Make ScrollbarAdapter for LazyList take contentPadding into account. (#…

…365)
JetBrains · Jan 13, 2023 · 795359d · 795359d
1 parent 221ca51
commit 795359d
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Showing 2 changed files with 39 additions and 2 deletions.
diff --git a/...dation/foundation/src/desktopMain/kotlin/androidx/compose/foundation/Scrollbar.desktop.kt b/...dation/foundation/src/desktopMain/kotlin/androidx/compose/foundation/Scrollbar.desktop.kt
@@ -472,7 +472,11 @@ private class LazyScrollbarAdapter(
     }
 
     override fun maxScrollOffset(containerSize: Int) =
-        (averageItemSize * itemCount - containerSize).coerceAtLeast(0f)
+        (averageItemSize * itemCount
+            + scrollState.layoutInfo.beforeContentPadding
+            + scrollState.layoutInfo.afterContentPadding
+            - containerSize
+        ).coerceAtLeast(0f)
 
     private val itemCount get() = scrollState.layoutInfo.totalItemsCount
 

diff --git a/...foundation/foundation/src/desktopTest/kotlin/androidx/compose/foundation/ScrollbarTest.kt b/...foundation/foundation/src/desktopTest/kotlin/androidx/compose/foundation/ScrollbarTest.kt
@@ -21,6 +21,7 @@ import androidx.compose.foundation.gestures.ScrollConfig
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.ColumnScope
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.size
@@ -286,6 +287,36 @@ class ScrollbarTest {
         }
     }
 
+    @Test
+    fun `scroll lazy column to bottom with content padding`() {
+        runBlocking(Dispatchers.Main) {
+            val listState = LazyListState()
+            rule.setContent {
+                LazyTestBox(
+                    state = listState,
+                    size = 100.dp,
+                    childSize = 10.dp,
+                    childCount = 20,
+                    scrollbarWidth = 10.dp,
+                    contentPadding = PaddingValues(vertical = 25.dp)
+                )
+            }
+            rule.awaitIdle()
+
+            // Drag to the bottom
+            rule.onNodeWithTag("scrollbar").performMouseInput {
+                instantDrag(start = Offset(0f, 20f), end = Offset(0f, 80f))
+            }
+
+            rule.awaitIdle()
+
+            // Note that if the scrolling is incorrect, this can fail not only with a wrong value, but also by not
+            // finding the box node, as it may have not scrolled into view.
+            // Last box should be at containerSize - bottomPadding - boxSize
+            rule.onNodeWithTag("box19").assertTopPositionInRootIsEqualTo(100.dp - 25.dp - 10.dp)
+        }
+    }
+
     // TODO(demin): write a test when we support DesktopComposeTestRule.mainClock:
     //  see https://github.com/JetBrains/compose-jb/issues/637
 //    fun `move mouse to the slider and drag it`() {
@@ -662,12 +693,14 @@ class ScrollbarTest {
         childSize: Dp,
         childCount: Int,
         scrollbarWidth: Dp,
-        reverseLayout: Boolean = false
+        contentPadding: PaddingValues = PaddingValues(0.dp),
+        reverseLayout: Boolean = false,
     ) = withTestEnvironment {
         Box(Modifier.size(size)) {
             LazyColumn(
                 Modifier.fillMaxSize().testTag("column"),
                 state,
+                contentPadding = contentPadding,
                 reverseLayout = reverseLayout
             ) {
                 items((0 until childCount).toList()) {