Since fa05c51b6f86d3bc705b9b9e9063255fd21b4dcf difficult to evenly space app launchers in sub-30 px panel

[lukefromdc]

Steps to Reproduce

1.Install mate-panel from current git master
2.add a string of app launcher icons next to oneanother

Expected Behavior

App launchers either space evenly under the "pack" model or can be moved small amounts to line them up as under the old pixel position model

Actual Behavior

App launchers come up irregularity spaced. Use of different scale icons by different apps a possible culprit. In the pack model icons cannot be moved except to reorder them or to change left/center/right position sets.

Error Output

none as this is not an application error

Version

git master as of 8/8/2026

Distribution

Debian Unstable

Additional Context

No response

Reproducibility

Every time

Checklist

• I have searched existing issues to avoid duplicates
• I have provided all the requested information above

[vkareh]

This is not really a bug in mate-panel, but a quirk of having icons that are inconsistent with the icon theme. The launchers are all the same size, but the icon inside each of them is driven by the dimensions of that icon itself. Nothing we can do about that. I wouldn't provide a way of nudging them a few pixels or anything, unless we want a panel-wide toggle for "packed" vs "pixels" (which I'd rather not - it would just be two different code paths to maintain and I don't see much value in the pixel positions, apart from that one issue you're describing).

What do you think?

[lukefromdc]

This means the fix is to go through all of the icons, find and fix differences. If either all the icons are shipped by apps or if all come from a single icon theme they should be consistant. If not, app developers or icon theme devs need to fix it. I will deal with this locally on my system to proof this. A toggle on the panel would mean two code paths to maintain and heavier code.

[vkareh]

Just for completeness, can you post a screenshot of what it looks like on your system and to see if there are any specific icons/applications that have this issue?

[lukefromdc]

This was as good as I was able to get it at a 26 px (scaled 2x) panel height, some icons of same size seem to be getting different positions. Panels above 30px get more even spacing

[vkareh]

So I tried to reproduce on my system, setting the panel to 26px at 2x scale, not entirely sure what all the applications are nor what theme you're using, but tried my best approximation. Then I colorized a 52px square (26px * 2x) around each icon to visualize the gaps on both your screenshot and mine:

In my case, every icon lines up precisely, fitting neatly inside a 52px square, with no gaps between one icon and the next. Yours really looks like a mess of non-uniform gaps!

The packing code doesn't really allow those gaps and the icons just snap together when you try to move them around within the same "pack zone", so I'm wondering if you're using a stale version of the panel or if this is a Wayland issue (assuming that's what you're using)?

[lukefromdc]

Yes, this is on wayland, and with mate-panel from the current git master

[lukefromdc]

Same results in making a new panel in the test session (another user), same results in xwayland. This is with a 4K monitor BTW, and some of the icons with gaps are of the same size. Same results with 1.0 scaling however

[lukefromdc]

The gaps seem to vary somewhat with the theme, they are present but far less obvious in Menta. Looks like we are getting some padding somewhere between the icons

[lukefromdc]

Running the panel from GTK_DEBUG=interactive --replace in terminal sometimes suppresses the gaps for an unknown reason. Difference could thus be GTK versions, I use the gtk3-classic version to remove some GNOMEisms and restore striped treeviews on my setup.

I have the current release version of gtk3-classic installed, it is available from
https://github.com/lah7/gtk3-classic
Version 3.24.52 is also the current version of upstream gtk3

[vkareh]

oh huh! interesting, I'll have to try gtk3-classic. That's probably the main difference between our systems, since I've tested different resolutions, scales, themes, and application launchers and they all show up lined up as in my screenshot above. I don't have Wayland though, so that's the other unknown for me.

Anyway, I'll test with gtk3-classic tomorrow and see what that shows.

[lukefromdc]

I just got the gaps to show with the debugger open, trying to find the source of a padding or margin. The gaps show in Adwaita, and any problem in Adwaita on a gtk3 app is a bug.

A panel height of 32 px suppresses the gaps, closing down to about 30 px they become visible but subtle. Whatever this padding it it exists only when icons are the 24 px or smaller size as rendered no matter what the native size of the icons. Changing that on any particular icon seemed to have minimal effect. The show desktop icon is the worst of all offenders.

If the panel height is reduced to 17px, some of the gaps become wider than the icons. This suggests the packing system may be getting it's cell dimensions from the larger possible icon sizes and when this is larger than the icon, the icon and the entire window containing it get packed into possibly the left side of an oversize cell.

[lukefromdc]

I also find "ghost" space left behind some of the time when removing an object from the panel, and it stays put even when restarting the panel. It is possible with some difficulty to force a new object into that space. Replacing the show desktop applet with the system monitor moves the gap on my setup from left of the librewolf launcher to left of the (wider) show desktop applet. On switching it back, the show desktop applet now has a gap to its left instead of its right side-and that left side gap shows up even at a 32px or larger panel height

The gaps are completely suppressed on a nonexpanded panel BTW