remove lodpi hack, don't assume physical DPI is always 72

aqt/__init__.py

@@ -223,8 +223,6 @@ def parseArgs(argv):
     parser.add_option("-b", "--base", help="path to base folder")
     parser.add_option("-p", "--profile", help="profile name to load")
     parser.add_option("-l", "--lang", help="interface language (en, de, etc)")
-    parser.add_option("--lodpi", action="store_true", dest="lodpi",
-                      help="disable Qt's high DPI support")
     return parser.parse_args(argv[1:])
 
 def run():
@@ -261,8 +259,7 @@ def _run(argv=None, exec=True):
         ctypes.CDLL('libGL.so.1', ctypes.RTLD_GLOBAL)
 
     # opt in to full hidpi support
-    if not opts.lodpi:
-        QCoreApplication.setAttribute(Qt.AA_EnableHighDpiScaling)
+    QCoreApplication.setAttribute(Qt.AA_EnableHighDpiScaling)
 
     # create the app
     app = AnkiApp(argv)

aqt/webview.py

@@ -160,20 +160,33 @@ class AnkiWebView(QWebEngineView):
         from aqt import mw
         if isMac:
             return 1
-        if isWin and mw.opts.lodpi:
-            return 1
         screen = QApplication.desktop().screen()
         dpi = screen.logicalDpiX()
         factor = dpi / 96.0
         if isLin:
             factor = max(1, factor)
             return factor
-        # compensate for qt's integer scaling
-        # on windows
-        qtIntScale = 72/screen.physicalDpiX()
+        # compensate for qt's integer scaling on windows
+        qtIntScale = self._getQtIntScale(screen)
         desiredScale = factor * qtIntScale
         newFactor = desiredScale / qtIntScale
-        return newFactor
+        return max(1, newFactor)
+
+    def _getQtIntScale(self, screen):
+        # try to detect if Qt has scaled the screen
+        # - qt will round the scale factor to a whole number, so a dpi of 125% = 1x,
+        #   and a dpi of 150% = 2x
+        # - a screen with a normal physical dpi of 72 will have a dpi of 32
+        #   if the scale factor has been rounded to 2x
+        # - different screens have different physical DPIs (eg 72, 93, 102)
+        # - until a better solution presents itself, assume a physical DPI at
+        #   or above 70 is unscaled
+        if screen.physicalDpiX() > 70:
+            return 1
+        elif screen.physicalDpiX() > 35:
+            return 2
+        else:
+            return 3
 
     def stdHtml(self, body, css=[], js=["jquery.js"], head=""):
         if isWin: