When I startup Xubuntu 18.04 beta on my 4K TV (connected by HDMI) the cursor is much too big. The system will boot into Full HD resolution and not 4K. If I then go to the Xfce Mouse settings under the tab "mouse themes" to change the cursor size I only need to change the size of the cursor 1 pixel up and down and everything is fine again and the cursor has again the correct size. In my case I change the cursor size from 24 to 25 and then back to 24.
I just installed a fresh copy of Xubuntu 18.04 on a new system with a 4k screen, and I am having the same issue. When I boot and login the mouse is huge when on the desktop, but changes sizes when hovering over certain applications. As was mentioned by Manuel, if I change the cursor size setting or simply change the cursor theme from "Default" to "DMZ (Black)" and then back to "Default", the problem disappears. The size is normal and constant no matter what application I hover over. I found this older post from someone who was using Xubuntu 14.04 a few years ago, and I believe it to be the same bug. The images and behavior accurately describe what we are seeing in 18.04. https://superuser.com/questions/768830/mouse-cursor-scaling-issues-in-xubuntu-14-04-with-xfce-4-10 I'm also wondering if the issue is somehow related to this bug: https://bugzilla.xfce.org/show_bug.cgi?id=7415 In that instance I see no mention of size changes, but they similarly have changes in the applied cursor theme based on whether the mouse is hovering over the desktop or other applications.
I have been having this problem for like a year now. I have a 4K screen on my laptop but resolution is usually 1920x1080 or 1600x900. Anytime I'm not using the 4K resolution, on boot up my cursor size is huge. To fix it all I have to do is what's said above, change cursor size up 1 and back down 1 (what it was set at) and it'll reset to what it's supposed to be. It's getting annoying for like a whole year everytime I boot the computer up I have to go into mouse settings and fix it.
The cursor size is internally set to 0 (default size). Changing the size via the mouse settings will set it explicitly to the chosen value. Related GTK3 issue: https://gitlab.gnome.org/GNOME/gtk/issues/1371
-- GitLab Migration Automatic Message -- This bug has been migrated to xfce.org's GitLab instance and has been closed from further activity. You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.xfce.org/xfce/xfce4-settings/-/issues/115. Please create an account or use an existing account on one of our supported OAuth providers. If you want to fork to submit patches and merge requests please continue reading here: https://docs.xfce.org/contribute/dev/git/start#gitlab_forks_and_merge_requests Also feel free to reach out to us on the mailing list https://mail.xfce.org/mailman/listinfo/xfce4-dev