Add checks to consider a fixed layer for compositing only if its

dimensions are actually more than zero.

Fix Bug:2545160

Change-Id: I08ca0c1f5a6729760dbf62084a96faee76d124f9

1 files changed, 11 insertions, 4 deletions

diff --git a/WebCore/rendering/RenderLayerCompositor.cpp b/WebCore/rendering/RenderLayerCompositor.cpp
index e8d476b..403ccc1 100644
--- a/WebCore/rendering/RenderLayerCompositor.cpp
+++ b/WebCore/rendering/RenderLayerCompositor.cpp
@@ -462,6 +462,13 @@ bool RenderLayerCompositor::overlapsCompositedLayers(OverlapMap& overlapMap, con
     return false;
 }
 
+#if ENABLE(COMPOSITED_FIXED_ELEMENTS)
+static bool needsCompositingForFixedLayer(const RenderLayer* layer)
+{
+  return layer->isFixed() && layer->width() > 0 && layer->height() > 0;
+}
+#endif
+
 //  Recurse through the layers in z-index and overflow order (which is equivalent to painting order)
 //  For the z-order children of a compositing layer:
 //      If a child layers has a compositing layer, then all subsequent layers must
@@ -505,7 +512,7 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* layer, O
 
 #if ENABLE(COMPOSITED_FIXED_ELEMENTS)
     // If we are a fixed layer, signal it to our siblings
-    if (layer->isFixed())
+    if (needsCompositingForFixedLayer(layer))
         compositingState.m_fixedSibling = true;
 
     if (!willBeComposited && compositingState.m_fixedSibling)
@@ -547,7 +554,7 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* layer, O
             // subsequent siblings as we do for the normal flow
             // and positive z-order.
             for (size_t j = 0; j < listSize; ++j) {
-                if ((negZOrderList->at(j))->isFixed()) {
+                if (needsCompositingForFixedLayer(negZOrderList->at(j))) {
                     childState.m_fixedSibling = true;
                     break;
                 }
@@ -974,7 +981,7 @@ bool RenderLayerCompositor::needsToBeComposited(const RenderLayer* layer) const
     // if an ancestor is fixed positioned, we need to be composited...
     const RenderLayer* currLayer = layer;
     while ((currLayer = currLayer->parent())) {
-        if (currLayer->isComposited() && currLayer->isFixed())
+        if (currLayer->isComposited() && needsCompositingForFixedLayer(currLayer))
             return true;
     }
 #endif
@@ -1007,7 +1014,7 @@ bool RenderLayerCompositor::requiresCompositingLayer(const RenderLayer* layer) c
              // 1) - the viewport width is either undefined (-1) or equal to device-width (0), and
              // 2) - no scaling is allowed
              (((settings->viewportWidth() == -1) || (settings->viewportWidth() == 0)) &&
-             !settings->viewportUserScalable() && layer->isFixed()) ||
+             !settings->viewportUserScalable() && needsCompositingForFixedLayer(layer)) ||
 #endif
 #else
              requiresCompositingForVideo(renderer) ||