<Swing Dev> RFR: 8189809: Large performance regression in Swing text layout.
philip.race at oracle.com
Thu Dec 7 20:54:14 UTC 2017
This partially addresses a slow-down in Swing.
Swing now usually calls Font.getStringBounds() instead of
FontMetrics().stringWidth for text measurement.
The latter has a fast-path for latin-only simple text.
The former does not .. and at a minimum uses GlyphVector.
This fix provides a similar fast path and for direct calls to these
methods (micro benchmarks)
that is latin text they are now very similar .. at least for typical
In this fix as well as making this change in the font code, I updated
Swing to more
be a little more efficient.
Before this fix I always saw Swing coming in with a char .. then
constructing a String from it.
Then it passes it to the font measurement code, which then decomposes
the string back into a char
If Swing directly uses the API that takes a char then we save some
It does not get back all of the loss by Swing since
1) Swing has other overhead elsewhere - it seems
2) Swing is making 90% of these calls for a single char.
This could be from where Swing naively tries to add up char advances
get a string advance.
We may have to come back to that later. Perhaps with new public API.
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