[sugar] frame auto-visibility configuration

[Erik Garrison]

Hello all,

On tabbing we are currently auto-toggling the frame.  Are we sure that
this is necessary?  Could we include a configuration option to change
this?

Drawing the frame animation during tabbing robs us of processor right
when we need it, slowing the perceived transition time between windows.
Furthermore, as the XO only has one processor the frame animation (which
requires available processor to run smoothly) will skip a lot of frames
if the processor is loaded.  As we're auto-saving and re-rendering the
windows of every window we pass during tabbing, the processor is
invariably quite loaded, and the frame draw consequently is quite
clunky.

The attached patch to sugar optionally disables frame appearance if
the file /home/olpc/no-frame-on-tabbing exists.  This is just a
proof-of-concept hack to make it easier to quickly enable and disable
the functionality and observe the performance change.

I have created a trac ticket: http://dev.laptop.org/ticket/8633

Erik