Getting window previews

[adlo]

How do I get the width, height and plane mask of the window?



> On 18 Jul 2015, at 00:48, Matthew Brush <mbrush at codebrainz.ca> wrote:
> 
>> On 15-07-17 02:09 PM, adlo wrote:
>> What functions does skippy-xd use to get the previews?
>> 
> 
> I have no idea what that is.
> 
>> [...]
>> 
>> What functions does xfwm4 use?
>> 
> 
> I have no idea, I would guess XGetImage or something else depending on X extensions maybe. There was a thread about it on this mailing list a while back (search for "Window previews in xfwm4"), maybe it gives some ideas.
> 
>> How CPU-efficient is XGetImage (or XShmGetImage) compared to the other two methods? Which method is the most CPU-efficient?
>> 
> 
> I don't know what the other two methods are but I would guess they're "efficient enough". If you got everything working and after using/profiling found too slow, then you could look to more advanced ways. I've used XGetImage before on dual-screen root window, showing a preview in a widget at ~30fps and it was "fast enough" for my use.
> 
>> Do you know any details about the methods I could use to convert the image to a GdkPixbuf?
>> 
> 
> If it's for preview you probably don't need GdkPixbuf as you can convert straight from an XImage to a Cairo image surface and paint it  onto a widget. There's probably tricks to avoid extra copying too, I'm no expert on Xlib stuff.
> 
> Cheers,
> Matthew Brush
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