Bug 624781. When converting from app units to pixels use an intermediate double to do the calculation so no precision is lost. r=roc a=blocking

gfx/src/nsCoord.h

@@ -411,6 +411,11 @@ inline PRInt32 NSToIntRoundUp(float aValue)
   return PRInt32(NS_floorf(aValue + 0.5f));
 }
 
+inline PRInt32 NSToIntRoundUp(double aValue)
+{
+  return PRInt32(NS_floor(aValue + 0.5));
+}
+
 /* 
  * App Unit/Pixel conversions
  */
@@ -433,6 +438,11 @@ inline float NSAppUnitsToFloatPixels(nscoord aAppUnits, float aAppUnitsPerPixel)
   return (float(aAppUnits) / aAppUnitsPerPixel);
 }
 
+inline double NSAppUnitsToDoublePixels(nscoord aAppUnits, nscoord aAppUnitsPerPixel)
+{
+  return (double(aAppUnits) / double(aAppUnitsPerPixel));
+}
+
 inline PRInt32 NSAppUnitsToIntPixels(nscoord aAppUnits, float aAppUnitsPerPixel)
 {
   return NSToIntRound(float(aAppUnits) / aAppUnitsPerPixel);

gfx/src/nsPoint.h

@@ -127,8 +127,8 @@ struct nsIntPoint {
 inline nsIntPoint
 nsPoint::ToNearestPixels(nscoord aAppUnitsPerPixel) const {
   return nsIntPoint(
-      NSToIntRoundUp(NSAppUnitsToFloatPixels(x, float(aAppUnitsPerPixel))),
-      NSToIntRoundUp(NSAppUnitsToFloatPixels(y, float(aAppUnitsPerPixel))));
+      NSToIntRoundUp(NSAppUnitsToDoublePixels(x, aAppUnitsPerPixel)),
+      NSToIntRoundUp(NSAppUnitsToDoublePixels(y, aAppUnitsPerPixel)));
 }
 
 inline nsPoint

gfx/src/nsRect.h

@@ -391,12 +391,12 @@ inline nsIntRect
 nsRect::ToNearestPixels(nscoord aAppUnitsPerPixel) const
 {
   nsIntRect rect;
-  rect.x = NSToIntRoundUp(NSAppUnitsToFloatPixels(x, float(aAppUnitsPerPixel)));
-  rect.y = NSToIntRoundUp(NSAppUnitsToFloatPixels(y, float(aAppUnitsPerPixel)));
-  rect.width  = NSToIntRoundUp(NSAppUnitsToFloatPixels(XMost(),
-                               float(aAppUnitsPerPixel))) - rect.x;
-  rect.height = NSToIntRoundUp(NSAppUnitsToFloatPixels(YMost(),
-                               float(aAppUnitsPerPixel))) - rect.y;
+  rect.x = NSToIntRoundUp(NSAppUnitsToDoublePixels(x, aAppUnitsPerPixel));
+  rect.y = NSToIntRoundUp(NSAppUnitsToDoublePixels(y, aAppUnitsPerPixel));
+  rect.width  = NSToIntRoundUp(NSAppUnitsToDoublePixels(XMost(),
+                               aAppUnitsPerPixel)) - rect.x;
+  rect.height = NSToIntRoundUp(NSAppUnitsToDoublePixels(YMost(),
+                               aAppUnitsPerPixel)) - rect.y;
   return rect;
 }