feat: add interceptor into selection service to custom the drag target node (#1044)

lib/src/editor/editor_component/service/selection/desktop_selection_service.dart

@@ -437,12 +437,21 @@ class _DesktopSelectionServiceWidgetState
   void renderDropTargetForOffset(
     Offset offset, {
     DragAreaBuilder? builder,
+    DragTargetNodeInterceptor? interceptor,
   }) {
     removeDropTarget();
 
-    final node = getNodeInOffset(offset);
-    final selectable = node?.selectable;
-    if (node == null || selectable == null) {
+    Node? node = getNodeInOffset(offset);
+    if (node == null) {
+      return;
+    }
+
+    if (interceptor != null) {
+      node = interceptor(context, node);
+    }
+
+    final selectable = node.selectable;
+    if (selectable == null) {
       return;
     }
 
@@ -461,7 +470,7 @@ class _DesktopSelectionServiceWidgetState
 
     _dropTargetEntry = OverlayEntry(
       builder: (context) {
-        if (builder != null) {
+        if (builder != null && node != null) {
           return builder(
             context,
             DragAreaBuilderData(
@@ -507,9 +516,21 @@ class _DesktopSelectionServiceWidgetState
   }
 
   @override
-  DropTargetRenderData? getDropTargetRenderData(Offset offset) {
-    final node = getNodeInOffset(offset);
-    final selectable = node?.selectable;
+  DropTargetRenderData? getDropTargetRenderData(
+    Offset offset, {
+    DragTargetNodeInterceptor? interceptor,
+  }) {
+    Node? node = getNodeInOffset(offset);
+
+    if (node == null) {
+      return null;
+    }
+
+    if (interceptor != null) {
+      node = interceptor(context, node);
+    }
+
+    final selectable = node.selectable;
     if (selectable == null) {
       return null;
     }
@@ -527,10 +548,10 @@ class _DesktopSelectionServiceWidgetState
 
     final isCloserToStart = topDistance < bottomDistance;
 
-    final dropPath = isCloserToStart ? node?.path : node?.path.next;
+    final dropPath = isCloserToStart ? node.path : node.path.next;
 
     return DropTargetRenderData(
-      dropPath: dropPath ?? node?.path,
+      dropPath: dropPath,
       cursorNode: node,
     );
   }

lib/src/editor/editor_component/service/selection/mobile_selection_service.dart

@@ -881,10 +881,18 @@ class _MobileSelectionServiceWidgetState
   }
 
   @override
-  void renderDropTargetForOffset(Offset offset, {DragAreaBuilder? builder}) {
+  void renderDropTargetForOffset(
+    Offset offset, {
+    DragAreaBuilder? builder,
+    DragTargetNodeInterceptor? interceptor,
+  }) {
     // Do nothing on mobile
   }
 
   @override
-  DropTargetRenderData? getDropTargetRenderData(Offset offset) => null;
+  DropTargetRenderData? getDropTargetRenderData(
+    Offset offset, {
+    DragTargetNodeInterceptor? interceptor,
+  }) =>
+      null;
 }

lib/src/editor/editor_component/service/selection_service.dart

@@ -19,6 +19,11 @@ typedef DragAreaBuilder = Widget Function(
   DragAreaBuilderData data,
 );
 
+typedef DragTargetNodeInterceptor = Node Function(
+  BuildContext context,
+  Node node,
+);
+
 /// [AppFlowySelectionService] is responsible for processing
 /// the [Selection] changes and updates.
 ///
@@ -105,9 +110,12 @@ abstract class AppFlowySelectionService {
   ///
   /// If [builder] is provided, the line will be drawn by [builder].
   /// Otherwise, the line will be drawn by default [DropTargetStyle].
+  ///
+  /// If [interceptor] is provided, the node will be intercepted by [interceptor].
   void renderDropTargetForOffset(
     Offset offset, {
     DragAreaBuilder? builder,
+    DragTargetNodeInterceptor? interceptor,
   });
 
   /// Removes the horizontal line drawn by [renderDropTargetForOffset].
@@ -116,7 +124,10 @@ abstract class AppFlowySelectionService {
 
   /// Returns the [DropTargetRenderData] for the [offset].
   ///
-  DropTargetRenderData? getDropTargetRenderData(Offset offset);
+  DropTargetRenderData? getDropTargetRenderData(
+    Offset offset, {
+    DragTargetNodeInterceptor? interceptor,
+  });
 }
 
 class SelectionGestureInterceptor {

lib/src/editor/editor_component/service/selection_service_widget.dart

@@ -124,10 +124,24 @@ class _SelectionServiceWidgetState extends State<SelectionServiceWidget>
   void removeDropTarget() => forward.removeDropTarget();
 
   @override
-  void renderDropTargetForOffset(Offset offset, {DragAreaBuilder? builder}) =>
-      forward.renderDropTargetForOffset(offset, builder: builder);
+  void renderDropTargetForOffset(
+    Offset offset, {
+    DragAreaBuilder? builder,
+    DragTargetNodeInterceptor? interceptor,
+  }) =>
+      forward.renderDropTargetForOffset(
+        offset,
+        builder: builder,
+        interceptor: interceptor,
+      );
 
   @override
-  DropTargetRenderData? getDropTargetRenderData(Offset offset) =>
-      forward.getDropTargetRenderData(offset);
+  DropTargetRenderData? getDropTargetRenderData(
+    Offset offset, {
+    DragTargetNodeInterceptor? interceptor,
+  }) =>
+      forward.getDropTargetRenderData(
+        offset,
+        interceptor: interceptor,
+      );
 }