Add dragging window with cursor feature (#1840)

* X11 implementation.

* Introduce example.

* Wayland implementation.

* Windows implementation.

* Improve Wayland seat passing.

* MacOS implementation.

* Correct windows implementation per specification.

* Update dependency smithay-client-toolkit from branch to master.

* Fixed blocking thread in windows implementation.

* Add multi-window example.

* Move Wayland to a different PR.

* Fix CHANGELOG.

* Improve example.

Co-authored-by: Markus Røyset <maroider@protonmail.com>

* Rename `set_drag_window` to `begin_drag`.

* Improve example.

* Fix CHANGELOG.

* Fix CHANGELOG.

Co-authored-by: Markus Røyset <maroider@protonmail.com>

* Rename to `drag_window`.

* Fix typo.

* Re-introduce Wayland implementation.

* Fixing Wayland build.

* Fixing Wayland build.

* Move SCTK to 0.12.3.

Co-authored-by: Markus Røyset <maroider@protonmail.com>

src/platform_impl/linux/mod.rs

@@ -358,6 +358,11 @@ impl Window {
         x11_or_wayland!(match self; Window(window) => window.set_cursor_visible(visible))
     }
 
+    #[inline]
+    pub fn drag_window(&self) -> Result<(), ExternalError> {
+        x11_or_wayland!(match self; Window(window) => window.drag_window())
+    }
+
     #[inline]
     pub fn scale_factor(&self) -> f64 {
         x11_or_wayland!(match self; Window(w) => w.scale_factor() as f64)

src/platform_impl/linux/wayland/seat/pointer/handlers.rs

@@ -4,6 +4,7 @@ use std::cell::RefCell;
 use std::rc::Rc;
 
 use sctk::reexports::client::protocol::wl_pointer::{self, Event as PointerEvent};
+use sctk::reexports::client::protocol::wl_seat::WlSeat;
 use sctk::reexports::protocols::unstable::relative_pointer::v1::client::zwp_relative_pointer_v1::Event as RelativePointerEvent;
 
 use sctk::seat::pointer::ThemedPointer;
@@ -28,6 +29,7 @@ pub(super) fn handle_pointer(
     event: PointerEvent,
     pointer_data: &Rc<RefCell<PointerData>>,
     winit_state: &mut WinitState,
+    seat: WlSeat,
 ) {
     let event_sink = &mut winit_state.event_sink;
     let mut pointer_data = pointer_data.borrow_mut();
@@ -59,6 +61,7 @@ pub(super) fn handle_pointer(
                 confined_pointer: Rc::downgrade(&pointer_data.confined_pointer),
                 pointer_constraints: pointer_data.pointer_constraints.clone(),
                 latest_serial: pointer_data.latest_serial.clone(),
+                seat,
             };
             window_handle.pointer_entered(winit_pointer);
 
@@ -101,6 +104,7 @@ pub(super) fn handle_pointer(
                 confined_pointer: Rc::downgrade(&pointer_data.confined_pointer),
                 pointer_constraints: pointer_data.pointer_constraints.clone(),
                 latest_serial: pointer_data.latest_serial.clone(),
+                seat,
             };
             window_handle.pointer_left(winit_pointer);
 

src/platform_impl/linux/wayland/seat/pointer/mod.rs

@@ -13,6 +13,7 @@ use sctk::reexports::protocols::unstable::pointer_constraints::v1::client::zwp_p
 use sctk::reexports::protocols::unstable::pointer_constraints::v1::client::zwp_confined_pointer_v1::ZwpConfinedPointerV1;
 
 use sctk::seat::pointer::{ThemeManager, ThemedPointer};
+use sctk::window::{ConceptFrame, Window};
 
 use crate::event::ModifiersState;
 use crate::platform_impl::wayland::event_loop::WinitState;
@@ -35,6 +36,9 @@ pub struct WinitPointer {
 
     /// Latest observed serial in pointer events.
     latest_serial: Rc<Cell<u32>>,
+
+    /// Seat.
+    seat: WlSeat,
 }
 
 impl PartialEq for WinitPointer {
@@ -144,6 +148,10 @@ impl WinitPointer {
             confined_pointer.destroy();
         }
     }
+
+    pub fn drag_window(&self, window: &Window<ConceptFrame>) {
+        window.start_interactive_move(&self.seat, self.latest_serial.get());
+    }
 }
 
