Bug 1026450 - Don't let clipped animated transforms trigger layerization of elements outside the clip. r=roc

--HG-- extra : rebase_source : 2e260272a4d6aa4271d4e3231d7da3dd224b838c
2014-06-25 10:36:13 +02:00 · 2014-06-25 10:36:13 +02:00 · 32deb51be9
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@ -2573,14 +2573,24 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
      ThebesLayerData* data = GetTopThebesLayerData();
      if (data) {
        // Prerendered transform items can be updated without layer building
-        // (async animations or an empty transaction), so we treat all other
-        // content as being above this so that the transformed layer can correctly
-        // move behind other content.
+        // (async animations or an empty transaction), so we need to put items
+        // that the transform item can potentially move under into a layer
+        // above this item.
        if (item->GetType() == nsDisplayItem::TYPE_TRANSFORM &&
            nsDisplayTransform::ShouldPrerenderTransformedContent(mBuilder,
                                                                  item->Frame(),
                                                                  false)) {
+          if (!itemClip.HasClip()) {
+            // The transform item can move anywhere, treat all other content
+            // as being above this item.
            data->SetAllDrawingAbove();
+          } else {
+            // The transform can't escape from the clip rect, and the clip
+            // rect can't change without new layer building. Treat all content
+            // that intersects the clip rect as being above this item.
+            data->AddVisibleAboveRegion(clipRect);
+            data->AddDrawAboveRegion(clipRect);
+          }
        } else {
          data->AddVisibleAboveRegion(itemVisibleRect);

--- a/layout/reftests/invalidation/clipped-animated-transform-1.html
+++ b/layout/reftests/invalidation/clipped-animated-transform-1.html
@ -0,0 +1,62 @@
+<!DOCTYPE html>
+<html lang="en" class="reftest-wait">
+<meta charset="utf-8">
+<title>The green box shouldn't be invalidated when the blue box starts to move.</title>
+
+<style>
+
+body {
+  margin: 0;
+}
+
+#clip {
+  border: 1px solid black;
+  margin: 50px;
+  overflow: hidden;
+  height: 200px;
+  width: 400px;
+  position: relative;
+}
+
+#animatedTransform {
+  border: 1px solid blue;
+  width: 100px;
+  height: 100px;
+  position: absolute;
+  z-index: 1;
+  top: 50px;
+  left: 50px;
+  transition: transform ease-in-out .4s;
+}
+
+#clip:hover > #animatedTransform,
+#animatedTransform.animate {
+  transform: translateX(200px);
+}
+
+#aboveTransform {
+  position: relative;
+  margin: 50px 100px;
+  border: 1px solid lime;
+  width: 80px;
+  height: 80px;
+  z-index: 2;
+}
+
+</style>
+
+<div id="clip">
+  <div id="animatedTransform"></div>
+</div>
+
+<div id="aboveTransform" class="reftest-no-paint"></div>
+
+<script>
+
+function doTest() {
+  document.getElementById("animatedTransform").className = "animate";
+  document.documentElement.removeAttribute("class");
+}
+document.addEventListener("MozReftestInvalidate", doTest, false);
+
+</script>
--- a/layout/reftests/invalidation/reftest.list
+++ b/layout/reftests/invalidation/reftest.list
@ -46,3 +46,4 @@ pref(layout.animated-image-layers.enabled,true) == test-animated-image-layers-ba
 != transform-floating-point-invalidation.html?reverse about:blank
 != nudge-to-integer-invalidation.html about:blank
 != nudge-to-integer-invalidation.html?reverse about:blank
+!= clipped-animated-transform-1.html about:blank