Use natural border width rounding.

Round subpixel border widths to nearest integer instead of nearest-below integer.
Split caret widths off from border widths and continue to use rounding to nearest-below integer for that.

Bump Goanna version for visual rendering change.

2 files changed, 9 insertions, 6 deletions

diff --git a/layout/base/nsCaret.cpp b/layout/base/nsCaret.cpp
index 2f08d156e..8ad435950 100644
--- a/layout/base/nsCaret.cpp
+++ b/layout/base/nsCaret.cpp
@@ -200,8 +200,8 @@ nsCaret::ComputeMetrics(nsIFrame* aFrame, int32_t aOffset, nscoord aCaretHeight)
   // between 0 and 1 goes up to 1 so we don't let the caret disappear.
   int32_t tpp = aFrame->PresContext()->AppUnitsPerDevPixel();
   Metrics result;
-  result.mCaretWidth = NS_ROUND_BORDER_TO_PIXELS(caretWidth, tpp);
-  result.mBidiIndicatorSize = NS_ROUND_BORDER_TO_PIXELS(bidiIndicatorSize, tpp);
+  result.mCaretWidth = NS_ROUND_CARET_TO_PIXELS(caretWidth, tpp);
+  result.mBidiIndicatorSize = NS_ROUND_CARET_TO_PIXELS(bidiIndicatorSize, tpp);
   return result;
 }
 
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index ca5d03056..05a6be91e 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -1197,11 +1197,14 @@ private:
   nsCSSShadowItem mArray[1]; // This MUST be the last item
 };
 
-// Border widths are rounded to the nearest-below integer number of pixels,
-// but values between zero and one device pixels are always rounded up to
-// one device pixel.
+// Border widths are rounded to the nearest integer number of pixels, but values
+// between zero and one device pixels are always rounded up to one device pixel.
 #define NS_ROUND_BORDER_TO_PIXELS(l,tpp) \
-  ((l) == 0) ? 0 : std::max((tpp), (l) / (tpp) * (tpp))
+  ((l) == 0) ? 0 : std::max((tpp), ((l) + ((tpp) / 2)) / (tpp) * (tpp))
+// Caret widths are rounded to the nearest-below integer number of pixels, but values
+// between zero and one device pixels are always rounded up to one device pixel.
+#define NS_ROUND_CARET_TO_PIXELS(l,tpp) \
+  ((l) == 0) ? 0 : std::max((tpp), (l) / (tpp) * (tpp)) 
 // Outline offset is rounded to the nearest integer number of pixels, but values
 // between zero and one device pixels are always rounded up to one device pixel.
 // Note that the offset can be negative.