I use Arch Linux. When I connect an external monitor to my ThinkPad, the cursor moves erratically on the touchpad. It moves slowly, stutters, doesn’t go where I want it to, or goes past the target. There’s no problem with the mouse. The touchpad doesn’t always cause problems—it happens sometimes, and it’s very frustrating.
Might I ask which:
- Which Thinkpad? (CPU model and graphics would be helpful)
- What resolution and refresh rate of monitor?
- What does the trackpoint do during this? I know you said it’s not the mouse, but I’m just curious.
If it’s a modern-ish Thinkpad (like ~2018 or newer), these problems are weird and I have no advice to offer, but if you’re one of those guys who daily-drives a Core 2 Duo Thinkpad, I’m curious how they do when hooked to a 4K monitor.
What DE/WM do you use? Have you tried replicating the problem on a different one?
KDE Plasma. I have not tried any other. XFCE is too basic and I hate Gnome. Even if it worked without any problem, I don’t think I could use another DE.
do you have both monitors on at the same time? if so it would be worth checking if the problem also occurs if you have only the external display on.
No, I only have one external monitor connectod. When I use the laptop screen and the external monitor at the same time, the cursor moves erratically on both.
