70 lines
2.5 KiB
Text
70 lines
2.5 KiB
Text
/*
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* Copyright (C) 2026 Behdad Esfahbod
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*
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* This is part of HarfBuzz, a text shaping library.
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*
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* Permission is hereby granted, without written agreement and without
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* license or royalty fees, to use, copy, modify, and distribute this
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* software and its documentation for any purpose, provided that the
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* above copyright notice and the following two paragraphs appear in
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* all copies of this software.
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*
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
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* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*/
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/* Requires Metal Shading Language 2.0. */
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/* Dilate a glyph vertex by half a pixel on screen.
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*
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* position: object-space vertex position (modified in place)
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* texcoord: em-space sample coordinates (modified in place)
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* normal: object-space outward normal at this vertex
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* jac: inverse of the 2x2 linear part of the em-to-object transform,
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* stored row-major as (j00, j01, j10, j11). Maps object-space
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* displacements back to em-space for texcoord adjustment.
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* For simple scaling with y-flip (the common case):
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* em-to-object = [[s, 0], [0, -s]]
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* jac = (1/s, 0, 0, -1/s)
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* m: model-view-projection matrix
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* viewport: viewport size in pixels
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*/
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void hb_gpu_dilate (thread float2& position, thread float2& texcoord,
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float2 normal, float4 jac,
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float4x4 m, float2 viewport)
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{
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float2 n = normalize (normal);
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float4 clipPos = m * float4 (position, 0.0, 1.0);
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float4 clipN = m * float4 (n, 0.0, 0.0);
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float s = clipPos.w;
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float t = clipN.w;
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float u = (s * clipN.x - t * clipPos.x) * viewport.x;
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float v = (s * clipN.y - t * clipPos.y) * viewport.y;
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float s2 = s * s;
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float st = s * t;
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float uv = u * u + v * v;
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float denom = uv - st * st;
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float d = abs (denom) > 1.0 / 16777216.0
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? s2 * (st + sqrt (uv)) / denom
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: 0.0;
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float2 dPos = d * normal;
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position += dPos;
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texcoord += float2 (dot (dPos, jac.xy), dot (dPos, jac.zw));
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}
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