Bug 678250 - Filter bounds rounded before scaling so small filters may be too large. r=roc

layout/reftests/svg/filter-scaled-01.svg

@@ -0,0 +1,18 @@
+<svg width="100%" height="100%" preserveAspectRatio="none" 
+     xmlns="http://www.w3.org/2000/svg"
+     xmlns:xlink="http://www.w3.org/1999/xlink">
+ 
+  <title>Testcase for scaled filter with non-integer x and y and objectBoundingBox</title> 
+  <defs>
+    <filter id="filter" filterUnits="objectBoundingBox" x="0.5" y="0.5" width="0.25" height="0.25">
+      <feFlood flood-color="red" width="1" height="1" />
+    </filter>
+  </defs>
+
+  <rect width="100%" height="100%" fill="lime"/>
+  <g transform="scale(400)">
+    <rect width="1" height="1" filter="url(#filter)" />
+  </g>
+  <rect x="200" y="200" width="100" height="100" fill="lime" />
+
+</svg>

layout/reftests/svg/filters/filter-nested-filtering-01.svg

@@ -5,7 +5,7 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.0">
   <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=461863 -->
   <desc>
-    This test checks that transforms and filtering a decedent of a
+    This test checks that transforms and filtering a descendant of a
     filtered element interact correctly.
   </desc>
   <filter id="a"><feGaussianBlur stdDeviation="0.001"/></filter>

layout/reftests/svg/objectBoundingBox-and-fePointLight-01-ref.svg

@@ -2,8 +2,7 @@
      Any copyright is dedicated to the Public Domain.
      http://creativecommons.org/publicdomain/zero/1.0/
 -->
-<svg width="100%" height="100%"
-  viewBox="0 0 480 360" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
   <title>Reference for objectBoundingBox with fePointLight</title>
   <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=544742 -->
 
@@ -16,7 +15,7 @@
     </filter>
   </defs>
 
-  <g stroke="black" transform="translate(20 20)">
+  <g transform="translate(20 20)">
     <rect width="40" height="20" filter="url(#light)" fill="black" stroke="none"/>
   </g>
 

layout/reftests/svg/objectBoundingBox-and-fePointLight-01.svg

@@ -2,8 +2,7 @@
      Any copyright is dedicated to the Public Domain.
      http://creativecommons.org/publicdomain/zero/1.0/
 -->
-<svg width="100%" height="100%"
-  viewBox="0 0 480 360" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
   <title>Testcase for objectBoundingBox with fePointLight</title>
   <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=544742 -->
 

layout/reftests/svg/reftest.list

@@ -111,6 +111,7 @@ random == dynamic-use-nested-01.svg dynamic-use-nested-01-ref.svg # bug 467498
 == filter-basic-03.svg pass.svg
 == filter-foreignObject-01.svg pass.svg
 == filter-invalidation-01.svg pass.svg
+== filter-scaled-01.svg pass.svg
 == filter-translated-01.svg filter-translated-01-ref.svg
 == filters-and-group-opacity-01.svg filters-and-group-opacity-01-ref.svg
 == foreignObject-01.svg pass.svg

layout/svg/base/src/nsSVGFilterFrame.cpp

@@ -135,7 +135,6 @@ nsAutoFilterInstance::nsAutoFilterInstance(nsIFrame *aTarget,
   
   gfxRect filterRegion = nsSVGUtils::GetRelativeRect(filterUnits,
     filter->mLengthAttributes, bbox, aTarget);
-  filterRegion.RoundOut();
 
   if (filterRegion.Width() <= 0 || filterRegion.Height() <= 0) {
     // 0 disables rendering, < 0 is error. dispatch error console warning
@@ -149,13 +148,19 @@ nsAutoFilterInstance::nsAutoFilterInstance(nsIFrame *aTarget,
   // temporary offscreen surface that we'll paint into):
 
   gfxIntSize filterRes;
-  if (filter->mIntegerPairAttributes[nsSVGFilterElement::FILTERRES].IsExplicitlySet()) {
-    PRInt32 filterResX =
-      filter->mIntegerPairAttributes[nsSVGFilterElement::FILTERRES].GetAnimValue(nsSVGIntegerPair::eFirst);
-    PRInt32 filterResY =
-      filter->mIntegerPairAttributes[nsSVGFilterElement::FILTERRES].GetAnimValue(nsSVGIntegerPair::eSecond);
-    // XXX what if the 'filterRes' attribute has a bad value? error console warning?
+  const nsSVGIntegerPair& filterResAttrs =
+    filter->mIntegerPairAttributes[nsSVGFilterElement::FILTERRES];
+  if (filterResAttrs.IsExplicitlySet()) {
+    PRInt32 filterResX = filterResAttrs.GetAnimValue(nsSVGIntegerPair::eFirst);
+    PRInt32 filterResY = filterResAttrs.GetAnimValue(nsSVGIntegerPair::eSecond);
+    if (filterResX <= 0 || filterResY <= 0) {
+      // 0 disables rendering, < 0 is error. dispatch error console warning?
+      return;
+    }
 
+    filterRegion.Scale(filterResX, filterResY);
+    filterRegion.RoundOut();
+    filterRegion.Scale(1.0 / filterResX, 1.0 / filterResY);
     // We don't care if this overflows, because we can handle upscaling/
     // downscaling to filterRes
     PRBool overflow;
@@ -168,16 +173,15 @@ nsAutoFilterInstance::nsAutoFilterInstance(nsIFrame *aTarget,
     // Match filterRes as closely as possible to the pixel density of the nearest
     // outer 'svg' device space:
     float scale = nsSVGUtils::MaxExpansion(userToDeviceSpace);
+
+    filterRegion.Scale(scale);
+    filterRegion.RoundOut();
     // We don't care if this overflows, because we can handle upscaling/
     // downscaling to filterRes
     PRBool overflow;
-    filterRes = nsSVGUtils::ConvertToSurfaceSize(filterRegion.Size() * scale,
+    filterRes = nsSVGUtils::ConvertToSurfaceSize(filterRegion.Size(),
                                                  &overflow);
-  }
-
-  if (filterRes.width <= 0 || filterRes.height <= 0) {
-    // 0 disables rendering, < 0 is error. dispatch error console warning?
-    return;
+    filterRegion.Scale(1.0 / scale);
   }
 
   // XXX we haven't taken account of the fact that filterRegion may be

layout/svg/base/src/nsSVGFilterInstance.cpp

@@ -371,7 +371,7 @@ nsSVGFilterInstance::BuildSourceImages()
     // (In theory it would be better to minimize error by having filtered SVG
     // graphics temporarily paint to user space when painting the sources and
     // only set a user space to filter space transform on the gfxContext
-    // (since that would elliminate the transform multiplications from user
+    // (since that would eliminate the transform multiplications from user
     // space to device space and back again). However, that would make the
     // code more complex while being hard to get right without introducing
     // subtle bugs, and in practice it probably makes no real difference.)