Re: Cygwin/X with Win10 display scaling corrupting font display of typed characters - Issue identified

[Ken Whitesell <KenWhitesell@comcast.net>]

On 1/17/2022 1:29 PM, Ken Whitesell wrote:
> Problem: When moving an XTerm window from the primary display to the 
> second monitor, characters typed into that window are "clipped" at the 
> top. Only about the bottom 75% is drawn. No lower-case letters taller 
> than the "half-height" letters render properly. (Letters such as "a", 
> "c", "m", "n", etc are all rendered correctly. All capital letters and 
> tall lower-case letters (e.g. "b" and "d") have the top quarter 
> clipped off. Additionally the XTerm window shows thin black bars on 
> the right side of the window and along the bottom of the window.
>
> The bash prompt and most all characters displayed as the result of the 
> output of a command all display correctly - this is *primarily* 
> affecting characters being typed, and before the "enter" key is 
> pressed. (There is one special case regarding displayed characters. If 
> a program is creating a full screen of output, such as "man", the top 
> line of the screen is clipped.)
>
> If the window is in the primary display when the characters are typed, 
> and then the window is moved to the second monitor, the 
> previously-typed characters remain correctly formed, and only new 
> characters typed while the window is in the second monitor are clipped.
>
> Environment: The primary display is the laptop's built-in display 
> (1920x1080, 17"). The second monitor is a 27" also at 1920x1080. 
> Operating system is Windows 10, with all current patches and updates. 
> (Ver reports Microsoft Windows [Version 10.0.19044.1466]). XWin server 
> is being started with this command line:
>
> E:\cygwin64\bin\run.exe --quote /usr/bin/bash.exe -l -c "cd; exec 
> /usr/bin/startxwin -- -listen tcp"
>
> Additional info: This appears to be related to using the display 
> "Scaling" option, where the laptop's display is set at 125% and the 
> external monitor's display is set at 100%. If I set both displays the 
> same - either both at 100% _or_ both at 125%, the problem does not 
> appear.
>
> If I change the scaling from 125% to 100% on the laptop's display, the 
> problem appears until I restart Cygwin/X. Restarting Cygwin/X shows it 
> displaying properly, until I change the scaling again.
>
> Note: XTerm is _not_ the only program that exhibits this behavior. 
> This is consistent among all applications tried, including geany, 
> hexedit, mate-terminal, and lxterminal. (The visual behavior is 
> slightly different for "full screen" application such as geany and 
> hexedit, but it's still apparent that some clipping is occurring with 
> characters being typed.)
>
> Other version information: Cygwin setup version 2.915, packages 
> showing as up-to-date include xterm 370-1, xinit 1.4.1-1, xorg-server 
> 21.1.3-1, xorg-x11-fonts-* 7.5-4. (Unsure what other information may 
> be useful.)
>
> I've tried searching the message archives, going back through 2018 and 
> have not seen anything that appears relevant. Other searches haven't 
> proved useful, other than indicating that I should try applications 
> other than XTerm.
>
> I have tried various settings in different locations, including 
> specifying "-resize=none" and/or -screen options for both monitors.
>
> No changes have been made to system.XWinrc.
>
> /etc/X11/xinit/startxwinrc has the following lines added before the 
> line "exec /usr/bin/xwin-xdg-menu" line at the bottom of the file:
>
>     /bin/xterm -fa 'DejaVu Sans Mono' -fs 12 -geometry 100x33 &
>     /bin/xterm -fa 'DejaVu Sans Mono' -fs 12 -geometry 100x33 &
>     /bin/xterm -fa 'DejaVu Sans Mono' -fs 12 -geometry 100x33 &
>     /bin/xterm -fa 'DejaVu Sans Mono' -fs 12 -geometry 100x33 &
>
> There is no .startxwinrc file in $HOME.
>
> I will gladly provide any additional information that may help.
>
> Is there a known solution for this? (Or is it known that there is no 
> solution?)
>
> Any guidance, pointers, suggestions of avenues for further research, 
> or other information, will all be greatly appreciated.
>
After more research and experimentation, it appears to be related to one 
of xorg-server, xorg-server-common, or xorg-server-xorg.

Installing the older version 1.20.12-1 of these packages allows the 
windows to be moved between monitors without any issues. Upgrading to 
the current version 21.1.3-1 creates the problems. I'm able to replicate 
this behavior on two different laptops with two different external monitors.