271 attempts at 720x1280 with no detection means either downsampling
killed the finder patterns or drawImage is silently painting blank
pixels (a known iOS WebKit failure mode for some video-stream sources).
- Drop the 600px scaling cap. Feed the full native video frame to
jsQR. Per-frame cost goes up but is still fine; the win is jsQR
sees finder patterns at full sharpness.
- Add a one-time sanity check that walks the first ImageData buffer
looking for a non-zero pixel. If everything is 0,0,0 the canvas is
blank (drawImage failed) and we surface that as 'px:BLANK' in the
status line — telling us instantly to switch decoder strategies
rather than chasing tuning.
- Status line now also shows the last jsQR call outcome:
r:found / r:no_code / r:empty / r:error: ...
So we can confirm whether jsQR is even being invoked successfully.
Status format compacted to fit one line on phone:
jsqr · f1234 a567 720x1280 rs4 px:ok r:no_code
Version: shopfloor 19.0.20 -> 19.0.21.
8e3169e49b
