Web browsers and text-editors are the only desktop apps that come to mind which support zooming via
0 or (
0) shortcuts. Why is this? Should my app / desktop apps in general support it?
No, desktop applications themselves should not be zoomable, but their viewed or edited content usually should scale. This can be a web page in a browser, a text document in a text editor, as the question mentions, but really anything else, especially images of all kinds (e.g. still : moving or bitmap : vector). It depends on the context whether zooming should work in pre-defined steps or continuously.
The common Windows/Linux keyboard shortcuts
0 translate to
0 on Mac OS. The scroll-wheel on a mouse can often do the same when a modifier key, e.g.
Cmd is being pressed. On touch-pads and touch-screens the usual pinch two-finger gestures should result in the same and are often accompanied by double-tap or two-finger double-tap for “zoom to fit”.
I don't think a software-independent function is necessary, since it is in your responsibility to serve the user a deserved user experience :)
For example: Your app comes with an "how to find us"-section where you have integrated a map. In this case you build in a zoom-function.
Another example would be: Why should you let your user zoom in your weather-app which only comes with a dynamic thermometer?
I think this zoom function can also have a negative impact on the UX of your app…
A Designer might not want you to experience his product, zoomed in or zoomed out.
Websites is a different case since Web is open for you to experiment with.
With apps, a far lot of power goes into the hands of the developers to exactly dictate how they would want you to view their app. And for a good reason, I believe zoom in hasn't been implemented.
If your point is, they could improve accessibility, it's the OS's function to make sure it scales the fonts and other elements of the UI accordingly to the user's set accessibility settings, but as far as a product goes, with great power comes great responsibility and developers need to take the extra effort to take their responsibility of this immense power of control they have over the app and provide the best experience they can.
For the same reason, stores should be far more vigilant before publishing half-baked apps.