gtk: allow running in the background

This patch fixes #2010 by implementing `quit-after-last-window-closed`
for the GTK apprt. It also adds the ability for the GTK apprt to exit
after a delay once all surfaces have been closed and adds the ability to
start Ghostty without opening an initial window.

src/apprt/gtk/App.zig

@@ -253,9 +253,13 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
         break :x11_xkb try x11.Xkb.init(display);
     };
 
-    // This just calls the "activate" signal but its part of the normal
+    // This just calls the `activate` signal but its part of the normal startup
-    // startup routine so we just call it:
+    // routine so we just call it, but only if the config allows it (this allows
+    // for launching Ghostty in the "background" without immediately opening
+    // a window)
+    //
     // https://gitlab.gnome.org/GNOME/glib/-/blob/bd2ccc2f69ecfd78ca3f34ab59e42e2b462bad65/gio/gapplication.c#L2302
+    if (config.@"initial-window")
         c.g_application_activate(gapp);
 
     // Register for dbus events
@@ -277,6 +281,10 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
     const css_provider = c.gtk_css_provider_new();
     try loadRuntimeCss(&config, css_provider);
 
+    // Run a small no-op function every 500 milliseconds so that we don't get
+    // stuck in g_main_context_iteration forever if there are no open surfaces.
+    _ = c.g_timeout_add(500, gtkTimeout, null);
+
     return .{
         .core_app = core_app,
         .app = app,
@@ -293,6 +301,12 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
     };
 }
 
+// This timeout function is run periodically so that we don't get stuck in
+// g_main_context_iteration forever if there are no open surfaces.
+pub fn gtkTimeout(_: ?*anyopaque) callconv(.C) c.gboolean {
+    return 1;
+}
+
 // Terminate the application. The application will not be restarted after
 // this so all global state can be cleaned up.
 pub fn terminate(self: *App) void {
@@ -463,6 +477,9 @@ pub fn run(self: *App) !void {
         self.transient_cgroup_base = path;
     } else log.debug("cgroup isoation disabled config={}", .{self.config.@"linux-cgroup"});
 
+    // The last instant that one or more surfaces were open
+    var last_one = try std.time.Instant.now();
+
     // Setup our menu items
     self.initActions();
     self.initMenu();
@@ -478,9 +495,48 @@ pub fn run(self: *App) !void {
     while (self.running) {
         _ = c.g_main_context_iteration(self.ctx, 1);
 
-        // Tick the terminal app
+        // Tick the terminal app and see if we should quit.
         const should_quit = try self.core_app.tick(self);
-        if (should_quit or self.core_app.surfaces.items.len == 0) self.quit();
+
+        // If there are one or more surfaces open, update the timer.
+        if (self.core_app.surfaces.items.len > 0) last_one = try std.time.Instant.now();
+
+        const q = q: {
+            // If we've been told by GTK that we should quit, do so regardless
+            // of any other setting.
+            if (should_quit) break :q true;
+
+            // If there are no surfaces check to see if we should stay in the
+            // background or not.
+            if (self.core_app.surfaces.items.len == 0) {
+                if (self.config.@"quit-after-last-window-closed") {
+                    // If the background timeout is not zero, check to see if
+                    // the timeout has elapsed.
+                    if (self.config.@"quit-after-last-window-closed-delay".duration != 0) {
+                        const now = try std.time.Instant.now();
+
+                        if (now.since(last_one) > self.config.@"quit-after-last-window-closed-delay".duration) {
+                            log.info("timeout elapsed", .{});
+                            // The timeout has elapsed, quit.
+                            break :q true;
+                        }
+
+                        // Not enough time has elapsed, don't quit.
+                        break :q false;
+                    }
+
+                    // `quit-after-last-window-closed-delay` is zero, don't quit.
+                    break :q false;
+                }
+
+                break :q false;
+            }
+
+            // there's at least one surface open, don't quit.
+            break :q false;
+        };
+
+        if (q) self.quit();
     }
 }
 
