Text jitters/jiggles relative to non-text rendering when scrolling at fractional scales.
While looking into the possible effects of #6534 (closed) (Drop the gtk-hint-font-metrics setting), I noticed when rendering at fractional scales that as a result of the new Gtk feature which vertically hints text to device pixels, the apparent relative positions of text vs other widgets changes during scrolling (since the steps made when scrolling are in fractional physical pixel amounts).
This causes some issues like:
- Text labels below an icon in an icon view jiggle relative to the icon when scrolling
- Labels in a button jiggle relative to the edges of the button when scrolling
- Text in a tree expander jiggles relative to the triangle icon of the expander
- Two separate but vertically adjacent widgets rendering text will jiggle relative to each-other.
Here's a screen capture of gtk inspector (4.14.0-65-ga23a7d4149
) at 150% fractional scale scrolling slowly, where you can see the jiggling both of text within buttons relative to the buttons, and text in separate rows jiggling compared to adjacent rows. Note that the video has been rescaled and is therefore somewhat blurry due to a gnome-shell issue, but the effect is still visible.