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Bug 1466332 - patch 1 - Update StretchDistance function to more closely follow CSS4 Fonts algorithm. r=jwatt

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This commit is contained in:
Jonathan Kew 2018-06-03 21:33:42 +01:00
parent 8752135981
commit b4b39146d3
1 changed files with 15 additions and 16 deletions
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31
gfx/thebes/gfxFontEntry.cpp
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@ -1448,29 +1448,28 @@ static inline double
StretchDistance(const gfxFontEntry* aFontEntry, FontStretch aTargetStretch)
{
const double kReverseDistance = 1000.0;
double distance = 0.0;
FontStretch minStretch = aFontEntry->Stretch().Min();
FontStretch maxStretch = aFontEntry->Stretch().Max();
if (aTargetStretch < minStretch || aTargetStretch > maxStretch) {
// stretch values are in the range 0 .. 1000
// if aTargetStretch is >100, we prefer larger values;
// if <=100, prefer smaller
// The stretch value is a (non-negative) percentage; currently we support
// values in the range 0 .. 1000. (If the upper limit is ever increased,
// the kReverseDistance value used here may need to be adjusted.)
// If aTargetStretch is >100, we prefer larger values if available;
// if <=100, we prefer smaller values if available.
if (aTargetStretch < minStretch) {
if (aTargetStretch > FontStretch::Normal()) {
distance = (minStretch - aTargetStretch);
} else {
distance = (aTargetStretch - maxStretch);
}
// if the computed "distance" here is negative, it means that
// aFontEntry lies in the "non-preferred" direction from aTargetStretch,
// so we treat that as larger than any preferred-direction distance
// (max possible is 1000) by adding an extra 1000 to the absolute value
if (distance < 0.0f) {
distance = kReverseDistance - distance;
return minStretch - aTargetStretch;
}
return (minStretch - aTargetStretch) + kReverseDistance;
}
return distance;
if (aTargetStretch > maxStretch) {
if (aTargetStretch <= FontStretch::Normal()) {
return aTargetStretch - maxStretch;
}
return (aTargetStretch - maxStretch) + kReverseDistance;
}
return 0.0;
}
// Calculate weight distance with values in the range (0..1000). In general,