ft2font: Add internal API for accessing font variations#31434
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QuLogic wants to merge 1 commit intomatplotlib:text-overhaulfrom
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ft2font: Add internal API for accessing font variations#31434QuLogic wants to merge 1 commit intomatplotlib:text-overhaulfrom
QuLogic wants to merge 1 commit intomatplotlib:text-overhaulfrom
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As an example, one can look at Roboto Flex, which has 13 axes (though more than half are hidden): >>> from matplotlib.ft2font import FT2Font
>>> font = FT2Font('RobotoFlex-VariableFont.ttf')
>>> axes, styles = font.get_variation_descriptor()
>>> for axis in axes:
... print(axis)
VariationAxis(name='OpticalSize', minimum=8, default=14, maximum=144, tag=1869640570, names={(3, 1, 1033): 'Optical Size'}, flags=VarAxisFlags.DEFAULT)
VariationAxis(name='Weight', minimum=100, default=400, maximum=1000, tag=2003265652, names={(3, 1, 1033): 'Weight'}, flags=VarAxisFlags.DEFAULT)
VariationAxis(name='GRAD', minimum=-200, default=0, maximum=150, tag=1196572996, names={(3, 1, 1033): 'Grade'}, flags=VarAxisFlags.DEFAULT)
VariationAxis(name='Width', minimum=25, default=100, maximum=151, tag=2003072104, names={(3, 1, 1033): 'Width'}, flags=VarAxisFlags.DEFAULT)
VariationAxis(name='Slant', minimum=-10, default=0, maximum=0, tag=1936486004, names={(3, 1, 1033): 'Slant'}, flags=VarAxisFlags.DEFAULT)
VariationAxis(name='XOPQ', minimum=27, default=96, maximum=175, tag=1481592913, names={(3, 1, 1033): 'Parametric Thick Stroke'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YOPQ', minimum=25, default=79, maximum=135, tag=1498370129, names={(3, 1, 1033): 'Parametric Thin Stroke'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='XTRA', minimum=323, default=468, maximum=603, tag=1481921089, names={(3, 1, 1033): 'Parametric Counter Width'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YTUC', minimum=528, default=712, maximum=760, tag=1498699075, names={(3, 1, 1033): 'Parametric Uppercase Height'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YTLC', minimum=416, default=514, maximum=570, tag=1498696771, names={(3, 1, 1033): 'Parametric Lowercase Height'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YTAS', minimum=649, default=750, maximum=854, tag=1498693971, names={(3, 1, 1033): 'Parametric Ascender Height'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YTDE', minimum=-305, default=-203, maximum=-98, tag=1498694725, names={(3, 1, 1033): 'Parametric Descender Depth'}, flags=VarAxisFlags.HIDDEN)
VariationAxis(name='YTFI', minimum=560, default=738, maximum=788, tag=1498695241, names={(3, 1, 1033): 'Parametric Figure Height'}, flags=VarAxisFlags.HIDDEN)
>>> for style in styles:
... print(style)
VariationNamedStyle(names={(3, 1, 1033): 'Thin'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraLight'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Light'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Regular'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Medium'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'SemiBold'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Bold'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraBold'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Black'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraBlack'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Thin Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraLight Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Light Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Medium Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'SemiBold Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Bold Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraBold Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'Black Italic'}, psnames=None)
VariationNamedStyle(names={(3, 1, 1033): 'ExtraBlack Italic'}, psnames=None)
>>> font.get_default_variation_style()
4
>>> font.get_variations()
[14.0, 400.0, 0.0, 100.0, 0.0, 96.0, 79.0, 468.0, 712.0, 514.0, 750.0, -203.0, 738.0]
>>> font.set_variations([i + 20 for i in font.get_variations()]) # Change all variation axes.
>>> font.get_variations()
[34.0, 420.0, 20.0, 120.0, 20.0, 116.0, 99.0, 488.0, 732.0, 534.0, 770.0, -183.0, 758.0]
>>> font.set_variations(11) # This is Thin Italic (it appears to be 1-based index; we may want to change that)
>>> font.get_variations()
[14.0, 100.0, 0.0, 100.0, -10.0, 96.0, 79.0, 468.0, 712.0, 514.0, 750.0, -203.0, 738.0] # Now [1] (weight) is 100 and [4] (slant) is -10You can see an example of using these font variations in mplcairo. Note that mplcairo uses the suffix-the-filename approach that was also used for font features. We likely won't do that here since we didn't do that for font features either. mplcairo calls Cairo's |
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PR summary
This is internal API for querying font variations and setting them. FreeType sometimes calls them MM (multiple master) vars or variation axes, but I tried to stick to variations/variation axis. For the named styles, FreeType sometimes calls that a named style or a named instance, and I tried to use named style everywhere.
Font variations essentially allow fonts to have multiple styles in one by varying some parameter along an "Axis". For example, one font can contain all weights with a Weight axis ranging from Thin to Extra Bold, or an upright and italic font with a Slant axis for the angle. Some fonts may contain named styles which group some specific settings together under a a name (e.g., Bold may be Weight=700 or whatever the designer decides.)
Current internal API additions are:
FT2Font.get_variation_descriptorwhich returns a list of the variation axes and a list of the named styles.FT2Font.get_default_variation_stylewhich returns the index of the default name style (in the above list.)FT2Font.get_variationswhich returns the float values for each axis (in the order of the above list.)FT2Font.set_variationswhich allows setting the float values for each axis as a list, or selecting a named style by index.This does not contain any public API; for that there are some questions that we might need to think about:
Text.set_fontvariationsand/orFontProperties.set_variations?I do not expect this to be ready for 3.11 until we discuss some of these options.
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