what is the code in xserver/miext

Adam Jackson ajax at nwnk.net
Tue Jun 27 08:04:40 PDT 2006

On Sunday 25 June 2006 14:22, Carlos Eduardo Rodrigues Diógenes wrote:
> Hi,
> The code in miext is a extension of the code in mi? This was created to
> addres what issues?

It was a poor choice of name.  The miext name was supposed to indicate that 
they were machine-independent extensions, ie, that the DDX need not be aware 
of their existance.  These days it's mostly a dumping ground for small 
subsystems that don't have a protocol extension associated with them.

> What the code in xserver/miext/shadow is intended for? Why this was
> created?

Shadow rendering buffers.  Occasionally you want to render to an intermediate 
surface before finally presenting it to the app or the user.  An example 
would be unaccelerated rotation support for when the driver can't accelerate 

> When these where inserted in the xserver code tree?

I think the original creation of the miext directory was back around XFree86 
4.1 or so, when Keith Packard originally wrote the shadow and (now-deleted) 
layer code.  This, if I'm remembering my mythology right, was an initial 
attempt at creating a composited window system entirely within the server.  
That it's now deleted, should give you an indication of how well it worked.  
The shadow code was useful on its own though.

miext/rootless was added for the Darwin DDX, and later significantly munged to 
support the Cygwin DDX and expose an acceleration layer.  miext/cw was the 
newest addition, which ostensibly hides the composite infrastructure from the 
DDX; this was seen as being preferable to hacking up XAA.

- ajax
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