Keyboard: eat key release event for mappings

Until now, only the event (press/release) for which a mapping was
present got eaten, and the other was passed to the client. From this
commit, a press mapping eats both events and a release mapping eats
nothing (and a press+release combo eats both).

This fixes behavior of some clients that do not make a difference
between press and release (e.g. Firefox with a fullscreen video
exiting fullscreen even on an Esc release event).

river/KeycodeSet.zig

@@ -0,0 +1,52 @@
+// 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 Self = @This();
+
+const std = @import("std");
+const assert = std.debug.assert;
+const log = std.log.scoped(.keyboard);
+
+const wlr = @import("wlroots");
+
+items: [32]u32 = undefined,
+len: usize = 0,
+
+pub fn add(self: *Self, new: u32) void {
+    for (self.items[0..self.len]) |item| if (new == item) return;
+
+    comptime assert(@typeInfo(std.meta.fieldInfo(Self, .items).field_type).Array.len ==
+        @typeInfo(std.meta.fieldInfo(wlr.Keyboard, .keycodes).field_type).Array.len);
+
+    if (self.len == self.items.len) {
+        log.err("KeycodeSet limit reached, code {d} omitted", .{new});
+        return;
+    }
+
+    self.items[self.len] = new;
+    self.len += 1;
+}
+
+pub fn remove(self: *Self, old: u32) bool {
+    for (self.items[0..self.len]) |item, idx| if (old == item) {
+        self.len -= 1;
+        if (self.len > 0) self.items[idx] = self.items[self.len];
+
+        return true;
+    };
+
+    return false;
+}