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[pdf] Fix complex mirrored gradients in Preview.

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An undocumented feature of Preview 11.0 (1033.3) is that `a n mod r eq`
(with a and n both integers, r integer or real) early aborts a function
when false would be put on the stack. Work around this by re-writing
`t 2 mod 1 eq` as `t 2 mod 0 gt`.

Bug: chromium:1316377, chromium:1170345
Change-Id: Ibb6eaaf36f276e9ef2906159622ab44b35289492
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/542638
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
This commit is contained in:
Ben Wagner 2022-05-20 12:18:13 -04:00 committed by SkCQ
parent 9c8b5c6566
commit d2fba4ac94
1 changed files with 13 additions and 9 deletions
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22
src/pdf/SkPDFGradientShader.cpp
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@ -300,16 +300,20 @@ static void tileModeCode(SkTileMode mode, SkDynamicMemoryWStream* result) {
}
if (mode == SkTileMode::kMirror) {
// In Preview 11.0 (1033.3) `a n mod r eq` (with a and n both integers, r integer or real)
// early aborts the function when false would be put on the stack.
// Work around this by re-writing `t 2 mod 1 eq` as `t 2 mod 0 gt`.
// Map t mod 2 into [0, 1, 1, 0].
// Code Stack
result->writeText("abs " // Map negative to positive.
"dup " // t.s t.s
"truncate " // t.s t
"dup " // t.s t t
"cvi " // t.s t T
"2 mod " // t.s t (i mod 2)
"1 eq " // t.s t true|false
"3 1 roll " // true|false t.s t
// Code Stack t
result->writeText("abs " // +t
"dup " // +t.s +t.s
"truncate " // +t.s +t
"dup " // +t.s +t +t
"cvi " // +t.s +t +T
"2 mod " // +t.s +t (+T mod 2)
/*"1 eq "*/ "0 gt " // +t.s +t true|false
"3 1 roll " // true|false +t.s +t
"sub " // true|false 0.s
"exch " // 0.s true|false
"{1 exch sub} if\n"); // 1 - 0.s|0.s