In D21869#481795, @zzag wrote:

Pixbuf engine prints that warning because sum of top and bottom border is greater than the height of line-h.png. The most interesting part is that pixbuf engine tries to adjust borders, i.e.

In D21869#481766, @mthw wrote:

We can only affect what goes into Stable (5.16) and what goes into Trunk (master), we cannot tell Debian team what package versions they should use.

In D21869#481760, @mthw wrote:

Could this also land in Plasma/5.16? It's a crash fix after all.

In D21869#481322, @mthw wrote:

I would say the default theme in gtk: Adwaita

In D21869#481317, @ngraham wrote:

Adding some before-and-after images to the Test Plan section would help since I'm still not totally sure what the issue actually is.

In D21869#481305, @mthw wrote:

Your change does fix the issue mentioned, so as long as this doesn't break anything, I would say it's good enough.

Also other themes have some other variants of separator-menu-item, for example
https://git.enlightenment.org/themes/detourious.git/tree/gtk/detourious/gtk-2.0/menu.rc?id=43e66ceaf5ffdd6293bca110643aaad731afc285#n121

In D21869#481220, @ngraham wrote:

"Edit Revision, which is on the sidebar in the top-right, or under the Actions hamburger menu in the top-right.

I know how to do it. But really have you read https://wiki.gnome.org/Attic/GnomeArt/Tutorials/GtkEngines/PixmapEngine
down to:
"How to theme a GtkHSeparator with an image:"

Can you add it yourself? Or propose a name for me. Besides that you should understand that I know nothing about themes and pixmap engine. Can you tell me if all 0s are good thing? Should not it me something connected with line-h.png size? Can you say that 1, 1, 1, 1 is no-no?