shadowfacts/fonttools
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Docs: add an explanation of ttGlyphSet glyphs.

Browse Source
This commit is contained in:
Nathan Williis 2024-12-07 16:34:53 +00:00
parent 3584705ea2
commit 97d11e0c92
1 changed files with 50 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
Doc/source/ttLib/ttFont.rst
View File

@ -21,10 +21,56 @@ font file, or it may be a member of a
constructed from scratch.
In addition to font-wide data, :mod:`.ttLib.ttFont` provides access to
individual glyphs through the :class:`.TTFont` object's
``glyphSet[]``. This is a dict-like object that is indexed by glyph
names. Users can use the glyphSet to interact with each glyph's
contours, components, points, and glyph metrics.
individual glyphs through a :class:`.TTFont` instance's
``glyphSet[]`` attribute. A ``glyphSet`` is a dict-like object that is
indexed by glyph names. Users can use the glyphSet to interact with
each glyph's contours, components, points, and glyph metrics.
ttGlyphs
--------
Informally, some fontTools code or documentation will make reference to
the individual glyphs in a ``glyphSet`` as a "ttGlyph" or the
like. This is convenient terminology, particularly for
discussion. However, it is important to note that there is not a
"ttGlyph" class. Instead, the ``glyphSet`` attribute of a
:class:`.TTFont` serves as an abstraction layer that provides a
uniform interface to the glyphs, regardless of whether the
:class:`.TTFont` instance in use comes from a font file with
TrueType-flavored glyphs (and, therefore, has a `glyf` table
containing glyph contours) or a font with PostScript-flavored outlines
(and, therefore, with a ``CFF`` or ``CFF2`` table containing the glyph
contours).
Regardless of the flavor, each "ttGlyph" entry in the ``glyphSet``
includes the corresponding Bezier outlines and components from the
``glyf`` or ``CFF``/``CFF2`` table and the glyph's metrics. Horizontal
metrics are drawn from the font's ``hmtx`` table, and vertical metrics
(if any) are drawn from the ``vmtx`` table. These attributes are:
width
The advance width of the glyph
lsb
The left sidebearing of the glyph
height
(For vertical-layout fonts) The advance height of the glyph
tsb
(for vertical-layout fonts) The top sidebearing of the glyph
Note that these attributes do not describe the bounding box of the
glyph filled shape, because the filled area might include negative
coordinate values or extend beyond the advance width due to overhang.
The bounds of the glyph are accessible as ``xMin``, ``xMax``,
``yMin``, and ``yMax`` attributes.
For implementation details regarding the different flavors of
"ttGlyph", see the :doc:`ttGlyphSet </ttLib/ttGlyphSet>`
documentation.
These glyph objects also implement the :doc:`Pen Protocol
</pens/index>` by providing ``.draw()`` and ``.drawPoints()``