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diff --git a/gfx/harfbuzz/src/hb-ot-shape-complex-arabic.cc b/gfx/harfbuzz/src/hb-ot-shape-complex-arabic.cc
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+++ b/gfx/harfbuzz/src/hb-ot-shape-complex-arabic.cc
@@ -0,0 +1,716 @@
+/*
+ * Copyright © 2010,2012 Google, Inc.
+ *
+ * This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#include "hb.hh"
+
+#ifndef HB_NO_OT_SHAPE
+
+#include "hb-ot-shape-complex-arabic.hh"
+#include "hb-ot-shape.hh"
+
+
+/* buffer var allocations */
+#define arabic_shaping_action() complex_var_u8_0() /* arabic shaping action */
+
+#define HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH HB_BUFFER_SCRATCH_FLAG_COMPLEX0
+
+/* See:
+ * https://github.com/harfbuzz/harfbuzz/commit/6e6f82b6f3dde0fc6c3c7d991d9ec6cfff57823d#commitcomment-14248516 */
+#define HB_ARABIC_GENERAL_CATEGORY_IS_WORD(gen_cat) \
+ (FLAG_UNSAFE (gen_cat) & \
+ (FLAG (HB_UNICODE_GENERAL_CATEGORY_UNASSIGNED) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_PRIVATE_USE) | \
+ /*FLAG (HB_UNICODE_GENERAL_CATEGORY_LOWERCASE_LETTER) |*/ \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_MODIFIER_LETTER) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_LETTER) | \
+ /*FLAG (HB_UNICODE_GENERAL_CATEGORY_TITLECASE_LETTER) |*/ \
+ /*FLAG (HB_UNICODE_GENERAL_CATEGORY_UPPERCASE_LETTER) |*/ \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_DECIMAL_NUMBER) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_LETTER_NUMBER) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_NUMBER) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_CURRENCY_SYMBOL) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_MODIFIER_SYMBOL) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_MATH_SYMBOL) | \
+ FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_SYMBOL)))
+
+
+/*
+ * Joining types:
+ */
+
+/*
+ * Bits used in the joining tables
+ */
+enum hb_arabic_joining_type_t {
+ JOINING_TYPE_U = 0,
+ JOINING_TYPE_L = 1,
+ JOINING_TYPE_R = 2,
+ JOINING_TYPE_D = 3,
+ JOINING_TYPE_C = JOINING_TYPE_D,
+ JOINING_GROUP_ALAPH = 4,
+ JOINING_GROUP_DALATH_RISH = 5,
+ NUM_STATE_MACHINE_COLS = 6,
+
+ JOINING_TYPE_T = 7,
+ JOINING_TYPE_X = 8 /* means: use general-category to choose between U or T. */
+};
+
+#include "hb-ot-shape-complex-arabic-table.hh"
+
+static unsigned int get_joining_type (hb_codepoint_t u, hb_unicode_general_category_t gen_cat)
+{
+ unsigned int j_type = joining_type(u);
+ if (likely (j_type != JOINING_TYPE_X))
+ return j_type;
+
+ return (FLAG_UNSAFE(gen_cat) &
+ (FLAG(HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) |
+ FLAG(HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
+ FLAG(HB_UNICODE_GENERAL_CATEGORY_FORMAT))
+ ) ? JOINING_TYPE_T : JOINING_TYPE_U;
+}
+
+#define FEATURE_IS_SYRIAC(tag) hb_in_range<unsigned char> ((unsigned char) (tag), '2', '3')
+
+static const hb_tag_t arabic_features[] =
