Kubuntu: Unwanted Full Screen Making It Impossible to Access Panels Etc

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1

I’m running Kubuntu 26.04 LTS, KDE Plasma 6.6.6, KDE Frameworks 6.24.0

I attempted to move a firefox window by dragging it using its title bar. It became full screen. Usually that can be undone by dragging it away from the top of the screen. Not this time.

The window covered everything, even the KDE panel, so I couldn’t use the panel to switch to a different virtual desktop so as to e.g. kill the out-of-control firefox window. Moving the mouse pointer to where the panel should be didn’t help.

There may be some control key combination that would have resized the offending window, but with only this one window available, there was no way to look up keyboard shortcuts.

Fortunately I remembered that there was at one time a key combination involving F4 that would kill either a window or an app, regardless of its state. (I think I learned it on MS-Windows) Fortunately, it worked on this version of KDE, so I was able to kill the offending window using it, after copying unsaved contents to the system cut buffer.

So I didn’t have to e.g. reboot using the power switch to get rid of the denial-of-service mis-feature.

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I’m sure there are people who like this sort of desktop hijacking full screen option, so I won’t strongly suggest that the possibility of this happening be removed from KDE, or at least from any default KDE installation.

So what I want to know is how to configure my own KDE system such that no window ever becomes full screen, both this type of full screen and the merely annoying type that can be fixed by dragging.

If this is not configurable, I’d be open to suggestions involving a minor change to the code, and building the relevant component from scratch. But I’d prefer to set a config. option.

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As always with this sort of feature, the problem is that I don’t know what the mis-feature is called. I guessed “full screen window”, but while that will be understood by humans, I don’t expect to find it - or anything else I’d recognize - in the system settings app. (I almost certainly disabled any option of this sort that I recognized when I first installed KDE, given that I have no use for full screen windows on my large monitors, and even less use for windows that become full screen without me doing anything I expect to have that effect.)

Note by the way that this is Firefox. I recently found that firefox windows on this system lacked the usual buttons at the top of each window, such as the x to close it. I had to google how to un-break that. So it’s possible that this misfeature might be firefox-specific rather than apply to all windows on KDE.

2

I found something in the system settings labelled “maximize” and turned it off, but I think it was the less annoying behaviour, which can be undone by reversing the mouse movement that did it.

3

I found additonal options in the system settings labelled “maximize” and turned them all off. No idea if I got them all; the built in search doesn’t find most of them.

I also don’t know whether there are additional ways to “maximize” windows I missed, possibly not controlled by system settings at all.

Or, for that matter, whether there’s a second term - I’ll call it “xyzzy” - which means “maximize so thoroughly that there’s no panel access, no window decorations, and basically no mouse-based/easily discoverable way to get out of the state.”

Given my past history with developer jargon, I figure the odds of a separate term are at least 50-50.

4

This sounds more like the window went full-screen as opposed to just being maximized, maybe? The F11 key key toggles that off/on for a window, and is iirc a universal type of shortcut, not just specific to Plasma or even Linux. Even here, mousing up to the top of the screen would casue the titlebar to appear in FF.

With the missing window controls, though, I wonder if this is some sort of odd
FF bug?

5

lots of good info here

you can also go into the customize tool bar settings and turn on the title bar so you will always have decorations to control the window

but i think F11 over rides that too, so it was probably F11 that you hit by accident.

6

Good question. I’m pretty clueless about the terminology here.

IIRC, Microsoft, Apple, and X-windows decided more than 26 years ago to use different terms for most of the common window effects. They also decided to user overlapping terminology, so that e.g. “close” meant one thing on X-windows and another on MS-Windows.

Given that I was routinely using more than one of these systems, I basically gave up on trying to name any of these effects. There simply wasn’t a commonly understood name for any of them.

If I want to be precise, I describe the effect - “window enlarged to use the whole screen, controls at the top of the window removed, panel at the bottom covered up” or “window enlarged to use all the normal working area of the screen, controls at top of window retained, sections owned by the window manager, such as the panel, not covered”.

One of those might be called “maximize” and the other “full screen” on KDE, but it seems vanishingly likely to me that the same terms would also be used on all of Windows, MacOS, Gnome, and XFCE. They probably don’t even all support precisely the same set of behaviours in this space, let alone using the same names.

And yes, I’d love to find a glossary of current terminology, provided it was written for (at least) all of MS-Windows, MacOS, and at least one common linux window manager.

In my dreams, the developers have finally converged on a common terminology. But I’d need evidence to believe that.

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I tried F11 on my KDE system. It produced much the same effect I saw with Firefox earlier.

I tested with a different program just in case Firefox was “special”.

FWIW, I’d never heard of this before. This behaviour doesn’t seem to be listed as a controllable keyboard shortcut in e.g. system settings, so how on earth would I have discovered it? (Similar story with the control-F4 hack I used to get rid of the offending window. It’s also not listed anywhere I know to look at. I knew about it because once, long ago, it was shown as a keyboard shortcut on some system I once used.)

I don’t currently have pets that press random keys on my keyboard, but if I had a cat, I could all too easily have got into the same mess via the keyboard rather than the mouse.

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This might be firefox but then again, F11 removed the window title and all the controls found with it in my mail client.

OTOH, I had to fix a missing controls problem on Firefox a few days ago. It had decided to make the title bar controls invisible until moused over. Apparently it likes to bypass the window manager and do things its own way. The fix turned out to be selecting Firefox’ “customize tool bar” option, and clicking the “title bar” selector at the bottom of the screen.

7

I’m about 99% certain I was only touching the mouse at the time, and not the keyboard.

8

if you press F11 do you get the behavior you saw?

press it again to get out.

maybe the mouse cord kit the key or do you have F11 bound to a mouse button somehow?