LastContentFocus.kt

Each line, with the release that last changed it.

0.5.0	1	package dev.stave.ui.nav
	2
	3	import androidx.compose.runtime.MutableState
	4	import androidx.compose.runtime.compositionLocalOf
	5	import androidx.compose.runtime.mutableStateOf
	6	import androidx.compose.ui.Modifier
	7	import androidx.compose.ui.focus.FocusRequester
	8	import androidx.compose.ui.focus.focusRequester
	9	import androidx.compose.ui.focus.onFocusChanged
	10
	11	/**
	12	* Holds the [FocusRequester] of the most recently focused content row so
	13	* the Now Playing bar's Up gesture can restore focus to it — the user
	14	* returns to exactly where they were, not wherever Compose's spatial
	15	* resolver happens to pick.
	16	*
	17	* Screens that render content above the bar (Browse's list, Queue's
	18	* list, etc.) write their row FRs here via [Modifier.trackLastContentFocus]
	19	* on focus gain. The bar's `onUpFromBar` reads the current value and
	20	* calls `requestFocus()` on it; when the row has been disposed (scrolled
	21	* out of a LazyColumn) the call fails and the caller should fall back to
	22	* [androidx.compose.ui.focus.FocusManager.moveFocus].
	23	*
	24	* Default value is a no-op sink so code that reads the Local without a
	25	* provider (unlikely, but harmless) doesn't null-pointer.
	26	*/
	27	val LocalLastContentFocus =
	28	compositionLocalOf<MutableState<FocusRequester?>> { mutableStateOf(null) }
	29
	30	/**
	31	* Register [requester] as the "last focused content" when the modified
	32	* element gains focus. Pair with a real [Modifier.focusRequester] and a
	33	* focusable modifier (e.g. staveFocusable + clickable).
	34	*/
	35	fun Modifier.trackLastContentFocus(
	36	requester: FocusRequester,
	37	sink: MutableState<FocusRequester?>,
	38	): Modifier = this
	39	.focusRequester(requester)
	40	.onFocusChanged { if (it.isFocused) sink.value = requester }