feat(v1.8.0): IMPL_023b Drag & Drop Flicker Fix - Straddle-Target-Center Detection

- Swap detection: Changed from midpoint check to straddle-target-center detection
  * Old: Checks if midpoint of dragged item lies within target
  * New: Checks if dragged item spans the midpoint of target
  * Prevents oscillation when items have different sizes

- Adjacency filter: Only adjacent items (index ± 1) as swap candidates
  * Prevents item jumps during fast drag
  * Reduces recalculation of visibleItemsInfo

- Race-condition fix for scroll + move
  * draggingItemIndex update moved after onMove() in coroutine block
  * Prevents inconsistent state between index update and layout change

Affected files:
- DragDropListState.kt: onDrag() method (~10 lines changed)

android/app/src/main/java/dev/dettmer/simplenotes/ui/editor/DragDropListState.kt

@@ -9,6 +9,7 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
@@ -22,6 +23,8 @@ import kotlinx.coroutines.launch
  *
  * Native Compose-Implementierung ohne externe Dependencies
  * v1.5.0: NoteEditor Redesign
+ * v1.8.0: IMPL_023 - Drag & Drop Fix (pointerInput key + Handle-only drag)
+ * v1.8.0: IMPL_023b - Flicker-Fix (Straddle-Target-Center-Erkennung statt Mittelpunkt)
  */
 class DragDropListState(
     private val state: LazyListState,
@@ -64,11 +67,17 @@ class DragDropListState(
         val startOffset = draggingItem.offset + draggingItemOffset
         val endOffset = startOffset + draggingItem.size
 
-        val middleOffset = startOffset + (endOffset - startOffset) / 2f
+        // 🆕 v1.8.0: IMPL_023b — Straddle-Target-Center + Adjazenz-Filter
-
+        // Statt den Mittelpunkt des gezogenen Items zu prüfen ("liegt mein Zentrum im Target?"),
-        val targetItem = state.layoutInfo.visibleItemsInfo.find { item ->
+        // wird geprüft ob das gezogene Item den MITTELPUNKT des Targets überspannt.
-            middleOffset.toInt() in item.offset..item.offsetEnd &&
+        // Dies verhindert Oszillation bei Items unterschiedlicher Größe.
-                draggingItem.index != item.index
+        // Zusätzlich: Nur adjazente Items (Index ± 1) als Swap-Kandidaten.
+        val targetItem = state.layoutInfo.visibleItemsInfo.firstOrNull { item ->
+            (item.index == draggingItem.index - 1 || item.index == draggingItem.index + 1) &&
+                run {
+                    val targetCenter = item.offset + item.size / 2
+                    startOffset < targetCenter && endOffset > targetCenter
+                }
         }
 
         if (targetItem != null) {
@@ -84,12 +93,13 @@ class DragDropListState(
                 scope.launch {
                     state.scrollToItem(scrollToIndex, state.firstVisibleItemScrollOffset)
                     onMove(draggingItem.index, targetItem.index)
+                    // 🆕 v1.8.0: IMPL_023b — Index-Update NACH dem Move (verhindert Race-Condition)
+                    draggingItemIndex = targetItem.index
                 }
             } else {
                 onMove(draggingItem.index, targetItem.index)
-            }
-            
                 draggingItemIndex = targetItem.index
+            }
         } else {
             val overscroll = when {
                 draggingItemDraggedDelta > 0 ->
@@ -130,14 +140,16 @@ fun rememberDragDropListState(
     }
 }
 
+@Composable
 fun Modifier.dragContainer(
     dragDropState: DragDropListState,
     itemIndex: Int
 ): Modifier {
-    return this.pointerInput(dragDropState) {
+    val currentIndex = rememberUpdatedState(itemIndex)  // 🆕 v1.8.0: rememberUpdatedState statt Key
+    return this.pointerInput(dragDropState) {  // Nur dragDropState als Key - verhindert Gesture-Restart
         detectDragGesturesAfterLongPress(
             onDragStart = { offset ->
-                dragDropState.onDragStart(offset, itemIndex)
+                dragDropState.onDragStart(offset, currentIndex.value)  // Aktuellen Wert lesen
             },
             onDragEnd = {
                 dragDropState.onDragInterrupted()

