xwayland: store and restore primary output

src/config/mod.rs

@@ -163,6 +163,8 @@ pub struct OutputConfig {
     pub enabled: OutputState,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub max_bpc: Option<u32>,
+    #[serde(default)]
+    pub xwayland_primary: bool,
 }
 
 impl Default for OutputConfig {
@@ -175,6 +177,7 @@ impl Default for OutputConfig {
             position: (0, 0),
             enabled: OutputState::Enabled,
             max_bpc: None,
+            xwayland_primary: false,
         }
     }
 }
@@ -590,6 +593,12 @@ impl Config {
         } else {
             // we don't have a config, so lets generate somewhat sane positions
             let mut w = 0;
+            if !outputs.iter().any(|o| o.config().xwayland_primary) {
+                // if we don't have a primary output for xwayland from a previous config, pick one
+                if let Some(primary) = outputs.iter().find(|o| o.mirroring().is_none()) {
+                    primary.config_mut().xwayland_primary = true;
+                }
+            }
             for output in outputs.iter().filter(|o| o.mirroring().is_none()) {
                 {
                     let mut config = output.config_mut();

src/state.rs

@@ -382,7 +382,10 @@ impl BackendData {
         // Update layout for changes in resolution, scale, orientation
         shell.workspaces.recalculate();
 
-        loop_handle.insert_idle(|state| state.common.update_xwayland_scale());
+        loop_handle.insert_idle(move |state| {
+            state.common.update_xwayland_scale();
+            state.common.update_xwayland_primary_output();
+        });
 
         Ok(())
     }

src/xwayland.rs

@@ -128,6 +128,7 @@ impl State {
                     data.notify_ready();
 
                     data.common.update_xwayland_scale();
+                    data.common.update_xwayland_primary_output();
                 }
                 XWaylandEvent::Error => {
                     if let Some(mut xwayland_state) = data.common.xwayland_state.take() {
@@ -637,6 +638,24 @@ impl Common {
             }
         }
     }
+
+    pub fn update_xwayland_primary_output(&mut self) {
+        let mut xwayland_primary_output = None;
+        for output in self.output_configuration_state.outputs() {
+            if output.config().xwayland_primary {
+                xwayland_primary_output = Some(output);
+                break;
+            }
+        }
+
+        if let Some(xstate) = self.xwayland_state.as_mut() {
+            if let Some(xwm) = xstate.xwm.as_mut() {
+                if let Err(err) = xwm.set_randr_primary_output(xwayland_primary_output.as_ref()) {
+                    warn!("Failed to set xwayland primary output: {}", err);
+                };
+            }
+        }
+    }
 }
 
 impl XwmHandler for State {
@@ -1115,6 +1134,17 @@ impl XwmHandler for State {
         }
     }
 
+    fn randr_primary_output_change(&mut self, _xwm: XwmId, output_name: Option<String>) {
+        for output in self.common.output_configuration_state.outputs() {
+            output.config_mut().xwayland_primary =
+                output_name.as_deref().is_some_and(|o| o == output.name());
+        }
+        self.common.output_configuration_state.update();
+        self.common
+            .config
+            .write_outputs(self.common.output_configuration_state.outputs());
+    }
+
     fn disconnected(&mut self, _xwm: XwmId) {
         let xwayland_state = self.common.xwayland_state.as_mut().unwrap();
         xwayland_state.xwm = None;