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

remoting/host/chromeos/pixel_rotator.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/pixel_rotator.h"
+
+#include "ash/shell.h"
+#include "ui/aura/window_tree_host.h"
+#include "ui/compositor/dip_util.h"
+
+namespace remoting {
+
+PixelRotator::PixelRotator()
+    : root_window_(nullptr) {

[Wez, 2014/12/06 01:55:16]

nit: no need to init to nullptr only to then overwrite it; consider moving the
GetPrimaryRootWindow call into the initializer.

[kelvinp, 2014/12/08 18:41:43]

Done.

+  root_window_ = ash::Shell::GetPrimaryRootWindow();
+  root_window_->AddObserver(this);
+}
+
+PixelRotator::~PixelRotator() {
+  root_window_->RemoveObserver(this);
+}
+
+void PixelRotator::OnWindowTransformed(aura::Window* window) {
+  if (window != root_window_) {

[Wez, 2014/12/06 01:55:16]

Since you only observed the root window, can you ever get other windows listed
here? Consider a DCHECK or CHECK if not.

[kelvinp, 2014/12/08 18:41:43]

Done.

+    return;
+  }
+
+  ui::Layer* layer = root_window_->layer();
+  float scale = ui::GetDeviceScaleFactor(layer);
+
+  // |layer->transform()| returns a transform comprising a rotation and a
+  // translation, but in DIP, so we need to switch device pixels to

[Wez, 2014/12/06 01:55:16]

DIPs

[kelvinp, 2014/12/08 18:41:43]

Done.

+  // 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;
+
+  ignore_result(rotation.GetInverse(&inverse_rotation));

[Wez, 2014/12/06 01:55:16]

Do we really want to ignore the result? Consider saving it to a bool and
DCHECKing it if it should never fail

[kelvinp, 2014/12/08 18:41:43]

Done.

+  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)
+  transform_ = to_device_pixels * rotation * to_dip;
+  inverse_ = to_device_pixels * inverse_rotation * to_dip;
+}
+
+gfx::PointF PixelRotator::ToScreenPixel(const gfx::PointF& window_location) {

[Wez, 2014/12/06 01:55:17]

nit: suggest root_location, here and elsewhere; otherwise it reads as though
this might just be a simple window-to/from-screen converter?

[kelvinp, 2014/12/08 18:41:44]

Done.

+  gfx::Point3F screen_location(window_location);
+  transform_.TransformPoint(&screen_location);
+  return screen_location.AsPointF();
+}
+
+gfx::PointF PixelRotator::FromScreenPixel(const gfx::PointF& screen_location) {
+  gfx::Point3F window_location(screen_location);
+  inverse_.TransformPoint(&window_location);
+  return window_location.AsPointF();
+}
+
+}  // namespace remoting