block gui updates while painting browser rows

If we processEvents() in the middle of a QItemDelegate, the recursion can
cause a crash on some OSes

aqt/browser.py

@@ -296,15 +296,19 @@ class StatusDelegate(QItemDelegate):
 
     def __init__(self, browser, model):
         QItemDelegate.__init__(self, browser)
+        self.browser = browser
         self.model = model
 
     def paint(self, painter, option, index):
+        self.browser.mw.progress.blockUpdates = True
         try:
             c = self.model.getCard(index)
         except:
             # in the the middle of a reset; return nothing so this row is not
             # rendered until we have a chance to reset the model
             return
+        finally:
+            self.browser.mw.progress.blockUpdates = True
         col = None
         if c.note().hasTag("Marked"):
             col = COLOUR_MARKED

aqt/progress.py

@@ -18,6 +18,7 @@ class ProgressManager(object):
         self.mw = mw
         self.app = QApplication.instance()
         self.inDB = False
+        self.blockUpdates = False
         self._win = None
         self._levels = 0
 
@@ -49,8 +50,9 @@ Your pysqlite2 is too old. Anki will appear frozen during long operations."""
         # ensure timers don't fire
         self.inDB = True
         # handle GUI events
-        self._maybeShow()
-        self.app.processEvents(QEventLoop.ExcludeUserInputEvents)
+        if not self.blockUpdates:
+          self._maybeShow()
+          self.app.processEvents(QEventLoop.ExcludeUserInputEvents)
         self.inDB = False
 
     # DB-safe timers