Implement touch control

tools/viewer/sk_app/Window.h

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef Window_DEFINED
 #define Window_DEFINED
 
 #include "DisplayParams.h"
+#include "SkRect.h"
+#include "SkTouchGesture.h"
 #include "SkTypes.h"
-#include "SkRect.h"
 
 class SkCanvas;
 
 namespace sk_app {
 
 class WindowContext;
 
 class Window {
 public:
     static Window* CreateNativeWindow(void* platformData);
@@ skipping 93 matching lines @@
     }
 
     void registerPaintFunc(OnPaintFunc func, void* userData) {
         fPaintFunc = func;
         fPaintUserData = userData;
     }
 
     bool onChar(SkUnichar c, uint32_t modifiers);
     bool onKey(Key key, InputState state, uint32_t modifiers);
     bool onMouse(int x, int y, InputState state, uint32_t modifiers);
+    bool onTouch(int owner, InputState state, float x, float y);  // multi-owner = multi-touch
     void onPaint();
     void onResize(uint32_t width, uint32_t height);
 
     uint32_t width() { return fWidth; }
     uint32_t height() { return fHeight;  }
 
     virtual const DisplayParams& getDisplayParams();
     void setDisplayParams(const DisplayParams& params);
 
+    const SkMatrix& getGestureLocalM();
+    const SkMatrix& getGestureGlobalM() const;
+
 protected:
     Window();
 
     uint32_t     fWidth;
     uint32_t     fHeight;
 
     OnCharFunc   fCharFunc;
     void*        fCharUserData;
     OnKeyFunc    fKeyFunc;
     void*        fKeyUserData;
     OnMouseFunc  fMouseFunc;
     void*        fMouseUserData;
     OnPaintFunc  fPaintFunc;
     void*        fPaintUserData;
 
-    WindowContext* fWindowContext;
+    WindowContext* fWindowContext = nullptr;
+
+    SkTouchGesture fGesture;
 };
 
 }   // namespace sk_app
 #endif