Scale / Pan Improvement Ideas

[JacobJaffe]

Hello! First off, this library is amazing. Thank you!

In mirroring native behavior on iOS, I'd like to have panning lock horizontally / vertically when zoomed in, if the zoom still fully shows the image fully on the reverse axis. For example, when zooming in on a portrait image, I'd like to prevent vertical panning until the image exceeds the container (screen).

This kinda occurs in this library, but only when not zoomed in. (like for swipe-down behavior).

In a similar vein, it would be really cool if double-tapping could automatically zoom to constrain the image fully in the cross-dimension (maybe only if the image is within a reasonable aspect ratio). This would mirror native behavior as well, and probably under-the-hood use the same kinda calculations to determine if the image is locked-in-frame on a single dimension.

I'm happy to take a stab at implementing this if this sounds reasonable.

[JacobJaffe]

Here's an example of what I mean.
See how in the native photos app, scrolling is locked horizontally while the entire height of the image is already in frame. Very smooth!

pan-example-420p.mov