android/app/src/main/java/dev/dettmer/simplenotes/ui/editor/NoteEditorScreen.kt

@@ -50,6 +50,7 @@ import androidx.compose.ui.platform.LocalSoftwareKeyboardController
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.IntOffset
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.zIndex
 import dev.dettmer.simplenotes.R
 import dev.dettmer.simplenotes.models.NoteType
 import dev.dettmer.simplenotes.ui.editor.components.ChecklistItemRow
@@ -351,14 +352,17 @@ private fun ChecklistEditor(
                     onDelete = { onDelete(item.id) },
                     onAddNewItem = { onAddNewItemAfter(item.id) },
                     requestFocus = shouldFocus,
+                    isDragging = isDragging,  // 🆕 v1.8.0: IMPL_023 - Drag state übergeben
+                    isAnyItemDragging = dragDropState.draggingItemIndex != null,  // 🆕 v1.8.0: IMPL_023 - Gradient während Drag ausblenden
+                    dragModifier = Modifier.dragContainer(dragDropState, index),  // 🆕 v1.8.0: IMPL_023 - Drag nur auf Handle
                     modifier = Modifier
-                        .dragContainer(dragDropState, index)
                         .offset {
                             IntOffset(
                                 0,
                                 if (isDragging) dragDropState.draggingItemOffset.roundToInt() else 0
                             )
                         }
+                        .zIndex(if (isDragging) 10f else 0f)  // 🆕 v1.8.0: IMPL_023 - Gedraggtes Item liegt über anderen
                         .shadow(elevation, shape = RoundedCornerShape(8.dp))
                         .background(
                             color = MaterialTheme.colorScheme.surface,

android/app/src/main/java/dev/dettmer/simplenotes/ui/editor/components/ChecklistItemRow.kt

@@ -4,12 +4,15 @@ import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.text.BasicTextField
 import androidx.compose.foundation.text.KeyboardActions
 import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Close
 import androidx.compose.material.icons.filled.DragHandle
@@ -32,6 +35,7 @@ import androidx.compose.ui.focus.FocusRequester
 import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.focus.onFocusChanged
 import androidx.compose.ui.graphics.SolidColor
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.LocalSoftwareKeyboardController
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.TextRange
@@ -39,6 +43,7 @@ import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.text.input.TextFieldValue
 import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import dev.dettmer.simplenotes.R
 import dev.dettmer.simplenotes.ui.editor.ChecklistItemState
@@ -48,6 +53,7 @@ import dev.dettmer.simplenotes.ui.editor.ChecklistItemState
  *
  * v1.5.0: Jetpack Compose NoteEditor Redesign
  * v1.8.0: Long text UX improvements (gradient fade, auto-expand on focus)
+ * v1.8.0: IMPL_023 - Enlarged drag handle (48dp touch target) + drag modifier
  */
 @Composable
 fun ChecklistItemRow(
@@ -57,12 +63,16 @@ fun ChecklistItemRow(
     onDelete: () -> Unit,
     onAddNewItem: () -> Unit,
     requestFocus: Boolean = false,
+    isDragging: Boolean = false,          // 🆕 v1.8.0: IMPL_023 - Drag state
+    isAnyItemDragging: Boolean = false,   // 🆕 v1.8.0: IMPL_023 - Hide gradient during any drag
+    dragModifier: Modifier = Modifier,    // 🆕 v1.8.0: IMPL_023 - Drag modifier for handle
     modifier: Modifier = Modifier
 ) {
     val focusRequester = remember { FocusRequester() }
     val keyboardController = LocalSoftwareKeyboardController.current
+    val density = LocalDensity.current
     var textFieldValue by remember(item.id) {
-        mutableStateOf(TextFieldValue(text = item.text, selection = TextRange(item.text.length)))
+        mutableStateOf(TextFieldValue(text = item.text, selection = TextRange(0)))
     }
 
     // 🆕 v1.8.0: Focus-State tracken für Expand/Collapse
@@ -71,8 +81,19 @@ fun ChecklistItemRow(
     // 🆕 v1.8.0: Overflow erkennen (Text länger als maxLines)
     var hasOverflow by remember { mutableStateOf(false) }
 
