Index: third_party/harfbuzz-ng/src/hb-ot-shape-normalize.cc |
diff --git a/third_party/harfbuzz-ng/src/hb-ot-shape-normalize.cc b/third_party/harfbuzz-ng/src/hb-ot-shape-normalize.cc |
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index 0000000000000000000000000000000000000000..eb9f32ad1bb5ec163722defb5751f570b62798e2 |
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+++ b/third_party/harfbuzz-ng/src/hb-ot-shape-normalize.cc |
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+/* |
+ * Copyright © 2011 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-ot-shape-private.hh" |
+#include "hb-ot-shape-complex-private.hh" |
+ |
+ |
+/* |
+ * HIGHLEVEL DESIGN: |
+ * |
+ * This file exports one main function: _hb_ot_shape_normalize(). |
+ * |
+ * This function closely reflects the Unicode Normalization Algorithm, |
+ * yet it's different. The shaper an either prefer decomposed (NFD) or |
+ * composed (NFC). |
+ * |
+ * In general what happens is that: each grapheme is decomposed in a chain |
+ * of 1:2 decompositions, marks reordered, and then recomposed if desired, |
+ * so far it's like Unicode Normalization. However, the decomposition and |
+ * recomposition only happens if the font supports the resulting characters. |
+ * |
+ * The goals are: |
+ * |
+ * - Try to render all canonically equivalent strings similarly. To really |
+ * achieve this we have to always do the full decomposition and then |
+ * selectively recompose from there. It's kinda too expensive though, so |
+ * we skip some cases. For example, if composed is desired, we simply |
+ * don't touch 1-character clusters that are supported by the font, even |
+ * though their NFC may be different. |
+ * |
+ * - When a font has a precomposed character for a sequence but the 'ccmp' |
+ * feature in the font is not adequate, use the precomposed character |
+ * which typically has better mark positioning. |
+ * |
+ * - When a font does not support a combining mark, but supports it precomposed |
+ * with previous base. This needs the itemizer to have this knowledge too. |
+ * We need ot provide assistance to the itemizer. |
+ * |
+ * - When a font does not support a character but supports its decomposition, |
+ * well, use the decomposition. |
+ * |
+ * - The Indic shaper requests decomposed output. This will handle splitting |
+ * matra for the Indic shaper. |
+ */ |
+ |
+static void |
+output_glyph (hb_ot_shape_context_t *c, |
+ hb_codepoint_t glyph) |
+{ |
+ hb_buffer_t *buffer = c->buffer; |
+ |
+ buffer->output_glyph (glyph); |
+ hb_glyph_info_set_unicode_props (&buffer->out_info[buffer->out_len - 1], buffer->unicode); |
+} |
+ |
+static bool |
+decompose (hb_ot_shape_context_t *c, |
+ bool shortest, |
+ hb_codepoint_t ab) |
+{ |
+ hb_codepoint_t a, b, glyph; |
+ |
+ if (!hb_unicode_decompose (c->buffer->unicode, ab, &a, &b) || |
+ (b && !hb_font_get_glyph (c->font, b, 0, &glyph))) |
+ return FALSE; |
+ |
+ bool has_a = hb_font_get_glyph (c->font, a, 0, &glyph); |
+ if (shortest && has_a) { |
+ /* Output a and b */ |
+ output_glyph (c, a); |
+ if (b) |
+ output_glyph (c, b); |
+ return TRUE; |
+ } |
+ |
+ if (decompose (c, shortest, a)) { |
+ if (b) |
+ output_glyph (c, b); |
+ return TRUE; |
+ } |
+ |
+ if (has_a) { |
+ output_glyph (c, a); |
+ if (b) |
+ output_glyph (c, b); |
+ return TRUE; |
+ } |
+ |
+ return FALSE; |
+} |
+ |
+static void |
+decompose_current_glyph (hb_ot_shape_context_t *c, |
+ bool shortest) |
+{ |
+ if (decompose (c, shortest, c->buffer->info[c->buffer->idx].codepoint)) |
+ c->buffer->skip_glyph (); |
+ else |
+ c->buffer->next_glyph (); |
