Under Ubuntu Shift-mouse wheel scrolling is fairly standard for horizontal scrolling. Kolourpaint does not support it. I propose to add that feature.
In the Qt world, the standard for horizontal scrolling is Alt+scroll, not Shift+scroll. This works in Kolourpaint. Personally I'm not super thrilled about it myself and I wish Qt would move to Shift+scroll. See https://bugreports.qt.io/browse/QTBUG-75949 Until that happens at the Qt level, it's not really appropriate for every single scrollview in every piece of Qt software to override this and use Shift+scroll instead.
Alt+scroll conflicts with Alt+Scroll on Ubuntu systems for "display zoom". Therefore this shortcut is non-existend. New proposal: Implement shortcut to be configurable. Reason: Apparently shortcuts are highly system-dependant. Enabling configuration would enable distro repo maintainers to set it according to their system. ( I reopened the report for this purpose )
That's not how this works. Since Alt+Scroll for horizontal scrolling comes from Qt, any such option would have to be exposed there. We can't do anything here in KDE-land. If Ubuntu has bound Alt+Scroll to full-screen zoom, that's a pretty lousy decision. Alt is a modifier key commonly used by applications, and as I mentioned before, Alt+Scroll is the standard horizontal scroll method for all Qt apps. I know that Ubuntu tends to focus on GTK apps more than Qt apps, but they really should have known this and avoided setting a shortcut that conflicts what a standard behavior of apps using a major GUI toolkit. Meta/Super+Scroll would have been much more appropriate.
> That's not how this works. Since Alt+Scroll for horizontal scrolling comes from Qt, any such option would have to be exposed there. Shouldn't a configuration be possible, if there was an event filter within the `keyPressEvent()` function (or some equivalent)? Don't get me wrong here: > If Ubuntu has bound Alt+Scroll to full-screen zoom, that's a pretty lousy decision. I'm not saying Ubuntu did a good job here. But I think it's a good idea to allow shortcuts to be configured by/for OSs and not toolkits. That's the only way of unifying behaviour of apps among different systems.
(In reply to DarkTrick from comment #4) > > That's not how this works. Since Alt+Scroll for horizontal scrolling comes from Qt, any such option would have to be exposed there. > > Shouldn't a configuration be possible, if there was an event filter within > the `keyPressEvent()` function (or some equivalent)? Because this is a standard behavior in the Qt toolkit's scrollview widget, we would have to implement this hack in literally every scrollview implementation in every piece of KDE software, which, as I hope you can understand, is not feasible. :) The code change needs to be made at the Qt level. Since you seem to have some programming knowledge, I would encourage you to submit a patch! Maybe they'll accept it.
Just for the record: I added a report on Qt. https://bugreports.qt.io/browse/QTBUG-90334 > we would have to implement this hack in literally every scrollview implementation in every piece of KDE software, With Kolourpaint being the only simple-to-use MS-Paint alternative + this is specifically painful on a canvas, I guess it has a special role compared to any other app though. But lets wait for what happens on Qt side :)