-    // 🆕 v1.8.0: Dynamische maxLines basierend auf Focus
+    // 🆕 v1.8.0: Höhe für collapsed-Ansicht (aus TextLayout berechnet)
-    val currentMaxLines = if (isFocused) Int.MAX_VALUE else COLLAPSED_MAX_LINES
+    var collapsedHeightDp by remember { mutableStateOf<Dp?>(null) }
+
+    // 🆕 v1.8.0: ScrollState für dynamischen Gradient
+    val scrollState = rememberScrollState()
+
+    // 🆕 v1.8.0: Scroll-basierter Ansatz aktiv wenn Höhe berechnet wurde
+    val useScrollClipping = hasOverflow && collapsedHeightDp != null
+
+    // 🆕 v1.8.0: Dynamische Gradient-Sichtbarkeit basierend auf Scroll-Position
+    val showGradient = useScrollClipping && !isFocused && !isAnyItemDragging
+    val showTopGradient = showGradient && scrollState.value > 0
+    val showBottomGradient = showGradient && scrollState.value < scrollState.maxValue
 
     // v1.5.0: Auto-focus AND show keyboard when requestFocus is true (new items)
     LaunchedEffect(requestFocus) {
@@ -82,12 +103,21 @@ fun ChecklistItemRow(
         }
     }
 
+    // 🆕 v1.8.0: Cursor ans Ende setzen wenn fokussiert (für Bearbeitung)
+    LaunchedEffect(isFocused) {
+        if (isFocused && textFieldValue.selection.start == 0) {
+            textFieldValue = textFieldValue.copy(
+                selection = TextRange(textFieldValue.text.length)
+            )
+        }
+    }
+
     // Update text field when external state changes
     LaunchedEffect(item.text) {
         if (textFieldValue.text != item.text) {
             textFieldValue = TextFieldValue(
                 text = item.text,
-                selection = TextRange(item.text.length)
+                selection = if (isFocused) TextRange(item.text.length) else TextRange(0)
             )
         }
     }
@@ -99,21 +129,27 @@ fun ChecklistItemRow(
     Row(
         modifier = modifier
             .fillMaxWidth()
-            .padding(horizontal = 8.dp, vertical = 4.dp),
+            .padding(end = 8.dp, top = 4.dp, bottom = 4.dp),  // 🆕 v1.8.0: IMPL_023 - links kein Padding (Handle hat eigene Fläche)
-        verticalAlignment = Alignment.Top  // 🆕 v1.8.0: Top statt CenterVertically für lange Texte
+        verticalAlignment = if (hasOverflow) Alignment.Top else Alignment.CenterVertically  // 🆕 v1.8.0: Dynamisch
+    ) {
+        // 🆕 v1.8.0: IMPL_023 - Vergrößerter Drag Handle (48dp Touch-Target)
+        Box(
+            modifier = dragModifier
+                .size(48.dp)  // Material Design minimum touch target
+                .alpha(if (isDragging) 1.0f else 0.6f),  // Visual feedback beim Drag
+            contentAlignment = Alignment.Center
         ) {
-        // Drag Handle
             Icon(
                 imageVector = Icons.Default.DragHandle,
                 contentDescription = stringResource(R.string.drag_to_reorder),
-            modifier = Modifier
+                modifier = Modifier.size(28.dp),  // Icon größer als vorher (24dp → 28dp)
-                .size(24.dp)
+                tint = if (isDragging) {
-                .padding(top = 12.dp)  // 🆕 v1.8.0: Visuell am oberen Rand ausrichten
+                    MaterialTheme.colorScheme.primary  // Primary color während Drag
-                .alpha(0.5f),
+                } else {
-            tint = MaterialTheme.colorScheme.onSurfaceVariant
+                    MaterialTheme.colorScheme.onSurfaceVariant
+                }
             )
-        
+        }
-        Spacer(modifier = Modifier.width(4.dp))
 
         // Checkbox
         Checkbox(
@@ -124,8 +160,18 @@ fun ChecklistItemRow(
 
         Spacer(modifier = Modifier.width(4.dp))
 
