Implement difference clip rects with window rectangles

src/gpu/gl/GrGLIRect.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 
 #ifndef GrGLIRect_DEFINED
 #define GrGLIRect_DEFINED
 
 #include "gl/GrGLInterface.h"
 #include "GrGLUtil.h"
 
 /**
  * Helper struct for dealing with the fact that Ganesh and GL use different
  * window coordinate systems (top-down vs bottom-up)
  */
 struct GrGLIRect {
     GrGLint   fLeft;
     GrGLint   fBottom;
     GrGLsizei fWidth;
     GrGLsizei fHeight;
 
+    /**
+     *  cast-safe way to treat the rect as an array of (4) ints.
+     */
+    const int* asInts() const {
+        return &fLeft;
+
+        GR_STATIC_ASSERT(0 == offsetof(GrGLIRect, fLeft));
+        GR_STATIC_ASSERT(4 == offsetof(GrGLIRect, fBottom));
+        GR_STATIC_ASSERT(8 == offsetof(GrGLIRect, fWidth));
+        GR_STATIC_ASSERT(12 == offsetof(GrGLIRect, fHeight));
+        GR_STATIC_ASSERT(16 == sizeof(GrGLIRect)); // For an array of GrGLIRect.
+    }
+    int* asInts() { return &fLeft; }
+
     void pushToGLViewport(const GrGLInterface* gl) const {
         GR_GL_CALL(gl, Viewport(fLeft, fBottom, fWidth, fHeight));
     }
 
     void pushToGLScissor(const GrGLInterface* gl) const {
         GR_GL_CALL(gl, Scissor(fLeft, fBottom, fWidth, fHeight));
     }
 
     void setFromGLViewport(const GrGLInterface* gl) {
         GR_STATIC_ASSERT(sizeof(GrGLIRect) == 4*sizeof(GrGLint));
         GR_GL_GetIntegerv(gl, GR_GL_VIEWPORT, (GrGLint*) this);
     }
 
     // sometimes we have a SkIRect from the client that we
     // want to simultaneously make relative to GL's viewport
     // and (optionally) convert from top-down to bottom-up.
+    void setRelativeTo(const GrGLIRect& glViewport, const SkIRect& devRect, GrSurfaceOrigin org) {
+        this->setRelativeTo(glViewport, devRect.x(), devRect.y(), devRect.width(), devRect.height(),
+                            org);
+    }
+
     void setRelativeTo(const GrGLIRect& glRect,
                        int leftOffset,
                        int topOffset,
                        int width,
                        int height,
                        GrSurfaceOrigin origin) {
         fLeft = glRect.fLeft + leftOffset;
         fWidth = width;
         if (kBottomLeft_GrSurfaceOrigin == origin) {
             fBottom = glRect.fBottom + (glRect.fHeight - topOffset - height);
@@ skipping 16 matching lines @@
     void invalidate() {fLeft = fWidth = fBottom = fHeight = -1;}
 
     bool operator ==(const GrGLIRect& glRect) const {
         return 0 == memcmp(this, &glRect, sizeof(GrGLIRect));
     }
 
     bool operator !=(const GrGLIRect& glRect) const {return !(*this == glRect);}
 };
 
 #endif