8000 [_g_l_y_f] fix float precision loss in GlyphCoordinates by anthrotype · Pull Request #964 · fonttools/fonttools · GitHub
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[_g_l_y_f] fix float precision loss in GlyphCoordinates #964

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Merged
merged 2 commits into from
May 16, 2017
Merged

[_g_l_y_f] fix float precision loss in GlyphCoordinates #964

merged 2 commits into from
May 16, 2017

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anthrotype
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This failing test is to show the issue #963.
The patch below fixes it.

I don't see problems with changing GlyphCoordinates to using doubles instead of floats, but I'd like to hear from others before committing the change in case I may be missing something.

diff --git a/Lib/fontTools/ttLib/tables/_g_l_y_f.py b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
index 1e255506..b4586e39 100644
--- a/Lib/fontTools/ttLib/tables/_g_l_y_f.py
+++ b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
@@ -1170,13 +1170,13 @@ class GlyphCoordinates(object):
 		return self._a
 
 	def isFloat(self):
-		return self._a.typecode == 'f'
+		return self._a.typecode == 'd'
 
 	def _ensureFloat(self):
 		if self.isFloat():
 			return
 		# The conversion to list() is to work around Jython bug
-		self._a = array.array("f", list(self._a))
+		self._a = array.array("d", list(self._a))
 
 	def _checkFloat(self, p):
 		if self.isFloat():

@anthrotype
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1c9198e failed:
https://travis-ci.org/fonttools/fonttools/jobs/232755422#L2538

71486bc passed:
https://travis-ci.org/fonttools/fonttools/jobs/232759516#L1264

(the other 5 test failures are unrelated)

@behdad
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behdad commented May 16, 2017

LGTM.

@anthrotype
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thanks

@anthrotype anthrotype merged commit ced61f7 into fonttools:master May 16, 2017
@anthrotype anthrotype deleted the coords-as-double branch May 16, 2017 16:16
@behdad
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behdad commented Apr 7, 2021

We now do rounding before serializing to tables. Should we consider changing back to float?

behdad added a commit that referenced this pull request Apr 7, 2021
@behdad
[GlyphCoordinates] Revert back from double to float
1d38580 
We do proper rounding these days, so revert this back.

#964 (comment)
behdad added a commit that referenced this pull request Apr 8, 2021
@behdad
[GlyphCoordinates] Revert back from double to float
3e9cc7f 
We do proper rounding these days, so revert this back.

#964 (comment)
behdad added a commit that referenced this pull request Apr 8, 2021
@behdad
[GlyphCoordinates] Revert back from double to float
83496b4 
We do proper rounding these days, so revert this back.

#964 (comment)
behdad added a commit that referenced this pull request Apr 8, 2021
@behdad
[GlyphCoordinates] Revert back from double to float
f6e8577 
We do proper rounding these days, so revert this back.

#964 (comment)
simoncozens pushed a commit to simoncozens/fonttools that referenced this pull request Oct 22, 2021
@behdad @simoncozens
[GlyphCoordinates] Revert back from double to float 65B3
e06a884 
We do proper rounding these days, so revert this back.

fonttools#964 (comment)
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@anthrotype @behdad
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