[cairo] Tentative patch for downscaling in Cairo

[Bryce W. Harrington]

>2013/6/4 Chris Wilson <chris at chris-wilson.co.uk>:
>> On Sun, Mar 31, 2013 at 05:03:36AM +0200, Krzysztof Kosiński wrote:
>>> Hello
>>>
>>> I had a look at how complex would it be to add correct downscaling to
>>> Cairo now that Pixman supports convolution filters. It turns out it
>>> this is rather easy. Here is an initial, minimal attempt. It uses
>>> convolution filters only if the image is being downscaled by more than
>>> half a pixel in at least one dimension.
>>
>> Looks very nice. My plan at the moment is to finish a bugfix 1.12
>> release, then start on 1.14 to add some new API. This improvement would
>> be better in a major release, so I'll add it then.
>
> Great! Having proper downscaling in Cairo would really make our life easier :)

Looks like this requires pixman 0.29.2 or newer for convolution filters.

diff --git a/configure.ac b/configure.ac
index 928a169..f65cf30 100644
--- a/configure.ac
+++ b/configure.ac
@@ -654,7 +654,7 @@ CAIRO_ENABLE(test_surfaces, test surfaces, no)
 dnl ===========================================================================
 
 CAIRO_ENABLE_SURFACE_BACKEND(image, image, always, [
-  pixman_REQUIRES="pixman-1 >= 0.22.0"
+  pixman_REQUIRES="pixman-1 >= 0.29.2"
   PKG_CHECK_MODULES(pixman, $pixman_REQUIRES, ,
     [use_image="no (requires $pixman_REQUIRES http://cairographics.org/releases/)"])
   image_REQUIRES=$pixman_REQUIRES
(END)