From 2aea08364b8e93916a4b984bd8ed622f1ee0f01d Mon Sep 17 00:00:00 2001
From: Rodrigo Dias Ferreira <rodrigo.dias.rdf@gmail.com>
Date: Mon, 15 Jul 2024 16:07:39 -0300
Subject: [PATCH] Bug fix: scroll bar thumb jumping when at the end of the
 LazyStaggeredList with more than one lane

Signed-off-by: Rodrigo Dias Ferreira <rodrigo.dias.rdf@gmail.com>
---
 .../scrollbar/LazyScrollbarUtilities.kt       | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/core/designsystem/src/main/kotlin/com/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/LazyScrollbarUtilities.kt b/core/designsystem/src/main/kotlin/com/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/LazyScrollbarUtilities.kt
index 57e567b5d..b7e610695 100644
--- a/core/designsystem/src/main/kotlin/com/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/LazyScrollbarUtilities.kt
+++ b/core/designsystem/src/main/kotlin/com/google/samples/apps/nowinandroid/core/designsystem/component/scrollbar/LazyScrollbarUtilities.kt
@@ -74,6 +74,19 @@ internal fun itemVisibilityPercentage(
     viewportEndOffset: Int,
 ): Float {
     if (itemSize == 0) return 0f
+    // TODO: Workaround due to issue b/353143657, monitor if compose team will agree it's an issue
+    //  and fix it, if so, below safeguard probably can be removed
+    if (
+        isItemOutOfViewport(
+            itemSize = itemSize,
+            itemStartOffset = itemStartOffset,
+            viewportStartOffset = viewportStartOffset,
+            viewportEndOffset = viewportEndOffset,
+        )
+    ) {
+        return 0f
+    }
+
     val itemEnd = itemStartOffset + itemSize
     val startOffset = when {
         itemStartOffset > viewportStartOffset -> 0
@@ -86,3 +99,28 @@ internal fun itemVisibilityPercentage(
     val size = itemSize.toFloat()
     return (size - startOffset - endOffset) / size
 }
+
+private fun isItemOutOfViewport(
+    itemSize: Int,
+    itemStartOffset: Int,
+    viewportStartOffset: Int,
+    viewportEndOffset: Int,
+) = isItemBeforeViewport(
+    itemSize = itemSize,
+    itemStartOffset = itemStartOffset,
+    viewportStartOffset = viewportStartOffset,
+) || isItemAfterViewport(
+    itemStartOffset = itemStartOffset,
+    viewportEndOffset = viewportEndOffset,
+)
+
+private fun isItemBeforeViewport(
+    itemSize: Int,
+    itemStartOffset: Int,
+    viewportStartOffset: Int,
+) = (viewportStartOffset - itemStartOffset) > itemSize
+
+private fun isItemAfterViewport(
+    itemStartOffset: Int,
+    viewportEndOffset: Int,
+) = itemStartOffset > viewportEndOffset