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[arabic] Implement Windows-1256 private shaping
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Bug 1045139 - The Arabic text with "MS Sans Serif" font is rendered bad
https://bugzilla.mozilla.org/show_bug.cgi?id=1045139

This is only enabled on Windows platforms, and requires support from
Uniscribe to work.  But for clients that do hook up to Uniscribe, this
fixes shaping of Windows-1256-encoded bitmap fonts like "MS Sans Serif".

The code and table together have just less than a 1kb footprint when
enabled.

UNTESTED.  I might even have broken regular Arabic fallback shaping.
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@behdad
behdad committed Jul 30, 2014
1 parent c86b3fa commit 479ae68
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Showing 4 changed files with 440 additions and 14 deletions.
1 change: 1 addition & 0 deletions src/Makefile.am
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,7 @@ HBSOURCES += \
hb-ot-shape-complex-arabic.cc \
hb-ot-shape-complex-arabic-fallback.hh \
hb-ot-shape-complex-arabic-table.hh \
hb-ot-shape-complex-arabic-win1256.hh \
hb-ot-shape-complex-default.cc \
hb-ot-shape-complex-hangul.cc \
hb-ot-shape-complex-hebrew.cc \
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2 changes: 1 addition & 1 deletion src/check-includes.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ echo 'Checking that source files #include "hb-*private.hh" first (or none)'

for x in $HBSOURCES; do
test -f "$srcdir/$x" && x="$srcdir/$x"
grep '#.*\<include\>' "$x" /dev/null | head -n 1
grep '#.*\<include\>' "$x" /dev/null | grep -v 'include _' | head -n 1
done |
grep -v '"hb-.*private[.]hh"' |
grep -v 'hb-private[.]hh:' |
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124 changes: 111 additions & 13 deletions src/hb-ot-shape-complex-arabic-fallback.hh
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Expand Up @@ -81,6 +81,9 @@ arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan HB_UNUS
num_glyphs++;
}

if (!num_glyphs)
return NULL;

/* Bubble-sort!
* May not be good-enough for presidential candidate interviews, but good-enough for us... */
hb_bubble_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
Expand Down Expand Up @@ -158,6 +161,9 @@ arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UN
}
}

if (!num_ligatures)
return NULL;

OT::Supplier<OT::GlyphID> first_glyphs_supplier (first_glyphs, num_first_glyphs);
OT::Supplier<unsigned int > ligature_per_first_glyph_count_supplier (ligature_per_first_glyph_count_list, num_first_glyphs);
OT::Supplier<OT::GlyphID> ligatures_supplier (ligature_list, num_ligatures);
Expand Down Expand Up @@ -198,13 +204,100 @@ struct arabic_fallback_plan_t
{
ASSERT_POD ();

unsigned int num_lookups;
bool free_lookups;

hb_mask_t mask_array[ARABIC_NUM_FALLBACK_FEATURES];
OT::SubstLookup *lookup_array[ARABIC_NUM_FALLBACK_FEATURES];
hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_NUM_FALLBACK_FEATURES];
};

static const arabic_fallback_plan_t arabic_fallback_plan_nil = {};

#if defined(_WIN32) || defined(__CYGWIN__)
#define HB_WITH_WIN1256
#endif

#ifdef HB_WITH_WIN1256
#include "hb-ot-shape-complex-arabic-win1256.hh"
#endif

struct ManifestLookup {
OT::USHORT fallbackType;
OT::OffsetTo<OT::SubstLookup> lookupOffset;
};
typedef OT::ArrayOf<ManifestLookup> Manifest;

static bool
arabic_fallback_plan_init_win1256 (arabic_fallback_plan_t *fallback_plan,
const hb_ot_shape_plan_t *plan,
hb_font_t *font)
{
#ifdef HB_WITH_WIN1256
/* Does this font look like it's Windows-1256-encoded? */
hb_codepoint_t g;
if (!(hb_font_get_glyph (font, 0x0627u, 0, &g) && g == 199 /* ALEF */ &&
hb_font_get_glyph (font, 0x0644u, 0, &g) && g == 225 /* LAM */ &&
hb_font_get_glyph (font, 0x0649u, 0, &g) && g == 236 /* ALEF MAKSURA */ &&
hb_font_get_glyph (font, 0x064Au, 0, &g) && g == 237 /* YEH */ &&
hb_font_get_glyph (font, 0x0652u, 0, &g) && g == 250 /* SUKUN */))
return false;

