Buffer layered sprites under SDL

This improves framerate and allows transparent overlay for complex
sprites. Two copies of the buffer are kept, one at full opacity,
one with variable opactiy, to reduce calls to setAlpha.

Reviewed-by: Bertram

1 files changed, 9 insertions, 5 deletions

diff --git a/src/imagesprite.h b/src/imagesprite.h
index 83fcfa12..20f9fbef 100644
--- a/src/imagesprite.h
+++ b/src/imagesprite.h
@@ -34,11 +34,14 @@ public:
 
     ~ImageSprite();
 
-    virtual void reset() {}
+    virtual bool reset()
+    { return false; }
 
-    virtual void play(SpriteAction action) {}
+    virtual bool play(SpriteAction action)
+    { return false; }
 
-    virtual void update(int time) {}
+    virtual bool update(int time)
+    { return false; }
 
     virtual bool draw(Graphics* graphics, int posX, int posY) const;
 
@@ -48,10 +51,11 @@ public:
     virtual int getHeight() const
     { return mImage->getHeight(); }
 
-    virtual Image* getImage() const
+    virtual const Image* getImage() const
     { return mImage; }
 
-    virtual void setDirection(SpriteDirection direction) {}
+    virtual bool setDirection(SpriteDirection direction)
+    { return false; }
 
     int getNumberOfLayers()
     { return 1; }