> Does this mean people who _don't_ buy 4K displays at those resolutions are going to be disadvantaged with strangely-huge UIs?
My experience so far is that if your monitor is "too small" for a given app the UI will be gigantic, sometimes to the point of being unusable.
If your monitor is "too big" for a given app, the UI will be tiny, sometimes to the point of being unusable.
Because of (I guess?) the way that Windows (so far?) has handled things, I keep ending up with apps which are too large on my laptop's 1080p screen running alongside apps which are too small on my laptop's external 1440p screen.
> It reminds me a little bit of when Apple's retina displays first came out and nobody knew how to handle widely-different resolutions, which resulted in huge UI/icons on normal-resolution monitors and fuzzy UI/icons on high-resolution ones, for the longest time.
This is a great comparison; I think the difference with MacOS is that if you're doing everything "natively" on MacOS, everything "just kinda worked" a lot of the time, but if your app does any custom drawing (e.g. for toolbar buttons) everything went to hell. In contrast, there are a lot of apps on Windows which use native controls and menus and so on which do not handle scaling well at all. Possibly they're using some API that wasn't properly updated, like Win32 or GDI or who knows what else.
I even have one app, which my company makes :/, which has an odd behaviour: if you launch it when you have a 1080p primary display, and then switch to having a 1440p primary display (by plugging into a dock or monitor or whatever) the right-click menu for the system tray icon shows up at the appropriate location for a 1080p monitor - the correct distance from the top and left of the screen - which, on a 1440p display, is near the middle of the screen.
Which reminds me, I need to report that bug.