Add windows position handling at open, fix #653

- Move offscreen windows back on screen
- Restore maximized state without impacting resored size
- Fullscreen comes back on primary screen, needs further work to support
  restore on other screens

qt/preferences_dialog.py

@@ -32,7 +32,7 @@ from PyQt5.QtGui import QPixmap, QIcon
 
 from hscommon.trans import trget
 from hscommon.plat import ISLINUX
-from qtlib.util import horizontal_wrap
+from qtlib.util import horizontal_wrap, move_to_screen_center
 from qtlib.preferences import get_langnames
 from enum import Flag, auto
 
@@ -369,6 +369,11 @@ use the modifier key to drag the floating window around"
                 section_to_update = Sections.DISPLAY
             self.resetToDefaults(section_to_update)
 
+    def showEvent(self, event):
+        # have to do this here as the frameGeometry is not correct until shown
+        move_to_screen_center(self)
+        super().showEvent(event)
+
 
 class ColorPickerButton(QPushButton):
     def __init__(self, parent):