Bug 1293125 - Work around a layout issue that causes StickyScrollContainer::GetScrollRanges() to compute malformed rects. r=mstange draft
authorBotond Ballo <botond@mozilla.com>
Fri, 07 Oct 2016 19:31:14 -0400
changeset 422596 8cc9e381cbb1b64570ff8d36f775fc9452a52bf9
parent 422595 4375d0268a633e964fd91427cb4b9e67c63d30b2
child 533321 e0d7cccba8f892355a25a1f52b00d5937304d216
push id31756
push userbballo@mozilla.com
push dateFri, 07 Oct 2016 23:32:10 +0000
reviewersmstange
bugs1293125
milestone52.0a1
Bug 1293125 - Work around a layout issue that causes StickyScrollContainer::GetScrollRanges() to compute malformed rects. r=mstange MozReview-Commit-ID: IClxdc8tfBh
layout/generic/StickyScrollContainer.cpp
layout/reftests/async-scrolling/reftest.list
layout/reftests/async-scrolling/sticky-pos-scrollable-2-ref.html
layout/reftests/async-scrolling/sticky-pos-scrollable-2.html
--- a/layout/generic/StickyScrollContainer.cpp
+++ b/layout/generic/StickyScrollContainer.cpp
@@ -278,17 +278,26 @@ StickyScrollContainer::GetScrollRanges(n
 
   nsRect stick;
   nsRect contain;
   ComputeStickyLimits(firstCont, &stick, &contain);
 
   aOuter->SetRect(nscoord_MIN/2, nscoord_MIN/2, nscoord_MAX, nscoord_MAX);
   aInner->SetRect(nscoord_MIN/2, nscoord_MIN/2, nscoord_MAX, nscoord_MAX);
 
-  const nsPoint normalPosition = firstCont->GetNormalPosition();
+  // Due to margin collapsing, |firstCont->GetNormalPosition()| can sometimes
+  // fall otuside of |contain|. (This is because GetNormalPosition() returns
+  // the actual position after margin collapsing, which |contain| is
+  // calculated based on the frame's GetUsedMargin() which is pre-collapsing.)
+  // This can cause |aInner|, as computed below, to not be contained inside
+  // |aOuter|, which confuses the code that consumes these values.
+  // This is hard to fix properly (TODO), but clamping |normalPosition| to
+  // |contain| works around it.
+  const nsPoint normalPosition =
+      contain.ClampPoint(firstCont->GetNormalPosition());
 
   // Bottom and top
   if (stick.YMost() != nscoord_MAX/2) {
     aOuter->SetTopEdge(contain.y - stick.YMost());
     aInner->SetTopEdge(normalPosition.y - stick.YMost());
   }
 
   if (stick.y != nscoord_MIN/2) {
--- a/layout/reftests/async-scrolling/reftest.list
+++ b/layout/reftests/async-scrolling/reftest.list
@@ -20,16 +20,17 @@ skip-if(!asyncPan) == position-fixed-bod
 skip-if(!asyncPan) == position-fixed-cover-1.html position-fixed-cover-1-ref.html
 skip-if(!asyncPan) == position-fixed-cover-2.html position-fixed-cover-2-ref.html
 skip-if(!asyncPan) == position-fixed-cover-3.html position-fixed-cover-3-ref.html
 fuzzy-if(Android,5,4) skip-if(!asyncPan) == position-fixed-transformed-1.html position-fixed-transformed-1-ref.html
 skip-if(!asyncPan) == split-layers-1.html split-layers-1-ref.html
 skip-if(!asyncPan) == split-layers-multi-scrolling-1.html split-layers-multi-scrolling-1-ref.html
 fuzzy-if(skiaContent,2,240000) fuzzy-if(browserIsRemote&&!skiaContent&&(cocoaWidget||winWidget),1,240000) skip-if(!asyncPan) == split-opacity-layers-1.html split-opacity-layers-1-ref.html
 skip-if(!asyncPan) == sticky-pos-scrollable-1.html sticky-pos-scrollable-1-ref.html
+skip-if(!asyncPan) == sticky-pos-scrollable-2.html sticky-pos-scrollable-2-ref.html
 skip-if(!asyncPan) == fixed-pos-scrollable-1.html fixed-pos-scrollable-1-ref.html
 skip-if(!asyncPan) == culling-1.html culling-1-ref.html
 skip-if(!asyncPan) == position-fixed-iframe-1.html position-fixed-iframe-1-ref.html
 skip-if(!asyncPan) == position-fixed-iframe-2.html position-fixed-iframe-2-ref.html
 fuzzy-if(skiaContent,1,11300) skip-if(!asyncPan) == position-fixed-in-scroll-container.html position-fixed-in-scroll-container-ref.html
 skip-if(!asyncPan) == position-fixed-inside-sticky-1.html position-fixed-inside-sticky-1-ref.html
 skip-if(!asyncPan) == position-fixed-inside-sticky-2.html position-fixed-inside-sticky-2-ref.html
 fuzzy(1,60000) skip-if(!asyncPan) == group-opacity-surface-size-1.html group-opacity-surface-size-1-ref.html
new file mode 100644
--- /dev/null
+++ b/layout/reftests/async-scrolling/sticky-pos-scrollable-2-ref.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+<style>
+body {
+  margin: 0;
+  height: 4000px;
+  overflow: hidden;
+}
+div {
+  background: blue;
+  width: 200px;
+  height: 200px;
+  margin-top: 300px;
+  position: sticky;
+  bottom: 100px;
+}
+</style>
+<div></div>
new file mode 100644
--- /dev/null
+++ b/layout/reftests/async-scrolling/sticky-pos-scrollable-2.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html reftest-async-scroll
+      reftest-displayport-x="0" reftest-displayport-y="0"
+      reftest-displayport-w="800" reftest-displayport-h="2000"
+      reftest-async-scroll-x="0" reftest-async-scroll-y="100">
+<style>
+body {
+  margin: 0;
+  height: 4000px;
+  overflow: hidden;
+}
+div {
+  background: blue;
+  width: 200px;
+  height: 200px;
+  margin-top: 400px;
+  position: sticky;
+  bottom: 100px;
+}
+</style>
+<div></div>