[DevTools] Handle emulated device scale factor and original device scale factor properly.

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 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 392 matching lines @@
     , m_chromeClientImpl(ChromeClientImpl::create(this))
     , m_contextMenuClientImpl(this)
     , m_dragClientImpl(this)
     , m_editorClientImpl(this)
     , m_spellCheckerClientImpl(this)
     , m_storageClientImpl(this)
     , m_shouldAutoResize(false)
     , m_zoomLevel(0)
     , m_minimumZoomLevel(zoomFactorToZoomLevel(minTextSizeMultiplier))
     , m_maximumZoomLevel(zoomFactorToZoomLevel(maxTextSizeMultiplier))
-    , m_zoomFactorForDeviceScaleFactor(1.f)
+    , m_zoomFactorForDeviceScaleFactor(0.f)
     , m_maximumLegibleScale(1)
     , m_doubleTapZoomPageScaleFactor(0)
     , m_doubleTapZoomPending(false)
     , m_enableFakePageScaleAnimationForTesting(false)
     , m_fakePageScaleAnimationPageScaleFactor(0)
     , m_fakePageScaleAnimationUseAnchor(false)
     , m_doingDragAndDrop(false)
     , m_ignoreInputEvents(false)
     , m_compositorDeviceScaleFactorOverride(0)
     , m_rootLayerScale(1)
@@ skipping 2624 matching lines @@
         m_zoomLevel = zoomLevel;
 
     // TODO(nasko): Setting zoom level needs to be refactored to support
     // out-of-process iframes. See https://crbug.com/528407.
     if (mainFrame()->isWebRemoteFrame())
         return m_zoomLevel;
 
     LocalFrame* frame = mainFrameImpl()->frame();
     if (!WebLocalFrameImpl::pluginContainerFromFrame(frame)) {
         float zoomFactor = m_zoomFactorOverride ? m_zoomFactorOverride : static_cast<float>(zoomLevelToZoomFactor(m_zoomLevel));
-        zoomFactor *= m_zoomFactorForDeviceScaleFactor;
+        if (m_zoomFactorForDeviceScaleFactor) {
+          if (m_compositorDeviceScaleFactorOverride) {

[dgozman, 2016/03/02 01:19:56]

style: 4 spaces in blink

[oshima, 2016/03/02 03:15:07]

Done.

+            page()->setDeviceScaleFactor(m_zoomFactorForDeviceScaleFactor / m_compositorDeviceScaleFactorOverride);

[dgozman, 2016/03/02 01:19:56]

This is surprising. I thought in new mode device_scale_factor would always be
one. This makes emulation conceptually different from the regular case, which
I'd like to avoid.
Also, do you plan to remove device scale factor from page eventually? This would
block it.

[oshima, 2016/03/02 03:15:07]

DPR (Device Pixel Ratio), which emulator sets, is different from Device Scale
Factor.

DPR is computed by "Device Scale Factor set in Page" * ZoomFactor.

In new mode, compositor's device scale factor is always one, and instead it'll
apply zoom factor to blink side.
The above is to get the produce DPR in new mode. This behaves exactly same as
old mode.

And my new test should cover both new and old mode. (ChromeOS runs with new
mode, while other platforms runs with old mode)

Once the migration is completed, we should simply have "emulated DPR", which
does not take zoom factor into account.

+            zoomFactor *= m_compositorDeviceScaleFactorOverride;
+          } else {
+            page()->setDeviceScaleFactor(1.f);
+            zoomFactor *= m_zoomFactorForDeviceScaleFactor;
+          }
+        }
         frame->setPageZoomFactor(zoomFactor);
     }
 
     return m_zoomLevel;
 }
 
 void WebViewImpl::zoomLimitsChanged(double minimumZoomLevel,
                                     double maximumZoomLevel)
 {
     m_minimumZoomLevel = minimumZoomLevel;
@@ skipping 696 matching lines @@
 unsigned long WebViewImpl::createUniqueIdentifierForRequest()
 {
     return createUniqueIdentifier();
 }
 
 void WebViewImpl::setCompositorDeviceScaleFactorOverride(float deviceScaleFactor)
 {
     if (m_compositorDeviceScaleFactorOverride == deviceScaleFactor)
         return;
     m_compositorDeviceScaleFactorOverride = deviceScaleFactor;
+    if (m_zoomFactorForDeviceScaleFactor) {
+        setZoomLevel(zoomLevel());
+        return;
+    }
     if (page() && m_layerTreeView)
         updateLayerTreeDeviceScaleFactor();
 }
 
 void WebViewImpl::setRootLayerTransform(const WebSize& rootLayerOffset, float rootLayerScale)
 {
     if (m_rootLayerScale == rootLayerScale && m_rootLayerOffset == rootLayerOffset)
         return;
     m_rootLayerScale = rootLayerScale;
     m_rootLayerOffset = rootLayerOffset;
@@ skipping 795 matching lines @@
 {
     // TODO(oshima): Investigate if this should return the ScreenInfo's scale factor rather than
     // page's scale factor, which can be 1 in use-zoom-for-dsf mode.
     if (!page())
         return 1;
 
     return page()->deviceScaleFactor();
 }
 
 } // namespace blink