Implements core logic for Pixel Canvas

ui/gfx/geometry/rect.h

Index: ui/gfx/geometry/rect.h
diff --git a/ui/gfx/geometry/rect.h b/ui/gfx/geometry/rect.h
index 4e914b8ca6555167b88c7e3446e2953fae622b35..18f97d112caf63f05d3ab49203f790611679d2ee 100644
--- a/ui/gfx/geometry/rect.h
+++ b/ui/gfx/geometry/rect.h
@@ -340,6 +340,35 @@ inline Rect ScaleToEnclosedRect(const Rect& rect, float scale) {
   return ScaleToEnclosedRect(rect, scale, scale);
 }
 
+inline Rect ScaleToRoundedRect(const Rect& rect, float x_scale, float y_scale) {

[sky, 2017/07/26 22:12:11]

Please add a description. Also, given the description I thought this was
creating a 'rounded' rect, which isn't what it does. Maybe ScaleUsingRounding? I
realize that is rather verbose, but it makes it obvious what is happening.

I also really worry about yet another way to scale, especially given this
function has no description as to *when* it should be used. Please motivate when
and why this should be used. Lastly, please add a description.

[malaykeshav, 2017/07/28 01:24:37]

This specific name was used to give consistency as it is used elsewhere in the
code as well. (gfx::ScaleToRoundedSize).

Adding a description of what it does and when it should be used.
Done

+  if (x_scale == 1.f && y_scale == 1.f)
+    return rect;
+
+  DCHECK(
+      base::IsValueInRangeForNumericType<int>(std::round(rect.x() * x_scale)));
+  DCHECK(
+      base::IsValueInRangeForNumericType<int>(std::round(rect.y() * y_scale)));
+  DCHECK(base::IsValueInRangeForNumericType<int>(
+      std::round(rect.right() * x_scale)));
+  DCHECK(base::IsValueInRangeForNumericType<int>(
+      std::round(rect.bottom() * y_scale)));
+
+  int x = static_cast<int>(std::round(rect.x() * x_scale));
+  int y = static_cast<int>(std::round(rect.y() * y_scale));
+  int r = rect.width() == 0
+              ? x
+              : static_cast<int>(std::round(rect.right() * x_scale));
+  int b = rect.height() == 0
+              ? y
+              : static_cast<int>(std::round(rect.bottom() * y_scale));
+
+  return Rect(x, y, r - x, b - y);
+}
+
+inline Rect ScaleToRoundedRect(const Rect& rect, float scale) {
+  return ScaleToRoundedRect(rect, scale, scale);
+}
+
 // This is declared here for use in gtest-based unit tests but is defined in
 // the //ui/gfx:test_support target. Depend on that to use this in your unit
 // test. This should not be used in production code - call ToString() instead.