文本在*内*边界框内对齐

文本框的对齐方式可以通过horizontalalignment (ha) and verticalalignment (va) 参数，例如

import matplotlib.pyplot as plt
fig, ax = plt.subplots(figsize=(8,5))
plt.subplots_adjust(right=0.5)
txt = "Test:\nthis is some text\ninside a bounding box."
fig.text(0.7, 0.5, txt, ha='left', va='center')

其产生：

有没有办法保持相同的边界框（bbox）对齐，同时更改该边界框中文本的对齐方式？例如使文本在边界框中居中。

（显然在这种情况下我可以只替换边界框，但在更复杂的情况下我想独立更改文本对齐方式。）

确切的 bbox 取决于特定后端的渲染器。以下示例保留文本 bbox 的 x 位置。精确地保留 x 和 y 有点棘手：

import matplotlib
import matplotlib.pyplot as plt

def get_bbox(txt):
    renderer = matplotlib.backend_bases.RendererBase()
    return txt.get_window_extent(renderer)

fig, ax = plt.subplots(figsize=(8,5))
plt.subplots_adjust(right=0.5)
txt = "Test:\nthis is some text\ninside a bounding box."
text_inst = fig.text(0.7, 0.5, txt, ha='left', va='center')

bbox = get_bbox(text_inst)
bbox_fig = bbox.transformed(fig.transFigure.inverted())
print("original bbox (figure system)\t:", bbox.transformed(fig.transFigure.inverted()))

# adjust horizontal alignment
text_inst.set_ha('right')
bbox_new = get_bbox(text_inst)
bbox_new_fig = bbox_new.transformed(fig.transFigure.inverted())
print("aligned bbox\t\t\t:", bbox_new_fig)

# shift back manually
offset = bbox_fig.x0 - bbox_new_fig.x0
text_inst.set_x(bbox_fig.x0 + offset)
bbox_shifted = get_bbox(text_inst)
print("shifted bbox\t\t\t:", bbox_shifted.transformed(fig.transFigure.inverted()))
plt.show()

打印输出

original bbox (figure system)   : Bbox(x0=0.7000000000000001, y0=0.467946875, x1=0.84201171875, y1=0.532053125)
aligned bbox            : Bbox(x0=0.55798828125, y0=0.467946875, x1=0.7000000000000001, y1=0.532053125)
shifted bbox            : Bbox(x0=0.7000000000000002, y0=0.467946875, x1=0.8420117187500001, y1=0.532053125)