Allow objects without scrollbars to be scrollable

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1300 matching lines @@
     }
 
     return 0;
 }
 
 IntRect RenderLayer::scrollableAreaBoundingBox() const
 {
     return renderer()->absoluteBoundingBoxRect();
 }
 
+bool RenderLayer::userInputScrollable(ScrollbarOrientation orientation) const
+{
+    RenderBox* box = renderBox();
+    ASSERT(box);
+
+    EOverflow overflowStyle = (orientation == HorizontalScrollbar) ?
+        renderer()->style()->overflowX() : renderer()->style()->overflowY();
+    return (overflowStyle == OSCROLL || overflowStyle == OAUTO);
+}
+
+int RenderLayer::pageStep(ScrollbarOrientation orientation) const
+{
+    RenderBox* box = renderBox();
+    ASSERT(box);
+
+    int length = (orientation == HorizontalScrollbar) ?
+        box->pixelSnappedClientWidth() : box->pixelSnappedClientHeight();
+    int minPageStep = static_cast<float>(length) * ScrollableArea::minFractionToStepWhenPaging();
+    int pageStep = max(minPageStep, length - ScrollableArea::maxOverlapBetweenPages());
+
+    return max(pageStep, 1);
+}
+
 RenderLayer* RenderLayer::enclosingTransformedAncestor() const
 {
     RenderLayer* curr = parent();
     while (curr && !curr->isRootLayer() && !curr->transform())
         curr = curr->parent();
 
     return curr;
 }
 
 static inline const RenderLayer* compositingContainer(const RenderLayer* layer)
@@ skipping 1134 matching lines @@
         element->setInlineStyleProperty(CSSPropertyHeight, roundToInt(baseHeight + difference.height()), CSSPrimitiveValue::CSS_PX);
     }
 
     document->updateLayout();
 
     // FIXME (Radar 4118564): We should also autoscroll the window as necessary to keep the point under the cursor in view.
 }
 
 int RenderLayer::scrollSize(ScrollbarOrientation orientation) const
 {
-    Scrollbar* scrollbar = ((orientation == HorizontalScrollbar) ? m_hBar : m_vBar).get();
-    return scrollbar ? (scrollbar->totalSize() - scrollbar->visibleSize()) : 0;
-}
-
-int RenderLayer::scrollPosition(Scrollbar* scrollbar) const
-{
-    if (scrollbar->orientation() == HorizontalScrollbar)
-        return scrollXOffset();
-    if (scrollbar->orientation() == VerticalScrollbar)
-        return scrollYOffset();
-    return 0;
+    IntSize scrollDimensions = maximumScrollPosition() - minimumScrollPosition();
+    return (orientation == HorizontalScrollbar) ? scrollDimensions.width() : scrollDimensions.height();
 }
 
 IntPoint RenderLayer::scrollPosition() const
 {
     return IntPoint(m_scrollOffset);
 }
 
 IntPoint RenderLayer::minimumScrollPosition() const
 {
     return -scrollOrigin();
 }
 
 IntPoint RenderLayer::maximumScrollPosition() const
 {
     RenderBox* box = renderBox();
     if (!box || !box->hasOverflowClip())
         return -scrollOrigin();
 
-    LayoutRect overflowRect(box->layoutOverflowRect());
-    box->flipForWritingMode(overflowRect);
-    return -scrollOrigin() + enclosingIntRect(overflowRect).size() - enclosingIntRect(box->clientBoxRect()).size();
+    return -scrollOrigin() + enclosingIntRect(m_overflowRect).size() - enclosingIntRect(box->clientBoxRect()).size();
 }
 
 IntRect RenderLayer::visibleContentRect(VisibleContentRectIncludesScrollbars scrollbarInclusion) const
 {
     int verticalScrollbarWidth = 0;
     int horizontalScrollbarHeight = 0;
     if (scrollbarInclusion == IncludeScrollbars) {
         verticalScrollbarWidth = (verticalScrollbar() && !verticalScrollbar()->isOverlayScrollbar()) ? verticalScrollbar()->width() : 0;
         horizontalScrollbarHeight = (horizontalScrollbar() && !horizontalScrollbar()->isOverlayScrollbar()) ? horizontalScrollbar()->height() : 0;
     }
@@ skipping 319 matching lines @@
             willRemoveHorizontalScrollbar(scrollbar.get());
         else
             willRemoveVerticalScrollbar(scrollbar.get());
     }
 
     scrollbar->removeFromParent();
     scrollbar->disconnectFromScrollableArea();
     scrollbar = 0;
 }
 
-bool RenderLayer::scrollsOverflow() const
-{
-    if (!renderer()->isBox())
-        return false;
-
-    return toRenderBox(renderer())->scrollsOverflow();
-}
-
 void RenderLayer::setHasHorizontalScrollbar(bool hasScrollbar)
 {
     if (hasScrollbar == hasHorizontalScrollbar())
         return;
 
     if (hasScrollbar)
         m_hBar = createScrollbar(HorizontalScrollbar);
     else
         destroyScrollbar(HorizontalScrollbar);
 
