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Fix the behavior of get_kerning to match FreeType's behavior #203

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Fix the behavior of get_kerning to match FreeType's behavior #203

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0dab63d
Fix the behavior of get_kerning to match the docs
ExplodingBottle Oct 21, 2025
b7e140f
Update the examples using get_kerning
ExplodingBottle Oct 21, 2025
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4 changes: 2 additions & 2 deletions examples/hello-vf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@
height = max(height,
bitmap.rows + max(0,-(slot.bitmap_top-bitmap.rows)))
baseline = max(baseline, max(0,-(slot.bitmap_top-bitmap.rows)))
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
width += (slot.advance.x >> 6) + (kerning.x >> 6)
previous = c

Expand All @@ -48,7 +48,7 @@
left = slot.bitmap_left
w,h = bitmap.width, bitmap.rows
y = (height - baseline - top) - (i * 48)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
x += (kerning.x >> 6)
Z[y:y+h,x+left:x+left+w] += numpy.array(bitmap.buffer, dtype='ubyte').reshape(h,w)
x += (slot.advance.x >> 6)
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4 changes: 2 additions & 2 deletions examples/hello-world-cairo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@
height = max(height,
bitmap.rows + max(0,-(slot.bitmap_top-bitmap.rows)))
baseline = max(baseline, max(0,-(slot.bitmap_top-bitmap.rows)))
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
width += (slot.advance.x >> 6) + (kerning.x >> 6)
previous = c

Expand All @@ -47,7 +47,7 @@
left = slot.bitmap_left
w,h = bitmap.width, bitmap.rows
y = height-baseline-top
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
x += (kerning.x >> 6)
# cairo does not like zero-width bitmap from the space character!
if (bitmap.width > 0):
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4 changes: 2 additions & 2 deletions examples/hello-world.py
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@
bitmap = slot.bitmap
top = max(top, slot.bitmap_top)
bot = min(bot, slot.bitmap_top - bitmap.rows)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
width += (slot.advance.x >> 6) + (kerning.x >> 6)
previous = c

Expand All @@ -43,7 +43,7 @@
bitmap = slot.bitmap
w,h = bitmap.width, bitmap.rows
y = top - slot.bitmap_top
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
x += (kerning.x >> 6)
Z[y:y+h,x+left:x+left+w] += numpy.array(bitmap.buffer, dtype='ubyte').reshape(h,w)
x += (slot.advance.x >> 6)
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4 changes: 2 additions & 2 deletions examples/texture_font.py
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Original file line number Diff line number Diff line change
Expand Up @@ -359,10 +359,10 @@ def load(self, charcodes = ''):
for g in self.glyphs.values():
# 64 * 64 because of 26.6 encoding AND the transform matrix used
# in texture_font_load_face (hres = 64)
kerning = face.get_kerning(g.charcode, charcode, mode=FT_KERNING_UNFITTED)
kerning = face.get_kerning(face.get_char_index(g.charcode), face.get_char_index(charcode), mode=FT_KERNING_UNFITTED)
if kerning.x != 0:
glyph.kerning[g.charcode] = kerning.x/(64.0*64.0)
kerning = face.get_kerning(charcode, g.charcode, mode=FT_KERNING_UNFITTED)
kerning = face.get_kerning(face.get_char_index(charcode), face.get_char_index(g.charcode), mode=FT_KERNING_UNFITTED)
if kerning.x != 0:
g.kerning[charcode] = kerning.x/(64.0*64.0)

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4 changes: 2 additions & 2 deletions examples/wordle-cairo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ def make_label(text, filename, size=12, angle=0):
ymin, ymax = 0, 0
for c in text:
face.load_char(c, flags)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
previous = c
bitmap = face.glyph.bitmap
pitch = face.glyph.bitmap.pitch
Expand All @@ -91,7 +91,7 @@ def make_label(text, filename, size=12, angle=0):
ctx = Context(L)
for c in text:
face.load_char(c, flags)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
previous = c
bitmap = face.glyph.bitmap
pitch = face.glyph.bitmap.pitch
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4 changes: 2 additions & 2 deletions examples/wordle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ def make_label(text, filename, size=12, angle=0):
ymin, ymax = 0, 0
for c in text:
face.load_char(c, flags)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
previous = c
bitmap = face.glyph.bitmap
pitch = face.glyph.bitmap.pitch
Expand All @@ -63,7 +63,7 @@ def make_label(text, filename, size=12, angle=0):
pen.x, pen.y = 0, 0
for c in text:
face.load_char(c, flags)
kerning = face.get_kerning(previous, c)
kerning = face.get_kerning(face.get_char_index(previous), face.get_char_index(c))
previous = c
bitmap = face.glyph.bitmap
pitch = face.glyph.bitmap.pitch
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4 changes: 1 addition & 3 deletions freetype/__init__.py
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Expand Up @@ -1591,11 +1591,9 @@ def get_kerning( self, left, right, mode = FT_KERNING_DEFAULT ):
of the scope of this API function -- they can be implemented through
format-specific interfaces.
'''
left_glyph = self.get_char_index( left )
right_glyph = self.get_char_index( right )
kerning = FT_Vector(0,0)
error = FT_Get_Kerning( self._FT_Face,
left_glyph, right_glyph, mode, byref(kerning) )
left, right, mode, byref(kerning) )
if error: raise FT_Exception( error )
return kerning

Expand Down
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