Pre-crop filled rects to avoid scissor

include/gpu/GrClip.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrClip_DEFINED
 #define GrClip_DEFINED
 
@@ skipping 91 matching lines @@
  */
 class GrClip {
 public:
     virtual bool quickContains(const SkRect&) const = 0;
     virtual void getConservativeBounds(int width, int height, SkIRect* devResult,
                                        bool* isIntersectionOfRects = nullptr) const = 0;
     virtual bool apply(GrContext*, const GrPipelineBuilder&, GrDrawContext*,
                        const SkRect* devBounds, GrAppliedClip*) const = 0;
 
     virtual ~GrClip() {}
+
+protected:
+    /**
+     * Returns true if a clip can safely disable its scissor test for a particular draw.
+     */
+    static bool CanIgnoreScissor(const SkIRect& scissorRect, const SkRect& drawBounds) {
+        // This is the maximum distance that a draw may extend beyond a clip's scissor and still
+        // count as inside. We use a sloppy compare because the draw may have chosen its bounds in a
+        // different coord system. The rationale for 1e-3 is that in the coverage case (and barring
+        // unexpected rounding), as long as coverage stays below 0.5 * 1/256 we ought to be OK.
+        constexpr SkScalar fuzz = 1e-3f;
+        SkASSERT(!scissorRect.isEmpty());
+        SkASSERT(!drawBounds.isEmpty());
+        return scissorRect.fLeft <= drawBounds.fLeft + fuzz &&
+               scissorRect.fTop <= drawBounds.fTop + fuzz &&
+               scissorRect.fRight >= drawBounds.fRight - fuzz &&
+               scissorRect.fBottom >= drawBounds.fBottom - fuzz;
+    }
+
+    friend class GrClipMaskManager;
 };
 
 /**
  * Specialized implementation for no clip.
  */
 class GrNoClip final : public GrClip {
 private:
     bool quickContains(const SkRect&) const final { return true; }
     void getConservativeBounds(int width, int height, SkIRect* devResult,
                                bool* isIntersectionOfRects) const final;
@@ skipping 89 matching lines @@
                                bool* isIntersectionOfRects) const final;
     bool apply(GrContext*, const GrPipelineBuilder&, GrDrawContext*,
                const SkRect* devBounds, GrAppliedClip*) const final;
 
 private:
     SkIPoint                          fOrigin;
     SkAutoTUnref<const SkClipStack>   fStack;
 };
 
 #endif