river: add keyboard-layout command

This allows switching river's keyboard layout at runtime.

river/command/keyboard.zig

@@ -0,0 +1,88 @@
+// 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, version 3.
+//
+// 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 mem = std.mem;
+
+const xkb = @import("xkbcommon");
+
+const server = &@import("../main.zig").server;
+const util = @import("../util.zig");
+
+const Error = @import("../command.zig").Error;
+const Seat = @import("../Seat.zig");
+
+pub fn keyboardLayout(
+    _: *Seat,
+    args: []const [:0]const u8,
+    _: *?[]const u8,
+) Error!void {
+    if (args.len < 2) return Error.NotEnoughArguments;
+    if (args.len % 2 != 0) return Error.InvalidValue;
+
+    // Do not carry over any previous keyboard layout configuration, always
+    // start fresh.
+    if (server.config.keyboard_layout) |kl| {
+        if (kl.rules) |s| util.gpa.free(mem.span(s));
+        if (kl.model) |s| util.gpa.free(mem.span(s));
+        if (kl.layout) |s| util.gpa.free(mem.span(s));
+        if (kl.variant) |s| util.gpa.free(mem.span(s));
+        if (kl.options) |s| util.gpa.free(mem.span(s));
+    }
+
+    server.config.keyboard_layout = xkb.RuleNames{
+        .layout = try util.gpa.dupeZ(u8, args[1]),
+        .rules = null,
+        .model = null,
+        .variant = null,
+        .options = null,
+    };
+
+    // TODO[zig]: this can be solved more elegantly with an inline for loop, but
+    //            on version 0.9.1 that crashes the compiler.
+    var i: usize = 2;
+    while (i < args.len - 1) : (i += 2) {
+        if (mem.eql(u8, args[i], "-variant")) {
+            // Do not allow duplicate flags.
+            if (server.config.keyboard_layout.?.variant != null) return error.InvalidValue;
+            server.config.keyboard_layout.?.variant = try util.gpa.dupeZ(u8, args[i + 1]);
+        } else if (mem.eql(u8, args[i], "-model")) {
+            if (server.config.keyboard_layout.?.model != null) return error.InvalidValue;
+            server.config.keyboard_layout.?.model = try util.gpa.dupeZ(u8, args[i + 1]);
+        } else if (mem.eql(u8, args[i], "-options")) {
+            if (server.config.keyboard_layout.?.options != null) return error.InvalidValue;
+            server.config.keyboard_layout.?.options = try util.gpa.dupeZ(u8, args[i + 1]);
+        } else if (mem.eql(u8, args[i], "-rules")) {
+            if (server.config.keyboard_layout.?.rules != null) return error.InvalidValue;
+            server.config.keyboard_layout.?.rules = try util.gpa.dupeZ(u8, args[i + 1]);
+        } else {
+            return error.InvalidValue;
+        }
+    }
+
+    const context = xkb.Context.new(.no_flags) orelse return error.OutOfMemory;
+    defer context.unref();
+
+    const keymap = xkb.Keymap.newFromNames(context, &server.config.keyboard_layout.?, .no_flags) orelse return error.InvalidValue;
+    defer keymap.unref();
+
+    var it = server.input_manager.devices.iterator(.forward);
+    while (it.next()) |device| {
+        if (device.wlr_device.type != .keyboard) continue;
+        const wlr_keyboard = device.wlr_device.toKeyboard();
+        if (!wlr_keyboard.setKeymap(keymap)) return error.OutOfMemory;
+    }
+}