const Manifest &manifest = reinterpret_cast<const Manifest&> (arabic_win1256_gsub_lookups);
/* TODO sanitize the table? */

unsigned j = 0;
unsigned int count = manifest.len;
assert (count <= ARABIC_NUM_FALLBACK_FEATURES);
for (unsigned int i = 0; i < count; i++)
{
fallback_plan->mask_array[j] = plan->map.get_1_mask (manifest[i].fallbackType);
if (fallback_plan->mask_array[j])
{
fallback_plan->lookup_array[j] = const_cast<OT::SubstLookup*> (&(&manifest+manifest[i].lookupOffset));
if (fallback_plan->lookup_array[j])
{
fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
j++;
}
}
}

fallback_plan->num_lookups = j;
fallback_plan->free_lookups = false;

return j > 0;
#else
return false;
#endif
}

static bool
arabic_fallback_plan_init_unicode (arabic_fallback_plan_t *fallback_plan,
const hb_ot_shape_plan_t *plan,
hb_font_t *font)
{
unsigned int j = 0;
for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
{
fallback_plan->mask_array[j] = plan->map.get_1_mask (arabic_fallback_features[i]);
if (fallback_plan->mask_array[j])
{
fallback_plan->lookup_array[j] = arabic_fallback_synthesize_lookup (plan, font, i);
if (fallback_plan->lookup_array[j])
{
fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
j++;
}
}
}

fallback_plan->num_lookups = j;
fallback_plan->free_lookups = true;

return j > 0;
}

static arabic_fallback_plan_t *
arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
hb_font_t *font)
Expand All @@ -213,17 +306,21 @@ arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
if (unlikely (!fallback_plan))
return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);

for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
{
fallback_plan->mask_array[i] = plan->map.get_1_mask (arabic_fallback_features[i]);
if (fallback_plan->mask_array[i]) {
fallback_plan->lookup_array[i] = arabic_fallback_synthesize_lookup (plan, font, i);
if (fallback_plan->lookup_array[i])
fallback_plan->accel_array[i].init (*fallback_plan->lookup_array[i]);
}
}
fallback_plan->num_lookups = 0;
fallback_plan->free_lookups = false;

/* Try synthesizing GSUB table using Unicode Arabic Presentation Forms,
* in case the font has cmap entries for the presentation-forms characters. */
if (arabic_fallback_plan_init_unicode (fallback_plan, plan, font))
return fallback_plan;

return fallback_plan;
/* See if this looks like a Windows-1256-encoded font. If it does, use a
* hand-coded GSUB table. */
if (arabic_fallback_plan_init_win1256 (fallback_plan, plan, font))
return fallback_plan;

free (fallback_plan);
return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
}

static void
Expand All @@ -232,11 +329,12 @@ arabic_fallback_plan_destroy (arabic_fallback_plan_t *fallback_plan)
if (!fallback_plan || fallback_plan == &arabic_fallback_plan_nil)
return;

for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
if (fallback_plan->lookup_array[i])
{
fallback_plan->accel_array[i].fini (fallback_plan->lookup_array[i]);
free (fallback_plan->lookup_array[i]);
if (fallback_plan->free_lookups)
free (fallback_plan->lookup_array[i]);
}

free (fallback_plan);
Expand All @@ -248,7 +346,7 @@ arabic_fallback_plan_shape (arabic_fallback_plan_t *fallback_plan,
hb_buffer_t *buffer)
{
OT::hb_apply_context_t c (0, font, buffer);
for (unsigned int i = 0; i < ARABIC_NUM_FALLBACK_FEATURES; i++)
for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
if (fallback_plan->lookup_array[i]) {
c.set_lookup_mask (fallback_plan->mask_array[i]);
hb_ot_layout_substitute_lookup (&c,
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