Cygwin/X with Win10 display scaling corrupting font display of typed characters - Issue identified - "Solution" found

Jon Turney
Sun Aug 14 11:08:25 GMT 2022

On 05/02/2022 14:25, Jon Turney wrote:
> On 27/01/2022 03:12, Ken Whitesell wrote:
>> First, the bottom line:
>> XWin.exe.manifest, line 21
>> change:
>> <dpiAwareness>PerMonitorV2,PerMonitor</dpiAwareness>
>> to
>> <dpiAwareness>PerMonitor</dpiAwareness>
>> Some details:
>> I managed to get to a point where I could build the packages from 
>> source and install them. I looked at the commit you referred me to, 
>> and started reverting changes, one-by-one - at least in so far as the 
>> change appeared to make sense to me.
>> Anyway, I got to this change, and sure enough, it worked. Removing the 
>> "PerMonitorV2" solved the issue. Also, I confirmed that it's the 
>> "PerMonitorV2" that is causing the issue and not having both of them 
>> by running another test with just the "PerMonitorV2" - and that still 
>> shows the problem.
> Thanks for taking the time to narrow this down.  It's been very helpful.
> Working through the documented effects of that [1], I was able to work 
> out that this mis-rendering is due to the non-client area scaling.
> If you turn off 'Hide Root Window' from the tray menu, you can kind of 
> see what's going wrong: normally the client area of the X window is 
> exactly aligned with that in the root window, but when the non-client 
> area is rescaled by a DPI change (the title bar changes size 
> significantly), it's misaligned so that part of the X window is outside 
> the client area (and thus clipped in updates).
> I think this is due to the AdjustWindowsRectEx() function not being DPI 
> aware (I guess it's always computing the non-client window rect based on 
> the processes initial DPI)
> Unfortunately, from an initial look, rewriting things to use 
> AdjustWindowRectExForDpi() isn't trivial (since we need to make 'DPI of 
> the monitor this Window is going to end up on' available to it)
> So for the moment, I think I'll apply your reversion (although this 
> probably comes at the cost of not scaling the window frame, the traymenu 
> and About... dialog)

I made this change in xserver 21.1.4-1.

Thanks again for tracking this down.

More information about the Cygwin mailing list