[ixuz]

What and why

An enlarged card picture had no zoom of its own. A pinch zoomed the whole page, and the picture often closed in the middle of it. Moving around the zoomed page counted as a scroll, which closed it, and the end of a pinch could count as a tap on the dimmed layer. Someone who pinched back out to see the whole picture found it back in the card instead.

The enlarged picture now takes every touch on its layer and zooms by itself:

• Pinch zooms around the fingers, up to four times the fitted size. Pinching out past the fitted size springs back to it and never closes the picture.
• Double tap zooms in on the spot tapped (2.5×). Another double tap goes back to the fitted size.
• Drag moves the picture while zoomed in. It settles where it covers as much of the screen as it can.
• Close with a single tap, Escape, or a throw up or down that goes far enough (15% of the screen height) or fast enough. A pinch or a drag never closes it. Focus leaving the picture and a resize still close it, as before.
• A single tap waits 250 ms for a second one. The wait pauses while a finger is down, so a slow double tap still zooms in. The delay applies only to the enlarged picture.
• With reduced motion, every change is instant. The stylesheet already turns off the transitions.

The gestures are covered in ZoomableImage.test.tsx, including regression tests for the gesture bugs found while building it. docs/user-guide.md and docs/data-model.md describe the new behavior.

Not yet tried on a real iOS device; the gestures are tested with simulated touch events. Zooming with the mouse wheel on desktop is left as a possible follow-up.

Closes: #508