Unable to cancel SendMessage when switching apps in some cases

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Reported by jteh on 2014-01-28 08:57
We hook SendMessage and SendMessageTimeout so that we can cancel them from watchdog. The hook uses SendMessageTimeout in a loop with a pretty short timeout. Unfortunately, it seems that SendMessageTimeout blocks until the window responds when switching apps in some cases, regardless of the timeout. SMTO_BLOCK fixes this, but it also breaks PowerPoint (#2900). I guess it gets stuck handling some sort of nonqueued message, but I can't see that in the stack.

Str:

1. Find an app that you can cause to freeze on demand. A manufactured test case is probably easiest. :)
2. Open that app and Notepad++.
3. Ensure you can switch from the freezing app to Notepad++ with one keystroke; e.g. fiddle with the alt+tab order.
4. Cause the freeze.
5. Switch to Notepad++.
   Watchdog can't recover from this freeze, no matter how hard it tries.

We can get around this by running SendMessageTimeout in a background thread.
Blocked by #3801, #3859

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Comment 2 by jteh on 2014-01-29 04:43
Changes:
Milestone changed from None to next

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Comment 3 by James Teh <jamie@... on 2014-01-29 04:44
In [3c44d74]:

Merge branch 't3825' into next: NVDA now recovers in more cases when switching away from applications that stop responding.

Incubates #3825.

Changes:
Added labels: incubating

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Comment 4 by James Teh <jamie@... on 2014-01-31 08:02
In [043b984]:

Merge branch 't3825' into next

Incubates #3825.

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Comment 5 by James Teh <jamie@... on 2014-02-03 10:39
In [2b2fd0a]:

Merge branch 't3825' into next

Incubates #3825.

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Comment 6 by jteh on 2014-02-04 04:45
This branch now depends on the code for #3801.

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Comment 7 by James Teh <jamie@... on 2014-02-04 05:54
In [74c3fb4]:

Merge branch 't3825' into next

Incubates #3825, #3801.

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Comment 9 by James Teh <jamie@... on 2014-02-10 08:57
In [b590520]:

Merge branch 't3825' into next

Incubates #3825.

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Comment 10 by James Teh <jamie@... on 2014-02-11 06:12
In [e145bbc]:

Merge branch 't3825' into next

Incubates #3825.

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Comment 11 by James Teh <jamie@... on 2014-05-01 06:24
In [9b97de0]:

NVDA now recovers in more cases when switching away from applications that stop responding.

Fixes #3825.

Changes:
Removed labels: incubating
State: closed

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Comment 12 by jteh on 2014-05-01 06:25
Changes:
Milestone changed from next to 2014.2