[UseZoomForDSF] Support drag&drop

third_party/WebKit/Source/core/page/DragController.cpp

Index: third_party/WebKit/Source/core/page/DragController.cpp
diff --git a/third_party/WebKit/Source/core/page/DragController.cpp b/third_party/WebKit/Source/core/page/DragController.cpp
index cd5db69054923e406dfdbe8d4f841baababf622c..5388ee4e823a22a047c6efd41df535d38de43cc1 100644
--- a/third_party/WebKit/Source/core/page/DragController.cpp
+++ b/third_party/WebKit/Source/core/page/DragController.cpp
@@ -60,6 +60,7 @@
 #include "core/layout/LayoutView.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/loader/FrameLoader.h"
+#include "core/page/ChromeClient.h"
 #include "core/page/DragClient.h"
 #include "core/page/DragData.h"
 #include "core/page/DragSession.h"
@@ -75,6 +76,7 @@
 #include "platform/graphics/ImageOrientation.h"
 #include "platform/network/ResourceRequest.h"
 #include "platform/weborigin/SecurityOrigin.h"
+#include "public/platform/WebScreenInfo.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
@@ -790,7 +792,7 @@ static const IntSize& maxDragImageSize()
     return maxDragImageSize;
 }
 
-static PassOwnPtr<DragImage> dragImageForImage(Element* element, Image* image, const IntPoint& dragOrigin, const IntRect& imageRect, IntPoint& dragLocation)
+static PassOwnPtr<DragImage> dragImageForImage(Element* element, Image* image, const IntPoint& dragOrigin, const IntPoint& imageLocation, const IntSize& imageSizeInDIP, IntPoint& dragLocation)
 {
     OwnPtr<DragImage> dragImage;
     IntPoint origin;
@@ -805,9 +807,9 @@ static PassOwnPtr<DragImage> dragImageForImage(Element* element, Image* image, c
     if (image->size().height() * image->size().width() <= MaxOriginalImageArea
         && (dragImage = DragImage::create(image, shouldRespectImageOrientation,
             1 /* deviceScaleFactor */, interpolationQuality, DragImageAlpha,
-            DragImage::clampedImageScale(orientation.usesWidthAsHeight() ? image->size().transposedSize() : image->size(), imageRect.size(), maxDragImageSize())))) {
-        IntSize originalSize = imageRect.size();
-        origin = imageRect.location();
+            DragImage::clampedImageScale(orientation.usesWidthAsHeight() ? image->size().transposedSize() : image->size(), imageSizeInDIP, maxDragImageSize())))) {
+        IntSize originalSize = imageSizeInDIP;
+        origin = imageLocation;
 
         IntSize newSize = dragImage->size();
 
@@ -886,7 +888,9 @@ bool DragController::startDrag(LocalFrame* src, const DragState& state, const Pl
         // This is an early detection for problems encountered later upon drop.
         ASSERT(!image->filenameExtension().isEmpty());
         if (!dragImage) {
-            dragImage = dragImageForImage(element, image, dragOrigin, hitTestResult.imageRect(), dragLocation);
+            const IntRect& imageRect = hitTestResult.imageRect();
+            const IntSize& imageSizeInDIP = src->page()->chromeClient().viewportToScreen(imageRect).size();
+            dragImage = dragImageForImage(element, image, dragOrigin, imageRect.location(), imageSizeInDIP, dragLocation);

[dcheng, 2016/01/22 17:37:41]

I don't really understand what transformations are needed and when. Is there
better documentation about this? Why are some things scaled to viewport, but
others to dips?

[oshima, 2016/01/22 22:49:02]

This is because dragImageForImage clips the image in screen coordinates in DIP,
which means that when it's drawn on high DPI display it becomes blurry.
I'm not sure if that's intentional or it was left unimplemented. I can work on a
fix
(but in a separate CL) unless there is a reason not to so. 

Please let me know.

         }
         doSystemDrag(dragImage.get(), dragLocation, dragOrigin, dataTransfer, src, false);
     } else if (state.m_dragType == DragSourceActionLink) {
@@ -902,8 +906,8 @@ bool DragController::startDrag(LocalFrame* src, const DragState& state, const Pl
 
         if (!dragImage) {
             ASSERT(src->page());
-            float deviceScaleFactor = src->page()->deviceScaleFactor();
-            dragImage = dragImageForLink(linkURL, hitTestResult.textContent(), deviceScaleFactor, mouseDraggedPoint, dragLocation);
+            float screenDeviceScaleFactor = src->page()->chromeClient().screenInfo().deviceScaleFactor;
+            dragImage = dragImageForLink(linkURL, hitTestResult.textContent(), screenDeviceScaleFactor, mouseDraggedPoint, dragLocation);
         }
         doSystemDrag(dragImage.get(), dragLocation, mouseDraggedPoint, dataTransfer, src, true);
     } else if (state.m_dragType == DragSourceActionDHTML) {