Move show() to somewhere naturally inheritable.

anntzer · anntzer · commit daee9500e20b · 2022-05-22T23:16:47.000+02:00
It's actually not clear whether to move it to FigureCanvas or
FigureManager.  FigureCanvas already has start_event_loop (cf.
start_main_loop), but pyplot_show/start_main_loop is more a
global/pyplot-only concept, so perhaps it belongs to FigureManager
instead?  OTOH, being on canvas_class makes it easier for switch_backend
to access it (it doesn't need to go through
`canvas_class.manager_class.pyplot_show`, which is relevant considering
that some designs of inheritable backends didn't even have a
manager_class attribute).
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -2494,6 +2494,42 @@ def stop_event_loop(self):
         """
         self._looping = False
 
+    @classmethod
+    def start_main_loop(cls):
+        """
+        Start the main event loop.
+
+        Interactive backends need to reimplement this method or `pyplot_show`.
+        """
+
+    @classmethod
+    def pyplot_show(cls, *, block=None):
+        """
+        Show all figures.  This method is the implementation of `.pyplot.show`.
+
+        Interactive backends need to reimplement this method or
+        `start_main_loop`.
+
+        `show` blocks by calling `mainloop` if *block* is ``True``, or if it
+        is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
+        `interactive` mode.
+        """
+        managers = Gcf.get_all_fig_managers()
+        if not managers:
+            return
+        for manager in managers:
+            try:
+                manager.show()  # Emits a warning for non-interactive backend.
+            except NonGuiException as exc:
+                _api.warn_external(str(exc))
+        if block is None:
+            # Hack: Are we in IPython's pylab mode?
+            from matplotlib import pyplot
+            ipython_pylab = hasattr(pyplot.show, "_needmain")
+            block = not ipython_pylab and not is_interactive()
+        if block:
+            cls.start_main_loop()
+
 
 def key_press_handler(event, canvas=None, toolbar=None):
     """
@@ -3473,7 +3509,12 @@ def new_figure_manager_given_figure(cls, num, figure):
 
     @classmethod
     def draw_if_interactive(cls):
-        if cls.mainloop is not None and is_interactive():
+        canvas_class = cls.FigureCanvas
+        interactive_backend = (
+            canvas_class.start_main_loop != FigureCanvasBase.start_main_loop
+            or canvas_class.show != FigureCanvasBase.show
+        )
+        if interactive_backend and is_interactive():
             manager = Gcf.get_active()
             if manager:
                 manager.canvas.draw_idle()
diff --git a/lib/matplotlib/backends/_backend_gtk.py b/lib/matplotlib/backends/_backend_gtk.py
@@ -9,7 +9,8 @@
 from matplotlib import _api, backend_tools, cbook
 from matplotlib._pylab_helpers import Gcf
 from matplotlib.backend_bases import (
-    _Backend, FigureManagerBase, NavigationToolbar2, TimerBase)
+    _Backend, FigureCanvasBase, FigureManagerBase, NavigationToolbar2,
+    TimerBase)
 from matplotlib.backend_tools import Cursors
 
 # The GTK3/GTK4 backends will have already called `gi.require_version` to set
@@ -112,6 +113,29 @@ def _on_timer(self):
             return False
 
 
+class _FigureCanvasGTK(FigureCanvasBase):
+    _timer_cls = TimerGTK
+
+    @classmethod
+    def start_main_loop(cls):
+        global _application
+        if _application is None:
+            return
+
+        try:
+            _application.run()  # Quits when all added windows close.
+        except KeyboardInterrupt:
+            # Ensure all windows can process their close event from
+            # _shutdown_application.
+            context = GLib.MainContext.default()
+            while context.pending():
+                context.iteration(True)
+            raise
+        finally:
+            # Running after quit is undefined, so create a new one next time.
+            _application = None
+
+
 class _FigureManagerGTK(FigureManagerBase):
     """
     Attributes
@@ -299,21 +323,4 @@ def trigger(self, *args):
 
 
 class _BackendGTK(_Backend):
-    @staticmethod
-    def mainloop():
-        global _application
-        if _application is None:
-            return
-
-        try:
-            _application.run()  # Quits when all added windows close.
-        except KeyboardInterrupt:
-            # Ensure all windows can process their close event from
-            # _shutdown_application.
-            context = GLib.MainContext.default()
-            while context.pending():
-                context.iteration(True)
-            raise
-        finally:
-            # Running after quit is undefined, so create a new one next time.
-            _application = None
+    mainloop = _FigureCanvasGTK.start_main_loop
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -396,6 +396,20 @@ def set_cursor(self, cursor):
         except tkinter.TclError:
             pass
 
