Make event loop implementation swappable.

CMakeLists.txt

@@ -31,13 +31,14 @@ option(ENABLE_DBUS "Enable DBus" On)
 option(ENABLE_DOC "Build doxygen" Off)
 option(ENABLE_SERVER "Build a fcitx as server, disable this option if you want to use fcitx as an embedded library." On)
 option(ENABLE_KEYBOARD "Enable key event translation with XKB and build keyboard engine" On)
-option(USE_SYSTEMD "Use systemd for event loop and dbus, will fallback to libuv/libdbus if not found." On)
+option(USE_SYSTEMD "Use systemd for event loop and dbus, will fallback to libuv/libdbus if not found. Only used when EVENT_LOOP_BACKEND is auto." On)
 option(ENABLE_XDGAUTOSTART "Enable xdg autostart desktop file installation" On)
 option(USE_FLATPAK_ICON "Use flatpak icon name for desktop files" Off)
 option(ENABLE_EMOJI "Enable emoji module" On)
 option(ENABLE_LIBUUID "Use libuuid for uuid generation" On)
 option(BUILD_SPELL_DICT "Build en_dict.fscd for English spell check" On)
 set(NO_PREEDIT_APPS "gvim.*,wps.*,wpp.*,et.*" CACHE STRING "Disable preedit for follwing app by default.")
+set(EVENT_LOOP_BACKEND "auto" CACHE STRING "Set the underlying event loop implementation, valid values are auto,systemd,libuv,none")
 
 if (ENABLE_EMOJI)
     find_package(ZLIB REQUIRED)
@@ -47,35 +48,67 @@ if ((ENABLE_WAYLAND OR ENABLE_X11) AND NOT ENABLE_KEYBOARD)
     message(FATAL_ERROR "X11 and Wayland require ENABLE_KEYBOARD to be set to ON.")
 endif ()
 
-
 #######################################################################
 # Find packages
 #######################################################################
 
 find_package(PkgConfig REQUIRED)
 
-if (USE_SYSTEMD)
-find_package(Systemd)
-endif ()
+set(CANDIDATE_EVENT_LOOP_BACKENDS)
 
-if (USE_FLATPAK_ICON)
-    set(FCITX_ICON_NAME "org.fcitx.Fcitx5")
-else()
-    set(FCITX_ICON_NAME "fcitx")
+if (EVENT_LOOP_BACKEND STREQUAL "auto")
+    if (USE_SYSTEMD)
+        list(APPEND CANDIDATE_EVENT_LOOP_BACKENDS systemd)
+    endif()
+
+    list(APPEND CANDIDATE_EVENT_LOOP_BACKENDS libuv)
+elseif (EVENT_LOOP_BACKEND STREQUAL "systemd")
+    list(APPEND CANDIDATE_EVENT_LOOP_BACKENDS systemd)
+elseif (EVENT_LOOP_BACKEND STREQUAL "libuv")
+    list(APPEND CANDIDATE_EVENT_LOOP_BACKENDS libuv)
+elseif (EVENT_LOOP_BACKEND STREQUAL "none")
+    list(APPEND CANDIDATE_EVENT_LOOP_BACKENDS none)
 endif()
 
-if (NOT TARGET Systemd::Systemd)
-    if (ENABLE_DBUS)
-        pkg_check_modules(DBus REQUIRED IMPORTED_TARGET "dbus-1")
-        pkg_get_variable(DBUS_SYSTEM_BUS_DEFAULT_ADDRESS "dbus-1" "system_bus_default_address")
-    endif()
+set(FCITX_EVENT_LOOP_BACKEND "")
+foreach(CANDIDATE_EVENT_LOOP_BACKEND IN LISTS CANDIDATE_EVENT_LOOP_BACKENDS)
+    if (CANDIDATE_EVENT_LOOP_BACKEND STREQUAL systemd)
+        find_package(Systemd)
+        if (TARGET Systemd::Systemd)
+            set(FCITX_EVENT_LOOP_BACKEND "systemd")
+            break()
+        endif()
+    elseif (CANDIDATE_EVENT_LOOP_BACKEND STREQUAL libuv)
+        if (NOT LIBUV_TARGET)
+            if (NOT (TARGET PkgConfig::LibUV))
+                pkg_check_modules(LibUV IMPORTED_TARGET "libuv")
+                set(LIBUV_TARGET PkgConfig::LibUV)
+            endif()
+        endif()
 
