From 9be9ed9c17333a6b8b03375189249e6342ebd36d Mon Sep 17 00:00:00 2001
From: Yves Rizoud <yrizoud@gmail.com>
Date: Wed, 30 Sep 2009 21:37:16 +0000
Subject: [PATCH] [layers] Sped up the switching from one active layer to
 another, when the new layer was already displayed (thanks to the depth
 buffer, again)

git-svn-id: svn://pulkomandy.tk/GrafX2/branches/layers@1049 416bcca6-2ee7-4201-b75f-2eb2f807beb1
---
 buttons.c | 12 ++++++++++--
 pages.c   | 45 +++++++++++++++++++++++++++++++++++++++++++++
 pages.h   |  4 ++++
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/buttons.c b/buttons.c
index 41c757ec..74edc017 100644
--- a/buttons.c
+++ b/buttons.c
@@ -2879,6 +2879,7 @@ void Load_picture(byte image)
       }
 
       Compute_optimal_menu_colors(Main_palette);
+      Redraw_layered_image();
       Display_all_screen();
 
       if (image)
@@ -2980,7 +2981,7 @@ void Button_Reload(void)
         Compute_limits();
         Compute_paintbrush_coordinates();
       }
-
+      Redraw_layered_image();
       Display_all_screen();
 
       Main_image_is_modified=0;
@@ -4260,6 +4261,10 @@ void Transparency_set(byte amount)
 
 void Layer_activate(short layer, short side)
 {
+  byte old_layers;
+  
+  // Keep a copy of which layers were visible
+  old_layers = Main_layers_visible;
   if (side == RIGHT_SIDE)
   {
     // Right-click on current layer
@@ -4290,7 +4295,10 @@ void Layer_activate(short layer, short side)
   }
 
   Hide_cursor();
-  Redraw_layered_image();
+  if (Main_layers_visible != old_layers)
+    Redraw_layered_image();
+  else
+    Update_depth_buffer(); // Only need the depth buffer
   //Download_infos_page_main(Main_backups->Pages);
   //Download_infos_backup(Main_backups);
   Display_all_screen();
diff --git a/pages.c b/pages.c
index 4a0e0b76..9a113213 100644
--- a/pages.c
+++ b/pages.c
@@ -191,6 +191,51 @@ void Redraw_layered_image(void)
   Download_infos_backup(Main_backups);
 }
 
+void Update_depth_buffer(void)
+{
+  // Re-construct the depth buffer with the visible layers.
+  // This function doesn't touch the visible buffer, it assumes
+  // that it was already up-to-date. (Ex. user only changed active layer)
+
+  int layer;  
+  // First layer
+  for (layer=0; layer<Main_backups->Pages->Nb_layers; layer++)
+  {
+    if ((1<<layer) & Main_layers_visible)
+    {
+       // Initialize the depth buffer
+       memset(Visible_image_depth_buffer.Image,
+         layer,
+         Main_image_width*Main_image_height);
+       
+       // skip all other layers
+       layer++;
+       break;
+    }
+  }
+  // subsequent layer(s)
+  for (; layer<Main_backups->Pages->Nb_layers; layer++)
+  {
+    // skip the current layer, whenever we reach it
+    if (layer == Main_current_layer)
+      continue;
+      
+    if ((1<<layer) & Main_layers_visible)
+    {
+      int i;
+      for (i=0; i<Main_image_width*Main_image_height; i++)
+      {
+        byte color = *(Main_backups->Pages->Image[layer]+i);
+        if (color != 0) /* transp color */
+        {
+          *(Visible_image_depth_buffer.Image+i) = layer;
+        }
+      }
+    }
+  }
+  Download_infos_backup(Main_backups);
+}
+
 void Redraw_current_layer(void)
 {
   int i;
diff --git a/pages.h b/pages.h
index 461c124e..ad22e7c6 100644
--- a/pages.h
+++ b/pages.h
@@ -82,4 +82,8 @@ void Free_current_page(void); // 'Kill' button
 void Exchange_main_and_spare(void);
 void End_of_modification(void);
 
+void Update_depth_buffer(void);
+void Redraw_layered_image(void);
+void Redraw_current_layer(void);
+
 #endif