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[instancer-solver] Port optimization from upstream

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Fixes https://github.com/harfbuzz/harfbuzz/issues/4291
This commit is contained in:
Behdad Esfahbod 2023-06-21 17:54:49 -06:00
parent 197bb35972
commit 244f3224b9
2 changed files with 103 additions and 72 deletions
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169
src/hb-subset-instancer-solver.cc
View file

@ -230,82 +230,115 @@ _solve (Triple tent, Triple axisLimit, bool negative = false)
}
}
/* Case 3: Outermost limit still fits within F2Dot14 bounds;
* we keep deltas as is and only scale the axes bounds. Deltas beyond -1.0
* or +1.0 will never be applied as implementations must clamp to that range.
*
* A second tent is needed for cases when gain is positive, though we add it
* unconditionally and it will be dropped because scalar ends up 0.
*
* TODO: See if we can just move upper closer to adjust the slope, instead of
* second tent.
*
* | peak |
* 1.........|............o...|..................
* | /x\ |
* | /xxx\ |
* | /xxxxx\|
* | /xxxxxxx+
* | /xxxxxxxx|\
* 0---|-----|------oxxxxxxxxx|xo---------------1
* axisMin | lower | upper
* | |
* axisDef axisMax
*/
else if (axisDef + (axisMax - axisDef) * 2 >= upper)
else
{
if (!negative && axisDef + (axisMax - axisDef) * MAX_F2DOT14 < upper)
{
// we clamp +2.0 to the max F2Dot14 (~1.99994) for convenience
upper = axisDef + (axisMax - axisDef) * MAX_F2DOT14;
assert (peak < upper);
}
// Special-case if peak is at axisMax.
if (axisMax == peak)
upper = peak;
Triple loc1 {hb_max (axisDef, lower), peak, upper};
float scalar1 = 1.f;
/* Case pre3:
* we keep deltas as is and only scale the axis upper to achieve
* the desired new tent if feasible.
*
* | peak |
* 1.........|............o...|..................
* | /x\ |
* | /xxx\ |
* | /xxxxx\|
* | /xxxxxxx+
* | /xxxxxxxx|\
* 0---|-----|------oxxxxxxxxx|xo---------------1
* axisMin | lower | upper
* | |
* axisDef axisMax
*/
float newUpper = peak + (1 - gain) * (upper - peak);
if (axisMax <= newUpper && newUpper <= axisDef + (axisMax - axisDef) * 2)
{
upper = newUpper;
if (!negative && axisDef + (axisMax - axisDef) * MAX_F2DOT14 < upper)
{
// we clamp +2.0 to the max F2Dot14 (~1.99994) for convenience
upper = axisDef + (axisMax - axisDef) * MAX_F2DOT14;
assert (peak < upper);
}
Triple loc2 {peak, upper, upper};
float scalar2 = 0.f;
Triple loc {hb_max (axisDef, lower), peak, upper};
float scalar = 1.f;
// Don't add a dirac delta!
if (axisDef < upper)
out.push (hb_pair (scalar1 - gain, loc1));
if (peak < upper)
out.push (hb_pair (scalar - gain, loc));
}
/* Case 3: Outermost limit still fits within F2Dot14 bounds;
* We keep axis bound as is. Deltas beyond -1.0 or +1.0 will never be
* applied as implementations must clamp to that range.
*
* A second tent is needed for cases when gain is positive, though we add it
* unconditionally and it will be dropped because scalar ends up 0.
*
* | peak |
* 1.........|............o...|..................
* | /x\ |
* | /xxx\ |
* | /xxxxx\|
* | /xxxxxxx+
* | /xxxxxxxx|\
* 0---|-----|------oxxxxxxxxx|xo---------------1
* axisMin | lower | upper
* | |
* axisDef axisMax
*/
else if (axisDef + (axisMax - axisDef) * 2 >= upper)
{
if (!negative && axisDef + (axisMax - axisDef) * MAX_F2DOT14 < upper)
{
// we clamp +2.0 to the max F2Dot14 (~1.99994) for convenience
upper = axisDef + (axisMax - axisDef) * MAX_F2DOT14;
assert (peak < upper);
}
Triple loc1 {hb_max (axisDef, lower), peak, upper};
float scalar1 = 1.f;
Triple loc2 {peak, upper, upper};
float scalar2 = 0.f;
// Don't add a dirac delta!
if (axisDef < upper)
out.push (hb_pair (scalar1 - gain, loc1));
if (peak < upper)
out.push (hb_pair (scalar2 - gain, loc2));
}
/* Case 4: New limit doesn't fit; we need to chop into two tents,
* because the shape of a triangle with part of one side cut off
* cannot be represented as a triangle itself.
*
* | peak |
* 1.........|......o.|....................
* ..........|...../x\|.............outGain
* | |xxy|\_
* | /xxxy| \_
* | |xxxxy| \_
* | /xxxxy| \_
* 0---|-----|-oxxxxxx| o----------1
* axisMin | lower | upper
* | |
* axisDef axisMax
*/
else
{
Triple loc1 {hb_max (axisDef, lower), peak, axisMax};
float scalar1 = 1.f;
Triple loc2 {peak, axisMax, axisMax};
float scalar2 = outGain;
out.push (hb_pair (scalar1 - gain, loc1));
// Don't add a dirac delta!
if (peak < axisMax)
out.push (hb_pair (scalar2 - gain, loc2));
}
/* Case 4: New limit doesn't fit; we need to chop into two tents,
* because the shape of a triangle with part of one side cut off
* cannot be represented as a triangle itself.
*
* | peak |
* 1.........|......o.|....................
* ..........|...../x\|.............outGain
* | |xxy|\_
* | /xxxy| \_
* | |xxxxy| \_
* | /xxxxy| \_
* 0---|-----|-oxxxxxx| o----------1
* axisMin | lower | upper
* | |
* axisDef axisMax
*/
else
{
Triple loc1 {hb_max (axisDef, lower), peak, axisMax};
float scalar1 = 1.f;
Triple loc2 {peak, axisMax, axisMax};
float scalar2 = outGain;
out.push (hb_pair (scalar1 - gain, loc1));
// Don't add a dirac delta!
if (peak < axisMax)
out.push (hb_pair (scalar2 - gain, loc2));
}
}
/* Now, the negative side

6
src/test-subset-instancer-solver.cc
View file

@ -191,13 +191,11 @@ main (int argc, char **argv)
Triple tent (0.f, 0.5f, 1.f);
Triple axis_range (0.25f, 0.25f, 0.75f);
result_t out = rebase_tent (tent, axis_range);
assert (out.length == 3);
assert (out.length == 2);
assert (out[0].first == 0.5f);
assert (out[0].second == Triple ());
assert (out[1].first == 0.5f);
assert (out[1].second == Triple (0.f, 0.5f, 1.5f));
assert (out[2].first == -0.5f);
assert (out[2].second == Triple (0.5f, 1.5f, 1.5f));
assert (out[1].second == Triple (0.f, 0.5f, 1.0f));
}
/* Case 1neg */