Fixed bug 5103 - Port fcitx support to both fcitx 4 & 5

wengxt

Due to the new major fcitx version is coming close, the existing code need to be ported to use new Fcitx dbus interface.

The new dbus interface is supported by both fcitx 4 and 5, and has a good side effect, which is that it will work with flatpak for free. Also the patch remove the dependency on fcitx header. Instead, it just hardcodes a few enum value in the code so need to handle the different header for fcitx4 or 5.

configure.ac

@@ -2731,24 +2731,13 @@ CheckFcitx()
 AS_HELP_STRING([--enable-fcitx], [enable fcitx support [[default=yes]]]),
                   , enable_fcitx=yes)
     if test x$enable_fcitx = xyes; then
-        PKG_CHECK_MODULES([FCITX], [fcitx], have_fcitx=yes, have_fcitx=no)
-        CFLAGS="$CFLAGS $FCITX_CFLAGS"
-        AC_CHECK_HEADER(fcitx/frontend.h,
-                        have_fcitx_frontend_h_hdr=yes,
-                        have_fcitx_frontend_h_hdr=no)
-        CFLAGS="$save_CFLAGS"
-        if test x$have_fcitx_frontend_h_hdr = xyes; then
-            if test x$enable_ime != xyes; then
-                AC_MSG_WARN([IME support is required for fcitx.])
-                have_fcitx_frontend_h_hdr=no
-            elif test x$enable_dbus != xyes; then
-                AC_MSG_WARN([DBus support is required for fcitx.])
-                have_fcitx_frontend_h_hdr=no
-            else
-                AC_DEFINE(HAVE_FCITX_FRONTEND_H, 1, [ ])
-                EXTRA_CFLAGS="$EXTRA_CFLAGS $FCITX_CFLAGS"
-                SOURCES="$SOURCES $srcdir/src/core/linux/SDL_fcitx.c"
-            fi
+        if test x$enable_ime != xyes; then
+            AC_MSG_WARN([IME support is required for fcitx.])
+        elif test x$enable_dbus != xyes; then
+            AC_MSG_WARN([DBus support is required for fcitx.])
+        else
+            AC_DEFINE(HAVE_FCITX, 1, [ ])
+            SOURCES="$SOURCES $srcdir/src/core/linux/SDL_fcitx.c"
         fi
     fi
 }
@@ -4408,7 +4397,7 @@ if test x$have_ibus_ibus_h_hdr = xyes; then
 else
     SUMMARY="${SUMMARY}Using ibus          : NO\n"
 fi
-if test x$have_fcitx_frontend_h_hdr = xyes; then
+if test x$enable_fcitx = xyes; then
     SUMMARY="${SUMMARY}Using fcitx         : YES\n"
 else
     SUMMARY="${SUMMARY}Using fcitx         : NO\n"