Add basic KMSCON support (closes #886)

It's not perfect yet, but at least it works!

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

build.zig

@@ -269,6 +269,9 @@ fn install_service(allocator: std.mem.Allocator, patch_map: PatchMap) !void {
 
             const patched_service = try patchFile(allocator, "res/ly@.service", patch_map);
             try installText(patched_service, service_dir, service_path, "ly@.service", .{ .mode = 0o644 });
+
+            const patched_kmsconvt_service = try patchFile(allocator, "res/ly-kmsconvt@.service", patch_map);
+            try installText(patched_kmsconvt_service, service_dir, service_path, "ly-kmsconvt@.service", .{ .mode = 0o644 });
         },
         .openrc => {
             const service_path = try std.fs.path.join(allocator, &[_][]const u8{ dest_directory, config_directory, "/init.d" });

res/config.ini

@@ -316,8 +316,9 @@ service_name = ly
 # Session log file path
 # This will contain stdout and stderr of Wayland sessions
 # By default it's saved in the user's home directory
-# Important: due to technical limitations, X11 and shell sessions aren't supported, which
-# means you won't get any logs from those sessions.
+# Important: due to technical limitations, X11, shell sessions as well as
+# launching session via KMSCON aren't supported, which means you won't get any
+# logs from those sessions.
 # If null, no session log will be created
 session_log = .local/state/ly-session.log
 

res/ly-kmsconvt@.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=TUI display manager using KMSCON
+After=systemd-user-sessions.service plymouth-quit-wait.service
+After=kmsconvt@%i.service
+Conflicts=kmsconvt@%i.service
+
+[Service]
+ExecStart=$PREFIX_DIRECTORY/bin/kmscon --vt=%I --seats=seat0 --login -- $PREFIX_DIRECTORY/bin/ly --use-kmscon-vt
+StandardInput=tty
+UtmpIdentifier=%I
+TTYPath=/dev/%I
+TTYReset=yes
+TTYVHangup=yes
+TTYVTDisallocate=yes
+
+[Install]
+WantedBy=multi-user.target

src/auth.zig

@@ -22,6 +22,7 @@ pub const AuthOptions = struct {
     x_cmd: []const u8,
     x_vt: ?u8,
     session_pid: std.posix.pid_t,
+    use_kmscon_vt: bool,
 };
 
 var xorg_pid: std.posix.pid_t = 0;
@@ -475,7 +476,7 @@ fn executeX11Cmd(log_file: *LogFile, allocator: std.mem.Allocator, shell: []cons
     xorg_pid = try std.posix.fork();
     if (xorg_pid == 0) {
         var cmd_buffer: [1024]u8 = undefined;
-        const cmd_str = std.fmt.bufPrintZ(&cmd_buffer, "{s} {s} {s}", .{ options.setup_cmd, options.login_cmd orelse "", desktop_cmd }) catch std.process.exit(1);
+        const cmd_str = std.fmt.bufPrintZ(&cmd_buffer, "{s} {s} {s} {s}", .{ if (options.use_kmscon_vt) "kmscon-launch-gui" else "", options.setup_cmd, options.login_cmd orelse "", desktop_cmd }) catch std.process.exit(1);
         try log_file.info("auth/x11", "executing: {s} -c {s}", .{ shell, cmd_str });
 
         const args = [_:null]?[*:0]const u8{ shell_z, "-c", cmd_str };
@@ -508,7 +509,12 @@ fn executeCmd(global_log_file: *LogFile, allocator: std.mem.Allocator, shell: []
     try global_log_file.info("auth/sys", "launching wayland/shell/custom session", .{});
 
     var maybe_log_file: ?std.fs.File = null;
-    if (!is_terminal) {
+    if (!is_terminal) redirect_streams: {
+        if (options.use_kmscon_vt) {
+            try global_log_file.err("auth/sys", "cannot redirect stdio & stderr with kmscon", .{});
+            break :redirect_streams;
+        }
+
         // For custom desktop entries, the "Terminal" value here determines if
         // we redirect standard output & error or not. That is, we redirect only
         // if it's equal to false (so if it's not running in a TTY).
@@ -523,7 +529,7 @@ fn executeCmd(global_log_file: *LogFile, allocator: std.mem.Allocator, shell: []
     defer allocator.free(shell_z);
 
     var cmd_buffer: [1024]u8 = undefined;
-    const cmd_str = try std.fmt.bufPrintZ(&cmd_buffer, "{s} {s} {s}", .{ options.setup_cmd, options.login_cmd orelse "", exec_cmd orelse shell });
+    const cmd_str = try std.fmt.bufPrintZ(&cmd_buffer, "{s} {s} {s} {s}", .{ if (!is_terminal and options.use_kmscon_vt) "kmscon-launch-gui" else "", options.setup_cmd, options.login_cmd orelse "", exec_cmd orelse shell });
 
     try global_log_file.info("auth/sys", "executing: {s} -c {s}", .{ shell, cmd_str });
     const args = [_:null]?[*:0]const u8{ shell_z, "-c", cmd_str };

src/main.zig

@@ -126,6 +126,7 @@ pub fn main() !void {
         \\-h, --help                Shows all commands.
         \\-v, --version             Shows the version of Ly.
         \\-c, --config <str>        Overrides the default configuration path. Example: --config /usr/share/ly
+        \\--use-kmscon-vt           Use KMSCON instead of kernel VT
     );
 
     var diag = clap.Diagnostic{};
@@ -141,6 +142,7 @@ pub fn main() !void {
     var old_save_parser: ?IniParser(OldSave) = null;
     defer if (old_save_parser) |*str| str.deinit();
 
+    var use_kmscon_vt = false;
     var start_cmd_exit_code: u8 = 0;
 
     var saved_users = SavedUsers.init();
@@ -161,6 +163,7 @@ pub fn main() !void {
             std.process.exit(0);
         }
         if (res.args.config) |path| config_parent_path = path;
+        if (res.args.@"use-kmscon-vt" != 0) use_kmscon_vt = true;
     }
 
     // Load configuration file
@@ -845,6 +848,7 @@ pub fn main() !void {
                             .x_cmd = config.x_cmd,
                             .x_vt = config.x_vt,
                             .session_pid = session_pid,
+                            .use_kmscon_vt = use_kmscon_vt,
                         };
 
                         // Signal action to give up control on the TTY