From b166e1ff1384c694962f57ac7d0dca9c337eae62 Mon Sep 17 00:00:00 2001
From: Kirill Chibisov <contact@kchibisov.com>
Date: Sat, 15 Jul 2023 08:09:28 +0000
Subject: [PATCH] On Wayland, make the CSD frame double click reliable

It was discovered that on GNOME the click sometimes being swallowed
by the mutter's `wl_pointer::enter/leave` sequences. This was happening
due to `xdg_toplevel::move` making the pointer to leave the surface.

To make handling of that more robust, we could start the
`xdg_toplevel::move` when the actual pointer motion is being performed.

Links: https://github.com/alacritty/alacritty/issues/7011
Links: https://gitlab.gnome.org/GNOME/mutter/-/issues/2669#note_1790825
---
 CHANGELOG.md                                  |  1 +
 .../linux/wayland/seat/pointer/mod.rs         |  2 +-
 .../linux/wayland/window/state.rs             | 29 +++++++++++++++++--
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4d1b990..e7819823 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 
 # Unreleased
 
+- On Wayland, make double clicking and moving the CSD frame more reliable.
 - On macOS, add tabbing APIs on `WindowExtMacOS` and `EventLoopWindowTargetExtMacOS`.
 - **Breaking:** Rename `Window::set_inner_size` to `Window::request_inner_size` and indicate if the size was applied immediately.
 - On X11, fix false positive flagging of key repeats when pressing different keys with no release between presses.
diff --git a/src/platform_impl/linux/wayland/seat/pointer/mod.rs b/src/platform_impl/linux/wayland/seat/pointer/mod.rs
index 607b0e1b..4d65e1fa 100644
--- a/src/platform_impl/linux/wayland/seat/pointer/mod.rs
+++ b/src/platform_impl/linux/wayland/seat/pointer/mod.rs
@@ -68,7 +68,7 @@ impl PointerHandler for WinitState {
                     if parent_surface != surface =>
                 {
                     if let Some(icon) =
-                        window.frame_point_moved(surface, event.position.0, event.position.1)
+                        window.frame_point_moved(seat, surface, event.position.0, event.position.1)
                     {
                         if let Some(pointer) = seat_state.pointer.as_ref() {
                             let surface = pointer
diff --git a/src/platform_impl/linux/wayland/window/state.rs b/src/platform_impl/linux/wayland/window/state.rs
index e67e1652..d9da53db 100644
--- a/src/platform_impl/linux/wayland/window/state.rs
+++ b/src/platform_impl/linux/wayland/window/state.rs
@@ -127,6 +127,11 @@ pub struct WindowState {
 
     viewport: Option<WpViewport>,
     fractional_scale: Option<WpFractionalScaleV1>,
+
+    /// Whether the client side decorations have pending move operations.
+    ///
+    /// The value is the serial of the event triggered moved.
+    has_pending_move: Option<u32>,
 }
 
 /// The state of the cursor grabs.
@@ -279,7 +284,7 @@ impl WindowState {
             FrameAction::Maximize => self.window.set_maximized(),
             FrameAction::UnMaximize => self.window.unset_maximized(),
             FrameAction::Close => WinitState::queue_close(updates, window_id),
-            FrameAction::Move => self.window.move_(seat, serial),
+            FrameAction::Move => self.has_pending_move = Some(serial),
             FrameAction::Resize(edge) => self.window.resize(seat, serial, edge),
             FrameAction::ShowMenu(x, y) => self.window.show_window_menu(seat, serial, (x, y)),
         };
@@ -294,9 +299,26 @@ impl WindowState {
     }
 
     // Move the point over decorations.
-    pub fn frame_point_moved(&mut self, surface: &WlSurface, x: f64, y: f64) -> Option<&str> {
+    pub fn frame_point_moved(
+        &mut self,
+        seat: &WlSeat,
+        surface: &WlSurface,
+        x: f64,
+        y: f64,
+    ) -> Option<&str> {
+        // Take the serial if we had any, so it doesn't stick around.
+        let serial = self.has_pending_move.take();
+
         if let Some(frame) = self.frame.as_mut() {
-            frame.click_point_moved(surface, x, y)
+            let cursor = frame.click_point_moved(surface, x, y);
+            // If we have a cursor change, that means that cursor is over the decorations,
+            // so try to apply move.
+            if let Some(serial) = cursor.is_some().then_some(serial).flatten() {
+                self.window.move_(seat, serial);
+                None
+            } else {
+                cursor
+            }
         } else {
             None
         }
@@ -419,6 +441,7 @@ impl WindowState {
             resizable: true,
             viewport,
             window: ManuallyDrop::new(window),
+            has_pending_move: None,
         }
     }