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, 37 insertions, 13 deletions

diff --git a/src/compoundsprite.h b/src/compoundsprite.h
index b3925216..c714c34b 100644
--- a/src/compoundsprite.h
+++ b/src/compoundsprite.h
@@ -25,18 +25,20 @@
 
 #include <vector>
 
-class CompoundSprite : public Sprite, public std::vector<Sprite*>
+class Image;
+
+class CompoundSprite : public Sprite, private std::vector<Sprite*>
 {
 public:
     CompoundSprite();
 
     ~CompoundSprite();
 
-    virtual void reset();
+    virtual bool reset();
 
-    virtual void play(SpriteAction action);
+    virtual bool play(SpriteAction action);
 
-    virtual void update(int time);
+    virtual bool update(int time);
 
     virtual bool draw(Graphics* graphics, int posX, int posY) const;
 
@@ -50,18 +52,40 @@ public:
      */
     virtual int getHeight() const;
 
-    virtual Image* getImage() const;
+    virtual const Image* getImage() const;
 
-    virtual void setDirection(SpriteDirection direction);
+    virtual bool setDirection(SpriteDirection direction);
 
-    virtual Sprite *getSprite(int index) const
-    { return at(index); }
+    int getNumberOfLayers() const;
 
-    int getNumberOfLayers()
-    { return size(); }
-};
+    size_t size() const
+    { return std::vector<Sprite*>::size(); }
+
+    void addSprite(Sprite* sprite);
+
+    void setSprite(int layer, Sprite* sprite);
+
+    Sprite *getSprite(int layer) const
+    { return at(layer); }
+
+    void removeSprite(int layer);
+
+    void clear();
 
-typedef CompoundSprite::iterator SpriteIterator;
-typedef CompoundSprite::const_iterator SpriteConstIterator;
+    void ensureSize(size_t layerCount);
+
+private:
+    typedef CompoundSprite::iterator SpriteIterator;
+    typedef CompoundSprite::const_iterator SpriteConstIterator;
+
+    void redraw() const;
+
+    mutable Image *mImage;
+    mutable Image *mAlphaImage;
+
+    mutable int mOffsetX, mOffsetY;
+
+    mutable bool mNeedsRedraw;
+};
 
 #endif // COMPOUNDSPRITE_H