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Message #08156
[Bug 1906138] Re: Indeterminate Qt progress bars don't display properly in 20.04
I finally found some time to look further into this, it appears to be an
upstream problem with qtstyleplugins.
The logic in the gtk2 plugin (used by Ubuntu MATE by default) doesn't
animate indeterminate progress bars if QT_NO_ANIMATION is defined, yet
it seems to be intentionally defined to disable animation for some
reason:
https://code.qt.io/cgit/qt/qtstyleplugins.git/commit/src/plugins/styles/gtk2/gtk2.pro?id=102da7d50231fc5723dba6e72340bef3d29471aa
Removing DEFINES += QT_NO_ANIMATION from gtk2.pro fixes the problem and
allows the indeterminate progress bars to animate properly.
** Also affects: qtstyleplugins-src (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1906138
Title:
Indeterminate Qt progress bars don't display properly in 20.04
Status in qtbase-opensource-src package in Ubuntu:
New
Status in qtstyleplugins-src package in Ubuntu:
New
Bug description:
In Ubuntu MATE 20.04, a Qt program with an indeterminate progress bar
(meaning its minimum and maximum values have both been set to zero)
does not display properly. It is supposed to animate in a way that
shows that something is happening with an unknown time remaining.
Instead, it sits still with its progress bar showing approximately 25
to 30% progress.
To test this, make a simple Qt program with a QProgressBar in the main
window, and add these lines to the constructor of the main window:
ui->progressBar->setMinimum(0);
ui->progressBar->setMaximum(0);
This problem is not present in standard Ubuntu 20.04. Standard Ubuntu
correctly animates the indeterminate progress bar. It's unclear to me
which package is at fault, but it seems to be something specific to
Ubuntu MATE because standard Ubuntu 20.04 doesn't have this problem.
Ubuntu MATE 18.04 also has this problem with Qt 5. With Qt 4 it
doesn't have this problem.
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