Reported: fully zoomed in, couldn't pan left/right at all — stuck
dead-center.
My previous fix pinned the zoom's transform-origin at a fixed 50% 50%
(the frame's own center) specifically to fix a *different* bug (the head
of a portrait being unreachable). That traded one bug for another: with a
fixed center, object-position's own pan formula only has room to move in
whichever axis has overflow at zoom=1. For a portrait photo in this
landscape frame, width is the *exact*-fit axis at zoom=1 — literally zero
horizontal slack — so there was nothing for a fixed-center zoom to
magnify away from, and horizontal dragging computed a division by
(essentially) zero, guarded down to a hard no-op.
The actual fix: transform-origin should match object-position (X% Y%),
not stay fixed at center. Re-derived from there — with a matching origin,
box position (X%, Y%) always shows exactly natural-image point
(X/100*naturalW, Y/100*naturalH), at any zoom, in either axis, with no
zero-slack case at all. Rewrote the drag-sensitivity and reference-
rectangle math to match this (both simplify to plain linear formulas).
Verified in the standalone test harness with the same portrait test image
that reproduces the zero-slack case: dragging now works at any zoom level
in both axes, and reaching an image edge (the original bug) still works
too — tested both scenarios explicitly before deploying, since the first
fix silently broke the second.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
pguzman
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