Fix use-case where canvas misses requests for a new draw

rendercanvas/_loop.py

@@ -360,7 +360,7 @@ def _schedule_next_tick(self):
             return
 
         # Determine delay
-        if self._mode == "fastest":
+        if self._mode == "fastest" or self._max_fps <= 0:
             delay = 0
         else:
             delay = 1 / self._max_fps

rendercanvas/qt.py

@@ -182,6 +182,11 @@ def paintEngine(self):  # noqa: N802 - this is a Qt method
     def paintEvent(self, event):  # noqa: N802 - this is a Qt method
         self._draw_frame_and_present()
 
+    def update(self):
+        # Bypass Qt's mechanics and request a draw so that the scheduling mechanics work as intended.
+        # Eventually this will call _request_draw().
+        self.request_draw()
+
     # Methods that we add for BaseRenderCanvas (snake_case)
 
     def _request_draw(self):
@@ -490,6 +495,10 @@ def __init__(self, *, size=None, title=None, **kwargs):
 
     # Qt methods
 
+    def update(self):
+        self._subwidget.request_draw()
+        super().update()
+
     def closeEvent(self, event):  # noqa: N802
         self._subwidget._is_closed = True
         self.submit_event({"event_type": "close"})