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TrueType subsetting: embed a cmap for latin subsets
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To support latin subsets in PDF, TrueType fonts require a cmap to map
unicode to glyph indices for all characters in the winansi encoding.
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Adrian Johnson committed Oct 1, 2010
1 parent 7c268bc commit 85c25d7
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Showing 3 changed files with 94 additions and 39 deletions.
3 changes: 3 additions & 0 deletions src/cairo-scaled-font-subsets-private.h
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Original file line number Diff line number Diff line change
Expand Up @@ -460,6 +460,9 @@ _cairo_truetype_subset_init (cairo_truetype_subset_t *truetype_subset,
cairo_private void
_cairo_truetype_subset_fini (cairo_truetype_subset_t *truetype_subset);

cairo_private int
_cairo_unicode_to_winansi (unsigned long unicode);

cairo_private const char *
_cairo_winansi_to_glyphname (int glyph);

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7 changes: 4 additions & 3 deletions src/cairo-scaled-font-subsets.c
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Original file line number Diff line number Diff line change
Expand Up @@ -343,7 +343,8 @@ static unsigned int _winansi_0x80_to_0x9f[] = {
0x02dc, 0x2122, 0x0161, 0x203a, 0x0153, 0x0000, 0x017e, 0x0178
};

static int _unicode_to_winansi (unsigned long unicode)
int
_cairo_unicode_to_winansi (unsigned long unicode)
{
int i;

Expand Down Expand Up @@ -618,7 +619,7 @@ _cairo_sub_font_map_glyph (cairo_sub_font_t *sub_font,
if (sub_font->parent->use_latin_subset &&
(! _cairo_font_face_is_user (sub_font->scaled_font->font_face)))
{
latin_character = _unicode_to_winansi (font_unicode);
latin_character = _cairo_unicode_to_winansi (font_unicode);
if (latin_character > 0 ||
(latin_character == 0 && sub_font->num_glyphs_in_latin_subset > 0))
{
Expand Down Expand Up @@ -1184,7 +1185,7 @@ _cairo_scaled_font_subset_create_glyph_names (cairo_scaled_font_subset_t *subset
}

if (utf16_len == 1) {
int ch = _unicode_to_winansi (utf16[0]);
int ch = _cairo_unicode_to_winansi (utf16[0]);
if (ch > 0)
strncpy (buf, _cairo_winansi_to_glyphname (ch), sizeof (buf));
else
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123 changes: 87 additions & 36 deletions src/cairo-truetype-subset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -393,51 +393,98 @@ cairo_truetype_font_check_boundary (cairo_truetype_font_t *font,
return CAIRO_STATUS_SUCCESS;
}

typedef struct _cmap_unicode_range {
unsigned int start;
unsigned int end;
} cmap_unicode_range_t;

static cmap_unicode_range_t winansi_unicode_ranges[] = {
{ 0x0020, 0x007f },
{ 0x00a0, 0x00ff },
{ 0x0152, 0x0153 },
{ 0x0178, 0x0178 },
{ 0x017d, 0x017e },
{ 0x0192, 0x0192 },
{ 0x02c6, 0x02c6 },
{ 0x02dc, 0x02dc },
{ 0x2013, 0x2026 },
{ 0x2030, 0x2030 },
{ 0x2039, 0x203a },
{ 0x2122, 0x2122 },
};

static cairo_status_t
cairo_truetype_font_write_cmap_table (cairo_truetype_font_t *font,
unsigned long tag)
{
unsigned int i;
int i;
unsigned int j;
int range_offset;
int num_ranges;
int entry_selector;
int length;

num_ranges = ARRAY_LENGTH (winansi_unicode_ranges);

length = 16 + (num_ranges + 1)*8;
for (i = 0; i < num_ranges; i++)
length += (winansi_unicode_ranges[i].end - winansi_unicode_ranges[i].start + 1)*2;

entry_selector = 0;
while ((1 << entry_selector) <= (num_ranges + 1))
entry_selector++;

entry_selector--;

cairo_truetype_font_write_be16 (font, 0); /* Table version */
cairo_truetype_font_write_be16 (font, 2); /* Num tables */
cairo_truetype_font_write_be16 (font, 1); /* Num tables */

cairo_truetype_font_write_be16 (font, 3); /* Platform */
cairo_truetype_font_write_be16 (font, 0); /* Encoding */
cairo_truetype_font_write_be32 (font, 20); /* Offset to start of table */
cairo_truetype_font_write_be16 (font, 1); /* Encoding */
cairo_truetype_font_write_be32 (font, 12); /* Offset to start of table */

cairo_truetype_font_write_be16 (font, 1); /* Platform */
cairo_truetype_font_write_be16 (font, 0); /* Encoding */
cairo_truetype_font_write_be32 (font, 52); /* Offset to start of table */

