opt in to qt's full hidpi support

doesn't seem to affect the webviews on Linux, so we need to keep the old
zoom code around for now

aqt/__init__.py

@@ -214,6 +214,9 @@ def _run():
         import ctypes
         ctypes.CDLL('libGL.so.1', ctypes.RTLD_GLOBAL)
 
+    # opt in to full hidpi support
+    QCoreApplication.setAttribute(Qt.AA_EnableHighDpiScaling)
+
     # create the app
     app = AnkiApp(sys.argv)
     QCoreApplication.setApplicationName("Anki")

aqt/webview.py

@@ -6,7 +6,7 @@ import sys
 from anki.hooks import runHook
 from aqt.qt import *
 from aqt.utils import openLink
-from anki.utils import isMac, isWin, devMode
+from anki.utils import isMac, isWin, isLin, devMode
 
 # Page for debug messages
 ##########################################################################
@@ -151,7 +151,10 @@ class AnkiWebView(QWebEngineView):
         if oldFocus:
             oldFocus.setFocus()
 
+    # need to do this manually for Linux as Qt doesn't automatically scale webview
     def zoomFactor(self):
+        if not isLin:
+            return 1
         screen = QApplication.desktop().screen()
         dpi = screen.logicalDpiX()
         return max(1, dpi / 96.0)