@@ -598,9 +654,8 @@ fn gtkQuitConfirmation(
     self.quitNow();
 }
 
-/// This is called by the "activate" signal. This is sent on program
+/// This is called by the `activate` signal. This is sent on program startup and
-/// startup and also when a secondary instance launches and requests
+/// also when a secondary instance launches and requests a new window.
-/// a new window.
 fn gtkActivate(app: *c.GtkApplication, ud: ?*anyopaque) callconv(.C) void {
     _ = app;
 

src/config/Config.zig

@@ -880,11 +880,46 @@ keybind: Keybinds = .{},
 /// true. If set to false, surfaces will close without any confirmation.
 @"confirm-close-surface": bool = true,
 
-/// Whether or not to quit after the last window is closed. This defaults to
+/// Whether or not to quit after the last surface is closed. This
-/// false. Currently only supported on macOS. On Linux, the process always exits
+/// defaults to `false`. On Linux, if this is `true`, Ghostty can delay
-/// after the last window is closed.
+/// quitting fully for a configurable amount. See the documentation of
+/// `quit-after-last-window-closed-delay` for more information.
 @"quit-after-last-window-closed": bool = false,
 
+/// If `quit-after-last-window-closed` is `true`, this controls how long
+/// Ghostty will stay running after the last open surface has been closed.  If
+/// `quit-after-last-window-closed-delay` is set to 0 ns Ghostty will remain
+/// running indefinitely. The duration should be at least long enough to allow
+/// Ghostty to initialize and open it's first window, but this is not enforced
+/// nor will a warning be issued. The duration is specified as a series of
+/// numbers followed by time units. Whitespace is allowed between numbers and
+/// units. The allowed time units are as follows:
+///
+///   * `y` - 365 SI days, or 8760 hours, or 31536000 seconds. No adjustments
+///     are made for leap years or leap seconds.
+///   * `d` - one SI day, or 86400 seconds.
+///   * `h` - one hour, or 3600 seconds.
+///   * `m` - one minute, or 60 seconds.
+///   * `s` - one second.
+///   * `ms` - one millisecond, or 0.001 second.
+///   * `us` or `µs` - one microsecond, or 0.000001 second.
+///   * `ns` - one nanosecond, or 0.000000001 second.
+///
+/// Examples:
+///   * `1h30m`
+///   * `45s`
+///
+/// The maximum value is `584y 49w 23h 34m 33s 709ms 551µs 615ns`.
+///
+/// By default `quit-after-last-window-closed-delay` is set to `0 ns`.
+///
+/// Only implemented on Linux.
+@"quit-after-last-window-closed-delay": Duration = .{ .duration = 0 },
+
+/// This controls whether an initial window is created when Ghostty is run. Only
+/// implemented on Linux.
+@"initial-window": bool = true,
+
 /// Whether to enable shell integration auto-injection or not. Shell integration
 /// greatly enhances the terminal experience by enabling a number of features:
 ///
@@ -1109,15 +1144,16 @@ keybind: Keybinds = .{},
 /// must always be able to move themselves into an isolated cgroup.
 @"linux-cgroup-hard-fail": bool = false,
 
