Open Shared Memory and Render Pictures

Michael Titke michael.tiedtke at
Fri Aug 5 12:53:06 UTC 2016

After some effort to modernize the IO path with shared memory segments 
XShmCreatePixmap fails with a Bad Access error. Maybe someone can 
confirm this is due to the security extension? (The actual system calls 
used and their flags correspond to the examples in the documentation of 
the X shared memory extension but then there's also version 1.2 ...)

The example setup contains a mismatch where the visual of the drawable 
should have a depth of 24 while MIT-SHM seems to ask for a format with a 
depth of 32 (if that undocumented field is interpreted correctly) but 
that should result in a Bad Match error and not in a Bad Access error.

Is it possible to use X render extension Pictures where a pixmap is 
requested in the core protocol?

I'm just asking because solving a puzzle is funny but maybe someone 
still knows about those "private" protocol "mechanics".

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