Zoomed images cannot be panned on mobile

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Describe the bug

On mobile, the image preview allows an image to be zoomed in, but the enlarged image cannot be moved or panned.

The zoom itself works, but once the image becomes larger than the viewport, there is no way to drag it left, right, up, or down. Parts of the enlarged image therefore become inaccessible.

This makes the zoom feature much less useful on mobile, because the user can enlarge an image but cannot inspect different areas of it.

The issue is reproducible both on the stable v0.31.0 release and on the current Memos demo build.

Expected behavior

After zooming an image, the user should be able to move around the enlarged image using touch gestures, as in a normal mobile image viewer.

Steps to reproduce

Open Memos in Chrome on an Android phone. Open a memo containing an image attachment. Tap the image to open the image preview. Zoom in using the available zoom controls. Try to move the enlarged image in any direction. The image remains fixed in place and cannot be panned.

Memos version

v0.31.0

Additional context

Also reproduced on the current demo build:

v0.31.0 commit cb42e326ba9cc266a6a9570c53e0fe04c62793f4

Browser: Google Chrome 153.0.8010.52 Platform: Android Browser mode: regular Chrome browser, not PWA

The zoom control itself works. The problem is specifically that there is no way to navigate around the image after it has been enlarged.

Related issues:

#5639 — Image viewer: cannot navigate between images and no pinch-to-zoom on mobile PWA #5616 — Lack of image zoom controls #5669 — added image navigation and only partially addressed #5639

Screenshot attached.