-/// If true, the Ghostty GTK application will run in single-instance mode:
+/// If `true`, the Ghostty GTK application will run in single-instance mode:
-/// each new `ghostty` process launched will result in a new window if there
+/// each new `ghostty` process launched will result in a new window if there is
-/// is already a running process.
+/// already a running process.
 ///
-/// If false, each new ghostty process will launch a separate application.
+/// If `false`, each new ghostty process will launch a separate application.
 ///
-/// The default value is `desktop` which will default to `true` if Ghostty
+/// The default value is `detect` which will default to `true` if Ghostty
-/// detects it was launched from the `.desktop` file such as an app launcher.
+/// detects that it was launched from the `.desktop` file such as an app
-/// If Ghostty is launched from the command line, it will default to `false`.
+/// launcher (like Gnome Shell)  or by D-Bus activation. If Ghostty is launched
+/// from the command line, it will default to `false`.
 ///
 /// Note that debug builds of Ghostty have a separate single-instance ID
 /// so you can test single instance without conflicting with release builds.
@@ -3753,3 +3789,211 @@ pub const LinuxCgroup = enum {
     always,
     @"single-instance",
 };
+
+pub const Duration = struct {
+    duration: u64 = 0,
+
+    pub fn clone(self: *const @This(), _: Allocator) !@This() {
+        return .{ .duration = self.duration };
+    }
+
+    pub fn equal(self: @This(), other: @This()) bool {
+        return self.duration == other.duration;
+    }
+
+    pub fn parseCLI(self: *@This(), _: Allocator, input: ?[]const u8) !void {
+        var remaining = input orelse {
+            self.duration = 0;
+            return;
+        };
+
+        const units = [_]struct {
+            name: []const u8,
+            factor: u64,
+        }{
+            .{ .name = "y", .factor = 365 * std.time.ns_per_day },
+            .{ .name = "w", .factor = std.time.ns_per_week },
+            .{ .name = "d", .factor = std.time.ns_per_day },
+            .{ .name = "h", .factor = std.time.ns_per_hour },
+            .{ .name = "m", .factor = std.time.ns_per_min },
+            .{ .name = "s", .factor = std.time.ns_per_s },
+            .{ .name = "ms", .factor = std.time.ns_per_ms },
+            .{ .name = "us", .factor = std.time.ns_per_us },
+            .{ .name = "µs", .factor = std.time.ns_per_us },
+            .{ .name = "ns", .factor = 1 },
+        };
+
+        var value: ?u64 = null;
+
+        while (remaining.len > 0) {
+            // Skip over whitespace before the number
+            while (remaining.len > 0 and std.ascii.isWhitespace(remaining[0])) {
+                remaining = remaining[1..];
+            }
+            // There was whitespace at the end, that's OK
+            if (remaining.len == 0) break;
+
+            // Find the longest number
+            const number = number: {
+                var prev_number: ?u64 = null;
+                var prev_remaining: ?[]const u8 = null;
+                for (1..remaining.len + 1) |index| {
+                    prev_number = std.fmt.parseUnsigned(u64, remaining[0..index], 10) catch {
+                        if (prev_remaining) |prev| remaining = prev;
+                        break :number prev_number;
+                    };
+                    prev_remaining = remaining[index..];
+                }
+                if (prev_remaining) |prev| remaining = prev;
+                break :number prev_number;
+            } orelse return error.InvalidValue;
+
+            // Skip over any whitespace between the number and the unit
+            while (remaining.len > 0 and std.ascii.isWhitespace(remaining[0])) {
+                remaining = remaining[1..];
+            }
+
+            // A number without a unit is invalid
+            if (remaining.len == 0) return error.InvalidValue;
+
+            // Find the longest matching unit. Needs to be the longest matching
+            // to distinguish 'm' from 'ms'.
+            const factor = factor: {
+                var prev_factor: ?u64 = null;
+                var prev_index: ?usize = null;
+                for (1..remaining.len + 1) |index| {
+                    const next_factor = next: {
+                        for (units) |unit| {
+                            if (std.mem.eql(u8, unit.name, remaining[0..index])) {
+                                break :next unit.factor;
+                            }
+                        }
+                        break :next null;
+                    };
+                    if (next_factor) |next| {
+                        prev_factor = next;
+                        prev_index = index;
