Add `ChartPlotWidget.main_viz: Viz` convenience `@property`

piker/ui/_app.py

@@ -178,8 +178,7 @@ def _main(
     tractor_kwargs,
 ) -> None:
     '''
-    Sync entry point to start a chart: a ``tractor`` + Qt runtime
-    entry point
+    Sync entry point to start a chart: a ``tractor`` + Qt runtime.
 
     '''
     run_qtractor(

piker/ui/_chart.py

@@ -1365,4 +1365,12 @@ class ChartPlotWidget(pg.PlotWidget):
         self,
         key: str,
     ) -> Viz:
+        '''
+        Try to get an underlying ``Viz`` by key.
+
+        '''
         return self._vizs.get(key)
+
+    @property
+    def main_viz(self) -> Viz:
+        return self.get_viz(self.name)