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wear: fix action bar disappearing at bottom - replace fragile distance-to-last-item geometry (dead-zoned by expanded padding, skewed by edge-scaling) with scroll-intent logic: canScrollForward=false always docks + shows buttons, any downward scroll reveals them, upward scroll hides

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callebtc 2026-07-29 00:32:45 +02:00
parent c06fa67ccc
commit 8f4c937e92
1 changed files with 23 additions and 30 deletions
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53
wear/src/main/java/com/bitchat/watch/ui/ChatScaffold.kt
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@ -55,21 +55,9 @@ fun ChatScaffold(
header: @Composable (expanded: Boolean) -> Unit,
actionBar: @Composable () -> Unit
) {
val palette = LocalBitchatPalette.current
val haptics = LocalHapticFeedback.current
val columnState = rememberTransformingLazyColumnState()
// Distance in px from the viewport's bottom edge to the end of the last item;
// Int.MAX_VALUE when the last message is not visible at all.
fun bottomDist(): Int {
if (messages.isEmpty()) return 0
val info = columnState.layoutInfo
val lastVisible = info.visibleItems.lastOrNull() ?: return Int.MAX_VALUE
if (lastVisible.index < messages.size - 1) return Int.MAX_VALUE
val viewportH = info.viewportSize.height
return viewportH - (lastVisible.offset + lastVisible.transformedHeight)
}
// Haptics on incoming messages.
var previousCount by remember { mutableStateOf(messages.size) }
LaunchedEffect(messages.size) {
@ -84,31 +72,36 @@ fun ChatScaffold(
// "Docked at newest" is the single source of truth for the chat's resting state:
// bottom clearance expanded (newest message sits above the floating buttons), action
// bar visible, header at full size. Scrolling into history collapses all three together;
// returning to the bottom restores them. Thresholds 40/120 straddle the 48dp padding
// delta, breaking the maxValue feedback loop, and give the header/buttons flicker-free
// hysteresis.
// bar visible, header at full size. It is driven by scroll intent, not layout geometry:
// reaching the end of the list docks; deliberately scrolling away undocks. Geometry-based
// detection (distance-to-last-item) was unreliable here because expanding the bottom
// clearance grows the scroll range, which read as "left the bottom", and the edge-scaled
// last item skewed the measurement further.
var dockedAtNewest by remember { mutableStateOf(true) }
// Action bar hides while scrolling into history, returns toward the newest.
// Action bar: ALWAYS visible while the list is scrolled to the bottom; hides when
// scrolling up into history and reappears as soon as the user scrolls back down, so
// replying is one short flick away even from the very top.
val buttonsVisible = remember { mutableStateOf(true) }
LaunchedEffect(columnState, messages.size) {
var lastPosition = 0
LaunchedEffect(columnState) {
var lastPosition = -1
snapshotFlow {
val first = columnState.layoutInfo.visibleItems.firstOrNull()
(first?.index ?: 0) * 100_000 + (first?.offset ?: 0)
}.collect { position ->
val dist = bottomDist()
if (dist < 40) {
Triple(columnState.canScrollForward, first?.index ?: 0, first?.offset ?: 0)
}.collect { (canScrollForward, index, offset) ->
val atBottom = !canScrollForward
if (atBottom) {
dockedAtNewest = true
buttonsVisible.value = true
} else if (dist in 121..10_000) {
// Clearly reading history (MAX_VALUE = last item not laid out yet; transient
// right after a new message arrives, so it must not undock the state).
dockedAtNewest = false
}
when {
dist >= 40 && position < lastPosition - 24 -> buttonsVisible.value = false
position > lastPosition + 24 -> buttonsVisible.value = true
val position = index * 100_000 + offset
if (lastPosition >= 0) {
when {
position > lastPosition + 24 -> buttonsVisible.value = true
position < lastPosition - 24 -> {
buttonsVisible.value = false
if (!atBottom) dockedAtNewest = false
}
}
}
lastPosition = position
}