I told myself that I wouldn’t post here again until I had a completely new computer, in order to exclude any possibility that my strange Plasma problems were hardware-related. I now finally have a new monster PC with a powerful Intel i9 CPU (GPU inside) and exclusively M.2 storage sticks (no more “slow” SATA cables). Debian is still at 12 (Plasma 5.x), so I can make a direct comparison and not wonder whether something has been fixed software-wise:
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Dolphin windows no longer take a full second to open: it’s now pretty much instant. However, I feel as if this is only because of the much faster processor and/or I/O in this new computer, rather than there being something wrong with the old one (which was only five years old). Out of curiosity, I removed all disks from the old PC (one of them was a mechanical 3.5") except the system SSD, but the same problem persisted with Dolphin taking a full second to open, so it can’t have been due to that slow disk acting as a bottleneck.
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As you may remember, the icons on my Plasma desktop were inexplicably extremely glitchy, “heavy” and sluggish. I finally stumbled upon the root cause when I noticed that the file ~/.config/plasma-org.kde.plasma.desktop-appletsrc was very big for being a config file. Turns out that the line
screenMapping=was made up of MILLIONS UPON MILLIONS (!) of characters, totalling nearly 40 megabytes of data! As it seems to me, Plasma constantly reads from, parses and writes to that line in that file whenever you move around or drop objects on the desktop, and because of the massively inflated size, it caused those issues.
Once I figured out how to manually clear that line (text editors crashed or took forever to respond when trying to edit that file), then quickly rebooted before it could update it again, the issue was gone: the objects on the desktop now behave sanely.
But how could that line ever get that big? All the items in the list were files that were long gone, and had not even been directly placed on the desktop, but rather in a dir which in turn was placed temporarily on the desktop (a backup of an entire drive while I was juggling around backups at some point). I don’t understand why it would put objects from inside that dir into that list, nor do I understand why these would remain over countless reboots and many months without ever getting “housekept” (automatically removed). In fact, isn’t that supposed to happen as soon as the object in question is deleted or moved away from the desktop? I don’t quite understand the basic purpose of the screenMapping= line, but it seems to have to do with how objects are placed on the desktop.
The only possible “lead” I have for this is that until recently, I was using my own script to detect changes to the “tmp” dir on the desktop, which for the longest time I thought was eating up those mysterious fs.inotify.max_user_instances and fs.inotify.max_user_watches things. I have since switched to using Linux’s own inotifywait program to do the same in a supposedly much more efficient and correct manner, which was a lot of extra work but hopefully will prevent this from happening again. But I still don’t understand why simply looking through the files of a dir that’s on the desktop for any changes would cause Plasma to fill that screenMapping= line up with all the filenames it finds (and then also never remove them again).
(Since I couldn’t bear yet another “start from scratch” after so many reinstallations, I copied the ~/.config dir from the previous installation to the new, and that’s how the bloated ~/.config/plasma-org.kde.plasma.desktop-appletsrc got to the new machine.)
- The selection rectangle on the desktop unfortunately keeps up its frustrating “smoothly-lag-far-behind-the-cursor” behaviour. The only way to (mostly) mitigate this is to run
kcmshell5 kcm_qtquicksettingsand change “Rendering backend” to “software”, which is a feature I heard is removed in Plasma 6.x and which worries me about the future upgrade. Even in this mode, it’s still not perfect even on this new and powerful machine, and only in 1080p resolution – definitely not in 4k mode (more on that later).
A Plasma developer did tell me that this selection rectangle issue “has been fixed in Plasma 6.3.0”, but didn’t provide any details as to what caused it or how it could exist for some but not all users. I’ve now had that issue on two completely different computers with all three different consumer GPU brands: first NVIDIA, then AMD and now Intel, so while it’s good to hear that it’s apparently been fixed, it’s a rather “unsatisfying” resolution. Especially as Debian 13 (which may or may not even get Plasma 6.3 depending on when they decide to “freeze”) is still far from released.
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The issue with the wastebin icon being full when it’s not and empty-looking when it’s full has seemingly gone away entirely. But it remains a complete mystery to me.
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The desktop is still not updating itself in terms of thumbnails if I put an image on the desktop, edit it in a program, save it, and then look at the desktop. It keeps the same thumbnail as before. Even if I wait for many seconds. Only when I press F5 or pick “Refresh Desktop” in the context menu does it update the icon, as if it’s been instructed to not do this automatically? I couldn’t find any working terminal command to force the desktop to refresh, or I would’ve added it to my own code as a (hopefully) temporary workaround.
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If I put a file on the desktop called a.jpg, rename it into b.jpg, then right-click it and pick an option in that context menu, it will get sent the old filename/path rather than the new one, unless I wait for several painful seconds before right-clicking it. So apparently the file names on the desktop (which have been visually changed) get internally updated only after some kind of delay, slowly enough for me to constantly get errors such as “could not find a.jpg” unless I really think about this and actively pause before right-clicking it.
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Not sure to what extent this can be said to be Plasma’s fault, but I’m unable to use my new monitor’s native 4k resolution and am forced to use 1080p still, because if I switch to 4k resolution, the entire Plasma GUI is unusably laggy (even though it’s perfectly smooth in 1080p) and the “Global scale” feature does absolutely nothing, so everything is also “super small” and unpleasant to work with.
There’s sadly no “backports” of the graphics drivers, or seemingly any updated ones at all even in the non-stable Debian. Still, even with outdated drivers, I don’t see how a top-of-the-line CPU whose integrated GPU supports far higher resolution than 4k would have any issues drawing windows and selection rectangles in 4k. Both “software” and “automatic” render modes show an extremely laggy selection rectangle on the desktop in 4k mode.
I’ve tried so many things over the last many months that I’ve forgotten most of them and mentioned even fewer here. This is a heavily compressed summary of the most important and interesting “findings” according to myself. Hopefully you can provide insight into why the remaining issues persist.