bug#28605: 26.0.60; Part of leftmost character hidden

[Ola Nilsson]

On Fri, Sep 29, 2017 at 10:36 AM, martin rudalics <rudalics@gmx.at> wrote:
>> It does seem the fringe is missing, but there is some other vertical bar
>> of empty space present.
>
> In fact, it appears so from the screenshot you sent.
>
>> Turning off the scroll bar (scrollbar-mode nil) makes the fringe appear,
>> and the characters are fully visible.
>
> From earlier reports, this seems to connect the problem to scaling.  To
> make sure: You do not observe anything the like with scaling turned off?

I've only seen this on my work system with Debian 8 and the hidpi monitor.
I tried on my home system with debian 9 and an old non-hidpi monitor and
did not see the problem.  Remoting to my work machine and exporting the
emacs window through X, and then using the scaling on my home system
did not show the problem.

>> Switching scroll bars off and from left to right with several
>> side-by-side windows
>>   shows that it is all window edges that are next to a scroll bar that
>> are affected.
>
> You mean that the scroll bar from the window on the left affects the
> things displayed in the window on the right?

Yes, the scroll bar affects the window on both sides. It's only the frame edge
with no scroll bar that shows a fringe.

> We clear the background of
> the scroll bars here and there.  Can you build Emacs yourself?  I could
> try to make up a (non-sensical) patch which would turn these clearings
> off to find out whether this is indeed the culprit.

I do build emacs myself, this is all on the emacs-26 branch. I can
rebuild with a patch.

>> I'm not sure I did this right; I set the variables with customize and then
>> moved window and frame edges around a bit.
>> Made no difference as far as I can tell.
>
> OK.  I'm afraid that we sometimes don't draw things correctly on screen
> with scaling turned on.  Maybe it's just x_fill_rectangle and/or
> x_clear_area which are incompatible with GTK's ideas of scaling.

The hidpi scaling in gnome works only so far, and I'm not sure all of gtk
is aware of the setting. But then I know next to nothing about gtk.
The menu-bar and scroll-bars get decent size, but I select a larger font
for emacs using X resources (turned off for the report). I noticed
yesterday that the fringes are dis-proportionally narrow and the fringe
symbols almost unreadable.

> Two additional things you could try in this context: Can your turn on
> window dividers and, independently, horizontal scroll bars (both from
> the Options Show/Hide menu) and look whether they cause additional
> problems?

I've had horizontal scroll bars disabled the entire time. I'll try the dividers
when I'm back at my machine again.

-- 
Ola Nilsson