Re: HiDPI doesn't appear to be handled by Cygwin/X11

On 10/07/2026 15:39, Hamish McIntyre-Bhatty via Cygwin wrote:
> Hi all,
> 
> Apologies if this has already been reported, but I couldn't find 
> anything about this exact issue. I've recently found that HiDPI screens 
> with scaling don't appear to be handled well by Cygwin/X11 - windows 
> render very small in this configuration. By contrast, if I use the 
> VcxSrv server with the same Cygwin application it displays at the size 
> you'd expect.
> 
> I'd be happy to send screenshots or logs, or anything else I can send to 
> help figure out why this is happening. I don't know much about X, other 
> than that it's hard to maintain, so I appreciate this may not be an easy 
> problem to fix.

Interesting.

The way this is supposed to work is (i) for windows owned by the X 
server, we turn off all the scaling that Windows might do automatically 
(so 1 pixel == 1 pixel), and (ii) advise X applications of the real DPI 
so they (or, usually, the toolkit they use, qt, gtk, etc.) can make 
appropriate scaling decisions.

(Differences with VcxSrv might be because that's not marked dpiAware and 
so let's Windows do scaling, or because it has some patches to do more 
intelligent things...)

It would be nice to know:

* the DPI of your display
* the dpi reported by xdpyinfo
* the name of an application you see this problem with

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