Add Mojo API for Blink hit testing

third_party/WebKit/public/web/WebWidget.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebWidget_h
 #define WebWidget_h
 
 #include "public/platform/WebBrowserControlsState.h"
 #include "public/platform/WebCanvas.h"
 #include "public/platform/WebCommon.h"
+#include "public/platform/WebFloatPoint.h"
 #include "public/platform/WebFloatSize.h"
 #include "public/platform/WebInputEventResult.h"
 #include "public/platform/WebMenuSourceType.h"
 #include "public/platform/WebPoint.h"
 #include "public/platform/WebRect.h"
 #include "public/platform/WebSize.h"
 #include "public/platform/WebTextInputInfo.h"
 #include "public/web/WebCompositionUnderline.h"
+#include "public/web/WebFrame.h"
 #include "public/web/WebRange.h"
 #include "public/web/WebTextDirection.h"
 
 namespace blink {
 
 class WebCompositeAndReadbackAsyncCallback;
 class WebCoalescedInputEvent;
 class WebLayoutAndPaintAsyncCallback;
 class WebPagePopup;
 struct WebPoint;
@@ skipping 57 matching lines @@
   // WebCompositeAndReadbackAsyncCallback object alive until it is called. This
   // should only be called when isAcceleratedCompositingActive() is true.
   virtual void CompositeAndReadbackAsync(
       WebCompositeAndReadbackAsyncCallback*) {}
 
   // Called to inform the WebWidget of a change in theme.
   // Implementors that cache rendered copies of widgets need to re-render
   // on receiving this message
   virtual void ThemeChanged() {}
 
+  // Finds out the frame that the point is positioned on.
+  virtual WebFrame* HitTestFrameAt(const WebFloatPoint& point) {

[bokan, 2017/07/18 19:26:35]

Would we generalise this a little? Instead of hit testing for Frames, Scroll
Unification
https://docs.google.com/document/d/1op5USoxDnN6yxB8EiFHYcGHacrZZRVKVqu4mSXFd6...)
will want the actual ElementId. Could we instead call this HitTestAt and return
a WebHitTestResult, possibly adding a method on there to return the WebFrame we
hit? I could then reuse this for the unification work.

[Navid Zolghadr, 2017/07/18 19:34:14]

I had something like that in mind. But I saw no method on WebHitTestResult to
return the frame thing and I didn't think it was worth digging more into. Now
that it seems it has a legit use case I'll take a closer look to see whether I
can manage with returning a WebHitTestResult.

[bokan, 2017/07/18 19:39:43]

Great, thanks! From the WebNode you can get a WebDocument which can give you the
WebLocalFrame. Alternatively you can just add a method right on
WebHitTestResult.

+    return nullptr;
+  }
+
   // Called to inform the WebWidget of an input event.
   virtual WebInputEventResult HandleInputEvent(const WebCoalescedInputEvent&) {
     return WebInputEventResult::kNotHandled;
   }
 
   // Called to inform the WebWidget of the mouse cursor's visibility.
   virtual void SetCursorVisibilityState(bool is_visible) {}
 
   // Check whether the given point hits any registered touch event handlers.
   virtual bool HasTouchEventHandlersAt(const WebPoint&) { return true; }
@@ skipping 96 matching lines @@
   // Called by client to request showing the context menu.
   virtual void ShowContextMenu(WebMenuSourceType) {}
 
  protected:
   ~WebWidget() {}
 };
 
 }  // namespace blink
 
 #endif