`Text.set_font` now performs a partial update for string arguments#

Text.set_font previously behaved identically to Text.set_fontproperties: passing a string caused all font properties (size, weight, style, etc.) to be reset to their defaults. This was surprising given that all other``set_font*`` methods (set_fontfamily, set_fontsize, set_fontweight, ...) update only the property they describe.

Starting with this release set_font performs a partial update when given a string:

The string is interpreted as a fontconfig pattern (same syntax as before).
Only the properties explicitly named in the pattern are changed.
All other font properties (size, weight, style, ...) are preserved.

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
t1 = ax.text(0.5, 0.5, "Hello", fontsize=20, fontweight="bold")
t2 = ax.text(0.5, 0.7, "Hello", fontsize=20, fontweight="bold")

# Example 1: Set family name:
t1.set_font("DejaVu Serif")
# Old behaviour: size and weight would be reset to defaults.
# New behaviour: only the family is updated; size=20 and bold weight are kept.

# Example 2: Set fontconfig pattern with multiple properties:
t2.set_font("DejaVu Serif:italic:size=14")
# - Old behaviour: weight would be reset to defaults.
# - New behaviour: family, italics, and size are updated, but bold weight is kept.

For a complete replacement of all font properties (i.e. the previous behaviour) use Text.set_fontproperties

t.set_fontproperties("DejaVu Serif")   # resets all other properties

Text.set_font now performs a partial update for string arguments#

`Text.set_font` now performs a partial update for string arguments#