@@ skipping 101 matching lines @@
 
     if (isComposited())
         backing()->positionOverflowControlsLayers(offsetFromRoot);
 }
 
 int RenderLayer::scrollWidth() const
 {
     ASSERT(renderBox());
     if (m_scrollDimensionsDirty)
         const_cast<RenderLayer*>(this)->computeScrollDimensions();
-    return snapSizeToPixel(m_scrollSize.width(), renderBox()->clientLeft() + renderBox()->x());
+    return snapSizeToPixel(m_overflowRect.width(), renderBox()->clientLeft() + renderBox()->x());
 }
 
 int RenderLayer::scrollHeight() const
 {
     ASSERT(renderBox());
     if (m_scrollDimensionsDirty)
         const_cast<RenderLayer*>(this)->computeScrollDimensions();
-    return snapSizeToPixel(m_scrollSize.height(), renderBox()->clientTop() + renderBox()->y());
-}
-
-LayoutUnit RenderLayer::overflowTop() const
-{
-    RenderBox* box = renderBox();
-    LayoutRect overflowRect(box->layoutOverflowRect());
-    box->flipForWritingMode(overflowRect);
-    return overflowRect.y();
-}
-
-LayoutUnit RenderLayer::overflowBottom() const
-{
-    RenderBox* box = renderBox();
-    LayoutRect overflowRect(box->layoutOverflowRect());
-    box->flipForWritingMode(overflowRect);
-    return overflowRect.maxY();
-}
-
-LayoutUnit RenderLayer::overflowLeft() const
-{
-    RenderBox* box = renderBox();
-    LayoutRect overflowRect(box->layoutOverflowRect());
-    box->flipForWritingMode(overflowRect);
-    return overflowRect.x();
-}
-
-LayoutUnit RenderLayer::overflowRight() const
-{
-    RenderBox* box = renderBox();
-    LayoutRect overflowRect(box->layoutOverflowRect());
-    box->flipForWritingMode(overflowRect);
-    return overflowRect.maxX();
+    return snapSizeToPixel(m_overflowRect.height(), renderBox()->clientTop() + renderBox()->y());
 }
 
 void RenderLayer::computeScrollDimensions()
 {
     RenderBox* box = renderBox();
     ASSERT(box);
 
     m_scrollDimensionsDirty = false;
 
-    m_scrollSize.setWidth(overflowRight() - overflowLeft());
-    m_scrollSize.setHeight(overflowBottom() - overflowTop());
+    m_overflowRect = box->layoutOverflowRect();
+    box->flipForWritingMode(m_overflowRect);
 
-    int scrollableLeftOverflow = overflowLeft() - box->borderLeft();
-    int scrollableTopOverflow = overflowTop() - box->borderTop();
+    int scrollableLeftOverflow = m_overflowRect.x() - box->borderLeft();
+    int scrollableTopOverflow = m_overflowRect.y() - box->borderTop();
     setScrollOrigin(IntPoint(-scrollableLeftOverflow, -scrollableTopOverflow));
 }
 
 bool RenderLayer::hasScrollableHorizontalOverflow() const
 {
     return hasHorizontalOverflow() && renderBox()->scrollsOverflowX();
 }
 
 bool RenderLayer::hasScrollableVerticalOverflow() const
 {
@@ skipping 62 matching lines @@
                 } else
                     renderer()->layout();
                 m_inOverflowRelayout = false;
             }
         }
     }
 
     // Set up the range (and page step/line step).
     if (m_hBar) {
         int clientWidth = box->pixelSnappedClientWidth();
-        int pageStep = max(max<int>(clientWidth * Scrollbar::minFractionToStepWhenPaging(), clientWidth - Scrollbar::maxOverlapBetweenPages()), 1);
-        m_hBar->setSteps(Scrollbar::pixelsPerLineStep(), pageStep);
-        m_hBar->setProportion(clientWidth, m_scrollSize.width());
+        m_hBar->setProportion(clientWidth, m_overflowRect.width());
     }
     if (m_vBar) {
         int clientHeight = box->pixelSnappedClientHeight();
-        int pageStep = max(max<int>(clientHeight * Scrollbar::minFractionToStepWhenPaging(), clientHeight - Scrollbar::maxOverlapBetweenPages()), 1);
-        m_vBar->setSteps(Scrollbar::pixelsPerLineStep(), pageStep);
-        m_vBar->setProportion(clientHeight, m_scrollSize.height());
+        m_vBar->setProportion(clientHeight, m_overflowRect.height());
     }
 
     updateScrollableAreaSet(hasScrollableHorizontalOverflow() || hasScrollableVerticalOverflow());
 }
 
 void RenderLayer::updateScrollInfoAfterLayout()
 {
     RenderBox* box = renderBox();
     if (!box)
         return;
@@ skipping 3238 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif