Implement Chrome OS accessibility features to highlight focus, caret & cursor.

chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc

+// 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.
+
+#include "chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.h"
+
+#include "ash/display/window_tree_host_manager.h"
+#include "ash/shell.h"
+#include "base/bind.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkPath.h"
+#include "ui/aura/window.h"
+#include "ui/compositor/layer.h"
+#include "ui/compositor/paint_recorder.h"
+#include "ui/gfx/canvas.h"
+
+namespace chromeos {
+
+namespace {
+
+// The number of pixels in the color gradient that fades to transparent.
+const int kGradientWidth = 8;
+
+// The radius of the ring in pixels.
+const int kCursorRingRadius = 24;
+
+// Extra margin to add to the layer in pixels.
+const int kLayerMargin = 8;
+
+}  // namespace
+
+AccessibilityCursorRingLayer::AccessibilityCursorRingLayer(
+    FocusRingLayerDelegate* delegate,
+    int red,
+    int green,
+    int blue)
+    : FocusRingLayer(delegate), red_(red), green_(green), blue_(blue) {}
+
+AccessibilityCursorRingLayer::~AccessibilityCursorRingLayer() {}
+
+void AccessibilityCursorRingLayer::Set(const gfx::Point& location) {
+  location_ = location;
+
+  gfx::Rect bounds = gfx::Rect(location.x(), location.y(), 0, 0);
+  int inset = kGradientWidth + kCursorRingRadius + kLayerMargin;
+  bounds.Inset(-inset, -inset, -inset, -inset);
+
+  gfx::Display display = gfx::Screen::GetScreen()->GetDisplayMatching(bounds);
+  aura::Window* root_window = ash::Shell::GetInstance()
+                                  ->window_tree_host_manager()
+                                  ->GetRootWindowForDisplayId(display.id());
+  CreateOrUpdateLayer(root_window, "AccessibilityCursorRing");
+
+  // Update the layer bounds.
+  layer()->SetBounds(bounds);
+}
+
+void AccessibilityCursorRingLayer::SetOpacity(float opacity) {
+  layer()->SetOpacity(opacity);
+}
+
+void AccessibilityCursorRingLayer::OnPaintLayer(
+    const ui::PaintContext& context) {
+  ui::PaintRecorder recorder(context, layer()->size());
+
+  SkPaint paint;
+  paint.setFlags(SkPaint::kAntiAlias_Flag);
+  paint.setStyle(SkPaint::kStroke_Style);
+  paint.setStrokeWidth(2);
+
+  gfx::Rect r = layer()->bounds();
+  r.Offset(-r.OffsetFromOrigin());
+  r.Inset(kLayerMargin, kLayerMargin, kLayerMargin, kLayerMargin);
+  const int w = kGradientWidth;
+  for (int i = 0; i < w; ++i) {
+    paint.setColor(
+        SkColorSetARGBMacro(255 * (i) * (i) / (w * w), red_, green_, blue_));
+    SkPath path;
+    path.addOval(SkRect::MakeXYWH(r.x(), r.y(), r.width(), r.height()));
+    r.Inset(1, 1, 1, 1);
+    recorder.canvas()->DrawPath(path, paint);
+  }
+}
+
+}  // namespace chromeos