Fix a Qt deprecation warning.

Author: DavidEGrayson

gui/qt/main_window.cpp

@@ -25,6 +25,7 @@
 #include <QProcessEnvironment>
 #include <QPushButton>
 #include <QRadioButton>
+#include <QScreen>
 #include <QShortcut>
 #include <QSpinBox>
 #include <QTabWidget>
@@ -1365,7 +1366,7 @@ void main_window::center_at_startup_if_needed()
         Qt::LeftToRight,
         Qt::AlignCenter,
         size(),
-        qApp->desktop()->availableGeometry()
+        qApp->primaryScreen()->availableGeometry()
         )
       );
   }

include/tic.h

@@ -1802,7 +1802,7 @@ tic_error * tic_halt_and_hold(tic_handle *);
 
 /// Sends a "Go Home" command, starting the Tic's homing procedure.
 ///
-/// The direcition argument should be 1 for forward or 0 for reverse.
+/// The direction argument should be 1 for forward or 0 for reverse.
 TIC_API TIC_WARN_UNUSED
 tic_error * tic_go_home(tic_handle *, uint8_t direction);