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Hint at draw_without_rendering() in Text.get_window_extent #22122

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Jan 6, 2022
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Hint at draw_without_rendering() in Text.get_window_extent #22122

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9 changes: 6 additions & 3 deletions lib/matplotlib/text.py
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Original file line number Diff line number Diff line change
Expand Up @@ -882,8 +882,9 @@ def get_window_extent(self, renderer=None, dpi=None):
A renderer is needed to compute the bounding box. If the artist
has already been drawn, the renderer is cached; thus, it is only
necessary to pass this argument when calling `get_window_extent`
before the first `draw`. In practice, it is usually easier to
trigger a draw first (e.g. by saving the figure).
before the first draw. In practice, it is usually easier to
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The draw link would go to Text.draw which is more or less an internal API and not helpful here (at worst the user might try and call that). It's better to not link to anything here.

trigger a draw first, e.g. by calling
`~.Figure.draw_without_rendering` or ``plt.show()``.
Comment on lines +886 to +887
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Saving is usually not a good way to trigger a draw in this case. You'll likely want to modify the figure somehow based on the extent.

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I'm 50/50 about including plt.show() as

plt.ion()
for j in range(5):
    fig, ax = plt.subplots()
    plt.show()
    sleep(5)

will not spin the GUI event loop (and hence in some cases not get the actual render to happen) until after the loop is done.

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OK, but 99.999% of cases, a draw will occur!


dpi : float, optional
The dpi value for computing the bbox, defaults to
Expand All @@ -904,7 +905,9 @@ def get_window_extent(self, renderer=None, dpi=None):
if self._renderer is None:
self._renderer = self.figure._cachedRenderer
if self._renderer is None:
raise RuntimeError('Cannot get window extent w/o renderer')
raise RuntimeError(
"Cannot get window extent of text w/o renderer. You likely "
"want to call 'figure.draw_without_rendering()' first.")

with cbook._setattr_cm(self.figure, dpi=dpi):
bbox, info, descent = self._get_layout(self._renderer)
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