/* Output a format 4 encoding table. */
/* Output a format 4 encoding table for the winansi encoding */

cairo_truetype_font_write_be16 (font, 4); /* Format */
cairo_truetype_font_write_be16 (font, 32); /* Length */
cairo_truetype_font_write_be16 (font, length); /* Length */
cairo_truetype_font_write_be16 (font, 0); /* Version */
cairo_truetype_font_write_be16 (font, 4); /* 2*segcount */
cairo_truetype_font_write_be16 (font, 4); /* searchrange */
cairo_truetype_font_write_be16 (font, 1); /* entry selector */
cairo_truetype_font_write_be16 (font, 0); /* rangeshift */
cairo_truetype_font_write_be16 (font, 0xf000 + font->base.num_glyphs - 1); /* end count[0] */
cairo_truetype_font_write_be16 (font, 0xffff); /* end count[1] */
cairo_truetype_font_write_be16 (font, num_ranges*2 + 2); /* 2*segcount */
cairo_truetype_font_write_be16 (font, (1 << (entry_selector + 1))); /* searchrange */
cairo_truetype_font_write_be16 (font, entry_selector); /* entry selector */
cairo_truetype_font_write_be16 (font, num_ranges*2 + 2 - (1 << (entry_selector + 1))); /* rangeshift */
for (i = 0; i < num_ranges; i++)
cairo_truetype_font_write_be16 (font, winansi_unicode_ranges[i].end); /* end count[] */
cairo_truetype_font_write_be16 (font, 0xffff); /* end count[] */

cairo_truetype_font_write_be16 (font, 0); /* reserved */
cairo_truetype_font_write_be16 (font, 0xf000); /* startCode[0] */
cairo_truetype_font_write_be16 (font, 0xffff); /* startCode[1] */
cairo_truetype_font_write_be16 (font, 0x1000); /* delta[0] */
cairo_truetype_font_write_be16 (font, 1); /* delta[1] */
cairo_truetype_font_write_be16 (font, 0); /* rangeOffset[0] */
cairo_truetype_font_write_be16 (font, 0); /* rangeOffset[1] */

/* Output a format 6 encoding table. */

cairo_truetype_font_write_be16 (font, 6);
cairo_truetype_font_write_be16 (font, 10 + 2 * font->base.num_glyphs);
cairo_truetype_font_write_be16 (font, 0);
cairo_truetype_font_write_be16 (font, 0); /* First character */
cairo_truetype_font_write_be16 (font, font->base.num_glyphs);
for (i = 0; i < font->base.num_glyphs; i++)
cairo_truetype_font_write_be16 (font, i);

for (i = 0; i < num_ranges; i++)
cairo_truetype_font_write_be16 (font, winansi_unicode_ranges[i].start); /* startCode[] */
cairo_truetype_font_write_be16 (font, 0xffff); /* startCode[] */

for (i = 0; i < num_ranges; i++)
cairo_truetype_font_write_be16 (font, 0x0000); /* delta[] */
cairo_truetype_font_write_be16 (font, 1); /* delta[] */

range_offset = num_ranges*2 + 2;
for (i = 0; i < num_ranges; i++) {
cairo_truetype_font_write_be16 (font, range_offset); /* rangeOffset[] */
range_offset += (winansi_unicode_ranges[i].end - winansi_unicode_ranges[i].start + 1)*2 - 2;
}
cairo_truetype_font_write_be16 (font, 0); /* rangeOffset[] */

for (i = 0; i < num_ranges; i++) {
for (j = winansi_unicode_ranges[i].start; j < winansi_unicode_ranges[i].end + 1; j++) {
int ch = _cairo_unicode_to_winansi (j);
int glyph;

if (ch > 0)
glyph = font->scaled_font_subset->latin_to_subset_glyph_index[ch];
else
glyph = 0;
cairo_truetype_font_write_be16 (font, glyph);
}
}

return font->status;
}
Expand Down Expand Up @@ -985,8 +1032,9 @@ cairo_truetype_font_add_truetype_table (cairo_truetype_font_t *font,
* The tables in the table directory must be listed in alphabetical
* order. The "cvt", "fpgm", and "prep" are optional tables. They
* will only be embedded in the subset if they exist in the source
* font. The pos parameter of cairo_truetype_font_add_truetype_table()
* specifies the position of the table in the table directory.
* font. "cmap" is only embedded for latin fonts. The pos parameter of
* cairo_truetype_font_add_truetype_table() specifies the position of
* the table in the table directory.
*/
static void
cairo_truetype_font_create_truetype_table_list (cairo_truetype_font_t *font)
Expand Down Expand Up @@ -1016,15 +1064,18 @@ cairo_truetype_font_create_truetype_table_list (cairo_truetype_font_t *font)
has_prep = TRUE;

font->num_tables = 0;
pos = 1;
pos = 0;
if (font->scaled_font_subset->is_latin)
pos++;
if (has_cvt)
pos++;
if (has_fpgm)
pos++;
cairo_truetype_font_add_truetype_table (font, TT_TAG_glyf, cairo_truetype_font_write_glyf_table, pos);

pos = 0;
cairo_truetype_font_add_truetype_table (font, TT_TAG_cmap, cairo_truetype_font_write_cmap_table, pos++);
if (font->scaled_font_subset->is_latin)
cairo_truetype_font_add_truetype_table (font, TT_TAG_cmap, cairo_truetype_font_write_cmap_table, pos++);
if (has_cvt)
cairo_truetype_font_add_truetype_table (font, TT_TAG_cvt, cairo_truetype_font_write_generic_table, pos++);
if (has_fpgm)
Expand Down

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