+    @classmethod
+    def start_main_loop(cls):
+        managers = Gcf.get_all_fig_managers()
+        if managers:
+            first_manager = managers[0]
+            manager_class = type(first_manager)
+            if manager_class._owns_mainloop:
+                return
+            manager_class._owns_mainloop = True
+            try:
+                first_manager.window.mainloop()
+            finally:
+                manager_class._owns_mainloop = False
+
 
 class FigureManagerTk(FigureManagerBase):
     """
@@ -1002,18 +1016,6 @@ def trigger(self, *args):
 
 @_Backend.export
 class _BackendTk(_Backend):
+    FigureCanvas = FigureCanvasTk
     FigureManager = FigureManagerTk
-
-    @staticmethod
-    def mainloop():
-        managers = Gcf.get_all_fig_managers()
-        if managers:
-            first_manager = managers[0]
-            manager_class = type(first_manager)
-            if manager_class._owns_mainloop:
-                return
-            manager_class._owns_mainloop = True
-            try:
-                first_manager.window.mainloop()
-            finally:
-                manager_class._owns_mainloop = False
+    mainloop = FigureCanvas.start_main_loop
diff --git a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
@@ -26,7 +26,7 @@
 from gi.repository import Gio, GLib, GObject, Gtk, Gdk
 from . import _backend_gtk
 from ._backend_gtk import (
-    _BackendGTK, _FigureManagerGTK, _NavigationToolbar2GTK,
+    _BackendGTK, _FigureCanvasGTK, _FigureManagerGTK, _NavigationToolbar2GTK,
     TimerGTK as TimerGTK3,
 )
 from ._backend_gtk import backend_version  # noqa: F401 # pylint: disable=W0611
@@ -68,9 +68,8 @@ def _mpl_to_gtk_cursor(mpl_cursor):
         _backend_gtk.mpl_to_gtk_cursor_name(mpl_cursor))
 
 
-class FigureCanvasGTK3(Gtk.DrawingArea, FigureCanvasBase):
+class FigureCanvasGTK3(Gtk.DrawingArea, _FigureCanvasGTK):
     required_interactive_framework = "gtk3"
-    _timer_cls = TimerGTK3
     manager_class = _api.classproperty(lambda cls: FigureManagerGTK3)
     # Setting this as a static constant prevents
     # this resulting expression from leaking
diff --git a/lib/matplotlib/backends/backend_gtk4.py b/lib/matplotlib/backends/backend_gtk4.py
@@ -23,16 +23,15 @@
 from gi.repository import Gio, GLib, GObject, Gtk, Gdk, GdkPixbuf
 from . import _backend_gtk
 from ._backend_gtk import (
-    _BackendGTK, _FigureManagerGTK, _NavigationToolbar2GTK,
+    _BackendGTK, _FigureCanvasGTK, _FigureManagerGTK, _NavigationToolbar2GTK,
     TimerGTK as TimerGTK4,
 )
 from ._backend_gtk import backend_version  # noqa: F401 # pylint: disable=W0611
 
 
-class FigureCanvasGTK4(Gtk.DrawingArea, FigureCanvasBase):
+class FigureCanvasGTK4(Gtk.DrawingArea, _FigureCanvasGTK):
     required_interactive_framework = "gtk4"
     supports_blit = False
-    _timer_cls = TimerGTK4
     manager_class = _api.classproperty(lambda cls: FigureManagerGTK4)
     _context_is_scaled = False
 
diff --git a/lib/matplotlib/backends/backend_macosx.py b/lib/matplotlib/backends/backend_macosx.py
@@ -97,6 +97,10 @@ def resize(self, width, height):
         FigureCanvasBase.resize_event(self)
         self.draw_idle()
 
+    @classmethod
+    def start_main_loop(cls):
+        _macosx.show()
+
 
 class NavigationToolbar2Mac(_macosx.NavigationToolbar2, NavigationToolbar2):
 
@@ -171,7 +175,4 @@ def show(self):
 class _BackendMac(_Backend):
     FigureCanvas = FigureCanvasMac
     FigureManager = FigureManagerMac
-
-    @staticmethod
-    def mainloop():
-        _macosx.show()
+    mainloop = FigureCanvas.start_main_loop
diff --git a/lib/matplotlib/backends/backend_qt.py b/lib/matplotlib/backends/backend_qt.py
@@ -518,6 +518,12 @@ def _draw_rect_callback(painter):
         self._draw_rect_callback = _draw_rect_callback
         self.update()
 
