feat: make file manager draggable

flutter/lib/desktop/widgets/dragable_divider.dart

@@ -0,0 +1,53 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/src/widgets/framework.dart';
+import 'package:flutter/src/widgets/placeholder.dart';
+
+class DraggableDivider extends StatefulWidget {
+  final Axis axis;
+  final double thickness;
+  final Color color;
+  final Function(double)? onPointerMove;
+  final VoidCallback? onHover;
+  final EdgeInsets padding;
+  const DraggableDivider({
+    super.key,
+    this.axis = Axis.horizontal,
+    this.thickness = 1.0,
+    this.color = const Color.fromARGB(200, 177, 175, 175),
+    this.onPointerMove,
+    this.padding = const EdgeInsets.symmetric(horizontal: 1.0),
+    this.onHover,
+  });
+
+  @override
+  State<DraggableDivider> createState() => _DraggableDividerState();
+}
+
+class _DraggableDividerState extends State<DraggableDivider> {
+  @override
+  Widget build(BuildContext context) {
+    return Listener(
+      onPointerMove: (event) {
+        final dl =
+            widget.axis == Axis.horizontal ? event.localDelta.dy : event.localDelta.dx;
+        widget.onPointerMove?.call(dl);
+      },
+      onPointerHover: (event) => widget.onHover?.call(),
+      child: MouseRegion(
+        cursor: SystemMouseCursors.resizeLeftRight,
+        child: Padding(
+          padding: widget.padding,
+          child: Container(
+            decoration: BoxDecoration(color: widget.color),
+            width: widget.axis == Axis.horizontal
+                ? double.infinity
+                : widget.thickness,
+            height: widget.axis == Axis.horizontal
+                ? widget.thickness
+                : double.infinity,
+          ),
+        ),
+      ),
+    );
+  }
+}