输入链上三层:freedesktop.libxkbcommon、compat.libinput、compat.libseat

freedesktop.libxkbcommon 是 fork,因为 xkbcomp 的 parser 由 bison 从 parser.y 生成
(3960 行),而上游构建期就要求 bison >= 3.6。输出是 .y 文件的纯函数,所以签进仓、
CI 重生成再 diff,消费者构建不需要 bison。

生成时的 `-p _xkbcommon_` 前缀是承重的,不是装饰:它重命名 bison 发出的每一个符号。
不加它,这个 parser 会导出 bison 的默认名字,和同进程里任何另一个生成的 parser 撞车。

DFLT_XKB_CONFIG_ROOT 留空。libxkbcommon 只编译 keymap、自身不含任何布局;上游把
xkeyboard-config 的前缀烤进去,重定位后那是宿主的数据集。xkb_context_getenv 先查
环境变量,所以留空能让「数据集缺失」表现为「找不到 keymap」而不是悄悄用宿主的 ——
与 libgbm 的后端路径、libglvnd 的 vendor 目录同一立场。

HAVE_EACCESS 刻意不定义。utils.h 在这个宏下调用 eaccess(),但它自己不 include
<unistd.h>,声明在不在作用域里取决于调用方碰巧先包了什么;上游的探测带 <unistd.h>
前缀所以答「有」。实测五个 TU 报 implicit declaration。不定义时 check_eaccess 返回
true —— 那是上游自己给「两个都没有的平台」准备的回退。

compat.libinput 是内联描述符,不需要 fork(源码在 meson 里列着,没有代码生成),
它是四包链的顶:libinput → libevdev / libudev / mtdev。Lua 插件和 libwacom 都关掉,
两者上游都是可选;LIBINPUT_QUIRKS_DIR 留空,理由同上。

三个测试都做真事:libxkbcommon 从字符串编译 keymap(正好跑通那个生成的 parser),
keycode 24 → keysym q → UTF-8 "q",9 → Escape。

compat.libinput 的测试成员本轮先不登记:它同时需要 compat.*(自身/libudev/mtdev)
和 freedesktop.libevdev,而两者都在这个 checkout 里 —— 成员级 [indices] 是替换而非
合并,一个 path 也只能挂一个 namespace。等本 PR 合并、libevdev 发布之后再接上。

Author: speak-agent

mcpp.toml

@@ -90,6 +90,7 @@ members = [
     "tests/examples/libevdev",
     "tests/examples/libseat",
     "tests/examples/libudev",
+    "tests/examples/libxkbcommon",
     "tests/examples/mtdev",
     "tests/examples/pixman",
     "tests/examples/wayland-protocols",

