Resize canvas when changing figures size in Qt5Agg

Author: dstansby

lib/matplotlib/backends/backend_qt5.py

@@ -631,7 +631,8 @@ def resize(self, width, height):
         # so we do not need to worry about dpi scaling here.
         extra_width = self.window.width() - self.canvas.width()
         extra_height = self.window.height() - self.canvas.height()
-        self.window.resize(width+extra_width, height+extra_height)
+        self.canvas.resize(width, height)
+        self.window.resize(width + extra_width, height + extra_height)
 
     def show(self):
         self.window.show()

lib/matplotlib/tests/test_backend_qt.py

@@ -272,3 +272,19 @@ def test_figureoptions():
             "matplotlib.backends.qt_editor._formlayout.FormDialog.exec_",
             lambda self: None):
         fig.canvas.manager.toolbar.edit_parameters()
+
+
+@pytest.mark.backend('Qt5Agg')
+def test_double_resize():
+    # Check that resizing a figure twice keeps the same window size
+    fig, ax = plt.subplots()
+    fig.canvas.draw()
+    window = fig.canvas.manager.window
+
+    fig.set_size_inches(2, 2)
+    old_width = window.width()
+    old_height = window.height()
+
+    fig.set_size_inches(2, 2)
+    assert window.width() == old_width
+    assert window.height() == old_height