chrome/browser/chromeos/ui/accessibility_focus_ring_layer.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/chromeos/ui/accessibility_focus_ring_layer.h"
   6
   7 #include "ash/display/display_controller.h"
   8 #include "ash/shell.h"
   9 #include "base/bind.h"
  10 #include "ui/aura/window.h"
  11 #include "ui/compositor/layer.h"
  12 #include "ui/compositor/paint_recorder.h"
  13 #include "ui/gfx/canvas.h"
  14
  15 namespace chromeos {
  16
  17 namespace {
  18
  19 // The number of pixels in the color gradient that fades to transparent.
  20 const int kGradientWidth = 6;
  21
  22 // The color of the focus ring. In the future this might be a parameter.
  23 const int kFocusRingColorRed = 247;
  24 const int kFocusRingColorGreen = 152;
  25 const int kFocusRingColorBlue = 58;
  26
  27 int sign(int x) {
  28   return ((x > 0) ? 1 : (x == 0) ? 0 : -1);
  29 }
  30
  31 SkPath MakePath(const AccessibilityFocusRing& input_ring,
  32                 int outset,
  33                 const gfx::Vector2d& offset) {
  34   AccessibilityFocusRing ring = input_ring;
  35
  36   for (int i = 0; i < 36; i++) {
  37     gfx::Point p = input_ring.points[i];
  38     gfx::Point prev;
  39     gfx::Point next;
  40
  41     int prev_index = i;
  42     do {
  43       prev_index = (prev_index + 35) % 36;
  44       prev = input_ring.points[prev_index];
  45     } while (prev.x() == p.x() && prev.y() == p.y() && prev_index != i);
  46
  47     int next_index = i;
  48     do {
  49       next_index = (next_index + 1) % 36;
  50       next = input_ring.points[next_index];
  51     } while (next.x() == p.x() && next.y() == p.y() && next_index != i);
  52
  53     gfx::Point delta0 = gfx::Point(sign(p.x() - prev.x()),
  54                                    sign(p.y() - prev.y()));
  55     gfx::Point delta1 = gfx::Point(sign(next.x() - p.x()),
  56                                    sign(next.y() - p.y()));
  57
  58     if (delta0.x() == delta1.x() && delta0.y() == delta1.y()) {
  59       ring.points[i] = gfx::Point(
  60           input_ring.points[i].x() + outset * delta0.y(),
  61           input_ring.points[i].y() - outset * delta0.x());
  62     } else {
  63       ring.points[i] = gfx::Point(
  64           input_ring.points[i].x() + ((i + 13) % 36 >= 18 ? outset : -outset),
  65           input_ring.points[i].y() + ((i + 4) % 36 >= 18 ? outset : -outset));
  66     }
  67   }
  68
  69   SkPath path;
  70   gfx::Point p0 = ring.points[0] - offset;
  71   path.moveTo(SkIntToScalar(p0.x()), SkIntToScalar(p0.y()));
  72   for (int i = 0; i < 12; i++) {
  73     int index0 = ((3 * i) + 1) % 36;
  74     int index1 = ((3 * i) + 2) % 36;
  75     int index2 = ((3 * i) + 3) % 36;
  76     gfx::Point p0 = ring.points[index0] - offset;
  77     gfx::Point p1 = ring.points[index1] - offset;
  78     gfx::Point p2 = ring.points[index2] - offset;
  79     path.lineTo(SkIntToScalar(p0.x()), SkIntToScalar(p0.y()));
  80     path.quadTo(SkIntToScalar(p1.x()), SkIntToScalar(p1.y()),
  81                 SkIntToScalar(p2.x()), SkIntToScalar(p2.y()));
  82   }
  83
  84   return path;
  85 }
  86
  87 }  // namespace
  88
  89 AccessibilityFocusRingLayer::AccessibilityFocusRingLayer(
  90     FocusRingLayerDelegate* delegate)
  91     : FocusRingLayer(delegate) {
  92 }
  93
  94 AccessibilityFocusRingLayer::~AccessibilityFocusRingLayer() {}
  95
  96 void AccessibilityFocusRingLayer::Set(const AccessibilityFocusRing& ring) {
  97   ring_ = ring;
  98
  99   gfx::Rect bounds = ring.GetBounds();
 100   int inset = kGradientWidth;
 101   bounds.Inset(-inset, -inset, -inset, -inset);
 102
 103   gfx::Display display =
 104       gfx::Screen::GetNativeScreen()->GetDisplayMatching(bounds);
 105   aura::Window* root_window = ash::Shell::GetInstance()->display_controller()
 106       ->GetRootWindowForDisplayId(display.id());
 107   CreateOrUpdateLayer(root_window, "AccessibilityFocusRing");
 108
 109   // Update the layer bounds.
 110   layer()->SetBounds(bounds);
 111 }
 112
 113 void AccessibilityFocusRingLayer::OnPaintLayer(
 114     const ui::PaintContext& context) {
 115   ui::PaintRecorder recorder(context, layer()->size());
 116
 117   SkPaint paint;
 118   paint.setFlags(SkPaint::kAntiAlias_Flag);
 119   paint.setStyle(SkPaint::kStroke_Style);
 120   paint.setStrokeWidth(2);
 121
 122   SkPath path;
 123   gfx::Vector2d offset = layer()->bounds().OffsetFromOrigin();
 124   const int w = kGradientWidth;
 125   for (int i = 0; i < w; ++i) {
 126     paint.setColor(
 127         SkColorSetARGBMacro(
 128             255 * (w - i) * (w - i) / (w * w),
 129             kFocusRingColorRed, kFocusRingColorGreen, kFocusRingColorBlue));
 130     path = MakePath(ring_, i, offset);
 131     recorder.canvas()->DrawPath(path, paint);
 132   }
 133 }
 134
 135 }  // namespace chromeos