The All-Singing, All-Dancing XCompMGR

Benjamin M. Schwartz bmschwar at
Thu Apr 29 20:21:16 EDT 2010

On Thu, 29 Apr 2010, Chris Ball wrote:
>    > It also increased the speed of switching between windows.
> Agreed, and this seems like the strongest reason in favor of shipping
> it

Before you do, please verify that there hasn't been a regression in  

1. Visibility
X Compositing makes it difficult for programs to work out whether they  
are visible to the user, and actions that rely on that information may  
not work.  I know that I have written several activities that use  
visibility to disable display functionality, in order to conserve CPU.  
  Sugar also checkpoints each activity on task-switch.  If xcompmgr is  
interfering with that switch detection, that could create a big  
speedup, at a cost in reliability.

2. Video
You'll at least have to test video playback, which was one of the  
sticking points with compositing on the XO-1.

On the XO-1, there were concerns that compositing could run the  
machine out of video memory if many windows were open, leading to all  
sorts of issues.  That might still be an issue on XO-1.5, especially  
at 32bpp.  XO-1.5 is also far from immune to OOM issues, so memory  
pressure in general is a concern.


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