Move inval dedup to Window for wider usages.

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 "../private/SkMutex.h"
 
 class SkCanvas;
 
 namespace sk_app {
 
 class WindowContext;
 
 class Window {
 public:
     static Window* CreateNativeWindow(void* platformData);
 
     virtual ~Window() {};
 
     virtual void setTitle(const char*) = 0;
     virtual void show() = 0;
+
+    // Make sure that onPaint is called in the subclasses' implementations of inval.
+    // We will unset fIsContentInvalided in onPaint, which allows checkAndInval
+    // to invalidate the content after the onPaint.
     virtual void inval() = 0;
 
+    // Check if the current window has any pending inval; call inval if not.
+    void checkAndInval();
+
     virtual bool scaleContentToFit() const { return false; }
     virtual bool supportsContentRect() const { return false; }
     virtual SkRect getContentRect() { return SkRect::MakeEmpty(); }
 
     enum BackendType {
         kNativeGL_BackendType,
         kVulkan_BackendType,
 
         kLast_BackendType = kVulkan_BackendType
     };
@@ skipping 115 matching lines @@
     OnKeyFunc    fKeyFunc;
     void*        fKeyUserData;
     OnMouseFunc  fMouseFunc;
     void*        fMouseUserData;
     OnTouchFunc  fTouchFunc;
     void*        fTouchUserData;
     OnPaintFunc  fPaintFunc;
     void*        fPaintUserData;
 
     WindowContext* fWindowContext = nullptr;
+
+    bool fIsContentInvalidated = false;  // use this to avoid duplicate invalidate events
+    SkMutex fMutex;
 };
 
 }   // namespace sk_app
 #endif