linux: fix potential segment faults

Fixes: #199

Signed-off-by: Yuhang Zhao <2546789017@qq.com>

include/FramelessHelper/Core/framelesshelper_linux.h

@@ -56,6 +56,18 @@
 // This one is not included in any public headers.
 using Display = struct _XDisplay;
 
+#ifndef FRAMELESSHELPER_HAS_XLIB
+extern "C"
+{
+
+FRAMELESSHELPER_CORE_API int
+XInitThreads(
+    void
+);
+
+} // extern "C"
+#endif // FRAMELESSHELPER_HAS_XLIB
+
 #if __has_include(<xcb/xcb.h>)
 #  include <xcb/xcb.h>
 #  define FRAMELESSHELPER_HAS_XCB

include/FramelessHelper/Core/private/sysapiloader_p.h

@@ -85,6 +85,7 @@ Q_DECLARE_METATYPE2(FRAMELESSHELPER_PREPEND_NAMESPACE(SysApiLoader))
 #endif // Q_OS_WINDOWS
 
 #ifdef Q_OS_LINUX
+#  define API_XLIB_AVAILABLE(func) API_AVAILABLE(libX11, func)
 #  define API_XCB_AVAILABLE(func) API_AVAILABLE(libxcb, func)
 #  define API_GTK_AVAILABLE(func) API_AVAILABLE(libgtk, func)
 #endif // Q_OS_LINUX

src/core/framelesshelpercore_global.cpp

@@ -174,6 +174,7 @@ void initialize()
     // enough, that is, before the construction of any Q(Gui)Application
     // instances. QCoreApplication won't instantiate the platform plugin.
     qputenv(QT_QPA_ENV_VAR, kxcb);
+    XInitThreads();
     gtk_init(nullptr, nullptr);
 #endif
 

src/core/platformsupport_linux.cpp

@@ -25,6 +25,28 @@
 #include "framelesshelper_linux.h"
 #include "sysapiloader_p.h"
 
+//////////////////////////////////////////////
+// Xlib
+
+#ifndef FRAMELESSHELPER_HAS_XLIB
+
+FRAMELESSHELPER_STRING_CONSTANT(libX11)
+
+FRAMELESSHELPER_STRING_CONSTANT(XInitThreads)
+
+extern "C" int
+XInitThreads(
+    void
+)
+{
+    if (!API_XLIB_AVAILABLE(XInitThreads)) {
+        return 0;
+    }
+    return API_CALL_FUNCTION(XInitThreads);
+}
+
+#endif // FRAMELESSHELPER_HAS_XLIB
+
 //////////////////////////////////////////////
 // XCB