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/window_tree_host_manager.h"
   8 #include "ash/shell.h"
   9 #include "base/bind.h"
  10 #include "third_party/skia/include/core/SkPaint.h"
  11 #include "third_party/skia/include/core/SkPath.h"
  12 #include "ui/aura/window.h"
  13 #include "ui/compositor/layer.h"
  14 #include "ui/compositor/paint_recorder.h"
  15 #include "ui/gfx/canvas.h"
  16
  17 namespace chromeos {
  18
  19 namespace {
  20
  21 // The number of pixels in the color gradient that fades to transparent.
  22 const int kGradientWidth = 6;
  23
  24 // The color of the focus ring. In the future this might be a parameter.
  25 const int kFocusRingColorRed = 247;
  26 const int kFocusRingColorGreen = 152;
  27 const int kFocusRingColorBlue = 58;
  28
  29 int sign(int x) {
  30   return ((x > 0) ? 1 : (x == 0) ? 0 : -1);
  31 }
  32
  33 SkPath MakePath(const AccessibilityFocusRing& input_ring,
  34                 int outset,
  35                 const gfx::Vector2d& offset) {
  36   AccessibilityFocusRing ring = input_ring;
  37
  38   for (int i = 0; i < 36; i++) {
  39     gfx::Point p = input_ring.points[i];
  40     gfx::Point prev;
  41     gfx::Point next;
  42
  43     int prev_index = i;
  44     do {
  45       prev_index = (prev_index + 35) % 36;
  46       prev = input_ring.points[prev_index];
  47     } while (prev.x() == p.x() && prev.y() == p.y() && prev_index != i);
  48
  49     int next_index = i;
  50     do {
  51       next_index = (next_index + 1) % 36;
  52       next = input_ring.points[next_index];
  53     } while (next.x() == p.x() && next.y() == p.y() && next_index != i);
  54
  55     gfx::Point delta0 = gfx::Point(sign(p.x() - prev.x()),
  56                                    sign(p.y() - prev.y()));
  57     gfx::Point delta1 = gfx::Point(sign(next.x() - p.x()),
  58                                    sign(next.y() - p.y()));
  59
  60     if (delta0.x() == delta1.x() && delta0.y() == delta1.y()) {
  61       ring.points[i] = gfx::Point(
  62           input_ring.points[i].x() + outset * delta0.y(),
  63           input_ring.points[i].y() - outset * delta0.x());
  64     } else {
  65       ring.points[i] = gfx::Point(
  66           input_ring.points[i].x() + ((i + 13) % 36 >= 18 ? outset : -outset),
  67           input_ring.points[i].y() + ((i + 4) % 36 >= 18 ? outset : -outset));
  68     }
  69   }
  70
  71   SkPath path;
  72   gfx::Point p0 = ring.points[0] - offset;
  73   path.moveTo(SkIntToScalar(p0.x()), SkIntToScalar(p0.y()));
  74   for (int i = 0; i < 12; i++) {
  75     int index0 = ((3 * i) + 1) % 36;
  76     int index1 = ((3 * i) + 2) % 36;
  77     int index2 = ((3 * i) + 3) % 36;
  78     gfx::Point p0 = ring.points[index0] - offset;
  79     gfx::Point p1 = ring.points[index1] - offset;
  80     gfx::Point p2 = ring.points[index2] - offset;
  81     path.lineTo(SkIntToScalar(p0.x()), SkIntToScalar(p0.y()));
  82     path.quadTo(SkIntToScalar(p1.x()), SkIntToScalar(p1.y()),
  83                 SkIntToScalar(p2.x()), SkIntToScalar(p2.y()));
  84   }
  85
  86   return path;
  87 }
  88
  89 }  // namespace
  90
  91 AccessibilityFocusRingLayer::AccessibilityFocusRingLayer(
  92     FocusRingLayerDelegate* delegate)
  93     : FocusRingLayer(delegate) {
  94 }
  95
  96 AccessibilityFocusRingLayer::~AccessibilityFocusRingLayer() {}
  97
  98 void AccessibilityFocusRingLayer::Set(const AccessibilityFocusRing& ring) {
  99   ring_ = ring;
 100
 101   gfx::Rect bounds = ring.GetBounds();
 102   int inset = kGradientWidth;
 103   bounds.Inset(-inset, -inset, -inset, -inset);
 104
 105   gfx::Display display =
 106       gfx::Screen::GetNativeScreen()->GetDisplayMatching(bounds);
 107   aura::Window* root_window = ash::Shell::GetInstance()
 108                                   ->window_tree_host_manager()
 109                                   ->GetRootWindowForDisplayId(display.id());
 110   CreateOrUpdateLayer(root_window, "AccessibilityFocusRing");
 111
 112   // Update the layer bounds.
 113   layer()->SetBounds(bounds);
 114 }
 115
 116 void AccessibilityFocusRingLayer::OnPaintLayer(
 117     const ui::PaintContext& context) {
 118   ui::PaintRecorder recorder(context, layer()->size());
 119
 120   SkPaint paint;
 121   paint.setFlags(SkPaint::kAntiAlias_Flag);
 122   paint.setStyle(SkPaint::kStroke_Style);
 123   paint.setStrokeWidth(2);
 124
 125   SkPath path;
 126   gfx::Vector2d offset = layer()->bounds().OffsetFromOrigin();
 127   const int w = kGradientWidth;
 128   for (int i = 0; i < w; ++i) {
 129     paint.setColor(
 130         SkColorSetARGBMacro(
 131             255 * (w - i) * (w - i) / (w * w),
 132             kFocusRingColorRed, kFocusRingColorGreen, kFocusRingColorBlue));
 133     path = MakePath(ring_, i, offset);
 134     recorder.canvas()->DrawPath(path, paint);
 135   }
 136 }
 137
 138 }  // namespace chromeos