-        // 🆕 v1.8.0: Text Input mit Overflow-Gradient
+        // 🆕 v1.8.0: Text Input mit dynamischem Overflow-Gradient
         Box(modifier = Modifier.weight(1f)) {
+            // Scrollbarer Wrapper: begrenzt Höhe auf ~5 Zeilen wenn collapsed
+            Box(
+                modifier = if (!isFocused && useScrollClipping) {
+                    Modifier
+                        .heightIn(max = collapsedHeightDp!!)
+                        .verticalScroll(scrollState)
+                } else {
+                    Modifier
+                }
+            ) {
                 BasicTextField(
                     value = textFieldValue,
                     onValueChange = { newValue ->
@@ -161,12 +207,21 @@ fun ChecklistItemRow(
                         onNext = { onAddNewItem() }
                     ),
                     singleLine = false,
-                maxLines = currentMaxLines,  // 🆕 v1.8.0: Dynamisch
+                    // maxLines nur als Fallback bis collapsedHeight berechnet ist
+                    maxLines = if (isFocused || useScrollClipping) Int.MAX_VALUE else COLLAPSED_MAX_LINES,
                     cursorBrush = SolidColor(MaterialTheme.colorScheme.primary),
                     onTextLayout = { textLayoutResult ->
-                    // 🆕 v1.8.0: Overflow erkennen
+                        // 🆕 v1.8.0: Overflow erkennen - ABER NUR wenn kein Drag aktiv ist
-                    hasOverflow = textLayoutResult.hasVisualOverflow ||
+                        if (!isAnyItemDragging) {
-                        textLayoutResult.lineCount > COLLAPSED_MAX_LINES
+                            val overflow = textLayoutResult.lineCount > COLLAPSED_MAX_LINES
+                            hasOverflow = overflow
+                            // Höhe der ersten 5 Zeilen berechnen (einmalig)
+                            if (overflow && collapsedHeightDp == null) {
+                                collapsedHeightDp = with(density) {
+                                    textLayoutResult.getLineBottom(COLLAPSED_MAX_LINES - 1).toDp()
+                                }
+                            }
+                        }
                     },
                     decorationBox = { innerTextField ->
                         Box {
@@ -182,16 +237,24 @@ fun ChecklistItemRow(
                         }
                     }
                 )
+            }
 
-            // 🆕 v1.8.0: Gradient-Fade Overlay wenn Text überläuft
+            // 🆕 v1.8.0: Dynamischer Gradient basierend auf Scroll-Position
-            // Zeige nur Gradient oben, da man am unteren Rand startet und nach oben scrollt
+            // Oben: sichtbar wenn nach unten gescrollt (Text oberhalb versteckt)
-            if (hasOverflow && !isFocused) {
+            if (showTopGradient) {
-                // Gradient oben (zeigt: es gibt Text oberhalb der sichtbaren Zeilen)
                 OverflowGradient(
                     modifier = Modifier.align(Alignment.TopCenter),
                     isTopGradient = true
                 )
             }
+
+            // Unten: sichtbar wenn noch Text unterhalb vorhanden
+            if (showBottomGradient) {
+                OverflowGradient(
+                    modifier = Modifier.align(Alignment.BottomCenter),
+                    isTopGradient = false
+                )
+            }
         }
 
         Spacer(modifier = Modifier.width(4.dp))
@@ -232,7 +295,9 @@ private fun ChecklistItemRowShortTextPreview() {
         onTextChange = {},
         onCheckedChange = {},
         onDelete = {},
-        onAddNewItem = {}
+        onAddNewItem = {},
+        isDragging = false,
+        dragModifier = Modifier
     )
 }
 
@@ -253,7 +318,9 @@ private fun ChecklistItemRowLongTextPreview() {
         onTextChange = {},
         onCheckedChange = {},
         onDelete = {},
-        onAddNewItem = {}
+        onAddNewItem = {},
+        isDragging = false,
+        dragModifier = Modifier
     )
 }
 
@@ -269,6 +336,27 @@ private fun ChecklistItemRowCheckedPreview() {
         onTextChange = {},
         onCheckedChange = {},
         onDelete = {},
-        onAddNewItem = {}
+        onAddNewItem = {},
+        isDragging = false,
+        dragModifier = Modifier
+    )
+}
+
+// 🆕 v1.8.0: IMPL_023 - Preview for dragging state
+@Preview(showBackground = true)
+@Composable
+private fun ChecklistItemRowDraggingPreview() {
+    ChecklistItemRow(
+        item = ChecklistItemState(
+            id = "preview-4",
+            text = "Wird gerade verschoben - Handle ist highlighted",
+            isChecked = false
+        ),
+        onTextChange = {},
+        onCheckedChange = {},
+        onDelete = {},
+        onAddNewItem = {},
+        isDragging = true,
+        dragModifier = Modifier
     )
 }