[cairo] Copying of clip not working for PS surface

[Vladimir Vukicevic]

Fred Kiefer wrote:
> About a week ago I send this mail to the mailing list, but didn't get
> any reply.
> What I need to know is if this is intended behaviour and if there is a
> way to work around it. If necessary, I could provide you with some
> background information, where and why the copying of the current clip
> range is needed in GNUstep (We use it to work around another limitation
> of cairo).

Unfortunately this is unimplemented behaviour -- the 
copy_clip_rectangle_list stuff only works when the backend implements 
clipping using a region.  The PS surface uses the path directly, and so 
even if the path is a rectangle, it's still stored as a path and not a 
region.  There are two things that could be done here:

1) copy_clip_rectangle_list could try to do a tessellation and a region 
extraction if the clip that's set is a path;

2) implement a copy_clip_path (since we already have a public way to 
represent a path).

     - Vlad

> 
> Cheers,
> Fred
> 
> 
> Fred Kiefer wrote:
>> Is anybody able to explain why the following short program gives the
>> output "Cairo status 'clip region not representable in desired format'
>> in copy clip"?
>>
>> The same operations work fine when applied to an image surface.
>>
>> Thank you
>> Fred
>>
>> #include <stddef.h>
>> #include <cairo.h>
>> #include <cairo-ps.h>
>>
>> int
>> main (int argc, const char *argv[])
>> {
>>   cairo_status_t status;
>>   cairo_t *ct;
>>   cairo_surface_t *surface;
>>   cairo_rectangle_list_t *clip_rects;
>>
>>   surface = cairo_ps_surface_create("test.ps", 100, 100);
>>   status = cairo_surface_status(surface);
>>   if (status != CAIRO_STATUS_SUCCESS)
>>     {
>>       printf("Cairo status '%s' for surface\n",
>> cairo_status_to_string(status));
>>       return 0;
>>     }
>>
>>   ct = cairo_create(surface);
>>   status = cairo_status(ct);
>>   if (status != CAIRO_STATUS_SUCCESS)
>>     {
>>       printf("Cairo status '%s' for context\n",
>> cairo_status_to_string(status));
>>       return 0;
>>     }
>>
>>   cairo_rectangle(ct, 10, 10, 80, 80);
>>   cairo_clip(ct);
>>   clip_rects = cairo_copy_clip_rectangle_list(ct);
>>   status = clip_rects->status;
>>   if (status != CAIRO_STATUS_SUCCESS)
>>     {
>>       printf("Cairo status '%s' in copy clip\n",
>> cairo_status_to_string(status));
>>     }
>>
>>   cairo_destroy(ct);
>>   cairo_surface_destroy(surface);
>> }
>>
>>
>>
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>>
> 
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