fix: Properly clean up state when revealable is disposed (#19)

reveal-core/src/main/kotlin/com/svenjacobs/reveal/RevealScope.kt

@@ -1,8 +1,10 @@
 package com.svenjacobs.reveal
 
 import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.Immutable
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.composed
 import androidx.compose.ui.layout.onGloballyPositioned
 import androidx.compose.ui.unit.dp
 
@@ -19,6 +21,9 @@ public interface RevealScope {
 	 * Internally [Modifier.onGloballyPositioned] is used. Hence elements are only registered after
 	 * they have been laid out.
 	 *
+	 * If the element that this modifier is applied to leaves the composition while the reveal
+	 * effect is shown for the element, the effect is finished.
+	 *
 	 * @param key     Unique key to identify the revealable content. Also see documentation of [Key].
 	 * @param padding Additional padding around the reveal area. Positive values increase area while
 	 *                negative values decrease it. Defaults to 8 dp on all sides.
@@ -40,13 +45,22 @@ internal class RevealScopeInstance(
 
 	override fun Modifier.revealable(key: Key, padding: PaddingValues, shape: RevealShape): Modifier =
 		this.then(
-			Modifier.onGloballyPositioned { layoutCoordinates ->
-				revealState.putRevealable(
-					key = key,
-					shape = shape,
-					padding = padding,
-					layoutCoordinates = layoutCoordinates,
-				)
-			},
+			Modifier
+				.onGloballyPositioned { layoutCoordinates ->
+					revealState.putRevealable(
+						key = key,
+						shape = shape,
+						padding = padding,
+						layoutCoordinates = layoutCoordinates,
+					)
+				}
+				.composed {
+					DisposableEffect(Unit) {
+						onDispose {
+							revealState.removeRevealable(key)
+						}
+					}
+					this
+				},
 		)
 }

reveal-core/src/main/kotlin/com/svenjacobs/reveal/RevealState.kt

@@ -116,6 +116,23 @@ public class RevealState internal constructor(
 		}
 	}
 
+	/**
+	 * Is called from [RevealScope.revealable] when the composable is disposed.
+	 */
+	internal fun removeRevealable(key: Key) {
+		revealables.remove(key)
+
+		// Hide effect if the current revealable left the composition.
+		// currentRevealable and previousRevealable are reset via onHideAnimationFinished().
+		if (currentRevealableKey == key) {
+			visible = false
+		}
+
+		if (previousRevealableKey == key) {
+			previousRevealable = null
+		}
+	}
+
 	internal companion object {
 
 		internal fun newSaver(keySaver: Saver<Key, Any>): Saver<RevealState, *> = listSaver(