Task Manager plugin: buttons shifting position when opening or closing windows

[isf63]

Current Behavior

Taskbar buttons shift slightly when opening or closing windows

Possible Solution

Steps to Reproduce (for bugs)

1. Set Maximum button width low enough in Task Manager settings to have all buttons stay at maximum width.
2. Open 2 to 4 windows and then open another.

There is a subtle shift in the buttons position.

Context

Minor UX issue
Sometimes displayed eliding is affected

Affects all LXQt themes, except KDE-Plasma for me.

System Information

• LXQt Version: 2.0.0
• Qt Version: 6.7.0

[isf63]

I can confirm this is unrelated to themeing by creating a blank theme (mkdir ~/.local/share/lxqt/themes/blank; touch ~/.local/share/lxqt/themes/blank/lxqt-panel.qss, and then inspecting the button widths with GammaRay. With Maximum button width set to 200px, 2 windows open the widths are: (200, 200) and 3 windows (200, 201, 200).

[tsujan]

Yes, that may be a sign of a small miscalculation somewhere. It isn't easy to find where but, fortunately, it hasn't had a serious side effect.

[tsujan]

Related to #2083 indirectly.

[tsujan]

My wild guess is that, in some line(s) of code, the special property of QRect::right() (see Qt doc's note) may have been ignored, resulting in a one-pixel miscalculation. I already found and fixed one case, but it wasn't related to this report.

[tsujan]

OK, the problem wasn't in lxqt-panel but in liblxqt → GridLayout::setGeometry(). After I changed its strange calculations to what looked reasonable to me, the shifting was gone.

I should check those calculations several times to make sure that I haven't missed anything. Then I'll make a PR. But in short, for a reason unknown to me, an extra one pixel was added in some places without being considered in others. I just removed it for testing.

[tsujan]

@isf63
If you use git, please test lxqt/liblxqt#351. The panel should be restarted.