https://bugs.kde.org/show_bug.cgi?id=368811
Vlad Zagorodniy <vladz...@gmail.com> changed:
What |Removed |Added
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Latest Commit|https://commits.kde.org/kwi |https://commits.kde.org/kwi
|n/30ad58f559aa0cfc5dba649be |n/4348cd56834cb17da5aa9d95d
|387578481e8db32 |16ddc27bf39e0e6
--- Comment #17 from Vlad Zagorodniy <vladz...@gmail.com> ---
Git commit 4348cd56834cb17da5aa9d95d16ddc27bf39e0e6 by Vlad Zagorodniy, on
behalf of Erik Kurzinger.
Committed on 28/10/2018 at 22:02.
Pushed by vladz into branch 'Plasma/5.12'.
[effects/presentwindows] Avoid potential freeze during fill-gaps
Summary:
When using the natural layout algorithm with the fill-gaps option, a small
error (less than one) is introduced in windows' aspect ratio each time they are
enlarged due to floating-point roundoff.
Currently, the algorithm computes the width and height enlargement factors and
then attempts to enlarge in each of the four possible directions, repeating
until it can't enlarge any windows any further. Hence, this aspect ratio error
can be multiplied by up to four. Especially for small, long, and narrow
windows, this can result in a total error of greater than one by the end of
that loop iteration. If this occurs, on subsequent iterations the height
enlargement factor might then be computed as negative violating some of the
core assumptions of the algorithm and resulting in the loop iterating endlessly
until one of the window dimensions overflows, freezing the program for up to
several minutes.
To fix this, the height enlargement factor should be re-computed based on the
new width each time the window is enlarged, ensuring the error introduced in
the aspect ratio never exceeds one.
Related: bug 364709, bug 380865
FIXED-IN: 5.15.0
Test Plan:
The most reliable way to reproduce the freeze seems to be to activate the
desktop-grid effect while a tool-tip window is fading in.
Ensure desktop-grid is configured to use present windows, and that present
windows is configured to use the natural layout algorithm with the fill gaps
option selected.
The freeze is still intermittent, but using this method should be able to be
triggered within about 10 tries without this fix.
After applying the fix, the freeze has never been observed.
Reviewers: #kwin, zzag
Reviewed By: #kwin, zzag
Subscribers: graesslin, kwin, zzag
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D16278
M +15 -3 effects/presentwindows/presentwindows.cpp
https://commits.kde.org/kwin/4348cd56834cb17da5aa9d95d16ddc27bf39e0e6
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