Update figure DPI when dpi_ratio changes

astrofrog · astrofrog · commit 379165447927 · 2017-07-24T17:40:41.000+01:00
Similarly to resizeEvent, we tell _set_dpi to not change the canvas size since we are doing it ourselves.
diff --git a/lib/matplotlib/backends/backend_qt5agg.py b/lib/matplotlib/backends/backend_qt5agg.py
@@ -68,9 +68,9 @@ def paintEvent(self, e):
         # As described in __init__ above, we need to be careful in cases with
         # mixed resolution displays if dpi_ratio is changing between painting
         # events.
-        if self._dpi_ratio_prev is None:
-            self._dpi_ratio_prev = self._dpi_ratio
-        elif self._dpi_ratio != self._dpi_ratio_prev:
+        if self._dpi_ratio_prev or self._dpi_ratio != self._dpi_ratio_prev:
+            # We need to update the figure DPI
+            self._update_figure_dpi()
             # The easiest way to resize the canvas is to emit a resizeEvent
             # since we implement all the logic for resizing the canvas for
             # that event.
@@ -196,6 +196,10 @@ def __init__(self, figure):
             self.figure._original_dpi = self.figure.dpi
         self.figure.dpi = self._dpi_ratio * self.figure._original_dpi
 
+    def _update_figure_dpi(self):
+        dpi = self._dpi_ratio * self.figure._original_dpi
+        self.figure._set_dpi(dpi, forward=False)
+
 
 @_BackendQT5.export
 class _BackendQT5Agg(_BackendQT5):
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -418,11 +418,16 @@ def _get_axes(self):
     def _get_dpi(self):
         return self._dpi
 
-    def _set_dpi(self, dpi):
+    def _set_dpi(self, dpi, forward=True):
+        """
+        The forward kwarg is passed on to set_size_inches
+        """
         self._dpi = dpi
         self.dpi_scale_trans.clear().scale(dpi, dpi)
-        self.set_size_inches(*self.get_size_inches())
+        w, h = self.get_size_inches()
+        self.set_size_inches(w, h, forward=forward)
         self.callbacks.process('dpi_changed', self)
+
     dpi = property(_get_dpi, _set_dpi)
 
     def get_tight_layout(self):