+    @classmethod
+    def start_main_loop(cls):
+        qapp = QtWidgets.QApplication.instance()
+        with _maybe_allow_interrupt(qapp):
+            qt_compat._exec(qapp)
+
 
 class MainWindow(QtWidgets.QMainWindow):
     closing = QtCore.Signal()
@@ -1040,9 +1046,4 @@ def trigger(self, *args, **kwargs):
 class _BackendQT(_Backend):
     FigureCanvas = FigureCanvasQT
     FigureManager = FigureManagerQT
-
-    @staticmethod
-    def mainloop():
-        qapp = QtWidgets.QApplication.instance()
-        with _maybe_allow_interrupt(qapp):
-            qt_compat._exec(qapp)
+    mainloop = FigureCanvas.start_main_loop
diff --git a/lib/matplotlib/backends/backend_webagg.py b/lib/matplotlib/backends/backend_webagg.py
@@ -55,6 +55,24 @@ class FigureManagerWebAgg(core.FigureManagerWebAgg):
 class FigureCanvasWebAgg(core.FigureCanvasWebAggCore):
     manager_class = FigureManagerWebAgg
 
+    @classmethod
+    def pyplot_show(cls, *, block=None):
+        WebAggApplication.initialize()
+
+        url = "http://{address}:{port}{prefix}".format(
+            address=WebAggApplication.address,
+            port=WebAggApplication.port,
+            prefix=WebAggApplication.url_prefix)
+
+        if mpl.rcParams['webagg.open_in_browser']:
+            import webbrowser
+            if not webbrowser.open(url):
+                print("To view figure, visit {0}".format(url))
+        else:
+            print("To view figure, visit {0}".format(url))
+
+        WebAggApplication.start()
+
 
 class WebAggApplication(tornado.web.Application):
     initialized = False
@@ -305,21 +323,3 @@ def ipython_inline_display(figure):
 class _BackendWebAgg(_Backend):
     FigureCanvas = FigureCanvasWebAgg
     FigureManager = FigureManagerWebAgg
-
-    @staticmethod
-    def show(*, block=None):
-        WebAggApplication.initialize()
-
-        url = "http://{address}:{port}{prefix}".format(
-            address=WebAggApplication.address,
-            port=WebAggApplication.port,
-            prefix=WebAggApplication.url_prefix)
-
-        if mpl.rcParams['webagg.open_in_browser']:
-            import webbrowser
-            if not webbrowser.open(url):
-                print("To view figure, visit {0}".format(url))
-        else:
-            print("To view figure, visit {0}".format(url))
-
-        WebAggApplication.start()
diff --git a/lib/matplotlib/backends/backend_wx.py b/lib/matplotlib/backends/backend_wx.py
@@ -831,6 +831,13 @@ def _on_enter(self, event):
         event.Skip()
         FigureCanvasBase.enter_notify_event(self, guiEvent=event, xy=(x, y))
 
+    @classmethod
+    def start_main_loop(cls):
+        if not wx.App.IsMainLoopRunning():
+            wxapp = wx.GetApp()
+            if wxapp is not None:
+                wxapp.MainLoop()
+
 
 class FigureCanvasWx(_FigureCanvasWxBase):
     # Rendering to a Wx canvas using the deprecated Wx renderer.
@@ -1364,10 +1371,4 @@ def trigger(self, *args, **kwargs):
 class _BackendWx(_Backend):
     FigureCanvas = FigureCanvasWx
     FigureManager = FigureManagerWx
-
-    @staticmethod
-    def mainloop():
-        if not wx.App.IsMainLoopRunning():
-            wxapp = wx.GetApp()
-            if wxapp is not None:
-                wxapp.MainLoop()
+    mainloop = FigureCanvas.start_main_loop
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -310,6 +310,9 @@ def new_figure_manager(num, *args, FigureClass=Figure, **kwargs):
             new_figure_manager_given_figure
         backend_mod.new_figure_manager = new_figure_manager
 
+    if show is None:
+        backend_mod.show = canvas_class.pyplot_show
+
     _log.debug("Loaded backend %s version %s.",
                newbackend, backend_mod.backend_version)
 
diff --git a/lib/matplotlib/tests/test_backend_template.py b/lib/matplotlib/tests/test_backend_template.py
@@ -4,6 +4,7 @@
 
 import sys
 from types import SimpleNamespace
+from unittest.mock import MagicMock
 
 import matplotlib as mpl
 from matplotlib import pyplot as plt
@@ -21,3 +22,13 @@ def test_new_manager(monkeypatch):
     monkeypatch.setitem(sys.modules, "mpl_test_backend", mpl_test_backend)
     mpl.use("module://mpl_test_backend")
     assert type(plt.figure().canvas) == backend_template.FigureCanvasTemplate
+
+
+def test_show(monkeypatch):
+    mpl_test_backend = SimpleNamespace(**vars(backend_template))
+    mock_show = backend_template.FigureCanvasTemplate.pyplot_show = MagicMock()
+    del mpl_test_backend.show
+    monkeypatch.setitem(sys.modules, "mpl_test_backend", mpl_test_backend)
+    mpl.use("module://mpl_test_backend")
+    plt.show()
+    mock_show.assert_called_with()
