Hello!
Sorry I’m posting this here since I don’t think is specifically related to KDE but since I use KDE and is where I found it the first time I figured some of you might be able to help!
I found a bug that seems too affect many apps and I’m not sure where to report it. Let me explain the issue and hope some of you know where to report that!
So the other day I reported the bug on Krita that you can see on the video but later on saw that this seems to happen to many apps in Linux! So I entered a bit into a rabbit hole and tried many things. This same thing happens to GIMP, KolourPaint, etc. and it seems to be independent on the distro or the Desktop environment!
I’ve checked on Fedora, CachyOS and SteamOS (with Wayland and with X11) and also tried KDE and Gnome. All of them had this issue and then tried Krita on a macbook and didn’t seem to have the issue (correction: seems it’s speed dependent. If you move the mouse too fast it doesn’t do it else it does). And some of them where different computers too.
Does any of you know where this kind of things should be reported? This seems to be very fundamental and I have no idea where this should be reported. Any iedeas?
Edit: Since there seems to be some confusion here’s the bug report:
SUMMARY Drawing a line with the brush creates a zig-zag pattern based on the zoom level
STEPS TO REPRODUCE
- Select the Freehand Brush Tool (B)
- Set size to 1 px (happens in all sizes but 1 px is very clear)
- Zoom out with the wheel
- Draw a diagonal line
- Zoom in with the mouse wheel
- Draw a diagonal line
OBSERVED RESULT The line drawn when zooming out has a zig-zag pattern to it (like a stair) while the zoom in line has less or none (depending on the zoom level).
EXPECTED RESULT Both lines should be a smooth diagonals instead of a zig-zag pattern.
SOFTWARE/OS VERSIONS Operating System: Fedora Linux 43 KDE Plasma Version: 6.6.3 KDE Frameworks Version: 6.24.0 Qt Version: 6.10.2 Kernel Version: 6.19.10-200.fc43.x86_64 (64-bit) Graphics Platform: Wayland
Hardare used to draw: Logitech Gaming Mouse G502 I’ve also tested with the touchpad and my brother’s computer with different hardware and mouse. This also happens there and even on the Steam Deck so it’s definetely not a hardware issue.
Link to the bug report I first did: https://bugs.kde.org/show_bug.cgi?id=518636
Does anyone know where this should be reported?
isn’t this just a fundamental issue with input resolution? ofc you get better resolution when zoomed in because you have more screen space
Yes that might be the case. I feel the expected result should be a straight line between the points though instead of a horizontal and vertical line connection.
I think in Krita is specially noticeable but this behaviour can be seen on GIMP and even in photopea though there is harder to reproduce. Maybe there’s nothing than can be done to fix it but I’m not sure.
I can’t even see what the bug is supposed to be from the video.
When zoomed out straight lines look like a staircase. I’ve updated the post with more details.
Damn. Yeah, that’s bad. Have you tried it with other compositors like Gnome?
Curious if that happens in BSD as well.
Yeah yesterday I tried using a live installation in Gnome and same issue. Seems some deeper thing going on!
@bjoern_tantau @4Robato not a bug. Mouse issue. Notice the squiggly lines - either it’s the mouse (crappy or dirty sensor) or he doesn’t have a mouse mat and is using a wood-grain (or some other un-even) desktop.
I’ve tested with touchpad and even on different computers with Linux all behave the same. Even on the Steam Deck.
What are we looking at?
Is it that when you zoom out your seemingly straight free hand drawn line isn’t actually straight?
Exactly. I’ve updated the post with more details.
For straight lines you better use the Line Tool in Krita right next to the Freehand Brush Tool.
Everything else and even when you try to use a ruler to guide your mouse doing the Freehand Brush Line, the mouse only has a limited resolution and thus will cause jagged lines due to interpolation.
yeah that’s not the complain, this happens to all drawing apps. This is some Linux rendering/composer thing going on. That behavior is not normal and it does’t happen on apple and in Windows I couldn’t test yet but I’m sure it doesn’t happen there either.
That behavior is not normal and it does’t happen on apple and in Windows
I am pretty sure that this physical principle still applies to macOs and Windows and is not dependant on screen composition.
When you want to draw straight lines use the straight line tool.
Tested on Android, doesn’t happen.
Test it myself too and it seems more smoth there but if you move slowly it also happens but it’s a lot harder to notice indeed!
I admit to having tested it only moving quickly. However, if moving slowly makes it appear and quickly makes it disappear, that means that Krita is probably just rendering the noise from the exact mouse position. If you see that in linux but not in Windows and Mac, it means that the probably the latter two have some kind of input smoothing option behind.
What hardware are you using to draw the lines?
A mouse but same with touchpad. I’ve updated the post with more details.
What’s the problem? I don’t get it from the video alone
The smoothness inconsistency of the drawn lines depends on how zoomed in/out the canvas is.
Thus its a problem with interpolation.
I can replicate this but only by drawing very slowly.
@4Robato that is neither a problem with Linux nor with Krita. That’s a problem with you having a really crappy mouse - or - a very dirty sensor on the mouse - or - you don’t have a mouse mat and are using a wood-grain desk - OR - a combination of any of the three aforementioned issues.
I’ve tested on different mouse, the touchpad and the steam deck. All do the same behavior.
