Scale TouchEvent's radius when touchscreen is in mirror mode

TouchEvent's radius on Pixel is reported in the touchscreen's
native resolution. When Pixel is connected to an external screen
and running in mirror mode, the radius value is too large for
the external screen's low display resolution. The radius value
needs to be scaled properly in this case.

BUG=229932
TEST=Switching to mirror mode when connecting Pixel to a low
resolution external display, following the test in the issue
and make sure the radius has a sensible value.

Review URL: https://chromiumcodereview.appspot.com/14279002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@195075 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 44 insertions, 0 deletions

diff --git a/chromeos/display/output_configurator.cc b/chromeos/display/output_configurator.cc
index 94b603f..903f49b 100644
--- a/chromeos/display/output_configurator.cc
+++ b/chromeos/display/output_configurator.cc
@@ -428,6 +428,8 @@ bool OutputConfigurator::EnterState(
           if (outputs[i].mirror_mode != outputs[i].native_mode &&
               outputs[i].is_aspect_preserving_scaling) {
             ctm = GetMirrorModeCTM(&outputs[i]);
+            mirrored_display_area_ratio_map_[outputs[i].touch_device_id] =
+              GetMirroredDisplayAreaRatio(&outputs[i]);
           }
           delegate_->ConfigureCTM(outputs[i].touch_device_id, ctm);
         }
@@ -562,4 +564,28 @@ OutputConfigurator::GetMirrorModeCTM(
   return ctm;  // Same aspect ratio - return identity
 }
 
+float OutputConfigurator::GetMirroredDisplayAreaRatio(
+    const OutputConfigurator::OutputSnapshot* output) {
+  float area_ratio = 1.0f;
+  int native_mode_width = 0, native_mode_height = 0;
+  int mirror_mode_width = 0, mirror_mode_height = 0;
+  if (!delegate_->GetModeDetails(output->native_mode,
+          &native_mode_width, &native_mode_height, NULL) ||
+      !delegate_->GetModeDetails(output->mirror_mode,
+          &mirror_mode_width, &mirror_mode_height, NULL))
+    return area_ratio;
+
+  if (native_mode_height == 0 || mirror_mode_height == 0 ||
+      native_mode_width == 0 || mirror_mode_width == 0)
+    return area_ratio;
+
+  float width_ratio = static_cast<float>(mirror_mode_width) /
+      static_cast<float>(native_mode_width);
+  float height_ratio = static_cast<float>(mirror_mode_height) /
+      static_cast<float>(native_mode_height);
+
+  area_ratio = width_ratio * height_ratio;
+  return area_ratio;
+}
+
 }  // namespace chromeos
diff --git a/chromeos/display/output_configurator.h b/chromeos/display/output_configurator.h
index 34e9384..faef729 100644
--- a/chromeos/display/output_configurator.h
+++ b/chromeos/display/output_configurator.h
@@ -5,6 +5,7 @@
 #ifndef CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 #define CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 
+#include <map>
 #include <vector>
 
 #include "base/basictypes.h"
@@ -283,6 +284,10 @@ class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
   // suspended.
   void ResumeDisplays();
 
+  const std::map<int, float>& GetMirroredDisplayAreaRatioMap() {
+    return mirrored_display_area_ratio_map_;
+  }
+
  private:
   // Configure outputs.
   void ConfigureOutputs();
@@ -307,9 +312,22 @@ class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
   CoordinateTransformation GetMirrorModeCTM(
       const OutputConfigurator::OutputSnapshot* output);
 
+  // Returns the ratio between mirrored mode area and native mode area:
+  // (mirror_mode_width * mirrow_mode_height) / (native_width * native_height)
+  float GetMirroredDisplayAreaRatio(
+      const OutputConfigurator::OutputSnapshot* output);
+
   StateController* state_controller_;
   scoped_ptr<Delegate> delegate_;
 
+  // Key of the map is the touch display's id, and the value of the map is the
+  // touch display's area ratio in mirror mode defined as :
+  // mirror_mode_area / native_mode_area.
+  // This is used for scaling touch event's radius when the touch display is in
+  // mirror mode :
+  // new_touch_radius = sqrt(area_ratio) * old_touch_radius
+  std::map<int, float> mirrored_display_area_ratio_map_;
+
   // This is detected by the constructor to determine whether or not we should
   // be enabled.  If we aren't running on ChromeOS, we can't assume that the
   // Xrandr X11 extension is supported.