fix(linux): fix DragDropEvent::Drop never fired on wayland (#1408)

* fix(linux): fix `DragDrop` never fired on wayland

closes tauri-apps/tauri#11282

* Update src/webkitgtk/drag_drop.rs

.changes/drag-drop-wayland.md

@@ -0,0 +1,5 @@
+---
+"wry": "patch"
+---
+
+Fix `DragDropEvent::Drop` event never fired on Wayland (and sometimes on X11).

src/webkitgtk/drag_drop.rs

@@ -13,9 +13,16 @@ use webkit2gtk::WebView;
 
 use crate::DragDropEvent;
 
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug)]
+enum DragControllerState {
+  Entered,
+  Leaving,
+  Left,
+}
+
 struct DragDropController {
   paths: UnsafeCell<Option<Vec<PathBuf>>>,
-  has_entered: Cell<bool>,
+  state: Cell<DragControllerState>,
   position: Cell<(i32, i32)>,
   handler: Box<dyn Fn(DragDropEvent) -> bool>,
 }
@@ -25,7 +32,7 @@ impl DragDropController {
     Self {
       handler,
       paths: UnsafeCell::new(None),
-      has_entered: Cell::new(false),
+      state: Cell::new(DragControllerState::Left),
       position: Cell::new((0, 0)),
     }
   }
@@ -43,15 +50,19 @@ impl DragDropController {
   }
 
   fn enter(&self) {
-    self.has_entered.set(true);
+    self.state.set(DragControllerState::Entered);
   }
 
-  fn has_entered(&self) -> bool {
-    self.has_entered.get()
+  fn leaving(&self) {
+    self.state.set(DragControllerState::Leaving);
   }
 
   fn leave(&self) {
-    self.has_entered.set(false);
+    self.state.set(DragControllerState::Left);
+  }
+
+  fn state(&self) -> DragControllerState {
+    self.state.get()
   }
 
   fn call(&self, event: DragDropEvent) -> bool {
@@ -81,7 +92,7 @@ pub(crate) fn connect_drag_event(webview: &WebView, handler: Box<dyn Fn(DragDrop
   {
     let controller = controller.clone();
     webview.connect_drag_motion(move |_, _, x, y, _| {
-      if controller.has_entered() {
+      if controller.state() == DragControllerState::Entered {
         controller.call(DragDropEvent::Over { position: (x, y) });
       } else {
         controller.store_position((x, y));
@@ -93,7 +104,7 @@ pub(crate) fn connect_drag_event(webview: &WebView, handler: Box<dyn Fn(DragDrop
   {
     let controller = controller.clone();
     webview.connect_drag_drop(move |_, ctx, x, y, time| {
-      if controller.has_entered() {
+      if controller.state() == DragControllerState::Leaving {
         if let Some(paths) = controller.take_paths() {
           ctx.drop_finish(true, time);
           controller.leave();
@@ -108,10 +119,16 @@ pub(crate) fn connect_drag_event(webview: &WebView, handler: Box<dyn Fn(DragDrop
     });
   }
 
-  webview.connect_drag_leave(move |_, _, time| {
-    if time == 0 {
-      controller.leave();
-      controller.call(DragDropEvent::Leave);
+  webview.connect_drag_leave(move |_w, _, _| {
+    if controller.state() != DragControllerState::Left {
+      controller.leaving();
+      let controller = controller.clone();
+      gtk::glib::idle_add_local_once(move || {
+        if controller.state() == DragControllerState::Leaving {
+          controller.leave();
+          controller.call(DragDropEvent::Leave);
+        }
+      });
     }
   });
 }