+{
+ HB_TAG('i','s','o','l'),
+ HB_TAG('f','i','n','a'),
+ HB_TAG('f','i','n','2'),
+ HB_TAG('f','i','n','3'),
+ HB_TAG('m','e','d','i'),
+ HB_TAG('m','e','d','2'),
+ HB_TAG('i','n','i','t'),
+ HB_TAG_NONE
+};
+
+
+/* Same order as the feature array */
+enum arabic_action_t {
+ ISOL,
+ FINA,
+ FIN2,
+ FIN3,
+ MEDI,
+ MED2,
+ INIT,
+
+ NONE,
+
+ ARABIC_NUM_FEATURES = NONE,
+
+ /* We abuse the same byte for other things... */
+ STCH_FIXED,
+ STCH_REPEATING,
+};
+
+static const struct arabic_state_table_entry {
+ uint8_t prev_action;
+ uint8_t curr_action;
+ uint16_t next_state;
+} arabic_state_table[][NUM_STATE_MACHINE_COLS] =
+{
+ /* jt_U, jt_L, jt_R, jt_D, jg_ALAPH, jg_DALATH_RISH */
+
+ /* State 0: prev was U, not willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,6}, },
+
+ /* State 1: prev was R or ISOL/ALAPH, not willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,FIN2,5}, {NONE,ISOL,6}, },
+
+ /* State 2: prev was D/L in ISOL form, willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {INIT,FINA,1}, {INIT,FINA,3}, {INIT,FINA,4}, {INIT,FINA,6}, },
+
+ /* State 3: prev was D in FINA form, willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {MEDI,FINA,1}, {MEDI,FINA,3}, {MEDI,FINA,4}, {MEDI,FINA,6}, },
+
+ /* State 4: prev was FINA ALAPH, not willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {MED2,ISOL,1}, {MED2,ISOL,2}, {MED2,FIN2,5}, {MED2,ISOL,6}, },
+
+ /* State 5: prev was FIN2/FIN3 ALAPH, not willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {ISOL,ISOL,1}, {ISOL,ISOL,2}, {ISOL,FIN2,5}, {ISOL,ISOL,6}, },
+
+ /* State 6: prev was DALATH/RISH, not willing to join. */
+ { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,FIN3,5}, {NONE,ISOL,6}, }
+};
+
+
+static void
+arabic_fallback_shape (const hb_ot_shape_plan_t *plan,
+ hb_font_t *font,
+ hb_buffer_t *buffer);
+
+static void
+record_stch (const hb_ot_shape_plan_t *plan,
+ hb_font_t *font,
+ hb_buffer_t *buffer);
+
+static void
+collect_features_arabic (hb_ot_shape_planner_t *plan)
+{
+ hb_ot_map_builder_t *map = &plan->map;
+
+ /* We apply features according to the Arabic spec, with pauses
+ * in between most.
+ *
+ * The pause between init/medi/... and rlig is required. See eg:
+ * https://bugzilla.mozilla.org/show_bug.cgi?id=644184
+ *
+ * The pauses between init/medi/... themselves are not necessarily
+ * needed as only one of those features is applied to any character.
+ * The only difference it makes is when fonts have contextual
+ * substitutions. We now follow the order of the spec, which makes
+ * for better experience if that's what Uniscribe is doing.
+ *
+ * At least for Arabic, looks like Uniscribe has a pause between
+ * rlig and calt. Otherwise the IranNastaliq's ALLAH ligature won't
+ * work. However, testing shows that rlig and calt are applied
+ * together for Mongolian in Uniscribe. As such, we only add a
+ * pause for Arabic, not other scripts.
+ *
+ * A pause after calt is required to make KFGQPC Uthmanic Script HAFS
+ * work correctly. See https://github.com/harfbuzz/harfbuzz/issues/505
+ */
+
+
+ map->enable_feature (HB_TAG('s','t','c','h'));
+ map->add_gsub_pause (record_stch);
+
+ map->enable_feature (HB_TAG('c','c','m','p'));
+ map->enable_feature (HB_TAG('l','o','c','l'));
+
+ map->add_gsub_pause (nullptr);
+
+ for (unsigned int i = 0; i < ARABIC_NUM_FEATURES; i++)
+ {
+ bool has_fallback = plan->props.script == HB_SCRIPT_ARABIC && !FEATURE_IS_SYRIAC (arabic_features[i]);
+ map->add_feature (arabic_features[i], has_fallback ? F_HAS_FALLBACK : F_NONE);
+ map->add_gsub_pause (nullptr);
+ }
+
+ /* Normally, Unicode says a ZWNJ means "don't ligate". In Arabic script
+ * however, it says a ZWJ should also mean "don't ligate". So we run
+ * the main ligating features as MANUAL_ZWJ. */
+
+ map->enable_feature (HB_TAG('r','l','i','g'), F_MANUAL_ZWJ | F_HAS_FALLBACK);
+
+ if (plan->props.script == HB_SCRIPT_ARABIC)
+ map->add_gsub_pause (arabic_fallback_shape);
+
+ /* No pause after rclt. See 98460779bae19e4d64d29461ff154b3527bf8420. */
+ map->enable_feature (HB_TAG('r','c','l','t'), F_MANUAL_ZWJ);
+ map->enable_feature (HB_TAG('c','a','l','t'), F_MANUAL_ZWJ);
+ map->add_gsub_pause (nullptr);
+
+ /* The spec includes 'cswh'. Earlier versions of Windows
+ * used to enable this by default, but testing suggests
+ * that Windows 8 and later do not enable it by default,
+ * and spec now says 'Off by default'.
+ * We disabled this in ae23c24c32.
+ * Note that IranNastaliq uses this feature extensively
+ * to fixup broken glyph sequences. Oh well...
+ * Test case: U+0643,U+0640,U+0631. */
+ //map->enable_feature (HB_TAG('c','s','w','h'));
+ map->enable_feature (HB_TAG('m','s','e','t'));
+}
+
+#include "hb-ot-shape-complex-arabic-fallback.hh"
+
+struct arabic_shape_plan_t
+{
+ /* The "+ 1" in the next array is to accommodate for the "NONE" command,
+ * which is not an OpenType feature, but this simplifies the code by not
+ * having to do a "if (... < NONE) ..." and just rely on the fact that
+ * mask_array[NONE] == 0. */
+ hb_mask_t mask_array[ARABIC_NUM_FEATURES + 1];
+
+ hb_atomic_ptr_t<arabic_fallback_plan_t> fallback_plan;
+
+ unsigned int do_fallback : 1;
+ unsigned int has_stch : 1;
+};
+
+void *
+data_create_arabic (const hb_ot_shape_plan_t *plan)
+{
+ arabic_shape_plan_t *arabic_plan = (arabic_shape_plan_t *) calloc (1, sizeof (arabic_shape_plan_t));
+ if (unlikely (!arabic_plan))
+ return nullptr;
+
+ arabic_plan->do_fallback = plan->props.script == HB_SCRIPT_ARABIC;
+ arabic_plan->has_stch = !!plan->map.get_1_mask (HB_TAG ('s','t','c','h'));
+ for (unsigned int i = 0; i < ARABIC_NUM_FEATURES; i++) {
+ arabic_plan->mask_array[i] = plan->map.get_1_mask (arabic_features[i]);
+ arabic_plan->do_fallback = arabic_plan->do_fallback &&
+ (FEATURE_IS_SYRIAC (arabic_features[i]) ||
+ plan->map.needs_fallback (arabic_features[i]));
+ }
+
+ return arabic_plan;
+}
+
+void
+data_destroy_arabic (void *data)
+{
+ arabic_shape_plan_t *arabic_plan = (arabic_shape_plan_t *) data;
+
+ arabic_fallback_plan_destroy (arabic_plan->fallback_plan);
+
+ free (data);
+}
+
+static void
+arabic_joining (hb_buffer_t *buffer)
+{
+ unsigned int count = buffer->len;
+ hb_glyph_info_t *info = buffer->info;
+ unsigned int prev = UINT_MAX, state = 0;
+
+ /* Check pre-context */
+ for (unsigned int i = 0; i < buffer->context_len[0]; i++)
+ {
+ unsigned int this_type = get_joining_type (buffer->context[0][i], buffer->unicode->general_category (buffer->context[0][i]));
+
+ if (unlikely (this_type == JOINING_TYPE_T))
+ continue;
+
+ const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
+ state = entry->next_state;
+ break;
+ }
+
+ for (unsigned int i = 0; i < count; i++)
+ {
+ unsigned int this_type = get_joining_type (info[i].codepoint, _hb_glyph_info_get_general_category (&info[i]));
+
+ if (unlikely (this_type == JOINING_TYPE_T)) {
+ info[i].arabic_shaping_action() = NONE;
+ continue;
+ }
+
+ const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
+
+ if (entry->prev_action != NONE && prev != UINT_MAX)
+ {
+ info[prev].arabic_shaping_action() = entry->prev_action;
+ buffer->unsafe_to_break (prev, i + 1);
+ }
+
+ info[i].arabic_shaping_action() = entry->curr_action;
+
+ prev = i;
+ state = entry->next_state;
+ }
+
+ for (unsigned int i = 0; i < buffer->context_len[1]; i++)
+ {
+ unsigned int this_type = get_joining_type (buffer->context[1][i], buffer->unicode->general_category (buffer->context[1][i]));
+
+ if (unlikely (this_type == JOINING_TYPE_T))
+ continue;
+
+ const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
+ if (entry->prev_action != NONE && prev != UINT_MAX)
+ info[prev].arabic_shaping_action() = entry->prev_action;
+ break;
+ }
+}
+
+static void
+mongolian_variation_selectors (hb_buffer_t *buffer)
+{
+ /* Copy arabic_shaping_action() from base to Mongolian variation selectors. */
+ unsigned int count = buffer->len;
+ hb_glyph_info_t *info = buffer->info;
+ for (unsigned int i = 1; i < count; i++)
+ if (unlikely (hb_in_range<hb_codepoint_t> (info[i].codepoint, 0x180Bu, 0x180Du)))
+ info[i].arabic_shaping_action() = info[i - 1].arabic_shaping_action();
+}
+
+void
+setup_masks_arabic_plan (const arabic_shape_plan_t *arabic_plan,
+ hb_buffer_t *buffer,
+ hb_script_t script)
+{
+ HB_BUFFER_ALLOCATE_VAR (buffer, arabic_shaping_action);
+
+ arabic_joining (buffer);
+ if (script == HB_SCRIPT_MONGOLIAN)
+ mongolian_variation_selectors (buffer);
+
+ unsigned int count = buffer->len;
+ hb_glyph_info_t *info = buffer->info;
+ for (unsigned int i = 0; i < count; i++)
+ info[i].mask |= arabic_plan->mask_array[info[i].arabic_shaping_action()];
+}
+
+static void
+setup_masks_arabic (const hb_ot_shape_plan_t *plan,
+ hb_buffer_t *buffer,
+ hb_font_t *font HB_UNUSED)
+{
+ const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
+ setup_masks_arabic_plan (arabic_plan, buffer, plan->props.script);
+}
+
+static void
+arabic_fallback_shape (const hb_ot_shape_plan_t *plan,
+ hb_font_t *font,
+ hb_buffer_t *buffer)
+{
+#ifdef HB_NO_OT_SHAPE_COMPLEX_ARABIC_FALLBACK
+ return;
+#endif
+
+ const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
+
+ if (!arabic_plan->do_fallback)
+ return;
+
+retry:
+ arabic_fallback_plan_t *fallback_plan = arabic_plan->fallback_plan;
+ if (unlikely (!fallback_plan))
+ {
+ /* This sucks. We need a font to build the fallback plan... */
+ fallback_plan = arabic_fallback_plan_create (plan, font);
+ if (unlikely (!arabic_plan->fallback_plan.cmpexch (nullptr, fallback_plan)))
+ {
+ arabic_fallback_plan_destroy (fallback_plan);
+ goto retry;
+ }
+ }
+
+ arabic_fallback_plan_shape (fallback_plan, font, buffer);
+}
+
+/*
+ * Stretch feature: "stch".
+ * See example here:
+ * https://docs.microsoft.com/en-us/typography/script-development/syriac
+ * We implement this in a generic way, such that the Arabic subtending
+ * marks can use it as well.
+ */
+
+static void
+record_stch (const hb_ot_shape_plan_t *plan,
+ hb_font_t *font HB_UNUSED,
+ hb_buffer_t *buffer)
+{
+ const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
+ if (!arabic_plan->has_stch)
+ return;
+
+ /* 'stch' feature was just applied. Look for anything that multiplied,
+ * and record it for stch treatment later. Note that rtlm, frac, etc
+ * are applied before stch, but we assume that they didn't result in
+ * anything multiplying into 5 pieces, so it's safe-ish... */
+
+ unsigned int count = buffer->len;
+ hb_glyph_info_t *info = buffer->info;
+ for (unsigned int i = 0; i < count; i++)
+ if (unlikely (_hb_glyph_info_multiplied (&info[i])))
+ {
+ unsigned int comp = _hb_glyph_info_get_lig_comp (&info[i]);
+ info[i].arabic_shaping_action() = comp % 2 ? STCH_REPEATING : STCH_FIXED;
+ buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH;
+ }
+}
+
+static void
+apply_stch (const hb_ot_shape_plan_t *plan HB_UNUSED,
+ hb_buffer_t *buffer,
+ hb_font_t *font)
+{
+ if (likely (!(buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH)))
+ return;
+
+ /* The Arabic shaper currently always processes in RTL mode, so we should
+ * stretch / position the stretched pieces to the left / preceding glyphs. */
+
+ /* We do a two pass implementation:
+ * First pass calculates the exact number of extra glyphs we need,
+ * We then enlarge buffer to have that much room,
+ * Second pass applies the stretch, copying things to the end of buffer.
+ */
+
+ int sign = font->x_scale < 0 ? -1 : +1;
+ unsigned int extra_glyphs_needed = 0; // Set during MEASURE, used during CUT
+ enum { MEASURE, CUT } /* step_t */;
+
+ for (unsigned int step = MEASURE; step <= CUT; step = step + 1)
+ {
+ unsigned int count = buffer->len;
+ hb_glyph_info_t *info = buffer->info;
+ hb_glyph_position_t *pos = buffer->pos;
+ unsigned int new_len = count + extra_glyphs_needed; // write head during CUT
+ unsigned int j = new_len;
+ for (unsigned int i = count; i; i--)
+ {
+ if (!hb_in_range<uint8_t> (info[i - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING))
+ {
+ if (step == CUT)
+ {
+ --j;
+ info[j] = info[i - 1];
+ pos[j] = pos[i - 1];
+ }
+ continue;
+ }
+
+ /* Yay, justification! */
+
+ hb_position_t w_total = 0; // Total to be filled
+ hb_position_t w_fixed = 0; // Sum of fixed tiles
+ hb_position_t w_repeating = 0; // Sum of repeating tiles
+ int n_fixed = 0;
+ int n_repeating = 0;
+
+ unsigned int end = i;
+ while (i &&
+ hb_in_range<uint8_t> (info[i - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING))
+ {
+ i--;
+ hb_position_t width = font->get_glyph_h_advance (info[i].codepoint);
+ if (info[i].arabic_shaping_action() == STCH_FIXED)
+ {
+ w_fixed += width;
+ n_fixed++;
+ }
+ else
+ {
+ w_repeating += width;
+ n_repeating++;
+ }
+ }
+ unsigned int start = i;
+ unsigned int context = i;
+ while (context &&
+ !hb_in_range<uint8_t> (info[context - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING) &&
+ (_hb_glyph_info_is_default_ignorable (&info[context - 1]) ||
+ HB_ARABIC_GENERAL_CATEGORY_IS_WORD (_hb_glyph_info_get_general_category (&info[context - 1]))))
+ {
+ context--;
+ w_total += pos[context].x_advance;
+ }
+ i++; // Don't touch i again.