 /// A pointer wrapper for easy releasing and managing pointers.
@@ -172,11 +180,18 @@ impl Pointers {
             pointer_constraints.clone(),
             modifiers_state,
         )));
+        let pointer_seat = seat.detach();
         let pointer = theme_manager.theme_pointer_with_impl(
             seat,
             move |event, pointer, mut dispatch_data| {
                 let winit_state = dispatch_data.get::<WinitState>().unwrap();
-                handlers::handle_pointer(pointer, event, &pointer_data, winit_state);
+                handlers::handle_pointer(
+                    pointer,
+                    event,
+                    &pointer_data,
+                    winit_state,
+                    pointer_seat.clone(),
+                );
             },
         );
 

src/platform_impl/linux/wayland/window/mod.rs

@@ -586,6 +586,18 @@ impl Window {
         Err(ExternalError::NotSupported(NotSupportedError::new()))
     }
 
+    #[inline]
+    pub fn drag_window(&self) -> Result<(), ExternalError> {
+        let drag_window_request = WindowRequest::DragWindow;
+        self.window_requests
+            .lock()
+            .unwrap()
+            .push(drag_window_request);
+        self.event_loop_awakener.ping();
+
+        Ok(())
+    }
+
     #[inline]
     pub fn set_ime_position(&self, position: Position) {
         let scale_factor = self.scale_factor() as f64;

src/platform_impl/linux/wayland/window/shim.rs

@@ -34,6 +34,9 @@ pub enum WindowRequest {
     /// Grab cursor.
     GrabCursor(bool),
 
+    /// Drag window.
+    DragWindow,
+
     /// Maximize the window.
     Maximize(bool),
 
@@ -268,6 +271,12 @@ impl WindowHandle {
             pointer.set_cursor(Some(cursor_icon));
         }
     }
+
+    pub fn drag_window(&self) {
+        for pointer in self.pointers.iter() {
+            pointer.drag_window(&self.window);
+        }
+    }
 }
 
 #[inline]
@@ -299,6 +308,9 @@ pub fn handle_window_requests(winit_state: &mut WinitState) {
                 WindowRequest::GrabCursor(grab) => {
                     window_handle.set_cursor_grab(grab);
                 }
+                WindowRequest::DragWindow => {
+                    window_handle.drag_window();
+                }
                 WindowRequest::Maximize(maximize) => {
                     if maximize {
                         window_handle.window.set_maximized();

src/platform_impl/linux/x11/window.rs

@@ -1276,6 +1276,46 @@ impl UnownedWindow {
         self.set_cursor_position_physical(x, y)
     }
 
+    pub fn drag_window(&self) -> Result<(), ExternalError> {
+        let pointer = self
+            .xconn
+            .query_pointer(self.xwindow, util::VIRTUAL_CORE_POINTER)
+            .map_err(|err| ExternalError::Os(os_error!(OsError::XError(err))))?;
+
+        let window = self.inner_position().map_err(ExternalError::NotSupported)?;
+
+        let message = unsafe { self.xconn.get_atom_unchecked(b"_NET_WM_MOVERESIZE\0") };
+
+        // we can't use `set_cursor_grab(false)` here because it doesn't run `XUngrabPointer`
+        // if the cursor isn't currently grabbed
+        let mut grabbed_lock = self.cursor_grabbed.lock();
+        unsafe {
+            (self.xconn.xlib.XUngrabPointer)(self.xconn.display, ffi::CurrentTime);
+        }
+        self.xconn
+            .flush_requests()
+            .map_err(|err| ExternalError::Os(os_error!(OsError::XError(err))))?;
+        *grabbed_lock = false;
+
+        // we keep the lock until we are done
+        self.xconn
+            .send_client_msg(
+                self.xwindow,
+                self.root,
+                message,
+                Some(ffi::SubstructureRedirectMask | ffi::SubstructureNotifyMask),
+                [
+                    (window.x as c_long + pointer.win_x as c_long),
+                    (window.y as c_long + pointer.win_y as c_long),
+                    8, // _NET_WM_MOVERESIZE_MOVE
+                    ffi::Button1 as c_long,
+                    1,
+                ],
+            )
+            .flush()
+            .map_err(|err| ExternalError::Os(os_error!(OsError::XError(err))))
+    }
+
     pub(crate) fn set_ime_position_physical(&self, x: i32, y: i32) {
         let _ = self
             .ime_sender