Activity crashes when using

Martin Langhoff martin.langhoff at
Thu Feb 10 08:50:36 EST 2011

On Thu, Feb 10, 2011 at 3:54 AM, Bert Freudenberg <bert at> wrote:
> libsugarize only works for "well-behaved" simple X11 programs. It relies on certain functions being called that have been redirected to the library's overrides. It's a preload-hack, not a proper library, so I'd expect many programs not to work correctly.

Indeed. At this point, we think the crash comes not so much from
libsugarize but from changing windows very quickly during startup.

If we don't use libsugarize, Sugar doesn't recognize the window as
interesting, and doesn't get the callbacks.

I have a fixed-up libsugarize that doesn't cache the call results in a
static var -- it was caching the window handle too. Not sure why it is
structured like that, it doesn't seem to make sense with apps that may
switch windows.

If we do use libsugarize, Sugar gets the callbacks
( and crashes querying the
window that was valid a ms ago, and now is no longer valid. This app
(Adobe AIR stuff) seems to trigger 4 window switches (that trigger the
callback) during startup. The crash doesn't always happen -- you gotta
get the timining "right" for the race condition.

We're tracing this to strengthen Sugar in the face of "flipping
windows" -- so it won't crash. But it won't be able to keep track of
the correct window for the app either.

On the other side of the fence, I'm working with the "upstream" on the
activity side so that it doesn't flip windows faster than the eye can

Where the eye has 'persistence of vision', xorg has race conditions. Progress?

 martin.langhoff at
 martin at -- Software Architect - OLPC
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first

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