Bug 556487 - Subimage API. r=roc a=blocking2.0

gfx/thebes/gfxImageSurface.cpp

@@ -192,3 +192,27 @@ gfxImageSurface::CopyFrom(gfxImageSurface *other)
 
     return PR_TRUE;
 }
+
+already_AddRefed<gfxSubimageSurface>
+gfxImageSurface::GetSubimage(const gfxRect& aRect)
+{
+    gfxRect r(aRect);
+    r.Round();
+    unsigned char* subData = Data() +
+        (Stride() * (int)r.Y()) +
+        (int)r.X() * gfxASurface::BytePerPixelFromFormat(Format());
+
+    nsRefPtr<gfxSubimageSurface> image =
+        new gfxSubimageSurface(this, subData,
+                               gfxIntSize((int)r.Width(), (int)r.Height()));
+
+    return image.forget().get();
+}
+
+gfxSubimageSurface::gfxSubimageSurface(gfxImageSurface* aParent,
+                                       unsigned char* aData,
+                                       const gfxIntSize& aSize)
+  : gfxImageSurface(aData, aSize, aParent->Stride(), aParent->Format())
+  , mParent(aParent)
+{
+}

gfx/thebes/gfxImageSurface.h

@@ -43,6 +43,8 @@
 
 // ARGB -- raw buffer.. wont be changed.. good for storing data.
 
+class gfxSubimageSurface;
+
 /**
  * A raw image buffer. The format can be set in the constructor. Its main
  * purpose is for storing read-only images and using it as a source surface,
@@ -99,6 +101,11 @@ public:
     /* Fast copy from another image surface; returns TRUE if successful, FALSE otherwise */
     PRBool CopyFrom (gfxImageSurface *other);
 
+    /* return new Subimage with pointing to original image starting from aRect.pos
+     * and size of aRect.size. New subimage keeping current image reference
+     */
+    already_AddRefed<gfxSubimageSurface> GetSubimage(const gfxRect& aRect);
+
 protected:
     gfxImageSurface();
     void InitFromSurface(cairo_surface_t *csurf);
@@ -111,4 +118,14 @@ protected:
     long mStride;
 };
 
+class THEBES_API gfxSubimageSurface : public gfxImageSurface {
+protected:
+    friend class gfxImageSurface;
+    gfxSubimageSurface(gfxImageSurface* aParent,
+                       unsigned char* aData,
+                       const gfxIntSize& aSize);
+private:
+    nsRefPtr<gfxImageSurface> mParent;
+};
+
 #endif /* GFX_IMAGESURFACE_H */