Scroll Customization Prototype (Not for review, WIP)

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 12 matching lines @@
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/dom/Element.h"
 
 #include "bindings/core/v8/DOMDataStore.h"
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/ScriptFunctionCall.h"
+#include "bindings/core/v8/ToV8.h"
 #include "bindings/core/v8/V8DOMWrapper.h"
 #include "bindings/core/v8/V8PerContextData.h"
 #include "core/CSSValueKeywords.h"
 #include "core/SVGNames.h"
 #include "core/XLinkNames.h"
 #include "core/XMLNames.h"
 #include "core/animation/AnimationTimeline.h"
 #include "core/animation/css/CSSAnimations.h"
 #include "core/css/CSSImageValue.h"
 #include "core/css/CSSStyleSheet.h"
@@ skipping 63 matching lines @@
 #include "core/layout/Layer.h"
 #include "core/layout/LayoutTextFragment.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/LayerCompositor.h"
 #include "core/page/Chrome.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/page/PointerLockController.h"
 #include "core/page/SpatialNavigation.h"
+#include "core/page/scrolling/ScrollState.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGElement.h"
 #include "platform/EventDispatchForbiddenScope.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/UserGestureIndicator.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "wtf/BitVector.h"
 #include "wtf/HashFunctions.h"
 #include "wtf/text/CString.h"
 #include "wtf/text/StringBuilder.h"
@@ skipping 348 matching lines @@
     if (!renderer())
         return;
 
     LayoutRect bounds = boundingBox();
     if (centerIfNeeded)
         renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignCenterIfNeeded, ScrollAlignment::alignCenterIfNeeded);
     else
         renderer()->scrollRectToVisible(bounds, ScrollAlignment::alignToEdgeIfNeeded, ScrollAlignment::alignToEdgeIfNeeded);
 }
 
+// Returns true iff a V8 method existed and was called.
+static bool callScrollCustomizationV8Method(Element* element, ScrollState* scrollState, String methodName)
+{
+    ASSERT(RuntimeEnabledFeatures::scrollCustomizationEnabled());
+
+    LocalFrame* frame = element->document().frame();
+    if (!frame)
+        return false;
+    ScriptState* scriptState = ScriptState::forMainWorld(frame);
+    ScriptState::Scope scope(scriptState);
+
+    v8::Handle<v8::Object> creationContext = scriptState->context()->Global();
+    ScriptValue thisWrapper = ScriptValue(scriptState, toV8(element, creationContext, scriptState->isolate()));
+    ScriptValue scrollStateWrapper = ScriptValue(scriptState, toV8(scrollState, creationContext, scriptState->isolate()));
+
+    v8::Handle<v8::Object> thisObject = v8::Handle<v8::Object>::Cast(thisWrapper.v8Value());
+    v8::Local<v8::Value> functionValue = thisObject->Get(v8String(scriptState->isolate(), methodName));
+    ASSERT(functionValue->IsFunction());
+    v8::Local<v8::Function> function = v8::Local<v8::Function>::Cast(functionValue);
+
+    // Native methods should avoid the performance overhead of a v8 method call.
+    if (function->ScriptId() == v8::UnboundScript::kNoScriptId)
+        return false;
+
+    ScriptFunctionCall functionCall(thisWrapper, methodName);
+    functionCall.appendArgument(scrollStateWrapper);
+    functionCall.call();
+    return true;
+}
+
+void Element::callDistributeScroll(ScrollState* scrollState)
+{
+    if (!callScrollCustomizationV8Method(this, scrollState, "distributeScroll"))
+        distributeScroll(scrollState);
+};
+
+void Element::distributeScroll(ScrollState* scrollState)
+{
+    ASSERT(RuntimeEnabledFeatures::scrollCustomizationEnabled());
+    if (!scrollState) {
+        // FIXME: Ideally we'd throw an exception here...
+        fprintf(stderr, "WE SHOULD HANDLE THIS CASE BETTER\n");
+        return;
+    }
+
+    if (scrollState->fullyConsumed())
+        return;
+
+    scrollState->distributeToScrollChainDescendant();
+
+    if (!scrollState->shouldPropagate() && scrollState->scrollLockedToElement() && scrollState->currentNativeScrollingElement() != this)
+        return;
+
+    const double deltaX = scrollState->deltaX();
+    const double deltaY = scrollState->deltaY();
+
+    callApplyScroll(scrollState);
+
+    bool scrolled = deltaX != scrollState->deltaX() || deltaY != scrollState->deltaY();
+    if (scrolled)
+        scrollState->setCurrentNativeScrollingElement(this);
+}
+
+void Element::callApplyScroll(ScrollState* scrollState)
+{
+    if (!callScrollCustomizationV8Method(this, scrollState, "applyScroll"))
+        applyScroll(scrollState);
+}
+
+void Element::applyScroll(ScrollState* scrollState)
+{
+    ASSERT(RuntimeEnabledFeatures::scrollCustomizationEnabled());
+
+    if (!scrollState) {
+        // FIXME: Ideally we'd throw an exception here...
+        fprintf(stderr, "WE SHOULD HANDLE THIS CASE BETTER\n");
+        return;
+    }
+
+    const double deltaX = scrollState->deltaX();
+    const double deltaY = scrollState->deltaY();
+    bool scrolled = false;
+
+    if (scrollState->fullyConsumed())
+        return;
+
+    // Handle the documentElement separately, as it scrolls the FrameView.
+    if (this == document().documentElement()) {
+        FloatSize delta(deltaX, deltaY);
+        if (!document().frame()->scrollByDelta(delta))
+            return;
+        scrolled = true;
+    } else {
+        LayoutBox* curBox = renderer()->enclosingBox();
+        if (deltaX && curBox->scroll(ScrollLeft, ScrollByPrecisePixel, deltaX))
+            scrolled = true;
+
+        if (deltaY && curBox->scroll(ScrollUp, ScrollByPrecisePixel, deltaY))
+            scrolled = true;
+    }
+
+    if (scrolled) {
+        scrollState->consumeDeltaNative(scrollState->deltaX(), scrollState->deltaY());
+
+        // We need to setCurrentNativeScrollingElement in both the
+        // distributeScroll and applyScroll default implementations so
+        // that if the user overrides one of these methods, but not the
+        // other, this bookkeeping remains accurate.
+        scrollState->setCurrentNativeScrollingElement(this);
+
+        if (scrollState->fromUserInput())
+            document().frame()->view()->setWasScrolledByUser(true);
+    }
+};
+
 static float localZoomForRenderer(LayoutObject& renderer)
 {
     // FIXME: This does the wrong thing if two opposing zooms are in effect and canceled each
     // other out, but the alternative is that we'd have to crawl up the whole render tree every
     // time (or store an additional bit in the LayoutStyle to indicate that a zoom was specified).
     float zoomFactor = 1;
     if (renderer.style()->effectiveZoom() != 1) {
         // Need to find the nearest enclosing LayoutObject that set up
         // a differing zoom, and then we divide our result by it to eliminate the zoom.
         LayoutObject* prev = &renderer;
@@ skipping 2887 matching lines @@
 {
 #if ENABLE(OILPAN)
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
 #endif
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink