I use a touchpad on my laptop, and use the two-finger multi-touch scroll. If I flick it, the scrolling possesses it's own inertia or momentum, and the window will continue scrolling. I also have yakuake bound to Ctrl+space. If I scroll with the touchpad, then immediately change to yakuake, the inertia of the scrolling acts with the holding of Ctrl, making the current page zoom (i.e. the same effect as ctrl+scroll). Ideally, the scrolling inertia should only apply with the initial modifier key (i.e. nothing), and to the original window. This may be difficult to implement, so perhaps it'd be easier to just stop passing the scrolling action when a modifier key is depressed. Reproducible: Always Steps to Reproduce: 1. scroll quickly with the touchpad 2. stop scrolling, then immediately hold ctrl Actual Results: Ctrl+scroll is passed to the window. Expected Results: Either scrolling should continue (with no zoom), or scrolling should stop when the modifier key is pressed.
Touchpad input is handled by the xorg server, please report this issue directly to xorg developers via https://bugs.freedesktop.org/
Thanks. Bug reported here. https://bugs.freedesktop.org/show_bug.cgi?id=58240
Hmm... I'm not sure if I understand correctly, but it seems that actually the bug *is* in the client (i.e. KDE, now that xorg has created a new version? https://bugs.freedesktop.org/show_bug.cgi?id=38909#c25
So, reading the upstream bug report, clients are expected to handle smooth scrolling themselfes, and announce support for that feature to the X server. It is a bit unfortunate, that the friction feature is not disabled for non-aware applications, effectively breaking them in the way you reported. Since KDE itself does not handle input X events, but uses the Qt library to do so, you could report an enhancement request to Qt developers, and request to handle the new X smooth scrolling feature. You can find them via https://qt-project.org/
Thanks again. Bug reported here: https://bugreports.qt-project.org/browse/QTBUG-28800
I thought I might mention a workaround here that is satisfactory to me. One can totally disable scrolling inertia/momentum when using the trackpad (N.B. that the mouse scroll wheel doesn't has intertia by default). Toggle trackpad inertia at System Settings > Hardware > Input Devices > Touchpad > Scrolling, and uncheck "Continue edge scrolling automatically". Doing so prevents this bug.