From 6582dac7502ef24f515719698393f565a30c09e9 Mon Sep 17 00:00:00 2001
From: Ed Morley <emorley@mozilla.com>
Date: Wed, 3 Oct 2012 13:43:19 +0100
Subject: [PATCH] Backout ffcdd896a1fa (bug 787947) for reftest failures

---
 layout/base/nsCSSRendering.cpp         | 42 ++++++++++++--------------
 layout/reftests/bugs/787947-1-ref.html |  3 --
 layout/reftests/bugs/787947-1.html     |  3 --
 layout/reftests/bugs/reftest.list      |  1 -
 4 files changed, 19 insertions(+), 30 deletions(-)
 delete mode 100644 layout/reftests/bugs/787947-1-ref.html
 delete mode 100644 layout/reftests/bugs/787947-1.html

diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index a6773f64b04..f8a773b8560 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -2283,7 +2283,6 @@ nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
   gfxRect areaToFill =
     nsLayoutUtils::RectToGfxRect(aFillArea, appUnitsPerPixel);
   gfxMatrix ctm = ctx->CurrentMatrix();
-  bool isCTMPreservingAxisAlignedRectangles = ctm.PreservesAxisAlignedRectangles();
 
   // xStart/yStart are the top-left corner of the top-left tile.
   nscoord xStart = FindTileStart(dirty.x, aOneCellArea.x, aOneCellArea.width);
@@ -2303,30 +2302,27 @@ nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
       gfxRect fillRect =
         pattern->mCoversTile ? areaToFill : tileRect.Intersect(areaToFill);
       ctx->NewPath();
-      // Try snapping the fill rect. Snap its top-left and bottom-right
-      // independently to preserve the orientation.
-      gfxPoint snappedFillRectTopLeft = fillRect.TopLeft();
-      gfxPoint snappedFillRectBottomRight = fillRect.BottomRight();
-      if (isCTMPreservingAxisAlignedRectangles &&
-          ctx->UserToDevicePixelSnapped(snappedFillRectTopLeft, true) &&
-          ctx->UserToDevicePixelSnapped(snappedFillRectBottomRight, true)) {
-        if (snappedFillRectTopLeft.x == snappedFillRectBottomRight.x ||
-            snappedFillRectTopLeft.y == snappedFillRectBottomRight.y) {
-          // Nothing to draw; avoid scaling by zero and other weirdness that
-          // could put the context in an error state.
-          continue;
-        }
-        // Set the context's transform to the transform that maps fillRect to
-        // snappedFillRect. The part of the gradient that was going to
-        // exactly fill fillRect will fill snappedFillRect instead.
+      // If we can snap the gradient tile and fill rects, do so, but make sure
+      // that the gradient is scaled precisely to the tile rect.
+      gfxRect fillRectSnapped = fillRect;
+      // Don't snap the tileRect directly since that would lose information
+      // about the orientation of the current transform (i.e. vertical or
+      // horizontal flipping). Instead snap the corners independently so if
+      // the CTM has a flip, our Scale() below preserves the flip.
+      gfxPoint tileRectSnappedTopLeft = tileRect.TopLeft();
+      gfxPoint tileRectSnappedBottomRight = tileRect.BottomRight();
+      if (ctx->UserToDevicePixelSnapped(fillRectSnapped, true) &&
+          ctx->UserToDevicePixelSnapped(tileRectSnappedTopLeft, true) &&
+          ctx->UserToDevicePixelSnapped(tileRectSnappedBottomRight, true)) {
         ctx->IdentityMatrix();
-        ctx->Translate(snappedFillRectTopLeft);
-        ctx->Scale((snappedFillRectBottomRight.x - snappedFillRectTopLeft.x)/fillRect.width,
-                   (snappedFillRectBottomRight.y - snappedFillRectTopLeft.y)/fillRect.height);
-        ctx->Translate(-fillRect.TopLeft());
+        ctx->Rectangle(fillRectSnapped);
+        ctx->Translate(tileRectSnappedTopLeft);
+        ctx->Scale((tileRectSnappedBottomRight.x - tileRectSnappedTopLeft.x)/tileRect.width,
+                   (tileRectSnappedBottomRight.y - tileRectSnappedTopLeft.y)/tileRect.height);
+      } else {
+        ctx->Rectangle(fillRect);
+        ctx->Translate(tileRect.TopLeft());
       }
-      ctx->Rectangle(fillRect);
-      ctx->Translate(tileRect.TopLeft());
       ctx->SetPattern(pattern->mPattern);
       ctx->Fill();
       ctx->SetMatrix(ctm);
diff --git a/layout/reftests/bugs/787947-1-ref.html b/layout/reftests/bugs/787947-1-ref.html
deleted file mode 100644
index 88e6fc66827..00000000000
--- a/layout/reftests/bugs/787947-1-ref.html
+++ /dev/null
@@ -1,3 +0,0 @@
-<!DOCTYPE HTML>
-<div style="position:absolute; left:10px; top:10px; width:100px; height:100px; border:1px solid black; background-image:linear-gradient(white, black);"></div>
-<p style="position:absolute; left:10px; z-index:2">Hello
diff --git a/layout/reftests/bugs/787947-1.html b/layout/reftests/bugs/787947-1.html
deleted file mode 100644
index c5ee3e0c127..00000000000
--- a/layout/reftests/bugs/787947-1.html
+++ /dev/null
@@ -1,3 +0,0 @@
-<!DOCTYPE HTML>
-<div style="position:absolute; left:10px; top:10px; width:100px; height:100px; border:1px solid black; background-image:linear-gradient(white, black); background-size:0.3px 100px;"></div>
-<p style="position:absolute; left:10px; z-index:2">Hello
diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index cdb3c3b9c7d..95950bf5fff 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -1719,4 +1719,3 @@ fuzzy-if(true,17,5859) == 759036-2.html 759036-2-ref.html
 == 776265-2b.html 776265-2-ref.html
 == 776265-2c.html 776265-2-ref.html
 == 776265-2d.html 776265-2-ref.html
-== 787947-1.html 787947-1-ref.html