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Don't fallback to agg in tight_layout.get_renderer. #15221

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Merged
merged 1 commit into from
May 26, 2020
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Don't fallback to agg in tight_layout.get_renderer. #15221

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9 changes: 6 additions & 3 deletions lib/matplotlib/backend_bases.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1501,7 +1501,7 @@ def __init__(self, name, canvas, key, x=0, y=0, guiEvent=None):
self.key = key


def _get_renderer(figure, print_method, *, draw_disabled=False):
def _get_renderer(figure, print_method=None, *, draw_disabled=False):
"""
Get the renderer that would be used to save a `~.Figure`, and cache it on
the figure.
Expand All @@ -1520,8 +1520,11 @@ class Done(Exception):
def _draw(renderer): raise Done(renderer)

with cbook._setattr_cm(figure, draw=_draw):
if print_method is None:
fmt = figure.canvas.get_default_filetype()
print_method = getattr(figure.canvas, f"print_{fmt}")
try:
print_method(io.BytesIO())
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dpi was many other things than figure.dpi in my quick skim of the code below, so is it really OK to use figure.dpi here? I'll block because I think this should be answered, but anyone should clear if this is really not a problem. I haven't looked carefully yet.

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If _get_renderer is called from print_figure(), then figure.dpi has already been set to match the requested savefig dpi (cbook._setattr_cm(self.figure, dpi=dpi)), so setting it a second time is a noop. If called from tight_layout.get_renderer, OTOH, we do need to pass in the figure dpi -- otherwise it's savefig.dpi which gets used, which is not correct when we want to tight-layout something not for the purpose of saving it.

print_method(io.BytesIO(), dpi=figure.dpi)
except Done as exc:
renderer, = figure._cachedRenderer, = exc.args

Expand Down Expand Up @@ -2089,7 +2092,7 @@ def print_figure(
renderer = _get_renderer(
self.figure,
functools.partial(
print_method, dpi=dpi, orientation=orientation),
print_method, orientation=orientation),
draw_disabled=True)
self.figure.draw(renderer)
bbox_inches = self.figure.get_tightbbox(
Expand Down
15 changes: 15 additions & 0 deletions lib/matplotlib/tests/test_tightlayout.py
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Expand Up @@ -310,3 +310,18 @@ def test_suptitle():
t = ax.set_title("bar")
fig.canvas.draw()
assert st.get_window_extent().y0 > t.get_window_extent().y1


@pytest.mark.backend("pdf")
def test_non_agg_renderer(monkeypatch, recwarn):
unpatched_init = mpl.backend_bases.RendererBase.__init__

def __init__(self, *args, **kwargs):
# Check that we don't instantiate any other renderer than a pdf
# renderer to perform pdf tight layout.
assert isinstance(self, mpl.backends.backend_pdf.RendererPdf)
unpatched_init(self, *args, **kwargs)

monkeypatch.setattr(mpl.backend_bases.RendererBase, "__init__", __init__)
fig, ax = plt.subplots()
fig.tight_layout()
15 changes: 5 additions & 10 deletions lib/matplotlib/tight_layout.py
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Expand Up @@ -166,19 +166,14 @@ def auto_adjust_subplotpars(

def get_renderer(fig):
if fig._cachedRenderer:
renderer = fig._cachedRenderer
return fig._cachedRenderer
else:
canvas = fig.canvas

if canvas and hasattr(canvas, "get_renderer"):
renderer = canvas.get_renderer()
else: # Some noninteractive backends have no renderer until draw time.
cbook._warn_external("tight_layout: falling back to Agg renderer")
from matplotlib.backends.backend_agg import FigureCanvasAgg
canvas = FigureCanvasAgg(fig)
renderer = canvas.get_renderer()

return renderer
return canvas.get_renderer()
else:
from . import backend_bases
return backend_bases._get_renderer(fig, draw_disabled=True)


def get_subplotspec_list(axes_list, grid_spec=None):
Expand Down