Improve mobile device rotation behavior.

Source/WebKit/chromium/src/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 54 matching lines @@
 #include "GeolocationClientProxy.h"
 #include "GeolocationController.h"
 #include "GraphicsContext.h"
 #include "GraphicsContext3D.h"
 #include "GraphicsContext3DPrivate.h"
 #include "GraphicsLayerFactoryChromium.h"
 #include "HTMLInputElement.h"
 #include "HTMLMediaElement.h"
 #include "HTMLNames.h"
 #include "HTMLTextAreaElement.h"
-#include "HitTestResult.h"
 #include "Image.h"
 #include "ImageBuffer.h"
 #include "InspectorController.h"
 #include "InspectorInstrumentation.h"
 #include "KeyboardCodes.h"
 #include "KeyboardEvent.h"
 #include "LayerPainterChromium.h"
 #include "LinkHighlight.h"
 #include "MIMETypeRegistry.h"
 #include "NodeRenderStyle.h"
@@ skipping 25 matching lines @@
 #include "SpeechInputClientImpl.h"
 #include "SpeechRecognitionClientProxy.h"
 #include "StyleResolver.h"
 #include "Text.h"
 #include "TextFieldDecoratorImpl.h"
 #include "TextIterator.h"
 #include "Timer.h"
 #include "TouchDisambiguation.h"
 #include "TraceEvent.h"
 #include "ValidationMessageClientImpl.h"
+#include "ViewportAnchor.h"
 #include "WebAccessibilityObject.h"
 #include "WebActiveWheelFlingParameters.h"
 #include "WebAutofillClient.h"
 #include "WebCompositorInputHandlerImpl.h"
 #include "WebDevToolsAgentImpl.h"
 #include "WebDevToolsAgentPrivate.h"
 #include "WebFrameImpl.h"
 #include "WebHelperPluginImpl.h"
 #include "WebHitTestResult.h"
 #include "WebInputElement.h"
@@ skipping 58 matching lines @@
 // (such as due to a double tap gesture or find in page etc.). These are
 // experimentally determined.
 static const int touchPointPadding = 32;
 static const int nonUserInitiatedPointPadding = 11;
 static const float minScaleDifference = 0.01f;
 static const float doubleTapZoomContentDefaultMargin = 5;
 static const float doubleTapZoomContentMinimumMargin = 2;
 static const double doubleTapZoomAnimationDurationInSeconds = 0.25;
 static const float doubleTapZoomAlreadyLegibleRatio = 1.2f;
 
+// Constants for viewport anchoring on resize.
+static const float viewportAnchorXCoord = 0.5f;
+static const float viewportAnchorYCoord = 0;
+
 // Constants for zooming in on a focused text field.
 static const double scrollAndScaleAnimationDurationInSeconds = 0.2;
 static const int minReadableCaretHeight = 18;
 static const float minScaleChangeToTriggerZoom = 1.05f;
 static const float leftBoxRatio = 0.3f;
 static const int caretPadding = 10;
 
 namespace WebKit {
 
 // Change the text zoom level by kTextSizeMultiplierRatio each time the user
@@ skipping 1437 matching lines @@
 {
     if (m_shouldAutoResize || m_size == newSize)
         return;
 
     FrameView* view = mainFrameImpl()->frameView();
     if (!view)
         return;
 
     WebSize oldSize = m_size;
     float oldPageScaleFactor = pageScaleFactor();
-    IntSize oldScrollOffset = view->scrollOffset();
-    int oldFixedLayoutWidth = fixedLayoutSize().width;
+    int oldContentsWidth = contentsSize().width();
 
     m_size = newSize;
 
 #if ENABLE(VIEWPORT)
+    ViewportAnchor viewportAnchor(mainFrameImpl()->frame()->eventHandler());
+    if (settings()->viewportEnabled())
+        viewportAnchor.setAnchor(view->visibleContentRect(),
+                                 FloatSize(viewportAnchorXCoord, viewportAnchorYCoord));
+
     ViewportArguments viewportArguments = mainFrameImpl()->frame()->document()->viewportArguments();
     m_page->chrome()->client()->dispatchViewportPropertiesDidChange(viewportArguments);
 #endif
 