+
+ DEBUG_MSG (ARABIC, nullptr, "%s stretch at (%d,%d,%d)",
+ step == MEASURE ? "measuring" : "cutting", context, start, end);
+ DEBUG_MSG (ARABIC, nullptr, "rest of word: count=%d width %d", start - context, w_total);
+ DEBUG_MSG (ARABIC, nullptr, "fixed tiles: count=%d width=%d", n_fixed, w_fixed);
+ DEBUG_MSG (ARABIC, nullptr, "repeating tiles: count=%d width=%d", n_repeating, w_repeating);
+
+ /* Number of additional times to repeat each repeating tile. */
+ int n_copies = 0;
+
+ hb_position_t w_remaining = w_total - w_fixed;
+ if (sign * w_remaining > sign * w_repeating && sign * w_repeating > 0)
+ n_copies = (sign * w_remaining) / (sign * w_repeating) - 1;
+
+ /* See if we can improve the fit by adding an extra repeat and squeezing them together a bit. */
+ hb_position_t extra_repeat_overlap = 0;
+ hb_position_t shortfall = sign * w_remaining - sign * w_repeating * (n_copies + 1);
+ if (shortfall > 0 && n_repeating > 0)
+ {
+ ++n_copies;
+ hb_position_t excess = (n_copies + 1) * sign * w_repeating - sign * w_remaining;
+ if (excess > 0)
+ extra_repeat_overlap = excess / (n_copies * n_repeating);
+ }
+
+ if (step == MEASURE)
+ {
+ extra_glyphs_needed += n_copies * n_repeating;
+ DEBUG_MSG (ARABIC, nullptr, "will add extra %d copies of repeating tiles", n_copies);
+ }
+ else
+ {
+ buffer->unsafe_to_break (context, end);
+ hb_position_t x_offset = 0;
+ for (unsigned int k = end; k > start; k--)
+ {
+ hb_position_t width = font->get_glyph_h_advance (info[k - 1].codepoint);
+
+ unsigned int repeat = 1;
+ if (info[k - 1].arabic_shaping_action() == STCH_REPEATING)
+ repeat += n_copies;
+
+ DEBUG_MSG (ARABIC, nullptr, "appending %d copies of glyph %d; j=%d",
+ repeat, info[k - 1].codepoint, j);
+ for (unsigned int n = 0; n < repeat; n++)
+ {
+ x_offset -= width;
+ if (n > 0)
+ x_offset += extra_repeat_overlap;
+ pos[k - 1].x_offset = x_offset;
+ /* Append copy. */
+ --j;
+ info[j] = info[k - 1];
+ pos[j] = pos[k - 1];
+ }
+ }
+ }
+ }
+
+ if (step == MEASURE)
+ {
+ if (unlikely (!buffer->ensure (count + extra_glyphs_needed)))
+ break;
+ }
+ else
+ {
+ assert (j == 0);
+ buffer->len = new_len;
+ }
+ }
+}
+
+
+static void
+postprocess_glyphs_arabic (const hb_ot_shape_plan_t *plan,
+ hb_buffer_t *buffer,
+ hb_font_t *font)
+{
+ apply_stch (plan, buffer, font);
+
+ HB_BUFFER_DEALLOCATE_VAR (buffer, arabic_shaping_action);
+}
+
+/* https://www.unicode.org/reports/tr53/ */
+
+static hb_codepoint_t
+modifier_combining_marks[] =
+{
+ 0x0654u, /* ARABIC HAMZA ABOVE */
+ 0x0655u, /* ARABIC HAMZA BELOW */
+ 0x0658u, /* ARABIC MARK NOON GHUNNA */
+ 0x06DCu, /* ARABIC SMALL HIGH SEEN */
+ 0x06E3u, /* ARABIC SMALL LOW SEEN */
+ 0x06E7u, /* ARABIC SMALL HIGH YEH */
+ 0x06E8u, /* ARABIC SMALL HIGH NOON */
+ 0x08D3u, /* ARABIC SMALL LOW WAW */
+ 0x08F3u, /* ARABIC SMALL HIGH WAW */
+};
+
+static inline bool
+info_is_mcm (const hb_glyph_info_t &info)
+{
+ hb_codepoint_t u = info.codepoint;