+                    }
+                }
+                if (prev_index) |index| {
+                    remaining = remaining[index..];
+                }
+                break :factor prev_factor;
+            } orelse return error.InvalidValue;
+
+            if (value) |v|
+                value = v + number * factor
+            else
+                value = number * factor;
+        }
+
+        self.duration = value orelse 0;
+    }
+
+    pub fn formatEntry(self: @This(), formatter: anytype) !void {
+        var buf: [64]u8 = undefined;
+        var fbs = std.io.fixedBufferStream(&buf);
+        const writer = fbs.writer();
+
+        var value = self.duration;
+
+        const units = [_]struct {
+            name: []const u8,
+            factor: u64,
+        }{
+            .{ .name = "y", .factor = 365 * std.time.ns_per_day },
+            .{ .name = "w", .factor = std.time.ns_per_week },
+            .{ .name = "d", .factor = std.time.ns_per_day },
+            .{ .name = "h", .factor = std.time.ns_per_hour },
+            .{ .name = "m", .factor = std.time.ns_per_min },
+            .{ .name = "s", .factor = std.time.ns_per_s },
+            .{ .name = "ms", .factor = std.time.ns_per_ms },
+            .{ .name = "µs", .factor = std.time.ns_per_us },
+            .{ .name = "ns", .factor = 1 },
+        };
+
+        var i: usize = 0;
+        for (units) |unit| {
+            if (value > unit.factor) {
+                if (i > 0) writer.writeAll(" ") catch unreachable;
+                const remainder = value % unit.factor;
+                const quotient = (value - remainder) / unit.factor;
+                writer.print("{d}{s}", .{ quotient, unit.name }) catch unreachable;
+                value = remainder;
+                i += 1;
+            }
+        }
+
+        try formatter.formatEntry([]const u8, fbs.getWritten());
+    }
+};
+
+test "parse duration" {
+    var d: Duration = undefined;
+
+    try d.parseCLI(std.testing.allocator, "");
+    try std.testing.expectEqual(@as(u64, 0), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "0ns");
+    try std.testing.expectEqual(@as(u64, 0), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1ns");
+    try std.testing.expectEqual(@as(u64, 1), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "100ns");
+    try std.testing.expectEqual(@as(u64, 100), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1µs");
+    try std.testing.expectEqual(@as(u64, 1000), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1µs1ns");
+    try std.testing.expectEqual(@as(u64, 1001), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1µs 1ns");
+    try std.testing.expectEqual(@as(u64, 1001), d.duration);
+
+    try d.parseCLI(std.testing.allocator, " 1µs1ns");
+    try std.testing.expectEqual(@as(u64, 1001), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1µs1ns ");
+    try std.testing.expectEqual(@as(u64, 1001), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1y");
+    try std.testing.expectEqual(@as(u64, 365 * std.time.ns_per_day), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1d");
+    try std.testing.expectEqual(@as(u64, std.time.ns_per_day), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1h");
+    try std.testing.expectEqual(@as(u64, std.time.ns_per_hour), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1m");
+    try std.testing.expectEqual(@as(u64, std.time.ns_per_min), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1s");
+    try std.testing.expectEqual(@as(u64, std.time.ns_per_s), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "1ms");
+    try std.testing.expectEqual(@as(u64, std.time.ns_per_ms), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "30s");
+    try std.testing.expectEqual(@as(u64, 30 * std.time.ns_per_s), d.duration);
+
+    try d.parseCLI(std.testing.allocator, "584y 49w 23h 34m 33s 709ms 551µs 615ns");
+    try std.testing.expectEqual(std.math.maxInt(u64), d.duration);
+
+    try std.testing.expectError(error.InvalidValue, d.parseCLI(std.testing.allocator, "1"));
+    try std.testing.expectError(error.InvalidValue, d.parseCLI(std.testing.allocator, "s"));
+    try std.testing.expectError(error.InvalidValue, d.parseCLI(std.testing.allocator, "1x"));
+    try std.testing.expectError(error.InvalidValue, d.parseCLI(std.testing.allocator, "1 "));
+}
+
+test "format duration" {
+    const testing = std.testing;
+    var buf = std.ArrayList(u8).init(testing.allocator);
+    defer buf.deinit();
+
+    var p: Duration = .{ .duration = std.math.maxInt(u64) };
+    try p.formatEntry(formatterpkg.entryFormatter("a", buf.writer()));
+    try std.testing.expectEqualStrings("a = 584y 49w 23h 34m 33s 709ms 551µs 615ns\n", buf.items);
+}