[cairo] Public API for pattern duplication

[Mark Vender]

On 02/27/2012 08:46 PM, Chris Wilson wrote:
> On Mon, 27 Feb 2012 20:23:20 +0200, Mark Vender<markv743 at yahoo.co.uk>  wrote:
>> Could someone indicate whether this function is still welcome to cairo?
>> If the problem is that just nobody else is interested, I could easily
>> contribute a patch adding this functionality myself.
>
> If you have a concrete use case and such functionality will be useful to
> you, please do submit the patch to give a public entry point to
> _cairo_pattern_create_copy(). Be prepared to justify your use case
> though. ;)
> -Chris
>

I have a fairly simple use case, in which it is almost impossible to 
workaround the lack of pattern copying routine. I have several threads, 
that do drawing on a separate surfaces using a separate contexts. An 
equivalent pattern needs to be passed to each of the threads. The 
pattern transformation matrix is modified during the drawing, therefore 
I can't use a single pattern without adding much complexity to the code 
and incurring a performance penalty. I don't use surface patterns, so 
_cairo_pattern_create_copy would solve this issue completely for me.

I attach a patch that adds new function cairo_pattern_create_copy, which 
acts as a wrapper to _cairo_pattern_create_copy. The pattern copying 
code currently doesn't use the freed pattern cache, this might be a 
possible addition in the future.

     Mark