Cursor: Add a hide-cursor command

From the riverctl.1 man page:

*hide-cursor* *timeout* _timeout_
    Hide the cursor if it wasn't moved in the last _timeout_
    milliseconds until it is moved again.
    The default value is 0, which disables automatically hiding the
    cursor. Show the cursor again on any movement.

*hide-cursor* *when-typing* *enabled*|*disabled*
    Hide the cursor when pressing any non-modifier key. Show the cursor
    again on any movement.

river/command/cursor.zig

@@ -0,0 +1,50 @@
+// This file is part of river, a dynamic tiling wayland compositor.
+//
+// Copyright 2022 The River Developers
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const util = @import("../util.zig");
+
+const server = &@import("../main.zig").server;
+
+const Config = @import("../Config.zig");
+const Error = @import("../command.zig").Error;
+const Seat = @import("../Seat.zig");
+
+pub fn cursor(
+    _: *Seat,
+    args: []const [:0]const u8,
+    _: *?[]const u8,
+) Error!void {
+    if (std.mem.eql(u8, "timeout", args[1])) {
+        if (args.len < 3) return Error.NotEnoughArguments;
+        if (args.len > 3) return Error.TooManyArguments;
+        server.config.cursor_hide_timeout = try std.fmt.parseInt(u31, args[2], 10);
+        var seat_it = server.input_manager.seats.first;
+        while (seat_it) |seat_node| : (seat_it = seat_node.next) {
+            const seat = &seat_node.data;
+            seat.cursor.unhide();
+        }
+    } else if (std.mem.eql(u8, "when-typing", args[1])) {
+        if (args.len < 3) return Error.NotEnoughArguments;
+        if (args.len > 3) return Error.TooManyArguments;
+        server.config.cursor_hide_when_typing = std.meta.stringToEnum(Config.HideCursorWhenTypingMode, args[2]) orelse
+            return Error.UnknownOption;
+    } else {
+        return Error.UnknownOption;
+    }
+}