I do not know why you are getting requests to do that but keep in mind that people who are fine with your MFC applications are not going to contact you - what y

I do not know why you are getting requests to do that but keep in mind that people who are fine with your MFC applications are not going to contact you - what you are seeing is only people who have issues, not all people (EDIT: also i'm certain you can make MFC applications work in hidpi monitors, you do not need to port them to Qt for that). Old applications will certainly not support "@2x pixmaps" (though many do support hidpi monitors if you use the "Override high DPI scaling behavior" to let the application do it - however the majority do not, which is why this isn't the default) but despite being blurred they'll still work (and that is assuming you are using a hidpi monitor, in practice nowadays hidpi monitors are still a very tiny minority so chances are you wont even notice it). Though FWIW i personally do not use hidpi monitors and one of the reasons is that (the other is that i play games a lot and i do not feel the slightly higher crispiness is worth the massively reduced performance). However breaking the ABI wont work at all, blurry or not. (also note that Windows 10 will not use bilinear filtering for integer scaling so in -e.g.- 4K monitors running at 200% scaling you shouldn't get blurriness)