Remote assistance on Chrome OS Part IX - Input injection on Ozone

remoting/host/chromeos/point_transformer.cc

+// Copyright 2014 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 "remoting/host/chromeos/point_transformer.h"
+
+#include "ash/shell.h"
+#include "ui/aura/window_tree_host.h"
+#include "ui/compositor/dip_util.h"
+
+namespace remoting {
+
+PointTransformer::PointTransformer() {
+  root_window_ = ash::Shell::GetPrimaryRootWindow();
+  root_window_->AddObserver(this);
+}
+
+PointTransformer::~PointTransformer() {
+  root_window_->RemoveObserver(this);
+}
+
+void PointTransformer::OnWindowTransformed(aura::Window* window) {
+  CHECK_EQ(window, root_window_);
+
+  ui::Layer* layer = root_window_->layer();
+  float scale = ui::GetDeviceScaleFactor(layer);
+
+  // |layer->transform()| returns a transform comprising a rotation and a
+  // translation, but in DIPs, so we need to switch device pixels to
+  // DIPs, apply it, then switch from DIPs back to device pixels.
+  gfx::Transform rotation = layer->transform();
+  gfx::Transform inverse_rotation;
+  gfx::Transform to_device_pixels;
+  gfx::Transform to_dip;
+
+  CHECK(!rotation.GetInverse(&inverse_rotation))
+      << "Cannot inverse the root transform." << rotation.ToString();
+
+  to_device_pixels.Scale(scale, scale);
+  to_dip.Scale(1 / scale, 1 / scale);
+
+  // Matrix transformations are applied from right to left.  See annotations.
+  //                (3)                (2)        (1)
+  root_to_screen_ = to_device_pixels * rotation * to_dip;
+  screen_to_root_ = to_device_pixels * inverse_rotation * to_dip;
+}
+
+gfx::PointF PointTransformer::ToScreenCoordinates(
+    const gfx::PointF& root_location) {
+  gfx::Point3F screen_location(root_location);
+  root_to_screen_.TransformPoint(&screen_location);
+  return screen_location.AsPointF();
+}
+
+gfx::PointF PointTransformer::FromScreenCoordinates(
+    const gfx::PointF& screen_location) {
+  gfx::Point3F root_location(screen_location);
+  screen_to_root_.TransformPoint(&root_location);
+  return root_location.AsPointF();
+}
+
+}  // namespace remoting