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font-patcher: Fix scaleGlyph related rounding error

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[why]
Sometimes the patched-in symbols are slightly too big, which shows up in
Nerd Font Mono fonts where the destination size is specified exactly.

That issues a warning like:
  Warning: Scaled glyph U+F077 wider than one monospace width

[how]
For the scaleGlyph groups we need to combine the bounding boxes of
several symbol glyphs to determine the 'combined' scale we need.
Unfortunately when the concrete glyph is finally copied over its size
can change minimally.

So we need to measure the glyphs in the scaleGroup _after_ they have
been copied to the to-be-patched font. This is a bit complicated,
because we need to know some glyph slot we can use for that.

[note]
See also commit
  e805b879  font-patcher: Resolve rounding error when rescaling

Fixes: #917

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>
This commit is contained in:
Fini Jastrow 2022-09-08 17:09:58 +02:00 committed by Fini
parent 67aa453436
commit 983226a70e
1 changed files with 15 additions and 5 deletions
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20
font-patcher
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@ -1161,7 +1161,7 @@ class font_patcher:
except:
pass
def prepareScaleGlyph(self, scaleGlyph, symbolFont):
def prepareScaleGlyph(self, scaleGlyph, symbolFont, destGlyph):
""" Prepare raw ScaleGlyph data for use """
# The GlyphData is a dict with these (possible) entries:
# 'GlyphsToScale': List of ((lists of glyph codes) or (ranges of glyph codes)) that shall be scaled
@ -1196,13 +1196,14 @@ class font_patcher:
else:
scaleGlyph['scales'] = []
for group in scaleGlyph['GlyphsToScale']:
sym_dim = get_multiglyph_boundingBox([ symbolFont[g] if g in symbolFont else None for g in group ])
sym_dim = get_multiglyph_boundingBox([ symbolFont[g] if g in symbolFont else None for g in group ], destGlyph)
scaleGlyph['scales'].append(self.get_scale_factor(sym_dim))
def get_glyph_scale(self, unicode_value, scaleGlyph, symbolFont):
""" Determines whether or not to use scaled glyphs for glyphs in passed glyph_list """
# Potentially destorys the contents of self.sourceFont[unicode_value]
if not 'scales' in scaleGlyph:
self.prepareScaleGlyph(scaleGlyph, symbolFont)
self.prepareScaleGlyph(scaleGlyph, symbolFont, self.sourceFont[unicode_value])
for glyph_list, scale in zip(scaleGlyph['GlyphsToScale'], scaleGlyph['scales']):
if unicode_value in glyph_list:
return scale
@ -1224,13 +1225,22 @@ def make_sure_path_exists(path):
if exception.errno != errno.EEXIST:
raise
def get_multiglyph_boundingBox(glyphs):
""" Returns dict of the dimensions of multiple glyphs combined """
def get_multiglyph_boundingBox(glyphs, destGlyph = None):
""" Returns dict of the dimensions of multiple glyphs combined(, as if they are copied into destGlyph) """
# If destGlyph is given the glyph(s) are first copied over into that
# glyph and measured in that font (to avoid rounding errors)
# Leaves the destGlyph in unknown state!
bbox = [ None, None, None, None ]
for glyph in glyphs:
if glyph is None:
# Glyph has been in defining range but is not in the actual font
continue
if destGlyph:
glyph.font.selection.select(glyph)
glyph.font.copy()
destGlyph.font.selection.select(destGlyph)
destGlyph.font.paste()
glyph = destGlyph
gbb = glyph.boundingBox()
bbox[0] = gbb[0] if bbox[0] is None or bbox[0] > gbb[0] else bbox[0]
bbox[1] = gbb[1] if bbox[1] is None or bbox[1] > gbb[1] else bbox[1]