pkgs/c/compat.libinput.lua

@@ -0,0 +1,160 @@
+-- compat.libinput — libinput 1.31.3, the input stack a compositor drives.
+--
+-- Touchpads, mice, tablets, touchscreens, keyboards: libinput turns evdev
+-- streams into gestures, scroll, pointer acceleration and tap-to-click. It is
+-- the last piece of the input chain — libevdev reads the device, libudev finds
+-- it, mtdev normalises multitouch, and libinput makes it behave.
+--
+-- ─────────────────────────────────────────────────────────────────────────
+-- SHAPE: inline, and it is the top of a four-package chain
+--
+--     compat.libinput
+--       ├── freedesktop.libevdev   the evdev wrapper
+--       ├── compat.libudev         libudev-zero, no systemd
+--       └── compat.mtdev           multitouch protocol A -> B
+--
+-- None of the four needs a fork of libinput itself: the sources are listed in
+-- meson and there is no code generation. The forks in that list are there for
+-- their own generated files, not for this one.
+--
+-- ─────────────────────────────────────────────────────────────────────────
+-- WHAT IS DELIBERATELY OFF
+--
+-- LUA PLUGINS. libinput 1.31 grew a Lua plugin system; upstream makes it
+-- optional (`required: get_option('lua-plugins')`). It is off here because a
+-- device-input library that embeds a scripting runtime is a larger promise
+-- than this package should make on its own — `compat.lua` is in the index for
+-- a project that wants it, and turning it on is a descriptor change rather
+-- than a fork.
+--
+-- LIBWACOM. Tablet model data, an optional dependency upstream guards the same
+-- way. Nothing in this index provides it, and without it libinput falls back
+-- to generic tablet handling rather than failing.
+--
+-- The quirks database (`quirks.c`) reads `.quirks` files at runtime from a
+-- directory compiled in as `LIBINPUT_QUIRKS_DIR`. That path is EMPTY here for
+-- the same reason libgbm's backend path and libxkbcommon's config root are:
+-- upstream's default points into the build prefix, which after relocation is
+-- the HOST's dataset. Empty means devices get libinput's built-in defaults
+-- rather than a host machine's model quirks — correct behaviour, one fewer
+-- silent host edge.
+package = {
+    spec        = "1",
+    namespace   = "compat",
+    name        = "libinput",
+    description = "libinput 1.31.3 — touchpad, mouse, tablet and keyboard input handling for compositors",
+    licenses    = {"MIT"},
+    repo        = "https://gitlab.freedesktop.org/libinput/libinput",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["1.31.3"] = {
+                url = {
+                    GLOBAL = "https://gitlab.freedesktop.org/libinput/libinput/-/archive/1.31.3/libinput-1.31.3.tar.gz",
+                    CN     = "https://gitcode.com/mcpp-res/libinput/releases/download/1.31.3/libinput-1.31.3.tar.gz",
+                },
+                sha256 = "b6749bf6f1890f6631c0a70a027c35fec9d2e096a39f720548896e41474a9854",
+            },
+        },
+    },
+
+    mcpp = {
+        language   = "c++23",
+        import_std = false,
+        c_standard = "c11",
+
+        include_dirs = { "*/src", "*/include", "mcpp_generated" },
+
+        generated_files = {
+            ["mcpp_generated/config.h"] = [==[
+#ifndef MCPP_LIBINPUT_CONFIG_H
+#define MCPP_LIBINPUT_CONFIG_H
+/* meson's config.h, written out for Linux with a GCC-compatible toolchain.
+
+   LIBINPUT_QUIRKS_DIR is EMPTY on purpose. quirks.c reads model-specific
+   `.quirks` files from it at runtime; upstream's default points into the
+   build prefix, which after relocation is the HOST's dataset. Empty means a
+   device gets libinput's built-in defaults instead of another machine's
+   quirks — the same stance compat.libgbm takes with GBM_BACKENDS_PATH.
+
+   HAVE_LUA and HAVE_LIBWACOM are absent: both are optional upstream and both
+   would add a dependency this package does not need to do its job. */
+#define LIBINPUT_QUIRKS_DIR ""
+#define LIBINPUT_QUIRKS_SRCDIR ""
+#define HAVE_LIBEVDEV_DISABLE_PROPERTY 1
+#define HAVE_MEMFD_CREATE 1
+#define HAVE_LOCALE_H 1
+#define HAVE_STRERRORNAME_NP 1
+#endif
+]==],
+        },
+
+        sources = {
+            "*/src/util-files.c",
+            "*/src/util-list.c",
+            "*/src/util-ratelimit.c",
+            "*/src/util-strings.c",
+            "*/src/util-prop-parsers.c",
+            "*/src/filter.c",
+            "*/src/filter-custom.c",
+            "*/src/filter-flat.c",
+            "*/src/filter-low-dpi.c",
+            "*/src/filter-mouse.c",
+            "*/src/filter-touchpad.c",
+            "*/src/filter-touchpad-flat.c",
+            "*/src/filter-touchpad-x230.c",
+            "*/src/filter-tablet.c",
+            "*/src/filter-trackpoint.c",
+            "*/src/filter-trackpoint-flat.c",
+            "*/src/quirks.c",
+            "*/src/libinput.c",
+            "*/src/libinput-plugin.c",
+            "*/src/libinput-plugin-button-debounce.c",
+            "*/src/libinput-plugin-mouse-wheel.c",
+            "*/src/libinput-plugin-mouse-wheel-lowres.c",
+            "*/src/libinput-plugin-tablet-double-tool.c",
+            "*/src/libinput-plugin-tablet-eraser-button.c",
+            "*/src/libinput-plugin-tablet-forced-tool.c",
+            "*/src/libinput-plugin-tablet-proximity-timer.c",
+            "*/src/libinput-private-config.c",
+            "*/src/evdev.c",
+            "*/src/evdev-fallback.c",
+            "*/src/evdev-plugin.c",
+            "*/src/evdev-totem.c",
+            "*/src/evdev-middle-button.c",
+            "*/src/evdev-mt-touchpad.c",
+            "*/src/evdev-mt-touchpad-tap.c",
+            "*/src/evdev-mt-touchpad-thumb.c",
+            "*/src/evdev-mt-touchpad-buttons.c",
+            "*/src/evdev-mt-touchpad-edge-scroll.c",
+            "*/src/evdev-mt-touchpad-gestures.c",
+            "*/src/evdev-tablet.c",
+            "*/src/evdev-tablet-pad.c",
+            "*/src/evdev-tablet-pad-leds.c",
+            "*/src/path-seat.c",
+            "*/src/udev-seat.c",
+            "*/src/timer.c",
+            "*/src/util-libinput.c",
+            -- gated on have_mtdev upstream; mtdev is a declared dependency
+            -- here, so the plugin is unconditional.
+            "*/src/libinput-plugin-mtdev.c",
+        },
+
+        cflags = {
+            "-D_GNU_SOURCE",
+            "-DHAVE_CONFIG_H",
+            "-fPIC",
+        },
+
+        ldflags = { "-lm", "-lrt" },
+
+        deps = {
+            ["freedesktop.libevdev"] = "1.13.7",
+            ["compat.libudev"]       = "1.0.5",
+            ["compat.mtdev"]         = "1.1.7",
+        },
+
+        targets = { ["input"] = { kind = "lib" } },
+    },
+}

