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