Bug 635035, part 3: Add gfxASurface::MovePixels() interface and generic impl. sr=roc

gfx/thebes/gfxASurface.cpp

@@ -40,9 +40,11 @@
 #include "nsMemory.h"
 
 #include "gfxASurface.h"
-
+#include "gfxContext.h"
 #include "gfxImageSurface.h"
 
+#include "nsRect.h"
+
 #include "cairo.h"
 
 #ifdef CAIRO_HAS_WIN32_SURFACE
@@ -474,6 +476,24 @@ gfxASurface::BytePerPixelFromFormat(gfxImageFormat format)
     return 0;
 }
 
+void
+gfxASurface::MovePixels(const nsIntRect& aSourceRect,
+                        const nsIntPoint& aDestTopLeft)
+{
+    gfxIntSize size = GetSize();
+    nsIntRect dest(aDestTopLeft, aSourceRect.Size());
+    // Assume that our cairo backend already knows how to properly
+    // self-copy.  gfxASurface subtypes whose backend can't self-copy
+    // need their own implementations, or their backends need to be
+    // fixed.
+    nsRefPtr<gfxContext> ctx = new gfxContext(this);
+    ctx->SetOperator(gfxContext::OPERATOR_SOURCE);
+    nsIntPoint srcOrigin = dest.TopLeft() - aSourceRect.TopLeft();
+    ctx->SetSource(this, gfxPoint(srcOrigin.x, srcOrigin.y));
+    ctx->Rectangle(gfxRect(dest.x, dest.y, dest.width, dest.height));
+    ctx->Fill();
+}
+
 /** Memory reporting **/
 
 static const char *sSurfaceNamesForSurfaceType[] = {

gfx/thebes/gfxASurface.h

@@ -48,6 +48,8 @@ typedef struct _cairo_user_data_key cairo_user_data_key_t;
 typedef void (*thebes_destroy_func_t) (void *data);
 
 class gfxImageSurface;
+struct nsIntPoint;
+struct nsIntRect;
 
 /**
  * A surface is something you can draw on. Instantiate a subclass of this
@@ -220,6 +222,19 @@ public:
 
     virtual PRBool SupportsSelfCopy() { return PR_TRUE; }
 
+    /**
+     * Move the pixels in |aSourceRect| to |aDestTopLeft|.  Like with
+     * memmove(), |aSourceRect| and the rectangle defined by
+     * |aDestTopLeft| are allowed to overlap, and the effect is
+     * equivalent to copying |aSourceRect| to a scratch surface and
+     * then back to |aDestTopLeft|.
+     *
+     * |aSourceRect| and the destination rectangle defined by
+     * |aDestTopLeft| are clipped to this surface's bounds.
+     */
+    virtual void MovePixels(const nsIntRect& aSourceRect,
+                            const nsIntPoint& aDestTopLeft);
+
     /**
      * Mark the surface as being allowed/not allowed to be used as a source.
      */