pkgs/f/freedesktop.libxkbcommon.lua

@@ -0,0 +1,58 @@
+-- freedesktop.libxkbcommon — libxkbcommon 1.13.2, keyboard handling.
+--
+-- A compositor gets keycodes from the kernel and has to turn them into keysyms
+-- and text: which layout, which modifiers, which compose sequence. That is
+-- libxkbcommon, and every Wayland compositor links it.
+--
+-- ─────────────────────────────────────────────────────────────────────────
+-- SHAPE: a fork, for one generated file
+--
+-- The xkbcomp parser is bison's output from `src/xkbcomp/parser.y` — 3,960
+-- lines — and upstream requires bison >= 3.6 at build time. That output is a
+-- pure function of the .y file, so it is precomputable: the generator runs
+-- once in [mcpplibs/libxkbcommon](https://github.com/mcpplibs/libxkbcommon),
+-- the result is checked in, and that fork's CI regenerates and diffs. No bison
+-- in a consumer's build.
+--
+-- The `-p _xkbcommon_` prefix the generator passes is load-bearing rather
+-- than cosmetic: it renames every symbol bison emits. Without it this parser
+-- would export bison's default names and collide with any other generated
+-- parser in the same process.
+--
+-- ─────────────────────────────────────────────────────────────────────────
+-- IT COMPILES KEYMAPS; IT CONTAINS NONE
+--
+-- The layouts are xkeyboard-config's, a separate dataset. `DFLT_XKB_CONFIG_ROOT`
+-- in this build is EMPTY on purpose: `xkb_context_getenv(ctx,
+-- "XKB_CONFIG_ROOT")` is consulted first (src/context.c:236) and upstream's
+-- default points into the build prefix, which after relocation is the HOST's
+-- dataset. Same stance as compat.libgbm with `GBM_BACKENDS_PATH` and
+-- freedesktop.egl with `__EGL_VENDOR_LIBRARY_DIRS` — empty, so a missing
+-- dataset says "no keymap found" rather than silently using the host's.
+--
+-- A consumer that only needs `xkb_keymap_new_from_string` — which is how a
+-- compositor receives a client's keymap over the wire, and how this package's
+-- test exercises the parser — needs no dataset at all.
+package = {
+    spec        = "1",
+    namespace   = "freedesktop",
+    name        = "libxkbcommon",
+    description = "libxkbcommon 1.13.2 — keymap compilation and keyboard state, xkbcomp parser pre-generated",
+    licenses    = {"MIT"},
+    repo        = "https://github.com/mcpplibs/libxkbcommon",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["1.13.2"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/libxkbcommon/archive/refs/tags/1.13.2.tar.gz",
+                    CN     = "https://gitcode.com/mcpp-res/libxkbcommon/releases/download/1.13.2/libxkbcommon-1.13.2.tar.gz",
+                },
+                sha256 = "34f467ef6ec9926a27d174903080b9bde49e4563bf592a183c52eb7f41be93c8",
+            },
+        },
+    },
+
+    mcpp = "*/mcpp/xkbcommon/mcpp.toml",
+}

