cc: Fix anti-aliasing of axis-aligned quads.

Axis-aligned quads with edges not aligned to pixel boundaries
are rendered incorrectly. These quads need anti-aliasing but
current code that determines if anti-aliasing is needed thinks
that no axis-aligned quads need it.

This fixes the problem by adding alignment to pixel boundaries
as an additional requirement to avoid anti-aliasing.

BUG=169374
TEST=GLRendererPixelTest.AxisAligned,GLRendererShaderTest.DrawSolidColorShad

Review URL: https://chromiumcodereview.appspot.com/12538005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@196423 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 23 insertions, 0 deletions

diff --git a/ui/gfx/rect_conversions.cc b/ui/gfx/rect_conversions.cc
index 251c0371..c548828 100644
--- a/ui/gfx/rect_conversions.cc
+++ b/ui/gfx/rect_conversions.cc
@@ -52,6 +52,24 @@ Rect ToNearestRect(const RectF& rect) {
   return Rect(min_x, min_y, max_x - min_x, max_y - min_y);
 }
 
+bool IsNearestRectWithinDistance(const gfx::RectF& rect, float distance) {
+  float float_min_x = rect.x();
+  float float_min_y = rect.y();
+  float float_max_x = rect.right();
+  float float_max_y = rect.bottom();
+
+  int min_x = ToRoundedInt(float_min_x);
+  int min_y = ToRoundedInt(float_min_y);
+  int max_x = ToRoundedInt(float_max_x);
+  int max_y = ToRoundedInt(float_max_y);
+
+  return
+      (std::abs(min_x - float_min_x) < distance) &&
+      (std::abs(min_y - float_min_y) < distance) &&
+      (std::abs(max_x - float_max_x) < distance) &&
+      (std::abs(max_y - float_max_y) < distance);
+}
+
 Rect ToFlooredRectDeprecated(const RectF& rect) {
   return Rect(ToFlooredInt(rect.x()),
               ToFlooredInt(rect.y()),
diff --git a/ui/gfx/rect_conversions.h b/ui/gfx/rect_conversions.h
index 7c971b3..854fb6e 100644
--- a/ui/gfx/rect_conversions.h
+++ b/ui/gfx/rect_conversions.h
@@ -22,6 +22,11 @@ UI_EXPORT Rect ToEnclosedRect(const RectF& rect);
 // you should use a different method.
 UI_EXPORT Rect ToNearestRect(const RectF& rect);
 
+// Returns true if the Rect produced after snapping the corners of the RectF
+// to an integer grid is withing |distance|.
+UI_EXPORT bool IsNearestRectWithinDistance(
+    const gfx::RectF& rect, float distance);
+
 // Returns a Rect obtained by flooring the values of the given RectF.
 // Please prefer the previous two functions in new code.
 UI_EXPORT Rect ToFlooredRectDeprecated(const RectF& rect);