Multiple DPI Tracking for ScreenWin

ui/gfx/win/rect_util.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 UI_GFX_WIN_RECT_UTIL_H_
+#define UI_GFX_WIN_RECT_UTIL_H_
+
+#include <stdint.h>
+
+#include "ui/gfx/gfx_export.h"
+
+namespace gfx {
+
+class Rect;
+
+namespace win {

[sky, 2016/02/17 04:40:28]

This file name is very generic. I don't think we want it to become a dumping
ground. How about a more specific name with comments?

[robliao, 2016/02/18 00:34:39]

Given that this is primarily used by ScreenWin, how about
screen_win_rect_util.*?

I'm holding off on the rename to preserve the comment comparison chain.

[sky, 2016/02/18 17:02:58]

SGTM

+
+enum class RectEdge {
+  BOTTOM = 0,
+  LEFT = 1,
+  TOP = 2,
+  RIGHT = 3,
+  NONE = 4,
+};
+
+// Returns |ref|'s RectEdge touching |test|.

[sky, 2016/02/17 17:28:48]

Clarify if the two rects are guaranteed to touch.

[robliao, 2016/02/18 00:34:39]

Done.

+GFX_EXPORT RectEdge FindTouchingRectEdge(const gfx::Rect& ref,
+                                         const gfx::Rect& test);
+
+// Returns a scaled and positioned rect based off of target_rect and context.

[sky, 2016/02/17 04:40:29]

there is no context param.

[robliao, 2016/02/18 00:34:39]

Clarified.

+// The reference rectangle and target rectangle may scale at different rates.
+// This function attempts to preserve the relative positioning of the target
+// rectangle with respect to the scaled rectangle in the face of differing
+// scale factors.

[sky, 2016/02/17 04:40:29]

Without looking at the implementation this description is confusing. It isn't
clear how ref_scaled_rect and ref_origin_rect related. I'm assuming
ref_scaled_rect is a scaled version of ref_origin_rect maybe with a different
origin. If that's true, then a scale and origin of the scaled would be less
error prone and less confusing.

[sky, 2016/02/17 17:28:48]

One more comment. It is also isn't clear if the rectangles always touch like you
have in the examples.

[robliao, 2016/02/18 00:34:39]

Clarified the comment and added another example. For ScaleAndPositionRect, the
new origin and scale factor are insufficient to calculate the new position since
reference edge positioning is critical to getting the right scaled rectangle
position.

+//
+// Examples:
+// +--------------+              Since both rectangles are of the same
+// |              |              scale factor, positions and sizes
+// |              |              remain the same.
+// |    REF 1x    +----------+
+// |              |          |
+// +--------------+    1x    |
+//                |          |
+//                +----------+
+//
+// Original
+// +--------------+              The 2x rectangle is scaled down while
+// |              |              maintaining a similar neighboring relationship
+// |              |              with the 1x rectangle.
+// |    REF 1x    +----------+
+// |              |          |
+// +--------------+    2x    |
+//                |          |
+//                +----------+
+// Scaled
+// +--------------+
+// |              |
+// |              |
+// |    REF 1x    |
+// |              +-----+
+// +--------------+  2x |
+//                +-----+
+GFX_EXPORT gfx::Rect ScaleAndPositionRect(gfx::Rect ref_scaled_rect,

[sky, 2016/02/17 04:40:29]

const& on the params here and below. Use different names in the function if you
want to modify the incoming values.

[robliao, 2016/02/18 00:34:39]

Done.

+                                          gfx::Rect ref_original_rect,
+                                          gfx::Rect target_rect,

[sky, 2016/02/17 17:28:48]

It's not clear if target_rect is scaled or not.

[robliao, 2016/02/18 00:34:39]

Clarified via rename.

+                                          float target_scale_factor);
+
+// Returns the squared distance between two rects.
+// The distance between two rects is the length of the shortest segment that can
+// be drawn between two rectangles. This segment generally connects two opposing
+// corners between rectangles like this...
+//
+// +----------+
+// |          |
+// +----------+
+//             \  <--- Shortest Segment
+//              \
+//               +---+
+//               |   |
+//               |   |
+//               +---+
+//
+// For rectangles that share coordinates within the same axis, that generally
+// means the segment is parallel to the axis and perpendicular to the edges.
+//
+//                 One of many shortest segments
+//  +----------+  /                            \    +--------+
+//  |          |  |                             \   |        |
+//  |          |  V  +---+                       \  +--------+
+//  |          |-----|   |                        \-->|
+//  +----------+     |   |                            +----+
+//                   |   |                            |    |
+//                   +---+                            +----+
+//
+// For rectangles that intersect each other, the distance is 0.
+//
+// The squared distance is used to avoid taking the square root as the common
+// usage is to compare distances greater than 1 unit.
+GFX_EXPORT int64_t SquaredDistanceBetweenRects(gfx::Rect ref, gfx::Rect rect);
+
+}  // namespace win
+}  // namespace gfx
+
+#endif  // UI_GFX_WIN_RECT_UTIL_H_