Fix scroll issue in media view on some logitech hi-res wheel mouse

[detiam]

on some hi-res wheel supported mouse, the scroll experience is not good. at least on my logitech g903 ls, when I ↑↓↑↓ my wheel for compare two picture, the first scroll that after scroll direction changed will always lost.

closes #27252

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related links:

• https://gitlab.freedesktop.org/libinput/libinput/-/issues/889
• https://gitlab.freedesktop.org/libinput/libinput/-/issues/814
• https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2668
• https://gitlab.freedesktop.org/xorg/xserver/-/issues/1578
• https://www.phoronix.com/news/Linux-Disable-HiRes-Scroll-USB

[CLAassistant]

All committers have signed the CLA.

[ilya-fedin]

Do you plan to add this hack to each & every app on your desktop? This honestly sounds counter-productive to me and I would rather suggest to add this to libinput or display server.

[detiam]

Do you plan to add this hack to each & every app on your desktop?

humm no? telegram is the only app I know that synthesizes discrete scroll events itself and use it for navigate pictures by mouse wheel. other app I often use either don't support hi-res wheel or don't support navigate pictures by mouse wheel, which don't have this issue, so I pr here.

This honestly sounds counter-productive to me and I would rather suggest to add this to libinput or display server.

about libinput https://gitlab.freedesktop.org/libinput/libinput/-/issues/814#note_1593617

they don't think so (ToT) if libinput just provide discrete scroll events, everything will be much easier.

[ilya-fedin]

telegram is the only app I know that synthesizes discrete scroll events itself

Then fix that piece of code instead of hacking here?

[detiam]

telegram is the only app I know that synthesizes discrete scroll events itself

Then fix that piece of code instead of hacking here?

ok my mistaken, the function handleWheelEvent is for use wheel event discretely, trigger moveToNext() or zoomOut() every when _verticalWheelDelta added 120...

[detiam]

btw why you call me hacking, the major thing I change is when ever scroll direction changes, moveToNext() or zoomOut() will Immediately been triggered, it's there anything don't fit handleWheelEvent's goal?

[ilya-fedin]

btw why you call me hacking

If it's not hacking then why do you add a comment explaining that it's a workaround for linux-specific bug in a system library?

[ilya-fedin]

they don't think so (ToT) if libinput just provide discrete scroll events, everything will be much easier.

It seems it's already fixed in the kernel and mutter according to your screenshot? Why a change in tdesktop is needed then?

[detiam]

It seems it's already fixed in the kernel and mutter according to your screenshot? Why a change in tdesktop is needed then?

it fixed for mutter and gtk, qt don't have such hi-res event -> low-res event feature builtin, and the function for similar thing in tdesktop handleWheelEvent still have this issue.

[ilya-fedin]

it fixed for mutter

Shouldn't that be enough? If compositor handles that, toolkits don't have to

[detiam]

Shouldn't that be enough? If compositor handles that, toolkits don't have to

because I'm using X11?

[ilya-fedin]

qt don't have such hi-res event -> low-res event feature builtin

It seems it has, in the QAbstractSlider class (QAbstractSliderPrivate::scrollByDelta). So if you want to re-use it, you can instantiate an instance of it or QScrollBar (which inherits QAbstractSlider), forward the wheel event to it and use some of the signals: https://doc.qt.io/qt-6/qabstractslider.html#signals

because I'm using X11?

Shouldn't we just wait for X11 to fix it?

[detiam]

1. ok..
2. I install wayland today and tested on it, problem still, so I open an issue for this in case anyone have better non-hacking way to resolve it.

[ilya-fedin]

Just to be clear, there's no decision on your PR, it will be done by @john-preston. Yet I recommend to report this to your compositor which is apparently kwin according to your issue (at least because he has little spare time and may be unable to review your PR as fast as you would like).