+ for (unsigned int i = 0; i < ARRAY_LENGTH (modifier_combining_marks); i++)
+ if (u == modifier_combining_marks[i])
+ return true;
+ return false;
+}
+
+static void
+reorder_marks_arabic (const hb_ot_shape_plan_t *plan HB_UNUSED,
+ hb_buffer_t *buffer,
+ unsigned int start,
+ unsigned int end)
+{
+ hb_glyph_info_t *info = buffer->info;
+
+ DEBUG_MSG (ARABIC, buffer, "Reordering marks from %d to %d", start, end);
+
+ unsigned int i = start;
+ for (unsigned int cc = 220; cc <= 230; cc += 10)
+ {
+ DEBUG_MSG (ARABIC, buffer, "Looking for %d's starting at %d", cc, i);
+ while (i < end && info_cc(info[i]) < cc)
+ i++;
+ DEBUG_MSG (ARABIC, buffer, "Looking for %d's stopped at %d", cc, i);
+
+ if (i == end)
+ break;
+
+ if (info_cc(info[i]) > cc)
+ continue;
+
+ unsigned int j = i;
+ while (j < end && info_cc(info[j]) == cc && info_is_mcm (info[j]))
+ j++;
+
+ if (i == j)
+ continue;
+
+ DEBUG_MSG (ARABIC, buffer, "Found %d's from %d to %d", cc, i, j);
+
+ /* Shift it! */
+ DEBUG_MSG (ARABIC, buffer, "Shifting %d's: %d %d", cc, i, j);
+ hb_glyph_info_t temp[HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS];
+ assert (j - i <= ARRAY_LENGTH (temp));
+ buffer->merge_clusters (start, j);
+ memmove (temp, &info[i], (j - i) * sizeof (hb_glyph_info_t));
+ memmove (&info[start + j - i], &info[start], (i - start) * sizeof (hb_glyph_info_t));
+ memmove (&info[start], temp, (j - i) * sizeof (hb_glyph_info_t));
+
+ /* Renumber CC such that the reordered sequence is still sorted.
+ * 22 and 26 are chosen because they are smaller than all Arabic categories,
+ * and are folded back to 220/230 respectively during fallback mark positioning.
+ *
+ * We do this because the CGJ-handling logic in the normalizer relies on
+ * mark sequences having an increasing order even after this reordering.
+ * https://github.com/harfbuzz/harfbuzz/issues/554
+ * This, however, does break some obscure sequences, where the normalizer
+ * might compose a sequence that it should not. For example, in the seequence
+ * ALEF, HAMZAH, MADDAH, we should NOT try to compose ALEF+MADDAH, but with this
+ * renumbering, we will.
+ */
+ unsigned int new_start = start + j - i;
+ unsigned int new_cc = cc == 220 ? HB_MODIFIED_COMBINING_CLASS_CCC22 : HB_MODIFIED_COMBINING_CLASS_CCC26;
+ while (start < new_start)
+ {
+ _hb_glyph_info_set_modified_combining_class (&info[start], new_cc);
+ start++;
+ }
+
+ i = j;
+ }
+}
+
+const hb_ot_complex_shaper_t _hb_ot_complex_shaper_arabic =
+{
+ collect_features_arabic,
+ nullptr, /* override_features */
+ data_create_arabic,
+ data_destroy_arabic,
+ nullptr, /* preprocess_text */
+ postprocess_glyphs_arabic,
+ HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
+ nullptr, /* decompose */
+ nullptr, /* compose */
+ setup_masks_arabic,
+ HB_TAG_NONE, /* gpos_tag */
+ reorder_marks_arabic,
+ HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE,
+ true, /* fallback_position */
+};
+
+
+#endif