Touch Zoom with two fingers don't work on Touch screen (but it works on Touch Pad)

Description of the new feature/enhancement

When I use two finger to zoom in or out (actually making text bigger or smaller), it works on my touch pad. But it actually don't work on my touch screen.

I think the experience would be much smoother if it worked the same on the touch pad and the touch screen.

What I also get is, if I scroll with finger on the touch screen it works. If I try to scroll with two fingers it flickers, as if the program doesn't realize I using two fingers and tries to read both inputs.

So the case with multiple fingers should probably be detected and handled specifically.

Proposed technical implementation details (optional)

If I use two fingers on the touch screen and move them together or away from each other the font size should decrease or increase respectively, exactly as it is now if I do that on the touch screen.

No source files or tests are named. Start by reproducing two-finger movement on a Windows touch screen and comparing it with touchpad zoom, then trace the terminal's touch-input and font-zoom handling. Done means pinch gestures change the font size and two-finger scrolling no longer flickers, while single-finger scrolling continues to work.