294 lines
8.7 KiB
C++
294 lines
8.7 KiB
C++
/*
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* Copyright © 2018 Ebrahim Byagowi
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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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#ifndef HB_OT_COLOR_SBIX_TABLE_HH
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#define HB_OT_COLOR_SBIX_TABLE_HH
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#include "hb-open-type.hh"
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/*
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* sbix -- Standard Bitmap Graphics
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* https://docs.microsoft.com/en-us/typography/opentype/spec/sbix
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* https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6sbix.html
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*/
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#define HB_OT_TAG_sbix HB_TAG('s','b','i','x')
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namespace OT {
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struct SBIXGlyph
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{
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HBINT16 xOffset; /* The horizontal (x-axis) offset from the left
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* edge of the graphic to the glyph’s origin.
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* That is, the x-coordinate of the point on the
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* baseline at the left edge of the glyph. */
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HBINT16 yOffset; /* The vertical (y-axis) offset from the bottom
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* edge of the graphic to the glyph’s origin.
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* That is, the y-coordinate of the point on the
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* baseline at the left edge of the glyph. */
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Tag graphicType; /* Indicates the format of the embedded graphic
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* data: one of 'jpg ', 'png ' or 'tiff', or the
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* special format 'dupe'. */
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UnsizedArrayOf<HBUINT8>
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data; /* The actual embedded graphic data. The total
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* length is inferred from sequential entries in
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* the glyphDataOffsets array and the fixed size
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* (8 bytes) of the preceding fields. */
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public:
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DEFINE_SIZE_ARRAY (8, data);
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};
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struct SBIXStrike
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{
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inline bool sanitize (hb_sanitize_context_t *c) const
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{
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TRACE_SANITIZE (this);
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return_trace (c->check_struct (this) &&
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imageOffsetsZ.sanitize_shallow (c, c->get_num_glyphs () + 1));
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}
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inline hb_blob_t *get_glyph_blob (unsigned int glyph_id,
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hb_blob_t *sbix_blob,
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hb_tag_t file_type,
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int *x_offset,
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int *y_offset,
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unsigned int num_glyphs,
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unsigned int *strike_ppem) const
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{
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if (unlikely (!ppem)) return hb_blob_get_empty (); /* To get Null() object out of the way. */
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unsigned int retry_count = 8;
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unsigned int sbix_len = sbix_blob->length;
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unsigned int strike_offset = (const char *) this - (const char *) sbix_blob->data;
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assert (strike_offset < sbix_len);
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retry:
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if (unlikely (glyph_id >= num_glyphs ||
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imageOffsetsZ[glyph_id + 1] <= imageOffsetsZ[glyph_id] ||
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imageOffsetsZ[glyph_id + 1] - imageOffsetsZ[glyph_id] <= SBIXGlyph::min_size ||
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(unsigned int) imageOffsetsZ[glyph_id + 1] > sbix_len - strike_offset))
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return hb_blob_get_empty ();
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unsigned int glyph_offset = strike_offset + (unsigned int) imageOffsetsZ[glyph_id] + SBIXGlyph::min_size;
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unsigned int glyph_length = imageOffsetsZ[glyph_id + 1] - imageOffsetsZ[glyph_id] - SBIXGlyph::min_size;
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const SBIXGlyph *glyph = &(this+imageOffsetsZ[glyph_id]);
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if (glyph->graphicType == HB_TAG ('d','u','p','e'))
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{
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if (glyph_length >= 2)
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{
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glyph_id = *((HBUINT16 *) &glyph->data);
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if (retry_count--)
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goto retry;
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}
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return hb_blob_get_empty ();
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}
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if (unlikely (file_type != glyph->graphicType))
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return hb_blob_get_empty ();
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if (strike_ppem) *strike_ppem = ppem;
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if (x_offset) *x_offset = glyph->xOffset;
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if (y_offset) *y_offset = glyph->yOffset;
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return hb_blob_create_sub_blob (sbix_blob, glyph_offset, glyph_length);
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}
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public:
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HBUINT16 ppem; /* The PPEM size for which this strike was designed. */
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HBUINT16 resolution; /* The device pixel density (in PPI) for which this
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* strike was designed. (E.g., 96 PPI, 192 PPI.) */
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protected:
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UnsizedArrayOf<LOffsetTo<SBIXGlyph> >
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imageOffsetsZ; /* Offset from the beginning of the strike data header
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* to bitmap data for an individual glyph ID. */
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public:
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DEFINE_SIZE_STATIC (8);
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};
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struct sbix
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{
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enum { tableTag = HB_OT_TAG_sbix };
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inline bool has_data (void) const { return version; }
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inline const SBIXStrike &get_strike (unsigned int i) const { return this+strikes[i]; }
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struct accelerator_t
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{
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inline void init (hb_face_t *face)
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{
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table = hb_sanitize_context_t().reference_table<sbix> (face);
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num_glyphs = face->get_num_glyphs ();
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}
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inline void fini (void)
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{
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table.destroy ();
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}
