Adjust gfx::Rect's width and height to avoid integer overflow

ui/gfx/geometry/rect.h

 // Copyright (c) 2012 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.
 
 // Defines a simple integer rectangle class.  The containment semantics
 // are array-like; that is, the coordinate (x, y) is considered to be
 // contained by the rectangle, but the coordinate (x + width, y) is not.
 // The class will happily let you create malformed rectangles (that is,
 // rectangles with negative width and/or height), but there will be assertions
 // in the operations (such as Contains()) to complain in this case.
@@ skipping 14 matching lines @@
 #if defined(OS_WIN)
 typedef struct tagRECT RECT;
 #elif defined(OS_MACOSX)
 typedef struct CGRect CGRect;
 #endif
 
 namespace gfx {
 
 class Insets;
 
+#define GetClampedValue(origin, size)                           \

[danakj, 2016/08/25 17:59:21]

can this be a constexpr function instead, in an internal namespace?

[sunxd, 2016/08/25 19:25:09]

Acknowledged.

+  origin > 0 && std::numeric_limits<int>::max() - origin < size \
+      ? std::numeric_limits<int>::max() - origin                \
+      : size
+
 class GFX_EXPORT Rect {
  public:
   constexpr Rect() = default;
   constexpr Rect(int width, int height) : size_(width, height) {}
   constexpr Rect(int x, int y, int width, int height)
-      : origin_(x, y), size_(width, height) {}
+      : origin_(x, y),
+        size_(GetClampedValue(x, width), GetClampedValue(y, height)) {}
   constexpr explicit Rect(const Size& size) : size_(size) {}
   constexpr Rect(const Point& origin, const Size& size)
-      : origin_(origin), size_(size) {}
+      : origin_(origin),
+        size_(GetClampedValue(origin.x(), size.width()),
+              GetClampedValue(origin.y(), size.height())) {}
 
 #if defined(OS_WIN)
   explicit Rect(const RECT& r);
 #elif defined(OS_MACOSX)
   explicit Rect(const CGRect& r);
 #endif
 
 #if defined(OS_WIN)
   // Construct an equivalent Win32 RECT object.
   RECT ToRECT() const;
 #elif defined(OS_MACOSX)
   // Construct an equivalent CoreGraphics object.
   CGRect ToCGRect() const;
 #endif
 
   constexpr int x() const { return origin_.x(); }
   void set_x(int x) { origin_.set_x(x); }
 
   constexpr int y() const { return origin_.y(); }
   void set_y(int y) { origin_.set_y(y); }
 
   constexpr int width() const { return size_.width(); }
   void set_width(int width) { size_.set_width(width); }

[danakj, 2016/08/25 17:59:21]

How about the non-const methods in this class that can change the size or
offset?

[sunxd, 2016/08/25 19:25:09]

I'm afraid that clamping values in these functions would hurt the performance.
The case where clamping is needed is when we have aggressively huge transforms,
which might be a rare case in the real world. But maybe the cost is acceptable?

We have both the set functions and operator+=/-= that may modify the components.

 
   constexpr int height() const { return size_.height(); }
   void set_height(int height) { size_.set_height(height); }
 
   constexpr const Point& origin() const { return origin_; }
   void set_origin(const Point& origin) { origin_ = origin; }
 
   constexpr const Size& size() const { return size_; }
   void set_size(const Size& size) { size_ = size; }
 
@@ skipping 193 matching lines @@
 }
 
 // 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.
 void PrintTo(const Rect& rect, ::std::ostream* os);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_RECT_H_