GeezerVison

bug (medium): a frame with no render does not mean no draw is pending. Cytoscape's texture caches dequeue in beforeRenderCallbacks on frames that do not draw. They then request the redraw through a lodash debounce set to deqRedrawThreshold, which is 50–100 ms (setupDequeueing in cytoscape 3.33.1). The LayeredTextureCache works the same way.

I tested this. A probe stayed inside settle() for 400 ms after the loop exited and counted render events. I also delayed animation frames by a random 0–400 ms, the same way your PR testing did.

• Idle machine: no late draws in the pixel tests.
• Late frames: in ~20 of ~70 settles per run, cytoscape drew again after the "quiet" frame. This included node text > draws the text itself… and the selection glow > paints nothing…. Wrapping renderer().redraw showed the callers were trailingEdge (debounce) → LayeredTextureCache, plus some BRp.notify.

The tests still passed, so these redraws seem to be mostly texture refinement. Still, the comment states something that is not true, and the probes can still read a frame that is about to change. One fix is to also require a quiet stretch longer than the debounce:

let last = performance.now()
const onRender = () => { last = performance.now() }
mountedCy.on('render', onRender)
// A frame with no draw is not enough: the texture caches ask for their redraw
// from a 50-100 ms debounce, so also wait out that delay.
let frames = 0
do {
  frames++
  await nextFrame()
} while (frames < 2 || performance.now() - last < 150)
mountedCy.off('render', onRender)

Also consider try/finally around the off, and resetting mountedCy in cleanup, so a later settle() does not wait on a removed instance.

Agreed, fixed in 0f12d9c. I traced the late draws to the same chain: element texture refinement, then scheduleElementRefinement (50 ms), then the LayeredTextureCache dequeue and its redraw debounce (50 ms).

I did not use the suggested condition (150 ms since the last render). With late frames it can still exit too early: if the last draw was 400 ms ago and the next frame starts a refinement, the loop exits and the debounced redraw comes after. A refinement step only advances in a frame, so the condition counts frames:

• settle() returns after 3 frames without a draw, each at least 120 ms after the one before (longer than the longest debounce).
• off is in finally, and cleanup() resets mountedCy.