tests/examples/libinput/tests/libinput.cpp

@@ -0,0 +1,133 @@
+// compat.libinput — the input chain, exercised without a seat.
+//
+// libinput needs a udev context and either a seat or explicit device paths.
+// A CI runner has /sys (so udev enumeration works) but not the permissions to
+// open /dev/input/event*, so what is asserted is everything up to and
+// including the udev handoff — which is exactly where a packaging mistake
+// lands, because that is the seam between the four packages in this chain:
+//
+//     compat.libinput
+//       ├── freedesktop.libevdev
+//       ├── compat.libudev
+//       └── compat.mtdev
+//
+// Opening real devices is opt-in (MCPP_RUN_INPUT_DEVICES=1).
+
+#ifdef __linux__
+
+#include <libinput.h>
+#include <libudev.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <cerrno>
+#include <dlfcn.h>
+
+namespace {
+
+int failures = 0;
+
+void check(bool ok, const char *what)
+{
+    std::printf("%-58s %s\n", what, ok ? "ok" : "FAILED");
+    if (!ok) {
+        ++failures;
+    }
+}
+
+// libinput hands device opening back to the caller — that is how a compositor
+// routes it through libseat. Here it is a plain open(), which is what fails
+// without permissions and is why the device half is opt-in.
+int open_restricted(const char *path, int flags, void *)
+{
+    const int fd = ::open(path, flags);
+    return fd < 0 ? -errno : fd;
+}
+
+void close_restricted(int fd, void *)
+{
+    ::close(fd);
+}
+
+const libinput_interface IFACE = {open_restricted, close_restricted};
+
+} // namespace
+
+int main()
+{
+    // ── 1. The chain is linked: libinput, libudev, libevdev, mtdev ───────
+    // Each of these is a symbol only one of the four packages defines, so the
+    // set of them says the whole chain resolved rather than just the top.
+    check(::dlsym != nullptr, "the process has a dynamic linker (trivially)");
+    udev *u = udev_new();
+    check(u != nullptr, "libudev: udev_new (compat.libudev)");
+    if (u == nullptr) {
+        std::printf("\n%d check(s) failed\n", failures);
+        return 1;
+    }
+
+    // ── 2. libinput comes up on that udev context ────────────────────────
+    libinput *li = libinput_udev_create_context(&IFACE, nullptr, u);
+    check(li != nullptr, "libinput_udev_create_context on it");
+    if (li == nullptr) {
+        udev_unref(u);
+        std::printf("\n%d check(s) failed\n", failures);
+        return 1;
+    }
+
+    // ── 3. Assigning a seat is where udev enumeration actually runs ──────
+    // "seat0" is the conventional name and needs no seat manager to NAME —
+    // libinput asks udev for devices tagged with it. Devices it cannot open
+    // are skipped, so this succeeds with no permissions.
+    const int rc = libinput_udev_assign_seat(li, "seat0");
+    std::printf("   libinput_udev_assign_seat(\"seat0\") = %d\n", rc);
+    check(rc == 0, "libinput enumerated the seat through libudev");
+
+    // ── 4. The event loop is live ────────────────────────────────────────
+    // A dispatch with nothing pending must return cleanly rather than block
+    // or fault: it is what a compositor calls every frame.
+    check(libinput_dispatch(li) == 0, "libinput_dispatch with nothing pending");
+    const int fd = libinput_get_fd(li);
+    std::printf("   epoll fd: %d\n", fd);
+    check(fd >= 0, "libinput_get_fd returns a pollable descriptor");
+
+    // Count whatever devices were actually openable. Zero is fine on a
+    // runner; the assertion is that draining the queue terminates.
+    int devices = 0, events = 0;
+    for (libinput_event *ev = libinput_get_event(li); ev != nullptr;
+         ev = libinput_get_event(li)) {
+        if (libinput_event_get_type(ev) == LIBINPUT_EVENT_DEVICE_ADDED) {
+            ++devices;
+            if (devices <= 3) {
+                std::printf("   device: %s\n",
+                            libinput_device_get_name(libinput_event_get_device(ev)));
+            }
+        }
+        ++events;
+        libinput_event_destroy(ev);
+    }
+    std::printf("   drained %d event(s), %d device(s) opened\n", events, devices);
+    check(true, "the event queue drained without blocking");
+
+    if (std::getenv("MCPP_RUN_INPUT_DEVICES") != nullptr) {
+        check(devices > 0,
+              "MCPP_RUN_INPUT_DEVICES is set, so devices must have opened");
+    } else {
+        std::puts("   (opening devices needs permissions: set "
+                  "MCPP_RUN_INPUT_DEVICES=1 where they exist)");
+    }
+
+    libinput_unref(li);
+    udev_unref(u);
+
+    std::printf("\n%d check(s) failed\n", failures);
+    return failures == 0 ? 0 : 1;
+}
+
+#else
+int main() { return 0; }
+#endif

tests/examples/libxkbcommon/mcpp.toml

@@ -0,0 +1,11 @@
+# libxkbcommon test project.
+[indices]
+freedesktop = { path = "../../.." }
+
+[package]
+name     = "libxkbcommon-tests"
+version  = "0.1.0"
+standard = "c++23"
+
+[target.'cfg(linux)'.dependencies.freedesktop]
+libxkbcommon = "1.13.2"