When xfce4-panel is started, the battery plugin's charge level bar is in the incorrect orientation for a horizontal panel (a very short horizontal bar instead of a thin vertical bar). The only way this can be fixed (short of patching the plugin) is to set the panel mode to vertical (or deskbar) and back to horizontal again. Note that this only happens when the panel is started in horizontal mode; the bar's orientation is correct when the panel is started in both vertical and deskbar mode.
This is version 1.0.4 of xfce4-battery-plugin BTW; I couldn't specify it in the Version field because the highest version in the list is 1.0.0.
Created attachment 4455 Screenshot of bug
I'll look into it.
I cant reproduce it here.. and i dont understand your screenshot. Is the panel horizontal ? i see a very thin vertical bar, like it should be.. With which version of panel is this ? 4.8 or 4.10 ?
Created attachment 4462 Better screenshot
This is with xfce4-panel 4.10, and it is set to horizontal mode. I've attached a new screenshot that should hopefully showcase the bug better.
Okay, reproduced and fixed in 69993c3.