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Changed axis selection when zooming datalim-adjustable fixed-aspect axes #14899

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Changed axis selection when zooming datalim-adjustable fixed-aspect axes #14899

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69 changes: 28 additions & 41 deletions lib/matplotlib/axes/_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1898,55 +1898,42 @@ def apply_aspect(self, position=None):
box_aspect = fig_aspect * (position.height / position.width)
data_ratio = box_aspect / aspect

y_expander = data_ratio * xsize / ysize - 1
# If y_expander > 0, the dy/dx viewLim ratio needs to increase
if abs(y_expander) < 0.005:
y_expander = data_ratio * xsize / ysize
# If y_expander > 1, the dy/dx viewLim ratio needs to increase
if abs(y_expander - 1) < 0.005:
return

dL = self.dataLim
x0, x1 = x_trf.transform(dL.intervalx)
y0, y1 = y_trf.transform(dL.intervaly)
xr = 1.05 * (x1 - x0)
yr = 1.05 * (y1 - y0)

xmarg = xsize - xr
ymarg = ysize - yr
Ysize = data_ratio * xsize
Xsize = ysize / data_ratio
Xmarg = Xsize - xr
Ymarg = Ysize - yr
# Setting these targets to, e.g., 0.05*xr does not seem to help.
xm = 0
ym = 0

# What axes do we adjust?
# - We can't adjust shared axes because it's too easy to break sharing
# given the sequential handling of axes (that may be possible if we
# first collected all the constraints on all axes and considered them
# all at once).
# - Assuming no constraints from sharing, prefer expanding axes rather
# than shrinking them, as the latter can hide plot elements.
shared_x = self in self._shared_x_axes
shared_y = self in self._shared_y_axes
# Not sure whether we need this check:
if shared_x and shared_y:
raise RuntimeError("adjustable='datalim' is not allowed when both "
"axes are shared")

# If y is shared, then we are only allowed to change x, etc.
if shared_y:
adjust_y = False
else:
if xmarg > xm and ymarg > ym:
adjy = ((Ymarg > 0 and y_expander < 0) or
(Xmarg < 0 and y_expander > 0))
else:
adjy = y_expander > 0
adjust_y = shared_x or adjy # (Ymarg > xmarg)

if adjust_y:
yc = 0.5 * (ymin + ymax)
y0 = yc - Ysize / 2.0
y1 = yc + Ysize / 2.0
self.set_ybound(y_trf.inverted().transform([y0, y1]))
if shared_x:
adjust = "y"
elif shared_y:
adjust = "x"
elif y_expander > 1:
adjust = "y"
else: # y_expander < 1
adjust = "x"

if adjust == "y":
yc = (ymin + ymax) / 2
ymin = yc - (yc - ymin) * y_expander
ymax = yc + (ymax - yc) * y_expander
self.set_ybound(*map(y_trf.inverted().transform, (ymin, ymax)))
else:
xc = 0.5 * (xmin + xmax)
x0 = xc - Xsize / 2.0
x1 = xc + Xsize / 2.0
self.set_xbound(x_trf.inverted().transform([x0, x1]))
xc = (xmin + xmax) / 2
xmin = xc - (xc - xmin) / y_expander
xmax = xc + (xmax - xc) / y_expander
self.set_xbound(*map(x_trf.inverted().transform, (xmin, xmax)))

def axis(self, *args, emit=True, **kwargs):
"""
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7 changes: 7 additions & 0 deletions lib/matplotlib/tests/test_axes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5039,6 +5039,13 @@ def test_pie_frame_grid():
frame=True, center=(3, 5))
# Set aspect ratio to be equal so that pie is drawn as a circle.
plt.axis('equal')
plt.gcf().canvas.draw()
xmin, xmax = plt.xlim()
ymin, ymax = plt.ylim()
assert xmin < 0 and xmax > 7 and ymin == 0 and ymax == 7
# These limits reproduce an old, buggy implementation of axis("equal").
plt.xlim(0, 7)
plt.ylim(0.7903225806451615, 6.209677419354838)


@image_comparison(['pie_rotatelabels_true.png'])
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