[PATCH libXrender] Fix alpha premultiplication in XRenderParseColor.

[Jeremy Huddleston]

Ah, ok.

Reviewed-by: Jeremy Huddleston <jeremyhu at apple.com>

On Jan 3, 2012, at 8:42 AM, Emanuele Giaquinta wrote:

> On Tue, Jan 03, 2012 at 08:21:32AM -0500, Jeremy Huddleston wrote:
>> I believe just the division is unsigned with those changes.  The multiplication will still be signed.
> 
> No, the type of XRenderColor fields is unsigned short.
> 
>> 
>> On Jan 2, 2012, at 2:58 PM, Emanuele Giaquinta wrote:
>> 
>>> Due to C arithmetic conversion rules we must use an unsigned constant (or a
>>> cast) to perform the multiplication using unsigned arithmetic.
>>> ---
>>> src/Color.c |    6 +++---
>>> 1 files changed, 3 insertions(+), 3 deletions(-)
>>> 
>>> diff --git a/src/Color.c b/src/Color.c
>>> index 9c76e58..23ef800 100644
>>> --- a/src/Color.c
>>> +++ b/src/Color.c
>>> @@ -85,8 +85,8 @@ XRenderParseColor(Display *dpy, char *spec, XRenderColor *def)
>>> 	def->blue = coreColor.blue;
>>> 	def->alpha = 0xffff;
>>>  }
>>> -    def->red = (def->red * def->alpha) / 65535;
>>> -    def->green = (def->green * def->alpha) / 65535;
>>> -    def->blue = (def->blue * def->alpha) / 65535;
>>> +    def->red = (def->red * def->alpha) / 0xffffU;
>>> +    def->green = (def->green * def->alpha) / 0xffffU;
>>> +    def->blue = (def->blue * def->alpha) / 0xffffU;
>>>  return 1;
>>> }
>>> -- 
>>> 1.7.7.3
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>> 
>