PR: Make %matplotlib magic to really change backends

spyder/plugins/tests/test_ipythonconsole.py

@@ -59,6 +59,37 @@ def close_widget():
 #==============================================================================
 # Tests
 #==============================================================================
+@flaky(max_runs=10)
+@pytest.mark.skipif(os.name == 'nt', reason="It times out on Windows")
+def test_mpl_backend_change(ipyconsole, qtbot):
+    """
+    Test that Matplotlib backend is changed correctly when
+    using the %matplotlib magic
+    """
+    shell = ipyconsole.get_current_shellwidget()
+    client = ipyconsole.get_current_client()
+    qtbot.waitUntil(lambda: shell._prompt_html is not None, timeout=SHELL_TIMEOUT)
+
+    # Import Matplotlib
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('import matplotlib.pyplot as plt')
+
+    # Generate an inline plot
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('plt.plot(range(10))')
+
+    # Change backends
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('%matplotlib tk')
+
+    # Generate another plot
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('plt.plot(range(10))')
+
+    # Assert that there's a single inline plot in the console
+    assert shell._control.toHtml().count('img src') == 1
+
+
 @flaky(max_runs=10)
 @pytest.mark.skipif(os.name == 'nt', reason="It times out on Windows")
 def test_forced_restart_kernel(ipyconsole, qtbot):
@@ -71,12 +102,13 @@ def test_forced_restart_kernel(ipyconsole, qtbot):
     qtbot.waitUntil(lambda: shell._prompt_html is not None, timeout=SHELL_TIMEOUT)
 
     # Do an assigment to verify that it's not there after restarting
-    shell.execute('a = 10')
-    qtbot.wait(500)
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('a = 10')
 
     # Generate a traceback and enter debugging mode
-    shell.execute('1/0')
-    qtbot.wait(500)
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('1/0')
+
     shell.execute('%debug')
     qtbot.wait(500)
 
@@ -99,8 +131,8 @@ def test_restart_kernel(ipyconsole, qtbot):
     qtbot.waitUntil(lambda: shell._prompt_html is not None, timeout=SHELL_TIMEOUT)
 
     # Do an assigment to verify that it's not there after restarting
-    shell.execute('a = 10')
-    qtbot.wait(500)
+    with qtbot.waitSignal(shell.executed):
+        shell.execute('a = 10')
 
     # Restart kernel and wait until it's up again
     shell._prompt_html = None
@@ -176,8 +208,8 @@ def test_load_kernel_file(ipyconsole, qtbot):
 
     new_client = ipyconsole.get_clients()[1]
     new_shell = new_client.shellwidget
-    new_shell.execute('a = 10')
-    qtbot.wait(500)
+    with qtbot.waitSignal(new_shell.executed):
+        new_shell.execute('a = 10')
 
     assert new_client.name == '1/B'
     assert shell.get_value('a') == new_shell.get_value('a')

spyder/widgets/ipythonconsole/client.py

@@ -158,7 +158,8 @@ def configure_shellwidget(self, give_focus=True):
         self.shellwidget.executing.connect(self.add_to_history)
 
         # For Mayavi to run correctly
-        self.shellwidget.executing.connect(self.set_backend_for_mayavi)
+        self.shellwidget.executing.connect(
+            self.shellwidget.set_backend_for_mayavi)
 
         # To update history after execution
         self.shellwidget.executed.connect(self.update_history)
@@ -182,6 +183,10 @@ def configure_shellwidget(self, give_focus=True):
         self.shellwidget.sig_dbg_kernel_restart.connect(
                 self.restart_kernel)
 
+        # To correctly change Matplotlib backend interactively
+        self.shellwidget.executing.connect(
+            self.shellwidget.change_mpl_backend)
+
     def enable_stop_button(self):
         self.stop_button.setEnabled(True)
 
@@ -405,23 +410,6 @@ def reset_namespace(self):
     def update_history(self):
         self.history = self.shellwidget._history
 
-    def set_backend_for_mayavi(self, command):
-        """
-        Mayavi plots require the Qt backend, so we try to detect if one is
-        generated to change backends
-        """
-        calling_mayavi = False
-        lines = command.splitlines()
-        for l in lines:
-            if not l.startswith('#'):
-                if 'import mayavi' in l or 'from mayavi' in l:
-                    calling_mayavi = True
-                    break
-        if calling_mayavi:
-            message = _("Changing backend to Qt for Mayavi")
-            self.shellwidget._append_plain_text(message + '\n')
-            self.shellwidget.execute("%gui inline\n%gui qt")
-
     #------ Private API -------------------------------------------------------
     def _create_loading_page(self):
         """Create html page to show while the kernel is starting"""

spyder/widgets/ipythonconsole/shell.py

@@ -265,6 +265,35 @@ def handle_exec_method(self, msg):
                 # Remove method after being processed
                 self._kernel_methods.pop(expression)
 
+    def set_backend_for_mayavi(self, command):
+        """
+        Mayavi plots require the Qt backend, so we try to detect if one is
+        generated to change backends
+        """
+        calling_mayavi = False
+        lines = command.splitlines()
+        for l in lines:
+            if not l.startswith('#'):
+                if 'import mayavi' in l or 'from mayavi' in l:
+                    calling_mayavi = True
+                    break
+        if calling_mayavi:
+            message = _("Changing backend to Qt for Mayavi")
+            self._append_plain_text(message + '\n')
+            self.silent_execute("%gui inline\n%gui qt")
+
+    def change_mpl_backend(self, command):
+        """
+        If the user is trying to change Matplotlib backends with
+        %matplotlib, send the same command again to the kernel to
+        correctly change it.
+
+        Fixes issue 4002
+        """
+        if command.startswith('%matplotlib') and \
+          len(command.splitlines()) == 1:
+            self.silent_execute(command)
+
     #---- Private methods (overrode by us) ---------------------------------
     def _context_menu_make(self, pos):
         """Reimplement the IPython context menu"""