Adding comment on scaling of coords.

pshriwise · pshriwise · commit 3c5cbd87f6e1 · 2019-06-05T11:17:56.000-05:00
diff --git a/lib/matplotlib/backends/backend_qt5agg.py b/lib/matplotlib/backends/backend_qt5agg.py
@@ -41,6 +41,8 @@ def paintEvent(self, event):
         # See documentation of QRect: bottom() and right() are off by 1, so use
         # left() + width() and top() + height().
         rect = event.rect()
+        # scale rect dimensions using the screen dpi ratio to get
+        # correct values for the Figure coordinates (rather than QT5's coords)
         width = rect.width() * self._dpi_ratio
         height = rect.height() * self._dpi_ratio
         left, top = self.mouseEventCoords(rect.topLeft())