-    if (NOT LIBUV_TARGET)
-        if (NOT (TARGET PkgConfig::LibUV))
-            pkg_check_modules(LibUV REQUIRED IMPORTED_TARGET "libuv")
+        if (TARGET LIBUV_TARGET)
+            set(FCITX_EVENT_LOOP_BACKEND "libuv")
+            break()
         endif()
-        set(LIBUV_TARGET PkgConfig::LibUV)
+    elseif (CANDIDATE_EVENT_LOOP_BACKEND STREQUAL none)
+        set(FCITX_EVENT_LOOP_BACKEND "none")
+        break()
     endif()
+endforeach()
+
+if (ENABLE_DBUS AND NOT (FCITX_EVENT_LOOP_BACKEND STREQUAL systemd))
+    pkg_check_modules(DBus REQUIRED IMPORTED_TARGET "dbus-1")
+    pkg_get_variable(DBUS_SYSTEM_BUS_DEFAULT_ADDRESS "dbus-1" "system_bus_default_address")
+endif()
+
+if (FCITX_EVENT_LOOP_BACKEND STREQUAL "")
+    message(FATAL_ERROR "Failed to find a valid event loop backend.")
+endif()
+
+if (USE_FLATPAK_ICON)
+    set(FCITX_ICON_NAME "org.fcitx.Fcitx5")
+else()
+    set(FCITX_ICON_NAME "fcitx")
 endif()
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "BSD|DragonFly")

src/lib/fcitx-utils/CMakeLists.txt

@@ -1,44 +1,42 @@
 set(FCITX_UTILS_SOURCES)
+set(FCITX_UTILS_DEPS)
 
 if (ENABLE_DBUS)
 
-    set(FCITX_UTILS_SOURCES
-        ${FCITX_UTILS_SOURCES}
+    list(APPEND FCITX_UTILS_SOURCES
         dbus/servicewatcher.cpp
         dbus/matchrule.cpp
         dbus/variant.cpp
         dbus/objectvtable.cpp
     )
 
-    if (NOT TARGET Systemd::Systemd)
-        set(FCITX_UTILS_SOURCES
-            ${FCITX_UTILS_SOURCES}
-            dbus/libdbus/bus.cpp
-            dbus/libdbus/message.cpp
-            dbus/libdbus/objectvtable_libdbus.cpp
-            dbus/libdbus/servicenamecache.cpp)
-    else()
-        set(FCITX_UTILS_SOURCES
-            ${FCITX_UTILS_SOURCES}
+    if (FCITX_EVENT_LOOP_BACKEND STREQUAL "systemd")
+        list(APPEND FCITX_UTILS_SOURCES
             dbus/sdbus/bus.cpp
             dbus/sdbus/message.cpp
             dbus/sdbus/objectvtablewrapper.c
             dbus/sdbus/objectvtable_sdbus.cpp)
+    else()
+        list(APPEND FCITX_UTILS_SOURCES
+            dbus/libdbus/bus.cpp
+            dbus/libdbus/message.cpp
+            dbus/libdbus/objectvtable_libdbus.cpp
+            dbus/libdbus/servicenamecache.cpp)
+        list(APPEND FCITX_UTILS_DEPS PkgConfig::DBus)
     endif()
 endif()
 
