Change: Set EnableHighDpiScaling flag for high DPI support

This is handled at the OS layer by OSX and at the server layer by Wayland, whereas X11 and Windows place the responsibility of scaling on the app. Qt includes a flag to enable high-dpi support trivially, though it causes the app to be unwieldly large.

Fixes reilleya#101

main.py

@@ -1,5 +1,11 @@
 import sys
-import app
+from app import App
+from PyQt5.QtCore import Qt
 
-app = app.App(sys.argv)
+# must be set before the app is constructed
+# cf. https://doc.qt.io/qt-5/highdpi.html
+# and https://www.riverbankcomputing.com/static/Docs/PyQt5/api/qtcore/qt.html#ApplicationAttribute
+App.setAttribute(Qt.AA_EnableHighDpiScaling)
+
+app = App(sys.argv)
 sys.exit(app.exec())