Add option 'focus-at-startup' to focus a chosen output on start (#1323)

* Implement default-output

* Fix incorrect wiki string

* Center mouse on start

* Move default-output to Output.focus-at-startup

* fixes

---------

Co-authored-by: lualeet <lualeet@null.null>
Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

niri-config/src/lib.rs

@@ -440,6 +440,8 @@ pub struct Output {
     pub mode: Option<ConfiguredMode>,
     #[knuffel(child)]
     pub variable_refresh_rate: Option<Vrr>,
+    #[knuffel(child)]
+    pub focus_at_startup: bool,
     #[knuffel(child, default = DEFAULT_BACKGROUND_COLOR)]
     pub background_color: Color,
 }
@@ -462,6 +464,7 @@ impl Default for Output {
     fn default() -> Self {
         Self {
             off: false,
+            focus_at_startup: false,
             name: String::new(),
             scale: None,
             transform: Transform::Normal,
@@ -3746,6 +3749,7 @@ mod tests {
             }
 
             output "eDP-1" {
+                focus-at-startup
                 scale 2
                 transform "flipped-90"
                 position x=10 y=20
@@ -4105,6 +4109,7 @@ mod tests {
                                 on_demand: true,
                             },
                         ),
+                        focus_at_startup: true,
                         background_color: Color {
                             r: 0.09803922,
                             g: 0.09803922,

src/niri.rs

@@ -630,6 +630,8 @@ impl State {
         state.load_xkb_file();
         // Initialize some IPC server state.
         state.ipc_keyboard_layouts_changed();
+        // Focus the default monitor if set by the user.
+        state.focus_default_monitor();
 
         Ok(state)
     }
@@ -794,6 +796,29 @@ impl State {
         rv
     }
 
+    pub fn focus_default_monitor(&mut self) {
+        // Our default target is the first output in sorted order.
+        let Some(mut target) = self.niri.sorted_outputs.first().cloned() else {
+            // No outputs are connected.
+            return;
+        };
+
+        let config = self.niri.config.borrow();
+        for config in &config.outputs.0 {
+            if !config.focus_at_startup {
+                continue;
+            }
+            if let Some(output) = self.niri.output_by_name_match(&config.name) {
+                target = output.clone();
+                break;
+            }
+        }
+        drop(config);
+
+        self.niri.layout.focus_output(&target);
+        self.move_cursor_to_output(&target);
+    }
+
     /// Focus a specific window, taking care of a potential active output change and cursor
     /// warp.
     pub fn focus_window(&mut self, window: &Window) {

wiki/Configuration:-Outputs.md

@@ -13,6 +13,7 @@ output "eDP-1" {
     transform "90"
     position x=1280 y=0
     variable-refresh-rate // on-demand=true
+    focus-at-startup
     background-color "#003300"
 }
 
@@ -164,6 +165,28 @@ output "HDMI-A-1" {
 }
 ```
 
+### `focus-at-startup`
+
+<sup>Since: next release</sup>
+
+Focus this output by default when niri starts.
+
+If multiple outputs with `focus-at-startup` are connected, they are prioritized in the order that they appear in the config.
+
+When none of the connected outputs are explicitly `focus-at-startup`, niri will focus the first one sorted by name (same output sorting as used elsewhere in niri).
+
+```kdl
+// Focus HDMI-A-1 by default.
+output "HDMI-A-1" {
+    focus-at-startup
+}
+
+// ...if HDMI-A-1 wasn't connected, focus DP-2 instead.
+output "DP-2" {
+    focus-at-startup
+}
+```
+
 ### `background-color`
 
 <sup>Since: 0.1.8</sup>