FIX: internally Matplotlib works in screen pixels not logical pixels

tacaswell · tacaswell · commit a40620af1b77 · 2017-04-17T17:02:44.000-04:00
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -261,17 +261,20 @@ def leaveEvent(self, event):
         FigureCanvasBase.leave_notify_event(self, guiEvent=event)
 
     def mouseEventCoords(self, pos):
-        """
-        Calculate mouse coordinates in logical pixels.
+        """Calculate mouse coordinates in physical pixels
+
+        Qt5 use logical pixels, but the figure is scaled to physical
+        pixels for rendering.   Transform to physical pixels so that
+        all of the down-stream transforms work as expected.
+
+        Also, the origin is different and needs to be corrected.
 
-        Qt5 and Matplotlib use logical pixels, but the figure is scaled to
-        physical pixels for rendering. Also, the origin is different and needs
-        to be corrected.
         """
+        dpi_ratio = self._dpi_ratio
         x = pos.x()
         # flip y so y=0 is bottom of canvas
-        y = self.figure.bbox.height / self._dpi_ratio - pos.y()
-        return x, y
+        y = self.figure.bbox.height / dpi_ratio - pos.y()
+        return x * dpi_ratio, y * dpi_ratio
 
     def mousePressEvent(self, event):
         x, y = self.mouseEventCoords(event.pos())
