[PD] Gem render out of the screen (and v4l2loopback)

Olivier Baudu olivier at labomedia.net
Tue Mar 3 00:58:11 CET 2015

Hi list,

Until now, and as far as I (think I) can remember, GEM was rendering 
frames even if the window (with or without border) was :
- out of the screen
- reduce in the tool-bar
- hidden by an other window

The last time I use this property was on an Ubuntu 13.10 both with 
"pd-vanilla + gem from the depot" and " pd-extended" (but I can't give 
you versions... because... well, I don't know them... sorry)

On several different patches, I recorded GEM content (which was not 
display on my desktop because of "offset" option) with the combo 
[pix_record] / v4l2loopback in order to make a "fake webcam" to stream.
It was working.
It is still working on computers where those patches where installed.

Now, I am on Ubuntu 14.04 / GEM: 0.93.3 and if anything is put over the 
GEM content, it seems to be that none of the pixel "under" is rendered.

If I open the v4l2loopback device on VLC (or whatever) and hide part of 
the GEM window (even by dragging icons from my desktop), those parts are 
not refresh anymore.

Does GEM change its way to render ?
Is the Ubuntu 14.04 display different ?
Do I misunderstood something ?

Sorry if I'm fuzzy...
If questions, I'll try to explain better.

Thanks in advance for any help.


"On ne peut pas vivre dans un monde où l'on croit que l'élégance exquise 
du plumage de la pintade est inutile. Ceci est tout à fait à part. J'ai 
eu envie de le dire, je l'ai dit." Jean Giono, Un roi sans 

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