config: Add grab_focus_tty (closes #1039)

Signed-off-by: AnErrupTion <anerruption@disroot.org>

res/config.lua

@@ -316,6 +316,13 @@ ly = {
     -- Example: a string of "23" makes the cell survive on 2 or 3 neighbors
     gameoflife_param_survival = "23",
 
+    -- Sets the TTY on which to always grab focus on.
+    -- This is useful if you want to have deterministic behavior when starting
+    -- Ly on multiple TTYs simultaneously.
+    -- If null, Ly will always try to grab focus on the TTY it is launched on,
+    -- even if multiple instances are launched.
+    grab_focus_tty = nil,
+
     -- Remove main box borders
     hide_borders = false,
 

src/config/Config.zig

@@ -67,6 +67,7 @@ gameoflife_frame_delay: usize = 6,
 gameoflife_initial_density: f32 = 0.4,
 gameoflife_param_birth: []const u8 = "3",
 gameoflife_param_survival: []const u8 = "23",
+grab_focus_tty: ?u8 = null,
 hide_borders: bool = false,
 inactivity_cmd: ?[]const u8 = null,
 inactivity_delay: u16 = 0,

src/main.zig

@@ -1007,7 +1007,10 @@ pub fn main(init: std.process.Init) !void {
         );
         break :no_tty_found build_options.fallback_tty;
     };
-    if (!state.use_kmscon_vt) {
+    if (!state.use_kmscon_vt) switch_tty: {
+        if (state.config.grab_focus_tty) |tty| {
+            if (tty != state.active_tty) break :switch_tty;
+        }
         interop.switchTty(state.active_tty) catch |err| {
             try state.info_line.addMessage(
                 state.lang.err_switch_tty,