx;
 
 	for (dx=Brush_height;dx!=0;dx--)
 		//Pour chaque ligne

misc.h

@@ -36,13 +36,14 @@ dword Round_div(dword numerator,dword divisor);
 word Count_used_colors(dword * usage);
 word Count_used_colors_area(dword* usage, word start_x, word start_y, word width, word height);
 word Count_used_colors_screen_area(dword* usage, word start_x, word start_y, word width, word height);
-void Pixel_in_current_screen      (word x,word y,byte color);
+void Pixel_in_current_screen      (word x,word y,byte color,int with_preview);
 void Pixel_in_brush             (word x,word y,byte color);
 byte Read_pixel_from_current_screen  (word x,word y);
 byte Read_pixel_from_spare_screen(word x,word y);
 byte Read_pixel_from_backup_screen   (word x,word y);
 byte Read_pixel_from_feedback_screen (word x,word y);
 byte Read_pixel_from_brush         (word x,word y);
+byte Read_pixel_from_current_layer(word x,word y);
 
 void Ellipse_compute_limites(short horizontal_radius,short vertical_radius);
 // Calcule les valeurs suivantes en fonction des deux paramètres:

operatio.c

@@ -3005,6 +3005,7 @@ void Brush_0_5(void)
     Brush_offset_Y=(Brush_offset_Y/Snap_height)*Snap_height;
   }
   
+  End_of_modification();
   End_of_modification();
   Return_to_draw_mode();
 }

pages.h

@@ -39,13 +39,12 @@ void Download_infos_page_main(T_Page * page);
 void Upload_infos_page_main(T_Page * page);
 
 // private
-void Init_page(T_Page * page);
+T_Page * New_page(void);
 void Download_infos_page_spare(T_Page * page);
 void Upload_infos_page_spare(T_Page * page);
 void Download_infos_backup(T_List_of_pages * list);
-void Free_a_page(T_Page * page);
+void Clear_page(T_Page * page);
 void Copy_S_page(T_Page * dest,T_Page * source);
-int Size_of_a_page(T_Page * page);
 
 
 
@@ -55,14 +54,11 @@ int Size_of_a_page(T_Page * page);
 
 void Init_list_of_pages(T_List_of_pages * list);
 // private
-int Allocate_list_of_pages(T_List_of_pages * list,int size);
+int Allocate_list_of_pages(T_List_of_pages * list);
-void Free_a_list_of_pages(T_List_of_pages * list);
-int Size_of_a_list_of_pages(T_List_of_pages * list);
 void Backward_in_list_of_pages(T_List_of_pages * list);
 void Advance_in_list_of_pages(T_List_of_pages * list);
-int New_page_is_possible(T_Page * new_page,T_List_of_pages * current_list,T_List_of_pages * secondary_list);
 void Free_last_page_of_list(T_List_of_pages * list);
-void Create_new_page(T_Page * new_page,T_List_of_pages * current_list,T_List_of_pages * secondary_list);
+int Create_new_page(T_Page * new_page,T_List_of_pages * current_list);
 void Change_page_number_of_list(T_List_of_pages * list,int number);
 void Free_page_of_a_list(T_List_of_pages * list);
 
@@ -72,7 +68,7 @@ void Free_page_of_a_list(T_List_of_pages * list);
 /// BACKUP HIGH-LEVEL FUNCTIONS
 ///
 
-int Init_all_backup_lists(int size,int width,int height);
+int Init_all_backup_lists(int width,int height);
 void Set_number_of_backups(int nb_backups);
 int Backup_with_new_dimensions(int upload,int width,int height);
 int Backup_and_resize_the_spare(int width,int height);
@@ -83,14 +79,4 @@ void Free_current_page(void); // 'Kill' button
 void Exchange_main_and_spare(void);
 void End_of_modification(void);
 
-
-///
-/// BORROWING MEMORY FROM PAGE
-///
-
-void * Borrow_memory_from_page(int size);
-// private
-int Can_borrow_memory_from_page(int size);
-
-
 #endif

struct.h

@@ -319,9 +319,8 @@ typedef struct
 // backup dans "graph.c".
 
 /// This is the data for one step of Undo/Redo, for one image.
-typedef struct
+typedef struct T_Page
 {
-  byte *    Image;   ///< Pixel data for the image.
   int       Width;   ///< Image width in pixels.
   int       Height;  ///< Image height in pixels.
   T_Palette Palette; ///< Image palette.
@@ -331,17 +330,27 @@ typedef struct
   char      File_directory[MAX_PATH_CHARACTERS];///< Directory that contains the file.
   char      Filename[MAX_PATH_CHARACTERS];      ///< Filename without directory.
   byte      File_format;                        ///< File format, in enum ::FILE_FORMATS
-
+  struct T_Page *Next;
+  struct T_Page *Prev;
+  byte *    Image[NB_LAYERS];///< Pixel data for the image.
 } T_Page;
 
 /// Collection of undo/redo steps.
 typedef struct
 {
   int      List_size;         ///< Number of ::T_Page in the vector "Pages".
-  int      Nb_pages_allocated;///< Number of ::T_Page used so far in the vector "Pages".
+  T_Page * Pages;             ///< Head of a linked list of pages, each one being a undo/redo step.
-  T_Page * Pages;             ///< Vector of Pages, each one being a undo/redo step.
 } T_List_of_pages;
 
+/// A single image bitmap
+typedef struct
+{
+  int       Width;   ///< Image width in pixels.
+  int       Height;  ///< Image height in pixels.
+  //int       Users;   ///< Number of references.
+  byte *    Image;   ///< Pixel data for the image.
+} T_Image;
+
 /// A single memorized brush from the Brush Container
 typedef struct
 {
@@ -355,7 +364,6 @@ typedef struct
   byte Transp_color;
 } T_Brush_template;
 
-
 /// GUI skin data
 typedef struct
 {