diff options
author | Mike Reed <reed@google.com> | 2018-05-23 12:12:21 -0400 |
---|---|---|
committer | Skia Commit-Bot <skia-commit-bot@chromium.org> | 2018-05-23 16:54:32 +0000 |
commit | ee43091c1b8ebf2f62918688494b0eb82ceedb38 (patch) | |
tree | fea93d4f7d455abea54ebd182fcbbe69e3ca3d19 /src | |
parent | d7e22273e1e522eab57976e08b339b1532a8fd01 (diff) |
fix 0.499999f rounding case for triangles
Bug: skia:7994
Change-Id: I83bb309a2c8fb0bddaf78ba32c0a07537e483900
Reviewed-on: https://skia-review.googlesource.com/129648
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Diffstat (limited to 'src')
-rw-r--r-- | src/core/SkScan_Path.cpp | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp index 4110b832a9..43240eae37 100644 --- a/src/core/SkScan_Path.cpp +++ b/src/core/SkScan_Path.cpp @@ -738,6 +738,37 @@ static void sk_fill_triangle(const SkPoint pts[], const SkIRect* clipRect, // walk_edges(&headEdge, SkPath::kEvenOdd_FillType, blitter, start_y, stop_y, nullptr); } +/** + * We need to match the rounding behavior of the line edge, which does this: + * 1. scale by 64 (to get into FDot6) + * 2. cast to an int + * 3. round that to an int (undoing the FDot6) + * This should (in theory) be the same as sk_float_round2int, except for float values very very + * close to 0.5 (like 0.49999997f). For those values, x + 0.5 gives 1.0 instead of 0.9999999, + * and therefore they round2int differently as floats than as FDot6 values in the edge code. + * + * A fix is to go into double temporarily, so that 0.49999997f + 0.5 stays < 1.0. + * + * This sample triangle triggers the problem (if we just use SkRect::round() instead of + * this double_round version. + * + * { 0.499069244f, 9.63295173f }, + * { 0.499402374f, 7.88207579f }, + * { 10.2363272f, 0.49999997f }, + * + * Note: this version is basically just more correct than SkRect::round(). If we thought we could + * afford the perf hit (assuming going to doubles cost more), then we might replace round()'s + * impl with this. + */ +static SkIRect double_round(const SkRect& r) { + return { + sk_double_round2int(r.fLeft), + sk_double_round2int(r.fTop), + sk_double_round2int(r.fRight), + sk_double_round2int(r.fBottom), + }; +} + void SkScan::FillTriangle(const SkPoint pts[], const SkRasterClip& clip, SkBlitter* blitter) { if (clip.isEmpty()) { @@ -757,7 +788,7 @@ void SkScan::FillTriangle(const SkPoint pts[], const SkRasterClip& clip, return; } - SkIRect ir = r.round(); + SkIRect ir = double_round(r); if (ir.isEmpty() || !SkIRect::Intersects(ir, clip.getBounds())) { return; } |