# Background-tab city texture loading, r337

The city texture uploader yielded after each four-image batch with
`requestAnimationFrame`. In the packaged Chrome session, a hidden viewer tab
stayed at `Uploading textures 4/128` while the screenshot feed tab was active.
Bringing the viewer forward resumed loading immediately. The renderer's frame
loop can be paused in a hidden tab, so an animation frame is not a reliable
loader yield there.

The uploader now yields on the next animation frame or after a 100 ms timer,
whichever happens first. A fresh packaged Route 450 page left in the background
while the review tab stayed active progressed through 72/128 textures at 21 s,
112/128 at 31 s, and `City scene ready` with 128/128 at 36 s. Its texture-upload
debug record reported `contextLost: false`. The elapsed times include this
headless Chrome and shared GPU setup; they are evidence that background loading
no longer stalls, not a general startup-time guarantee.

The captured ready view is [`480-r337-background-texture-load-ready.png`](../webgl-city/review/images/480-r337-background-texture-load-ready.png).