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[varLib] Tweak support-resolution algorithm

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Improve varLib model algorithm.

This, basically means any varfont built that had an unusual master
configuration will change when rebuilt.

Here's a good test: a two-axis with 8 masters at unusual locations:

2-----------------5----------3
|                            |
|                    7       |
|                            |
|              6             |
|                            |
|                            |
|                            |
0-----------4----------------1

Previously, the reach of master 3 (Black Extended) would
have started from A=.4, ie, the A position of master 4.
It now correctly starts from 0. Same thing with masters
after it. Ie, master 5 gets a span on the A axis from
0 to 1, whereas before it was getting from .4 to 1.

Previously, the on-axis masters always cut the space. They
don't anymore. That's more consistent, and fixes the main
issue Erik showed at TYPO Labs 2017.  Same issue was also
causing the reach of master 3 to be limited, which I think
is the issue being discussed in the linked issue. Both should
be fixed.

It's hard to describe exactly what happened before / after.
Best to read the actual support values:

Before:
Sorted locations:
$ ./fonttools varLib.models 0,0 0,1 1,0 1,1 .4,0 .6,1 .5,.5 .7,.7
[{},
 {'A': 0.4},
 {'A': 1.0},
 {'B': 1.0},
 {'A': 1.0, 'B': 1.0},
 {'A': 0.6, 'B': 1.0},
 {'A': 0.5, 'B': 0.5},
 {'A': 0.7, 'B': 0.7}]
Supports:
[{},
 {'A': (0.0, 0.4, 1.0)},
 {'A': (0.4, 1.0, 1.0)},
 {'B': (0.0, 1.0, 1.0)},
 {'A': (0.4, 1.0, 1.0), 'B': (0.0, 1.0, 1.0)},
 {'A': (0.4, 0.6, 1.0), 'B': (0.0, 1.0, 1.0)},
 {'A': (0.4, 0.5, 1.0), 'B': (0.0, 0.5, 1.0)},
 {'A': (0.5, 0.7, 1.0), 'B': (0.5, 0.7, 1.0)}]

After:
$ ./fonttools varLib.models 0,0 0,1 1,0 1,1 .4,0 .6,1 .5,.5 .7,.7
Sorted locations:
[{},
 {'A': 0.4},
 {'A': 1.0},
 {'B': 1.0},
 {'A': 1.0, 'B': 1.0},
 {'A': 0.6, 'B': 1.0},
 {'A': 0.5, 'B': 0.5},
 {'A': 0.7, 'B': 0.7}]
Supports:
[{},
 {'A': (0, 0.4, 1.0)},
 {'A': (0.4, 1.0, 1.0)},
 {'B': (0, 1.0, 1.0)},
 {'A': (0, 1.0, 1.0), 'B': (0, 1.0, 1.0)},
 {'A': (0, 0.6, 1.0), 'B': (0, 1.0, 1.0)},
 {'A': (0, 0.5, 1.0), 'B': (0, 0.5, 1.0)},
 {'A': (0.5, 0.7, 1.0), 'B': (0.5, 0.7, 1.0)}]

TODO: We should add this as a test case.

There's another improvement I want to make, but that's separate.
This commit is contained in:
Behdad Esfahbod 2018-03-26 20:31:06 -07:00
parent 05e2ec4d3a
commit 42bef176a3
2 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
Lib/fontTools/varLib/models.py
View File

@ -152,12 +152,12 @@ class VariationModel(object):
{0: 1.0},
{0: 1.0},
{0: 1.0, 4: 1.0, 5: 1.0},
{0: 1.0, 3: 0.75, 4: 0.25, 5: 1.0, 6: 0.25},
{0: 1.0, 3: 0.75, 4: 0.25, 5: 1.0, 6: 0.6666666666666666},
{0: 1.0,
3: 0.75,
4: 0.25,
5: 0.6666666666666667,
6: 0.16666666666666669,
6: 0.4444444444444445,
7: 0.6666666666666667}]
"""
@ -233,7 +233,10 @@ class VariationModel(object):
if not axis in loc:
continue
locV = loc[axis]
box[axis] = (self.lowerBound(locV, values), locV, self.upperBound(locV, values))
if locV > 0:
box[axis] = (0, locV, max({locV}|values))
else:
box[axis] = (min({locV}|values), locV, 0)
locAxes = set(loc.keys())
# Walk over previous masters now
@ -244,7 +247,7 @@ class VariationModel(object):
# If it's NOT in the current box, it does not participate
relevant = True
for axis, (lower,_,upper) in box.items():
if axis in m and not (lower < m[axis] < upper):
if axis not in m or not (lower < m[axis] < upper):
relevant = False
break
if not relevant:

4
Tests/varLib/models_test.py
View File

@ -68,10 +68,10 @@ def test_VariationModel():
{0: 1.0},
{0: 1.0},
{0: 1.0, 4: 1.0, 5: 1.0},
{0: 1.0, 3: 0.75, 4: 0.25, 5: 1.0, 6: 0.25},
{0: 1.0, 3: 0.75, 4: 0.25, 5: 1.0, 6: 0.6666666666666666},
{0: 1.0,
3: 0.75,
4: 0.25,
5: 0.6666666666666667,
6: 0.16666666666666669,
6: 0.4444444444444445,
7: 0.6666666666666667}]