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inline bool has_data () const
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{
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return table->has_data ();
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}
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inline bool get_extents (hb_font_t *font,
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hb_codepoint_t glyph,
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hb_glyph_extents_t *extents) const
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{
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/* We only support PNG right now, and following function checks type. */
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return get_png_extents (font, glyph, extents);
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}
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inline hb_blob_t *reference_png (hb_font_t *font,
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hb_codepoint_t glyph_id,
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int *x_offset,
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int *y_offset,
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unsigned int *available_ppem) const
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{
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return choose_strike (font).get_glyph_blob (glyph_id, table.get_blob (),
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HB_TAG ('p','n','g',' '),
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x_offset, y_offset,
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num_glyphs, available_ppem);
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}
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private:
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inline const SBIXStrike &choose_strike (hb_font_t *font) const
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{
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unsigned count = table->strikes.len;
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if (unlikely (!count))
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return Null(SBIXStrike);
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unsigned int requested_ppem = MAX (font->x_ppem, font->y_ppem);
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if (!requested_ppem)
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requested_ppem = 1<<30; /* Choose largest strike. */
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/* TODO Add DPI sensitivity as well? */
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unsigned int best_i = 0;
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unsigned int best_ppem = table->get_strike (0).ppem;
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for (unsigned int i = 1; i < count; i++)
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{
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unsigned int ppem = (table->get_strike (i)).ppem;
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if ((requested_ppem <= ppem && ppem < best_ppem) ||
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(requested_ppem > best_ppem && ppem > best_ppem))
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{
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best_i = i;
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best_ppem = ppem;
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}
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}
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return table->get_strike (best_i);
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}
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struct PNGHeader
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{
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HBUINT8 signature[8];
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struct
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{
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struct
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{
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HBUINT32 length;
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Tag type;
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} header;
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HBUINT32 width;
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HBUINT32 height;
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HBUINT8 bitDepth;
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HBUINT8 colorType;
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HBUINT8 compressionMethod;
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HBUINT8 filterMethod;
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HBUINT8 interlaceMethod;
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} IHDR;
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public:
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DEFINE_SIZE_STATIC (29);
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};
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inline bool get_png_extents (hb_font_t *font,
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hb_codepoint_t glyph,
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hb_glyph_extents_t *extents) const
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{
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/* Following code is safe to call even without data.
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* But faster to short-circuit. */
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if (!has_data ())
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return false;
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int x_offset = 0, y_offset = 0;
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unsigned int strike_ppem = 0;
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hb_blob_t *blob = reference_png (font, glyph, &x_offset, &y_offset, &strike_ppem);
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const PNGHeader &png = *blob->as<PNGHeader>();
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extents->x_bearing = x_offset;
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extents->y_bearing = y_offset;
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extents->width = png.IHDR.width;
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extents->height = png.IHDR.height;
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/* Convert to font units. */
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if (strike_ppem)
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{
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double scale = font->face->get_upem () / (double) strike_ppem;
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extents->x_bearing = round (extents->x_bearing * scale);
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extents->y_bearing = round (extents->y_bearing * scale);
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extents->width = round (extents->width * scale);
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extents->height = round (extents->height * scale);
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}
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hb_blob_destroy (blob);
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return strike_ppem;
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}
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private:
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hb_blob_ptr_t<sbix> table;
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unsigned int num_glyphs;
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};
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inline bool sanitize (hb_sanitize_context_t *c) const
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{
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TRACE_SANITIZE (this);
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return_trace (likely (c->check_struct (this) &&
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version >= 1 &&
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strikes.sanitize (c, this)));
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}
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protected:
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HBUINT16 version; /* Table version number — set to 1 */
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HBUINT16 flags; /* Bit 0: Set to 1. Bit 1: Draw outlines.
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* Bits 2 to 15: reserved (set to 0). */
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LOffsetLArrayOf<SBIXStrike>
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strikes; /* Offsets from the beginning of the 'sbix'
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* table to data for each individual bitmap strike. */
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public:
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DEFINE_SIZE_ARRAY (8, strikes);
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};
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struct sbix_accelerator_t : sbix::accelerator_t {};
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} /* namespace OT */
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#endif /* HB_OT_COLOR_SBIX_TABLE_HH */
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