Apr 15, 2021 · Apr 15, 2021
diff --git a/doc/users/next_whats_new/fig_draw_no_output.rst b/doc/users/next_whats_new/fig_draw_no_output.rst
 Figure now has draw_no_output method
 ------------------------------------

 Rarely, the user will want to trigger a draw without making output to
 either the screen or a file.  This is useful for determining the final
 position of artists on the figure that require a draw like text.
 This could be accomplished via ``fig.canvas.draw()`` but that is
 not user-facing, so a new method on `.Figure.draw_no_output` is provided.
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
 from matplotlib.artist import (
    Artist, allow_rasterization, _finalize_rasterization)
 from matplotlib.backend_bases import (
    FigureCanvasBase, NonGuiException, MouseButton)
    FigureCanvasBase, NonGuiException, MouseButton, _no_output_draw)
 import matplotlib._api as _api
 import matplotlib.cbook as cbook
 import matplotlib.colorbar as cbar

        self.canvas.draw_event(renderer)

    def draw_no_output(self):
        """
        Draw the figure with no output.  Useful to get the final size of
        artists that require a draw before their size is known (e.g. text).
        """
        _no_output_draw(self)

    def draw_artist(self, a):
        """
        Draw `.Artist` *a* only.
diff --git a/lib/matplotlib/tests/test_constrainedlayout.py b/lib/matplotlib/tests/test_constrainedlayout.py
        for gs in gsl:
            fig.add_subplot(gs)
        # need to trigger a draw to get warning
        fig.draw(fig.canvas.get_renderer())

        fig.draw_no_output()

 @image_comparison(['constrained_layout8.png'])
 def test_constrained_layout8():
    ax2 = ax.twinx()
    example_plot(ax)
    example_plot(ax2, fontsize=24)
    fig.canvas.draw()
    fig.draw_no_output()
    assert all(ax.get_position().extents == ax2.get_position().extents)


diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
 @pytest.mark.style('default')
 def test_change_dpi():
    fig = plt.figure(figsize=(4, 4))
    fig.canvas.draw()
    fig.draw_no_output()
    assert fig.canvas.renderer.height == 400
    assert fig.canvas.renderer.width == 400
    fig.dpi = 50
    fig.canvas.draw()
    fig.draw_no_output()
    assert fig.canvas.renderer.height == 200
    assert fig.canvas.renderer.width == 200
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,8 @@
		Figure now has draw_no_output method
		------------------------------------

		Rarely, the user will want to trigger a draw without making output to
		either the screen or a file. This is useful for determining the final
		position of artists on the figure that require a draw like text.
		This could be accomplished via ``fig.canvas.draw()`` but that is
		not user-facing, so a new method on `.Figure.draw_no_output` is provided.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -26,7 +26,7 @@
		from matplotlib.artist import (
		Artist, allow_rasterization, _finalize_rasterization)
		from matplotlib.backend_bases import (
		FigureCanvasBase, NonGuiException, MouseButton)
		FigureCanvasBase, NonGuiException, MouseButton, _no_output_draw)
		import matplotlib._api as _api
		import matplotlib.cbook as cbook
		import matplotlib.colorbar as cbar
Expand DownExpand Up		@@ -2739,6 +2739,13 @@ def draw(self, renderer):

		self.canvas.draw_event(renderer)

		def draw_no_output(self):
		"""
		Draw the figure with no output. Useful to get the final size of
		artists that require a draw before their size is known (e.g. text).
		"""
		_no_output_draw(self)

		def draw_artist(self, a):
		"""
		Draw `.Artist` a only.
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -134,8 +134,7 @@ def test_constrained_layout7():
		for gs in gsl:
		fig.add_subplot(gs)
		# need to trigger a draw to get warning
		fig.draw(fig.canvas.get_renderer())

		fig.draw_no_output()

		@image_comparison(['constrained_layout8.png'])
		def test_constrained_layout8():
Expand DownExpand Up		@@ -327,7 +326,7 @@ def test_constrained_layout18():
		ax2 = ax.twinx()
		example_plot(ax)
		example_plot(ax2, fontsize=24)
		fig.canvas.draw()
		fig.draw_no_output()
		assert all(ax.get_position().extents == ax2.get_position().extents)


Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -415,11 +415,11 @@ def test_autofmt_xdate(which):
		@pytest.mark.style('default')
		def test_change_dpi():
		fig = plt.figure(figsize=(4, 4))
		fig.canvas.draw()
		fig.draw_no_output()
		assert fig.canvas.renderer.height == 400
		assert fig.canvas.renderer.width == 400
		fig.dpi = 50
		fig.canvas.draw()
		fig.draw_no_output()
		assert fig.canvas.renderer.height == 200
		assert fig.canvas.renderer.width == 200

Expand Down