-if (NOT TARGET Systemd::Systemd)
-  set(FCITX_UTILS_SOURCES
-    ${FCITX_UTILS_SOURCES}
-    event_libuv.cpp)
-else()
-  set(FCITX_UTILS_SOURCES
-    ${FCITX_UTILS_SOURCES}
-    event_sdevent.cpp)
+if (FCITX_EVENT_LOOP_BACKEND STREQUAL "libuv")
+    list(APPEND FCITX_UTILS_SOURCES event_libuv.cpp)
+    list(APPEND FCITX_UTILS_DEPS "${LIBUV_TARGET}")
+elseif (FCITX_EVENT_LOOP_BACKEND STREQUAL "systemd")
+    list(APPEND FCITX_UTILS_SOURCES event_sdevent.cpp)
+    list(APPEND FCITX_UTILS_DEPS Systemd::Systemd)
+elseif (FCITX_EVENT_LOOP_BACKEND STREQUAL "none")
+    list(APPEND FCITX_UTILS_SOURCES event_none.cpp)
 endif()
 
-set(FCITX_UTILS_SOURCES
-    ${FCITX_UTILS_SOURCES}
+list(APPEND FCITX_UTILS_SOURCES
     stringutils.cpp
     testing.cpp
     key.cpp
@@ -135,15 +133,7 @@ target_link_libraries(Fcitx5Utils PRIVATE DL::DL LibIntl::LibIntl Pthread::Pthre
 if(LIBKVM_FOUND)
     target_link_libraries(Fcitx5Utils PRIVATE LibKVM::LibKVM)
 endif()
-
-if (NOT TARGET Systemd::Systemd)
-    target_link_libraries(Fcitx5Utils PRIVATE ${LIBUV_TARGET})
-    if (ENABLE_DBUS)
-        target_link_libraries(Fcitx5Utils PRIVATE PkgConfig::DBus)
-    endif()
-else()
-    target_link_libraries(Fcitx5Utils PRIVATE Systemd::Systemd)
-endif()
+target_link_libraries(Fcitx5Utils PRIVATE ${FCITX_UTILS_DEPS})
 
 configure_file(Fcitx5Utils.pc.in ${CMAKE_CURRENT_BINARY_DIR}/Fcitx5Utils.pc @ONLY)
 

src/lib/fcitx-utils/dbus/sdbus/bus.cpp

@@ -6,6 +6,7 @@
  */
 
 #include <stdexcept>
+#include <string_view>
 #include "../../log.h"
 #include "bus_p.h"
 #include "message_p.h"
@@ -117,9 +118,15 @@ void Bus::attachEventLoop(EventLoop *loop) {
     if (d->eventLoop_) {
         return;
     }
-    sd_event *event = static_cast<sd_event *>(loop->nativeHandle());
-    if (sd_bus_attach_event(d->bus_, event, 0) >= 0) {
-        d->eventLoop_ = loop;
+    if (loop->implementation() == std::string_view("sd-event")) {
+        sd_event *event = static_cast<sd_event *>(loop->nativeHandle());
+        if (sd_bus_attach_event(d->bus_, event, 0) >= 0) {
+            d->eventLoop_ = loop;
+        }
+    } else {
+        // TODO: support sd-bus + generic event loop implementation.
+        throw std::invalid_argument(
+            "not support sd-bus with non-sdevent implementation.");
     }
 }
 

src/lib/fcitx-utils/event.cpp

@@ -11,6 +11,7 @@
 #include <cstring>
 #include <ctime>
 #include <memory>
+#include <stdexcept>
 #include <utility>
 #include "event_p.h"
 #include "eventloopinterface.h"
@@ -21,12 +22,28 @@ namespace fcitx {
 class EventLoopPrivate {
 public:
     EventLoopPrivate(std::unique_ptr<EventLoopInterface> impl)
-        : impl_(std::move(impl)) {}
+        : impl_(std::move(impl)) {
+        if (!impl_) {
+            throw std::runtime_error("No available event loop implementation.");
+        }
+    }
 
     std::unique_ptr<EventLoopInterface> impl_;
+
+    static EventLoopFactory factory_;
 };
 
