[Android] Use DIP coordinates with MotionEventAndroid

content/browser/renderer_host/input/motion_event_android.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 CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_
 
 #include <jni.h>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "ui/events/gesture_detection/motion_event.h"
 #include "ui/gfx/geometry/point_f.h"
 
 namespace content {
 
 // Implementation of ui::MotionEvent wrapping a native Android MotionEvent.
+// All *input* coordinates are in device pixels (as with Android MotionEvent),
+// while all *output* coordinates are in DIPs (as with WebTouchEvent).
 class MotionEventAndroid : public ui::MotionEvent {
  public:
   // Forcing the caller to provide all cached values upon construction
   // eliminates the need to perform a JNI call to retrieve values individually.
-  MotionEventAndroid(JNIEnv* env,
+  MotionEventAndroid(float pix_to_dip,
+                     JNIEnv* env,
                      jobject event,
                      jlong time_ms,
                      jint android_action,
                      jint pointer_count,
                      jint history_size,
                      jint action_index,
-                     jfloat pos_x_0,
-                     jfloat pos_y_0,
-                     jfloat pos_x_1,
-                     jfloat pos_y_1,
+                     jfloat pos_x_0_pixels,
+                     jfloat pos_y_0_pixels,
+                     jfloat pos_x_1_pixels,
+                     jfloat pos_y_1_pixels,
                      jint pointer_id_0,
                      jint pointer_id_1,
-                     jfloat touch_major_0,
-                     jfloat touch_major_1);
+                     jfloat touch_major_0_pixels,
+                     jfloat touch_major_1_pixels);
   virtual ~MotionEventAndroid();
 
   // ui::MotionEvent methods.
   virtual int GetId() const OVERRIDE;
   virtual Action GetAction() const OVERRIDE;
   virtual int GetActionIndex() const OVERRIDE;
   virtual size_t GetPointerCount() const OVERRIDE;
   virtual int GetPointerId(size_t pointer_index) const OVERRIDE;
   virtual float GetX(size_t pointer_index) const OVERRIDE;
   virtual float GetY(size_t pointer_index) const OVERRIDE;
@@ skipping 22 matching lines @@
   base::TimeTicks GetDownTime() const;
 
   static bool RegisterMotionEventAndroid(JNIEnv* env);
 
   static base::android::ScopedJavaLocalRef<jobject> Obtain(
       const MotionEventAndroid& event);
   static base::android::ScopedJavaLocalRef<jobject> Obtain(
       base::TimeTicks down_time,
       base::TimeTicks event_time,
       Action action,
-      float x,
-      float y);
+      float x_pixels,
+      float y_pixels);
 
  private:
   MotionEventAndroid();
-  MotionEventAndroid(JNIEnv* env, jobject event);
+  MotionEventAndroid(float pix_to_dip, JNIEnv* env, jobject event);
   MotionEventAndroid(const MotionEventAndroid&);
   MotionEventAndroid& operator=(const MotionEventAndroid&);
 
+  float ToDips(float pixels) const;
+  gfx::PointF ToDips(const gfx::PointF& pixels) const;
+
   // Cache pointer coords, id's and major lengths for the most common
   // touch-related scenarios, i.e., scrolling and pinching.  This prevents
   // redundant JNI fetches for the same bits.
   enum { MAX_POINTERS_TO_CACHE = 2 };
 
   // The Java reference to the underlying MotionEvent.
   base::android::ScopedJavaGlobalRef<jobject> event_;
 
   base::TimeTicks cached_time_;
   Action cached_action_;
   size_t cached_pointer_count_;
   size_t cached_history_size_;
   int cached_action_index_;
   gfx::PointF cached_positions_[MAX_POINTERS_TO_CACHE];
   int cached_pointer_ids_[MAX_POINTERS_TO_CACHE];
   float cached_touch_majors_[MAX_POINTERS_TO_CACHE];
 
+  // Used to convert pixel coordinates from the Java-backed MotionEvent to
+  // DIP coordinates cached/returned by the MotionEventAndroid.
+  const float pix_to_dip_;
+
   // Whether |event_| should be recycled on destruction. This will only be true
   // for those events generated via |Obtain(...)|.
   bool should_recycle_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_MOTION_EVENT_ANDROID_H_