From 7589e34b758622dbb9903cee7d53ae947acc7858 Mon Sep 17 00:00:00 2001
From: Nathan Froyd <froydnj@mozilla.com>
Date: Tue, 6 Mar 2012 13:47:13 -0500
Subject: [PATCH] Bug 719173 - handle pixels and numbers specially in
 ProcessTranslatePart; r=bz, f=mattwoodrow

---
 layout/style/nsStyleTransformMatrix.cpp | 38 ++++++++++---------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/layout/style/nsStyleTransformMatrix.cpp b/layout/style/nsStyleTransformMatrix.cpp
index 88d480804c74..5a1c8983da6d 100644
--- a/layout/style/nsStyleTransformMatrix.cpp
+++ b/layout/style/nsStyleTransformMatrix.cpp
@@ -39,27 +39,6 @@ static double FlushToZero(double aVal)
     return aVal;
 }
 
-/* Helper function to fill in an nscoord with the specified nsCSSValue. */
-static nscoord CalcLength(const nsCSSValue &aValue,
-                          nsStyleContext* aContext,
-                          nsPresContext* aPresContext,
-                          bool &aCanStoreInRuleTree)
-{
-  if (aValue.GetUnit() == eCSSUnit_Pixel ||
-      aValue.GetUnit() == eCSSUnit_Number) {
-    // Handle this here (even though nsRuleNode::CalcLength handles it
-    // fine) so that callers are allowed to pass a null style context
-    // and pres context to SetToTransformFunction if they know (as
-    // nsStyleAnimation does) that all lengths within the transform
-    // function have already been computed to pixels and percents.
-    //
-    // Raw numbers are treated as being pixels.
-    return nsPresContext::CSSPixelsToAppUnits(aValue.GetFloatValue());
-  }
-  return nsRuleNode::CalcLength(aValue, aContext, aPresContext,
-                                aCanStoreInRuleTree);
-}
-
 static float
 ProcessTranslatePart(const nsCSSValue& aValue,
                      nsStyleContext* aContext,
@@ -72,6 +51,19 @@ ProcessTranslatePart(const nsCSSValue& aValue,
 
   if (aValue.GetUnit() == eCSSUnit_Percent) {
     percent = aValue.GetPercentValue();
+  } else if (aValue.GetUnit() == eCSSUnit_Pixel ||
+             aValue.GetUnit() == eCSSUnit_Number) {
+    // Handle this here (even though nsRuleNode::CalcLength handles it
+    // fine) so that callers are allowed to pass a null style context
+    // and pres context to SetToTransformFunction if they know (as
+    // nsStyleAnimation does) that all lengths within the transform
+    // function have already been computed to pixels and percents.
+    //
+    // Raw numbers are treated as being pixels.
+    //
+    // Don't convert to aValue to AppUnits here to avoid precision issues.
+    return aValue.GetFloatValue() *
+           (float(nsPresContext::AppUnitsPerCSSPixel()) / aAppUnitsPerMatrixUnit);
   } else if (aValue.IsCalcUnit()) {
     nsRuleNode::ComputedCalc result =
       nsRuleNode::SpecifiedCalcToComputedCalc(aValue, aContext, aPresContext,
@@ -79,8 +71,8 @@ ProcessTranslatePart(const nsCSSValue& aValue,
     percent = result.mPercent;
     offset = result.mLength;
   } else {
-    offset = CalcLength(aValue, aContext, aPresContext,
-                         aCanStoreInRuleTree);
+    offset = nsRuleNode::CalcLength(aValue, aContext, aPresContext,
+                                    aCanStoreInRuleTree);
   }
 
   return (percent * NSAppUnitsToFloatPixels(aSize, aAppUnitsPerMatrixUnit)) +