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178761dcb3
This patch contains the core of the path stream processing, though some integration bits are missing. The core logic is tested, though combinations of path types, transforms, and line widths are not (yet). Progress towards #119
50 lines
1.5 KiB
GLSL
50 lines
1.5 KiB
GLSL
// SPDX-License-Identifier: Apache-2.0 OR MIT OR Unlicense
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// Common data structures and functions for the path tag stream.
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// This is the layout for tag bytes in the path stream. See
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// doc/pathseg.md for an explanation.
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#define PATH_TAG_PATHSEG_BITS 0xf
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#define PATH_TAG_PATH 0x10
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#define PATH_TAG_TRANSFORM 0x20
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#define PATH_TAG_LINEWIDTH 0x40
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struct TagMonoid {
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uint trans_ix;
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uint linewidth_ix;
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uint pathseg_ix;
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uint path_ix;
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uint pathseg_offset;
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};
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TagMonoid tag_monoid_identity() {
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return TagMonoid(0, 0, 0, 0, 0);
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}
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TagMonoid combine_tag_monoid(TagMonoid a, TagMonoid b) {
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TagMonoid c;
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c.trans_ix = a.trans_ix + b.trans_ix;
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c.linewidth_ix = a.linewidth_ix + b.linewidth_ix;
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c.pathseg_ix = a.pathseg_ix + b.pathseg_ix;
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c.path_ix = a.path_ix + b.path_ix;
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c.pathseg_offset = a.pathseg_offset + b.pathseg_offset;
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return c;
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}
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TagMonoid reduce_tag(uint tag_word) {
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TagMonoid c;
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// Some fun bit magic here, see doc/pathseg.md for explanation.
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uint point_count = tag_word & 0x3030303;
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c.pathseg_ix = bitCount((point_count * 7) & 0x4040404);
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c.linewidth_ix = bitCount(tag_word & (PATH_TAG_LINEWIDTH * 0x1010101));
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c.path_ix = bitCount(tag_word & (PATH_TAG_PATH * 0x1010101));
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c.trans_ix = bitCount(tag_word & (PATH_TAG_TRANSFORM * 0x1010101));
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uint n_points = point_count + ((tag_word >> 2) & 0x1010101);
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uint a = n_points + (n_points & (((tag_word >> 3) & 0x1010101) * 15));
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a += a >> 8;
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a += a >> 16;
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c.pathseg_offset = a & 0xff;
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return c;
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}
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