-EventLoop::EventLoop() : EventLoop(createDefaultEventLoop()) {}
+EventLoopFactory EventLoopPrivate::factory_ = createDefaultEventLoop;
+
+void EventLoop::setEventLoopFactory(EventLoopFactory factory) {
+    if (factory) {
+        EventLoopPrivate::factory_ = std::move(factory);
+    } else {
+        EventLoopPrivate::factory_ = createDefaultEventLoop;
+    }
+}
+
+EventLoop::EventLoop() : EventLoop(EventLoopPrivate::factory_()) {}
 
 EventLoop::EventLoop(std::unique_ptr<EventLoopInterface> impl)
     : d_ptr(std::make_unique<EventLoopPrivate>(std::move(impl))) {}

src/lib/fcitx-utils/event.h

@@ -16,6 +16,8 @@
 
 namespace fcitx {
 
+using EventLoopFactory = std::function<std::unique_ptr<EventLoopInterface>()>;
+
 class EventLoopPrivate;
 class FCITXUTILS_EXPORT EventLoop {
 public:
@@ -27,9 +29,18 @@ class FCITXUTILS_EXPORT EventLoop {
 
     /**
      * Return the default implementation name.
+     *
+     * This will only return the default implementation name.
+     * Do not rely on this value.
+     *
+     * @see EventLoop::implementation
      */
     FCITXUTILS_DEPRECATED static const char *impl();
 
+    /**
+     * Return the name of implementation of event loop.
+     * @since 5.1.12
+     */
     const char *implementation() const;
     void *nativeHandle();
 
@@ -45,6 +56,15 @@ class FCITXUTILS_EXPORT EventLoop {
     FCITX_NODISCARD std::unique_ptr<EventSource>
     addPostEvent(EventCallback callback);
 
+    /**
+     * Set an external event loop implementation.
+     *
+     * This is useful if you need to integrate fcitx with another event loop.
+     *
+     * @since 5.1.12
+     */
+    static void setEventLoopFactory(EventLoopFactory factory);
+
 private:
     const std::unique_ptr<EventLoopPrivate> d_ptr;
     FCITX_DECLARE_PRIVATE(EventLoop);

src/lib/fcitx-utils/event_libuv.cpp

@@ -249,7 +249,12 @@ void PostEventCallback(uv_prepare_t *handle) {
             source->setEnabled(false);
         }
         auto callback = source->callback_;
-        (*callback)(source);
+        auto ret = (*callback)(source);
+        if (sourceRef.isValid()) {
+            if (!ret) {
+                source->setEnabled(false);
+            }
+        }
     } catch (const std::exception &e) {
         // some abnormal things threw{
         FCITX_FATAL() << e.what();

src/lib/fcitx-utils/event_none.cpp

@@ -0,0 +1,16 @@
+
+/*
+ * SPDX-FileCopyrightText: 2015-2015 CSSlayer <wengxt@gmail.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ */
+#include "event_p.h"
+
+namespace fcitx {
+
+std::unique_ptr<EventLoopInterface> createDefaultEventLoop() { return nullptr; }
+
+const char *defaultEventLoopImplementation() { return "none"; }
+
+} // namespace fcitx

test/CMakeLists.txt

@@ -3,6 +3,9 @@ include_directories(${CMAKE_CURRENT_BINARY_DIR})
 
 add_subdirectory(addon)
 
+add_library(eventlooptests STATIC eventlooptests.cpp)
+target_link_libraries(eventlooptests Fcitx5::Utils)
+
 set(FCITX_UTILS_TEST
     testflags
     teststringutils
@@ -11,6 +14,7 @@ set(FCITX_UTILS_TEST
     testcolor
     testi18nstring
     testevent
+    testcustomeventloop
     testlist
     testfs
     testlibrary
@@ -33,7 +37,8 @@ set(FCITX_UTILS_DBUS_TEST
 
 set(testdbus_LIBS Pthread::Pthread)
 set(testeventdispatcher_LIBS Pthread::Pthread)
-set(testevent_LIBS Pthread::Pthread)
+set(testevent_LIBS Pthread::Pthread eventlooptests)
+set(testcustomeventloop_LIBS Pthread::Pthread eventlooptests)
 
 find_program(XVFB_BIN Xvfb)