Compute rounded-ness of visual rects

third_party/WebKit/Source/platform/graphics/paint/GeometryMapper.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GeometryMapper_h
 #define GeometryMapper_h
 
 #include "platform/graphics/paint/FloatClipRect.h"
 #include "platform/graphics/paint/PropertyTreeState.h"
 #include "platform/transforms/TransformationMatrix.h"
@@ skipping 30 matching lines @@
   // localToAncestorVisualRect. Otherwise, maps the input rect to the
   // transform state which is the lowest common ancestor of
   // |sourceState.transform| and |destinationState.transform|, then multiplies
   // it by the the inverse transform mapping from the lowest common ancestor to
   // |destinationState.transform|.
   //
   // DCHECK fails if the clip of |destinationState| is not an ancestor of the
   // clip of |sourceState|, or the inverse transform is not invertible.
   //
   // |mappingRect| is both input and output.
+  //
+  // The output FloatClipRect may contain false positives for rounded-ness
+  // if a rounded clip is clipped out, and overly conservative results
+  // in the presences of transforms.
+  //
+  // TODO(chrishtr): we should provide a variant of these methods that
+  // guarantees a tight result, or else signals an error. crbug.com/708741
   static void sourceToDestinationVisualRect(
       const PropertyTreeState& sourceState,
       const PropertyTreeState& destinationState,
-      FloatRect& mappingRect);
+      FloatClipRect& mappingRect);
 
   // Same as sourceToDestinationVisualRect() except that only transforms are
   // applied.
   //
   // |mappingRect| is both input and output.
   static void sourceToDestinationRect(
       const TransformPaintPropertyNode* sourceTransformNode,
       const TransformPaintPropertyNode* destinationTransformNode,
       FloatRect& mappingRect);
 
   // Maps from a rect in |localTransformSpace| to its visual rect in
   // |ancestorState|. This is computed by multiplying the rect by its combined
   // transform between |localTransformSpace| and |ancestorSpace|, then
   // flattening into 2D space, then intersecting by the "clip visual rect" for
   // |localTransformState|'s clips. See above for the definition of "clip visual
   // rect".
   //
   // Note that the clip of |ancestorState| is *not* applied.
   //
   // DCHECK fails if any of the paint property tree nodes in
   // |localTransformState| are not equal to or a descendant of that in
   // |ancestorState|.
   //
   // |mappingRect| is both input and output.
+  //
+  // The output FloatClipRect may contain false positives for rounded-ness
+  // if a rounded clip is clipped out, and overly conservative results
+  // in the presences of transforms.
   static void localToAncestorVisualRect(
       const PropertyTreeState& localTransformState,
       const PropertyTreeState& ancestorState,
-      FloatRect& mappingRect);
+      FloatClipRect& mappingRect);
 
   // Maps from a rect in |localTransformNode| space to its transformed rect in
   // |ancestorTransformNode| space. This is computed by multiplying the rect by
   // the combined transform between |localTransformNode| and
   // |ancestorTransformNode|, then flattening into 2D space.
   //
   // DCHECK fails if |localTransformNode| is not equal to or a descendant of
   // |ancestorTransformNode|.
   //
   //|mappingRect| is both input and output.
@@ skipping 23 matching lines @@
   // This matrix may not be flattened. Since GeometryMapper only supports
   // flattened ancestor spaces, the returned matrix must be flattened to have
   // the correct semantics (calling mapRect() on it implicitly applies
   // flattening to the input; flattenTo2d() does it explicitly to tme matrix).
   static const TransformationMatrix& localToAncestorMatrix(
       const TransformPaintPropertyNode* localTransformNode,
       const TransformPaintPropertyNode* ancestorTransformNode);
 
   // Returns the "clip visual rect" between |localTransformState| and
   // |ancestorState|. See above for the definition of "clip visual rect".
+  //
+  // The output FloatClipRect may contain false positives for rounded-ness
+  // if a rounded clip is clipped out, and overly conservative results
+  // in the presences of transforms.
   static FloatClipRect localToAncestorClipRect(
       const PropertyTreeState& localTransformState,
       const PropertyTreeState& ancestorState);
 
   // Like localToAncestorClipRect, except it can handle destination transform
   // spaces which are not direct ancestors of the source transform space.
+  //
+  // The output FloatClipRect may contain false positives for rounded-ness
+  // if a rounded clip is clipped out, and overly conservative results
+  // in the presences of transforms.
   static const FloatClipRect& sourceToDestinationClipRect(
       const PropertyTreeState& sourceState,
       const PropertyTreeState& destinationState);
 
   // Returns the lowest common ancestor in the paint property tree.
   template <typename NodeType>
   static PLATFORM_EXPORT const NodeType* lowestCommonAncestor(const NodeType*,
                                                               const NodeType*);
 
   static void clearCache();
 
  private:
   // The internal methods do the same things as their public counterparts, but
   // take an extra |success| parameter which indicates if the function is
   // successful on return. See comments of the public functions for failure
   // conditions.
 
   static void sourceToDestinationVisualRectInternal(
       const PropertyTreeState& sourceState,
       const PropertyTreeState& destinationState,
-      FloatRect& mappingRect,
+      FloatClipRect& mappingRect,
       bool& success);
 
   static void localToAncestorVisualRectInternal(
       const PropertyTreeState& localTransformState,
       const PropertyTreeState& ancestorState,
-      FloatRect& mappingRect,
+      FloatClipRect& mappingRect,
       bool& success);
 
   static void localToAncestorRectInternal(
       const TransformPaintPropertyNode* localTransformNode,
       const TransformPaintPropertyNode* ancestorTransformNode,
       FloatRect&,
       bool& success);
 
   static const TransformationMatrix& localToAncestorMatrixInternal(
       const TransformPaintPropertyNode* localTransformNode,
       const TransformPaintPropertyNode* ancestorTransformNode,
       bool& success);
 
   static const FloatClipRect& localToAncestorClipRectInternal(
       const ClipPaintPropertyNode* descendant,
       const ClipPaintPropertyNode* ancestorClip,
       const TransformPaintPropertyNode* ancestorTransform,
       bool& success);
 
   static const FloatClipRect& sourceToDestinationClipRectInternal(
       const PropertyTreeState& sourceState,
       const PropertyTreeState& destinationState,
       bool& success);
 
   static void slowLocalToAncestorVisualRectWithEffects(
       const PropertyTreeState& localState,
       const PropertyTreeState& ancestorState,
-      FloatRect& mappingRect,
+      FloatClipRect& mappingRect,
       bool& success);
 
   static const TransformationMatrix& identityMatrix();
   static const FloatClipRect& infiniteClip();
   static FloatClipRect& tempRect();
 
   friend class GeometryMapperTest;
   friend class PaintLayerClipperTest;
 };
 
 }  // namespace blink
 
 #endif  // GeometryMapper_h