This is something that I noticed had changed from Win7 (could be it was there in Win8, but I wasn’t there for it). But anyway, the Magnifier I suspect is the reason that MS took away so many of the easy ways to change text sizes for Win10—- they want you to use Magnifier more often, whenever you want to get in closer.
That was workable (in a way) for Windows 7, but not for high-contrast themes. <- For them, the Magnifier would only affect whatever was immediately under the cursor. This could be disorienting. All you had to do is try it in Win7 and you’d soon be turning it off, because the rest of the screen stays as is, and other portions become surreal
But in Windows 10, Magnifier works better with the high contrast themes, much the same as it does for the others. The whole screen gets the treatment, which I think is a welcome change.
The usual keys are available: Win key and the plus (+) sign to start and to zoom in, Win key and the minus (-) key to zoom out, and Win key combined with ESC closes out of the Magnifier.
I can see tooltips now. : )
I tried all the registry changes that are supposed to make display text larger and smaller, or bold etc, but those tweaks didn’t work for me. So it’s nice to see that MS improved the magnifier for high contrast themes.