If too small sizes are defined in a Gtk3 theme for scrollbars, the scrollbar can not be chatched by the mouse, if moving it over the thump.
Steps to Reproduce:
1. Choose a gtk3 theme, where small sizes are defined for scrollbars. If not available, change the theme breeze for example:
Open file /usr/share/themes/Breeze/gtk-3.20/gtk.css,
search for the section "Scrollbars" and set min-width and min-height to 5px
2. Open writer and try to grab the thump.
Directly over the thump, it is not possible to use the mouse. Scrolling is only possible by mouse-wheels.
The mouse should be able to grab the thump and move it by holding the left mouse button.
User Profile Reset: No
Could you please mention a few gtk3 themes we could you for this test ?
Created attachment 152592 [details]
Sample gtk file
This is my installation file /usr/share/themes/Breeze/gtk-3.20/gtk.css
where at line 3133 and 3134, I've changed the values from 14px to 5px.
[Automated Action] NeedInfo-To-Unconfirmed
I already encountered the same issue some days ago with gtk3 on Ubuntu 18.04 LTS, not only on Writer, but also in Calc. The horizental scroll bar in Calc is so tiny that I always clicked to the wrong position.
Now, I switched one of my laptap to Fedora 31. On Fedora 31, the scroll bar works much better.
Ubuntu 18.04 uses Gnome 3.24, while Fedora 31 uses Gnome 3.34.