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FIX: when creating a canvas from a Figure use original dpi #30750

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Merged
ksunden merged 2 commits into from
Dec 11, 2025
+10 −8
Merged

FIX: when creating a canvas from a Figure use original dpi #30750

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c0041fb
FIX: when creating a canvas from a Figure use original dpi
tacaswell Nov 13, 2025
973c99e
FIX: correctly restore the size of unpickled figures with hi-dpi
tacaswell Nov 14, 2025
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2 changes: 1 addition & 1 deletion lib/matplotlib/backend_bases.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1763,7 +1763,7 @@ def __init__(self, figure=None):
self.toolbar = None # NavigationToolbar2 will set me
self._is_idle_drawing = False
# We don't want to scale up the figure DPI more than once.
figure._original_dpi = figure.dpi
figure._original_dpi = getattr(figure, '_original_dpi', figure.dpi)
self._device_pixel_ratio = 1
super().__init__() # Typically the GUI widget init (if any).

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13 changes: 6 additions & 7 deletions lib/matplotlib/figure.py
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Expand Up @@ -3003,12 +3003,10 @@ def _set_base_canvas(self):
This is used upon initialization of the Figure, but also
to reset the canvas when decoupling from pyplot.
"""
# check if we have changed the DPI due to hi-dpi screens
orig_dpi = getattr(self, '_original_dpi', self._dpi)
FigureCanvasBase(self) # Set self.canvas as a side-effect
# put it back to what it was
if orig_dpi != self._dpi:
self.dpi = orig_dpi
# undo any high-dpi scaling
if self._dpi != self._original_dpi:
self.dpi = self._original_dpi

def set_canvas(self, canvas):
"""
Expand Down Expand Up @@ -3323,8 +3321,9 @@ def __setstate__(self, state):
self.__dict__ = state

# re-initialise some of the unstored state information
FigureCanvasBase(self) # Set self.canvas.

self._set_base_canvas()
# force the bounding boxes to respect current dpi
self.dpi_scale_trans.clear().scale(self._dpi)
if restore_to_pylab:
# lazy import to avoid circularity
import matplotlib.pyplot as plt
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3 changes: 3 additions & 0 deletions lib/matplotlib/tests/test_figure.py
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Expand Up @@ -1688,6 +1688,9 @@ def test_unpickle_with_device_pixel_ratio():
assert fig.dpi == 42*7
fig2 = pickle.loads(pickle.dumps(fig))
assert fig2.dpi == 42
assert all(
[orig / 7 == restore for orig, restore in zip(fig.bbox.max, fig2.bbox.max)]
)


def test_gridspec_no_mutate_input():
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