Owner, 2026-08-04: «цвет фона не меняется сам с течением времени суток, только
после обновления страницы».
WHAT IS NOT THE BUG. The model layer was already live: `_stageBg` and the
`planDim` filter are read straight out of `hass.states['sun.sun']` on every
render, `hass` is a plain reactive property, and a bare `card.hass = {...}` in
the demo rig does move the style attribute — smoke_sun.mjs has asserted exactly
that since v1.56.0 and it has always passed.
WHAT IS. The sky is DELIVERED by a 45 s CSS transition, and a CSS transition
only advances while the element is being painted. Every second of a background
tab, another dashboard view, an editor session or a sleeping wall tablet is a
second the sun keeps moving and the sky does not; when the card comes back, the
transition restarts from the stale colour and crawls, 45 s at a time, toward a
target that has meanwhile moved again. A page reload, by contrast, paints the
right colour outright — a freshly mounted element has nothing to transition
FROM. That is the owner's sentence, word for word.
THE FIX. Measure the gap and decide. HA refreshes `sun.sun` every ~4 minutes by
day (verified on the home instance: 08:58:56, 09:02:56, 09:06:56, …), i.e. ≤1°
of elevation per update, so anything from SKY_SNAP_DEG = 3° up can only mean
"we were not watching". Such a step is painted with `transition: none` for a
single frame (`.stage.daynight.skysnap`, released on the next
requestAnimationFrame, so the very next change glides again); everything
smaller keeps the 45 s breathing untouched. `visibilitychange → visible` clears
the marker outright, so a tab that comes back is right immediately.
The elevation the sky is computed from is now rounded to 0.1° (`skyElevation`,
shared by the stage background and the plan dimming) — invisible across a 45 s
glide and it keeps lit from re-committing the style attribute on every hass
tick. The ray GEOMETRY memo is deliberately untouched and keeps its own,
coarser key: the sky is cheap, polygon clipping is not.
Tests: unit — skyNeedsSnap (null/NaN, a real 4-minute step glides, 3° in either
direction jumps), skyElevation. Smoke — demo/smoke_sun_live_bg.mjs, which
asserts the COMPUTED background of the stage (not the style attribute) after a
plain `hass` assignment with no reload and no requestUpdate, plus planDim and
the 3° ray threshold both ways. It fails on the previous tip with
dayComputedWhite, nightComputedDark, backToDayComputed, smallStepMovesSky and
returnFromHiddenSnaps, and it also pins that a REAL sun step still glides
rather than jumps.
Sergey Matyunin