QFontDatabase is all static in Qt 6

src/calibre/gui2/font_family_chooser.py

@@ -48,7 +48,7 @@ def add_fonts(parent):
 
 def writing_system_for_font(font):
     has_latin = True
-    systems = QFontDatabase().writingSystems(font.family())
+    systems = QFontDatabase.writingSystems(font.family())
 
     # this just confuses the algorithm below. Vietnamese is Latin with lots of
     # special chars
@@ -140,7 +140,7 @@ class FontFamilyDelegate(QStyledItemDelegate):
         if (system != QFontDatabase.WritingSystem.Any):
             w = painter.fontMetrics().width(text + "  ")
             painter.setFont(font2)
-            sample = QFontDatabase().writingSystemSample(system)
+            sample = QFontDatabase.writingSystemSample(system)
             if (option.direction == Qt.LayoutDirection.RightToLeft):
                 r.setRight(r.right() - w)
             else:

src/calibre/gui2/tweak_book/editor/text.py

@@ -66,7 +66,7 @@ _dff = None
 def default_font_family():
     global _dff
     if _dff is None:
-        families = set(map(str, QFontDatabase().families()))
+        families = set(map(str, QFontDatabase.families()))
         for x in ('Ubuntu Mono', 'Consolas', 'Liberation Mono'):
             if x in families:
                 _dff = x

src/calibre/gui2/viewer/web_view.py

@@ -616,7 +616,7 @@ class WebView(RestartingWebEngineView):
         if family in ('.AppleSystemUIFont', 'MS Shell Dlg 2'):
             family = 'system-ui'
         ui_data = {
-            'all_font_families': QFontDatabase().families(),
+            'all_font_families': QFontDatabase.families(),
             'ui_font_family': family,
             'ui_font_sz': f'{fi.pixelSize()}px',
             'show_home_page_on_ready': self.show_home_page_on_ready,