bug#27830: 26.0.50; Left fringe gets truncated by a pixel in window not sharing that edge with frame

[martin rudalics <rudalics@gmx.at>]

 > In the past month or two, I have noticed that left edge of the fringe gets
 > cut by a pixel if that fringe is on the the left-most window (i.e. not in a
 > window that shares the left edge of the frame too).

...

 > Notice how the green bracket in the fringe covering the changed line looks
 > on the left window (sharing the left edge with frame), and how the window
 > divider overlaps the vertical line of the green bracket in the fringe in
 > the right-hand-side window.
 >
 > This did not happen in emacs 25.x or until "recently" (about a month or two
 > back).

 From the attached image it's easy to see that both fringes of the window
on the right miss one pixel.  Please try:

- C-x 3 with emacs -Q

- C-x 3 with emacs -Q and scrollbars disabled

and look at the right edge of any truncation glyphs in the window on the
right.  I suppose that the diff-hl fringe customizations are needed to
reproduce the problem but who knows.

Next, on the frame shown in your image do another C-x 3 so we can tell
whether only the rightmost window is affected.  Also, please
double-check whether disabling the scroll bars is needed to show the
effect.

Finally, on the frame shown in your image, do

M-: (window--dump-frame)

This should get you a buffer *window-frame-dump*.  Please post its
contents here.

Thanks, martin