Use `nullptr` instead of `0`.

src/Platform/AbstractXApplication.cpp

@@ -50,7 +50,7 @@ void AbstractXApplication::createContext(AbstractXApplication::Configuration* co
     viewportSize = configuration->size();
 
     /* Get default X display */
-    display = XOpenDisplay(0);
+    display = XOpenDisplay(nullptr);
 
     /* Get visual ID */
     VisualID visualId = contextHandler->getVisualId(display);
@@ -74,7 +74,7 @@ void AbstractXApplication::createContext(AbstractXApplication::Configuration* co
     attr.event_mask = 0;
     unsigned long mask = CWBackPixel|CWBorderPixel|CWColormap|CWEventMask;
     window = XCreateWindow(display, root, 20, 20, configuration->size().x(), configuration->size().y(), 0, visInfo->depth, InputOutput, visInfo->visual, mask, &attr);
-    XSetStandardProperties(display, window, configuration->title().c_str(), 0, None, 0, 0, 0);
+    XSetStandardProperties(display, window, configuration->title().c_str(), nullptr, None, nullptr, 0, nullptr);
     XFree(visInfo);
 
     /* Be notified about closing the window */

src/Platform/GlxContextHandler.cpp

@@ -84,7 +84,7 @@ void GlxContextHandler::createContext(Window nativeWindow) {
 
     /** @todo Use some extension wrangler for this, not GLEW, as it apparently needs context to create context, yo dawg wtf. */
     PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB = (PFNGLXCREATECONTEXTATTRIBSARBPROC) glXGetProcAddress((const GLubyte*)"glXCreateContextAttribsARB");
-    context = glXCreateContextAttribsARB(display, configs[0], 0, True, attributes);
+    context = glXCreateContextAttribsARB(display, configs[0], nullptr, True, attributes);
     XFree(configs);
     if(!context) {
         Error() << "GlxContextHandler: cannot create context.";

src/Platform/WindowlessGlxApplication.cpp

@@ -74,7 +74,7 @@ void WindowlessGlxApplication::createContext(Configuration* configuration) {
 
     /** @todo Use some extension wrangler for this, not GLEW, as it apparently needs context to create context, yo dawg wtf. */
     PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB = (PFNGLXCREATECONTEXTATTRIBSARBPROC) glXGetProcAddress((const GLubyte*)"glXCreateContextAttribsARB");
-    context = glXCreateContextAttribsARB(display, configs[0], 0, True, contextAttributes);
+    context = glXCreateContextAttribsARB(display, configs[0], nullptr, True, contextAttributes);
     if(!context) {
         Error() << "WindowlessGlxApplication: cannot create context.";
         std::exit(1);