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

remoting/host/chromeos/pixel_rotator.h

+// 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.
+
+#ifndef REMOTING_HOST_CHROMEOS_PIXEL_ROTATOR_H_
+#define REMOTING_HOST_CHROMEOS_PIXEL_ROTATOR_H_
+
+#include "ui/aura/window_observer.h"
+#include "ui/gfx/geometry/point_f.h"
+#include "ui/gfx/transform.h"
+
+namespace aura {
+class Window;
+}  // namespace aura
+
+namespace remoting {
+
+// A class that performs coordinates system transformation between the root

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

coordinate transformations

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

Done.

+// window coordinates and the native screen coordinates, according to the
+// current display rotation settings.
+//
+// The root window coordinate of a pixel is its relative location to the top

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

Root window coordinates are expressed relative to the top left...

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

Done.

+// left corner of the root window whereas the native screen coordinate is the
+// physical location of the pixel that is rendered on the display.  Both

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

What does "physical location" mean? Presumably you mean relative to the top-left
of the framebuffer, which may not match the root window either in origin nor
orientation?

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

Done.

+// coordinates systems are always in device pixels.
+
+// The root window coordinate of a pixel is different from its native screen
+// coordinate when the display is rotated.  For example, when the display is
+// rotated by 90 deg, the pixel located (x, y) in the window is rendered at
+// (height - y, x) on the display.

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

This comment just seems a more specific example of the previous paragraph?

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

Yes, it is always better to illustrate with an example

+class PixelRotator : public aura::WindowObserver {

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

This doesn't touch pixels, and it may translate as well as rotate - it
transforms points so call it e.g. OzoneCoordinateTransformer?

+ public:
+  PixelRotator();

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

Presumably the root window is bound when the ctor is invoked?

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

Yes

+  ~PixelRotator();

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

override

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

Done.

+
+  // aura::WindowObserver interface.
+  void OnWindowTransformed(aura::Window* window) override;

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

Is this part of the PixelRotator interface? If not then move it into the private
section.

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

Done.

+
+  // Converts from the root window coordinate system to the native screen
+  // coordinate system.
+  gfx::PointF ToScreenPixel(const gfx::PointF& window_location);
+
+  // Converts from the native screen coordinate system to the root window
+  // coordinate system.
+  gfx::PointF FromScreenPixel(const gfx::PointF& screen_location);
+
+ private:
+  aura::Window* root_window_;
+  gfx::Transform transform_;

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

suggest root_to_screen or root_to_native

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

Done.

+  gfx::Transform inverse_;

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

similarly here

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

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(PixelRotator);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_CHROMEOS_PIXEL_ROTATOR_H_