Re: [XFree86] An idea: Any comments?

[Richard L. Kitchen]

Hmmm   Maybe this is a tenderfoot answer...
but why can't you just use the shared memory extension to the Xserver ?
That gives you a window into the Xserver and retains the event processing.



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Re: [XFree86] An idea: Any comments?

[Richard L. Kitchen]

 Thanks for your reply, but I'm not entirely sure what you mean...

 I'm really not that well acquainted with the details of how the Xserver
 works; I realise I'd have to do a lot of reading if I'm actually to get
 anywhere with this idea :-) but is your suggestion to take care of what I
 had envisioned mini-X doing?

yes.  It seems like the problem you are trying to solve is to speed up drwing
operations in X by eliminating the need to send all of the individual cmds
to the Xserver and/or by copying pixmaps over to the server for display.

The shared memory extension allows you to create an Ximage data structure
in shared memory which can then be accessed directly by the Xserver rather
than by copying via the X protocol.

You write your changes into the Ximage and then send a command via X
protocol to cause the Xserver to update the display using the updated
shared memory image.

As you can imagine there is quite a bit of speed gain doing things this way.

The advantage is as I already said, you gain speed but since the Xserver
and the window manager are still in the loop the desktop remains
undisturbed.

I think you may find that people writing games use this feature.

Anyone else have any thoughts or comments ?

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[XFree86] X server startup removes shared memory partitions

[Richard L. Kitchen]

I am running version 4.3.0 of XFree86 and I have a problem with
the Xserver removing shared memory partitions that belong to other
processes when it starts.

Apparently when I originally wrote my code which uses shared
memory I unwisely choose to use shared memory keys in the
range 1 - 200.

I notice that the Xserver seems to create shm partitions with
key values of 0 and 2 and most likely other values that I haven't
yet gleaned.

If I change the key value to some rather large number my problem
goes away,  i.e. my partition is not marked for deletion by the
server.

My question is: what ranges of shared memory key values are
being used by the Xserver and friends ?  I would like to change
my code to avoid the problem now and in the future.





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