wayland: Improve cursor (#10516)

Fixes the cursor not updating when (a) switching windows from another
program via a shortcut and (b) when cursor updates were triggered by
something other than moving the mouse (e.g. when scrolling or pressing a
key).

Release Notes:

- N/A

crates/gpui/src/platform/linux/wayland/cursor.rs

@@ -8,7 +8,7 @@ use wayland_cursor::{CursorImageBuffer, CursorTheme};
 
 pub(crate) struct Cursor {
     theme: Option<CursorTheme>,
-    current_icon_name: String,
+    current_icon_name: Option<String>,
     surface: WlSurface,
     serial_id: u32,
 }
@@ -24,19 +24,29 @@ impl Cursor {
     pub fn new(connection: &Connection, globals: &Globals, size: u32) -> Self {
         Self {
             theme: CursorTheme::load(&connection, globals.shm.clone(), size).log_err(),
-            current_icon_name: "default".to_string(),
+            current_icon_name: None,
             surface: globals.compositor.create_surface(&globals.qh, ()),
             serial_id: 0,
         }
     }
 
+    pub fn mark_dirty(&mut self) {
+        self.current_icon_name = None;
+    }
+
     pub fn set_serial_id(&mut self, serial_id: u32) {
         self.serial_id = serial_id;
     }
 
-    pub fn set_icon(&mut self, wl_pointer: &WlPointer, mut cursor_icon_name: Option<&str>) {
-        let mut cursor_icon_name = cursor_icon_name.unwrap_or("default");
-        if self.current_icon_name != cursor_icon_name {
+    pub fn set_icon(&mut self, wl_pointer: &WlPointer, mut cursor_icon_name: &str) {
+        let need_update = self
+            .current_icon_name
+            .as_ref()
+            .map_or(true, |current_icon_name| {
+                current_icon_name != cursor_icon_name
+            });
+
+        if need_update {
             if let Some(theme) = &mut self.theme {
                 let mut buffer: Option<&CursorImageBuffer>;
 
@@ -68,7 +78,7 @@ impl Cursor {
                     self.surface.damage(0, 0, width as i32, height as i32);
                     self.surface.commit();
 
-                    self.current_icon_name = cursor_icon_name.to_string();
+                    self.current_icon_name = Some(cursor_icon_name.to_string());
                 }
             } else {
                 log::warn!("Linux: Wayland: Unable to load cursor themes");