fix mouse jumping: query GDK pointer position at call time

Flutter's globalPosition is window-relative, not screen-absolute.
Now using gdk_device_get_position() on the native side to get
the actual screen coordinates at the moment startDrag/startResize
is called. Dart no longer passes coordinates — the native handler
queries the pointer directly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/app.dart

@@ -221,7 +221,7 @@ class _HatBar extends StatelessWidget {
   Widget build(BuildContext context) {
     final tokens = ClideTheme.of(context).surface;
     return GestureDetector(
-      onPanStart: (d) => kernel.window.startDrag(d.globalPosition),
+      onPanStart: (_) => kernel.window.startDrag(),
       child: Container(
         height: hatHeight,
         decoration: BoxDecoration(

lib/kernel/src/window_controls.dart

@@ -17,24 +17,17 @@ class WindowControls extends ChangeNotifier {
     notifyListeners();
   }
 
-  Future<void> startResize(ResizeEdge edge, Offset screenPosition) async {
+  Future<void> startResize(ResizeEdge edge) async {
     try {
-      await _channel.invokeMethod('startResize', {
-        'edge': edge.index,
-        'x': screenPosition.dx.round(),
-        'y': screenPosition.dy.round(),
-      });
+      await _channel.invokeMethod('startResize', edge.index);
     } on MissingPluginException {
       // no-op
     }
   }
 
-  Future<void> startDrag(Offset screenPosition) async {
+  Future<void> startDrag() async {
     try {
-      await _channel.invokeMethod('startDrag', {
-        'x': screenPosition.dx.round(),
-        'y': screenPosition.dy.round(),
-      });
+      await _channel.invokeMethod('startDrag');
     } on MissingPluginException {
       // no-op
     }

lib/widgets/src/clide_column_hat.dart

@@ -33,7 +33,7 @@ class ColumnHat extends StatelessWidget {
   Widget build(BuildContext context) {
     final tokens = ClideTheme.of(context).surface;
     return GestureDetector(
-      onPanStart: (d) => windowControls.startDrag(d.globalPosition),
+      onPanStart: (_) => windowControls.startDrag(),
       child: Container(
         height: hatHeight,
         color: tokens.panelHeader,

lib/widgets/src/clide_resize_border.dart

@@ -45,7 +45,7 @@ class ClideResizeBorder extends StatelessWidget {
     return MouseRegion(
       cursor: cursor,
       child: GestureDetector(
-        onPanStart: (d) => windowControls.startResize(edge, d.globalPosition),
+        onPanStart: (_) => windowControls.startResize(edge),
         child: const ColoredBox(color: Color(0x00000000)),
       ),
     );

linux/runner/my_application.cc

@@ -157,28 +157,28 @@ static void my_application_activate(GApplication* application) {
         g_autoptr(FlMethodResponse) response = nullptr;
 
         if (g_strcmp0(method, "startDrag") == 0) {
-          FlValue* args = fl_method_call_get_args(method_call);
-          int x = 0, y = 0;
-          if (fl_value_get_type(args) == FL_VALUE_TYPE_MAP) {
-            FlValue* vx = fl_value_lookup_string(args, "x");
-            FlValue* vy = fl_value_lookup_string(args, "y");
-            if (vx) x = (int)fl_value_get_int(vx);
-            if (vy) y = (int)fl_value_get_int(vy);
-          }
+          GdkDisplay* display = gtk_widget_get_display(GTK_WIDGET(w));
+          GdkSeat* seat = gdk_display_get_default_seat(display);
+          GdkDevice* pointer = gdk_seat_get_pointer(seat);
+          gint x = 0, y = 0;
+          gdk_device_get_position(pointer, nullptr, &x, &y);
           gtk_window_begin_move_drag(w, 1, x, y, GDK_CURRENT_TIME);
           response = FL_METHOD_RESPONSE(
               fl_method_success_response_new(fl_value_new_null()));
         } else if (g_strcmp0(method, "startResize") == 0) {
           FlValue* args = fl_method_call_get_args(method_call);
-          int edge = 7, x = 0, y = 0;
+          int edge = 7;
           if (fl_value_get_type(args) == FL_VALUE_TYPE_MAP) {
             FlValue* ve = fl_value_lookup_string(args, "edge");
-            FlValue* vx = fl_value_lookup_string(args, "x");
-            FlValue* vy = fl_value_lookup_string(args, "y");
             if (ve) edge = (int)fl_value_get_int(ve);
-            if (vx) x = (int)fl_value_get_int(vx);
-            if (vy) y = (int)fl_value_get_int(vy);
+          } else if (fl_value_get_type(args) == FL_VALUE_TYPE_INT) {
+            edge = (int)fl_value_get_int(args);
           }
+          GdkDisplay* display = gtk_widget_get_display(GTK_WIDGET(w));
+          GdkSeat* seat = gdk_display_get_default_seat(display);
+          GdkDevice* pointer = gdk_seat_get_pointer(seat);
+          gint x = 0, y = 0;
+          gdk_device_get_position(pointer, nullptr, &x, &y);
           static const GdkWindowEdge edges[] = {
             GDK_WINDOW_EDGE_NORTH_WEST, GDK_WINDOW_EDGE_NORTH,
             GDK_WINDOW_EDGE_NORTH_EAST, GDK_WINDOW_EDGE_WEST,