     WebDevToolsAgentPrivate* agentPrivate = devToolsAgentPrivate();
     if (agentPrivate)
         agentPrivate->webViewResized(newSize);
     if (!agentPrivate || !agentPrivate->metricsOverridden()) {
         WebFrameImpl* webFrame = mainFrameImpl();
         if (webFrame->frameView())
             webFrame->frameView()->resize(m_size);
     }
 
 #if ENABLE(VIEWPORT)
     if (settings()->viewportEnabled()) {

[aelias_OOO_until_Jul13, 2013/04/16 16:35:42]

Please change this to if (settings()->viewportEnabled() && oldSize.width &&
oldContentsWidth).  We should just bail out on the whole logic if one of them is
zero.

[jdduke (slow), 2013/04/16 18:58:26]

There appear to be some assumptions that view->layout() is called if necessary,
even when there's no re-scaling.  After that, it's safe to bail and definitely
cleaner.

         // Relayout immediately to recalculate the minimum scale limit.
         if (view->needsLayout())
             view->layout();
 
-        // When the device rotates:
-        // - If the page width is unchanged, then zoom by new width/old width
-        //   such as to keep the same content horizontally onscreen.
-        // - If the page width stretches proportionally to the change in
-        //   screen width, then don't zoom at all (assuming the content has
-        //   scaled uniformly, then the same content will be horizontally
-        //   onscreen).
-        //   - If the page width partially stretches, then zoom partially to
-        //   make up the difference.
-        // In all cases try to keep the same content at the top of the screen.
         float viewportWidthRatio = !oldSize.width ? 1 : newSize.width / (float) oldSize.width;

[aelias_OOO_until_Jul13, 2013/04/16 16:35:42]

And you can then delete both of the ternary operators here.

[jdduke (slow), 2013/04/16 18:58:26]

Done.

-        float fixedLayoutWidthRatio = !oldFixedLayoutWidth ? 1 : fixedLayoutSize().width / (float) oldFixedLayoutWidth;
-        float scaleMultiplier = viewportWidthRatio / fixedLayoutWidthRatio;
-        if (scaleMultiplier != 1)
-            setPageScaleFactor(oldPageScaleFactor * scaleMultiplier, WebPoint(oldScrollOffset.width(), oldScrollOffset.height()));
+        float contentsWidthRatio = (!oldSize.width || !oldContentsWidth) ? 1 : contentsSize().width() / (float) oldContentsWidth;
+        float scaleMultiplier = viewportWidthRatio / contentsWidthRatio;
+
+        IntSize viewportSize = view->visibleContentRect().size();
+        if (scaleMultiplier != 1) {
+            float newPageScaleFactor = oldPageScaleFactor * scaleMultiplier;
+            viewportSize.scale(pageScaleFactor() / newPageScaleFactor);
+            IntPoint scrollOffsetAtNewScale = viewportAnchor.computeOrigin(viewportSize);
+            setPageScaleFactor(newPageScaleFactor, scrollOffsetAtNewScale);
+        } else {
+            IntPoint scrollOffsetAtNewScale = clampOffsetAtScale(viewportAnchor.computeOrigin(viewportSize), pageScaleFactor());
+            updateMainFrameScrollPosition(scrollOffsetAtNewScale, false);
+        }
     }
 #endif
 
     sendResizeEventAndRepaint();
 }
 
 void WebViewImpl::willEndLiveResize()
 {
     if (mainFrameImpl() && mainFrameImpl()->frameView())
         mainFrameImpl()->frameView()->willEndLiveResize();
@@ skipping 2485 matching lines @@
 }
 
 bool WebViewImpl::shouldDisableDesktopWorkarounds()
 {
     ViewportArguments arguments = mainFrameImpl()->frame()->document()->viewportArguments();
     return arguments.width == ViewportArguments::ValueDeviceWidth || !arguments.userZoom
         || (arguments.minZoom == arguments.maxZoom && arguments.minZoom != ViewportArguments::ValueAuto);
 }
 
 } // namespace WebKit