Offset Path now turns the overlap sweep the way Outline Stroke and
Unite do. When the estimate for its fill, the ring stroked around it
and the outline of its open subpaths is under two thirds as large for
the parts turned a quarter turn, the faces are found on the turned
parts, the faces within the offset distance of the path are dropped by
testing their points turned back, and the result is turned back.
On an open path of 10,000 anchors in rows of 1,000, offsetting by 2 pt
takes 1.0 s of processor time instead of 1.8 s in a release build.
The offset of a long, low path has as many subpaths as the offset of
the same path stood on end, and the area where the two differ is no
larger than the refit precision times the outline's length.
The overlap sweep moves a horizontal line down the page, and its time
per event grows with the number of segments on that line. A long, low
path, such as rows of a zigzag, puts a whole row on the line at once.
stroke_region, unite_all_with and try_unite_all_with now estimate how
many segments the sweep holds at once in each direction, from up to
4,096 segment boxes (one from each run of segments, at a position that
changes from run to run). When the estimate for the input turned a
quarter turn is under two thirds of the upright one (2,048 segments or
more), the operation runs on the turned input and the result is turned
back. A quarter turn swaps and negates coordinates, so no point moves
by rounding. Offset Path is not turned. Callers of unite_all,
try_unite_all and outline_stroke take the turned sweep through these
functions.
Tidy's lookups of the input curves around a piece and of the kept
anchors can search along y: once lookups with more than 64 candidates
along x have scanned 16 per item, a lookup sorts the list along y once
and uses that window when it holds fewer candidates (under a quarter as
many for curves). Where the y window rarely helps, only one lookup in
32 measures it. is_kept counts the few points within its tolerance
directly instead of searching for the window's end.
In the sweep_axis tests, a turned result has as many subpaths as the
result without the turn, and the area where the two differ is no
larger than the refit precision times the outline's length.
On one open path of 200,000 anchors in rows of 1,000, Outline Stroke
takes 17.3 s of processor time instead of 31.3 s and Unite 2.9 s
instead of 6.5 s in a release build. Unite of 2,000 circles takes the
same time as before.
dotCooCoo