Implement rudimentary touchscreen support in mus.

components/mus/ws/touch_controller.cc

Index: components/mus/ws/touch_controller.cc
diff --git a/components/mus/ws/touch_controller.cc b/components/mus/ws/touch_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e78b3489dc90b3486f1b6514095d079a1c9b3ff2
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+++ b/components/mus/ws/touch_controller.cc
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+// 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 "components/mus/ws/touch_controller.h"
+
+#include <set>
+#include <vector>
+
+#include "base/logging.h"
+#include "components/mus/ws/display.h"
+#include "components/mus/ws/display_manager.h"
+#include "ui/events/devices/device_data_manager.h"
+#include "ui/events/devices/touchscreen_device.h"
+#include "ui/gfx/geometry/size.h"
+#include "ui/gfx/transform.h"
+
+namespace mus {
+namespace ws {
+
+namespace {
+
+// Computes the scale ratio for the TouchEvent's radius.
+double ComputeTouchResolutionScale(const Display* touch_display,
+                                   const ui::TouchscreenDevice& touch_device) {
+  gfx::Size touch_display_size = touch_display->GetSize();
+
+  if (touch_device.size.IsEmpty() || touch_display_size.IsEmpty())
+    return 1.0;
+
+  double display_area = touch_display_size.GetArea();
+  double touch_area = touch_device.size.GetArea();
+  double ratio = std::sqrt(display_area / touch_area);
+
+  return ratio;
+}
+
+// Computes a touch transform that maps from window bounds to touchscreen size.
+// Assumes scale factor of 1.0.
+gfx::Transform ComputeTouchTransform(
+    const Display* touch_display,
+    const ui::TouchscreenDevice& touch_device) {
+  gfx::Size touch_display_size = touch_display->GetSize();
+
+  gfx::SizeF current_size(touch_display_size);
+  gfx::SizeF touch_area(touch_device.size);
+  gfx::Transform transform;
+
+  if (current_size.IsEmpty() || touch_area.IsEmpty())
+    return transform;
+
+  // Take care of scaling between touchscreen area and display resolution.
+  transform.Scale(current_size.width() / touch_area.width(),
+                  current_size.height() / touch_area.height());
+  return transform;
+}
+
+}  // namespace
+
+TouchController::TouchController(DisplayManager* display_manager)
+    : display_manager_(display_manager) {
+  DCHECK(display_manager_);
+  ui::DeviceDataManager::GetInstance()->AddObserver(this);
+}
+
+TouchController::~TouchController() {
+  ui::DeviceDataManager::GetInstance()->RemoveObserver(this);
+}
+
+void TouchController::UpdateTouchTransforms() const {
+  ui::DeviceDataManager* device_manager = ui::DeviceDataManager::GetInstance();
+  device_manager->ClearTouchDeviceAssociations();
+
+  const std::set<Display*>& touch_displays = display_manager_->displays();
+  const std::vector<ui::TouchscreenDevice>& touch_devices =
+      device_manager->GetTouchscreenDevices();
+
+  // Mash can only handle a single display so this doesn't implement support for
+  // matching touchscreens with multiple displays.
+  // TODO(kylechar): Implement support for multiple displays when needed.
+  if (touch_displays.size() == 1 && touch_devices.size() == 1) {
+    const Display* touch_display = *touch_displays.begin();
+    const ui::TouchscreenDevice& touch_device = touch_devices[0];
+
+    int64_t touch_display_id = touch_display->GetPlatformDisplayId();
+    int touch_device_id = touch_device.id;
+
+    if (touch_device_id != ui::InputDevice::kInvalidId) {
+      device_manager->UpdateTouchRadiusScale(
+          touch_device_id,
+          ComputeTouchResolutionScale(touch_display, touch_device));
+
+      device_manager->UpdateTouchInfoForDisplay(
+          touch_display_id, touch_device_id,
+          ComputeTouchTransform(touch_display, touch_device));
+    }
+  }
+}
+
+void TouchController::OnTouchscreenDeviceConfigurationChanged() {
+  UpdateTouchTransforms();
+}
+
+}  // namespace ws
+}  // namespace mus