Re: supportsDrawGState

[Eric Wasylishen]

What I'd like to do is have DPSgsave and DPSgrestore use cairo_save and 
cairo_restore directly, and only go to the trouble of trying to set the cairo 
gstate using the GNUstep gstate data when one of the unusal ops like DPScopy: 
or DPSexecuserobject: are used.

--Eric

On 2011-06-13, at 1:37 PM, Fred Kiefer wrote:

> On 13.06.2011 20:19, Quentin Mathé wrote:
>> Le 13 juin 2011 à 14:41, Fred Kiefer a écrit :
>> 
>>> I had to restrict the usage of the new image drawing mechanism for
>>> the cairo backend to the cases where the clipping region is
>>> representable as a list of rectangles. With the new drawing code we
>>> store and restore the GState and this only works correctly when the
>>> clipping region is composed of rectangles.
>> 
>> I don't see where the gstate is saved/restored in the new drawing
>> code and not in the old code path. I checked both Back and  Gui.
>> Which lines are you referring to precisely? In Back cairo_save() and
>> cairo_restore() seems to be used in both cases. On the Gui side,
>> PSgsave(), DPSgsave(), PSgrestore() or DPSgrestore() seems to be used
>> in the same way in the two drawing methods.
>> 
>>> The problem became obvious in the JigSaw Application which is now
>>> part of GAP and which does use non-rectangular shapes for its
>>> pieces. These pieces where drawn incorrectly with the new drawing
>>> mechanism but correctly with the old one.
>> 
>> Are they drawn correctly on Mac OS X?
>> 
>>> I would love to see a better solution for this, so feel free to
>>> suggest one.
>> 
>> Agreed :-)
> 
> Quentin,
> 
> I would have expected a little trust in my analysis here :-)
> But anyway you are free to ask and not just take my word for it. The
> difference is between the methods guiDrawInRect:... and
> nativeDrawInRect:... If you carefully count the PSgsave calls you will
> see that each has exactly one in each call path. The difference is that
> in guiDrawInRect:.. the save happens while drawing on the cache surface
> whereas for nativeDrawInRect:.. we use the save while drawing on the
> main surface. This may look only slightly different but changed the whole 
> thing.
> 
> The annoying bit here is that we now know that we have a general problem. For 
> this image drawing issue I was able to resolve it, but if somebody manually 
> sets a non rectangular clip and than uses PSsave we are in trouble.
> 
> Fred
> 
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