+} |
+ |
+static void |
+decompose_single_char_cluster (hb_ot_shape_context_t *c, |
+ bool will_recompose) |
+{ |
+ hb_codepoint_t glyph; |
+ |
+ /* If recomposing and font supports this, we're good to go */ |
+ if (will_recompose && hb_font_get_glyph (c->font, c->buffer->info[c->buffer->idx].codepoint, 0, &glyph)) { |
+ c->buffer->next_glyph (); |
+ return; |
+ } |
+ |
+ decompose_current_glyph (c, will_recompose); |
+} |
+ |
+static void |
+decompose_multi_char_cluster (hb_ot_shape_context_t *c, |
+ unsigned int end) |
+{ |
+ /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */ |
+ for (unsigned int i = c->buffer->idx; i < end; i++) |
+ if (unlikely (is_variation_selector (c->buffer->info[i].codepoint))) { |
+ while (c->buffer->idx < end) |
+ c->buffer->next_glyph (); |
+ return; |
+ } |
+ |
+ while (c->buffer->idx < end) |
+ decompose_current_glyph (c, FALSE); |
+} |
+ |
+static int |
+compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb) |
+{ |
+ unsigned int a = pa->combining_class(); |
+ unsigned int b = pb->combining_class(); |
+ |
+ return a < b ? -1 : a == b ? 0 : +1; |
+} |
+ |
+void |
+_hb_ot_shape_normalize (hb_ot_shape_context_t *c) |
+{ |
+ hb_buffer_t *buffer = c->buffer; |
+ bool recompose = !hb_ot_shape_complex_prefer_decomposed (c->plan->shaper); |
+ bool has_multichar_clusters = FALSE; |
+ unsigned int count; |
+ |
+ /* We do a fairly straightforward yet custom normalization process in three |
+ * separate rounds: decompose, reorder, recompose (if desired). Currently |
+ * this makes two buffer swaps. We can make it faster by moving the last |
+ * two rounds into the inner loop for the first round, but it's more readable |
+ * this way. */ |
+ |
+ |
+ /* First round, decompose */ |
+ |
+ buffer->clear_output (); |
+ count = buffer->len; |
+ for (buffer->idx = 0; buffer->idx < count;) |
+ { |
+ unsigned int end; |
+ for (end = buffer->idx + 1; end < count; end++) |
+ if (buffer->info[buffer->idx].cluster != buffer->info[end].cluster) |
+ break; |
+ |
+ if (buffer->idx + 1 == end) |
+ decompose_single_char_cluster (c, recompose); |
+ else { |
+ decompose_multi_char_cluster (c, end); |
+ has_multichar_clusters = TRUE; |
+ } |
+ } |
+ buffer->swap_buffers (); |
+ |
+ |
+ /* Technically speaking, two characters with ccc=0 may combine. But all |
+ * those cases are in languages that the indic module handles (which expects |
+ * decomposed), or in Hangul jamo, which again, we want decomposed anyway. |
+ * So we don't bother combining across cluster boundaries. This is a huge |
+ * performance saver if the compose() callback is slow. |
+ * |
+ * TODO: Am I right about Hangul? If I am, we should add a Hangul module |
+ * that requests decomposed. If for Hangul we end up wanting composed, we |
+ * can do that in the Hangul module. |
+ */ |
+ |
+ if (!has_multichar_clusters) |
+ return; /* Done! */ |
+ |
+ |
+ /* Second round, reorder (inplace) */ |
+ |
+ count = buffer->len; |
+ for (unsigned int i = 0; i < count; i++) |
+ { |
+ if (buffer->info[i].combining_class() == 0) |
+ continue; |
+ |
+ unsigned int end; |
+ for (end = i + 1; end < count; end++) |
+ if (buffer->info[end].combining_class() == 0) |
+ break; |
+ |
+ /* We are going to do a bubble-sort. Only do this if the |
+ * sequence is short. Doing it on long sequences can result |
+ * in an O(n^2) DoS. */ |
+ if (end - i > 10) { |
+ i = end; |
+ continue; |
+ } |
+ |
+ hb_bubble_sort (buffer->info + i, end - i, compare_combining_class); |
+ |
+ i = end; |
+ } |
+ |
+ |
+ if (!recompose) |
+ return; |
+ |
+ /* Third round, recompose */ |
+ |
+ /* As noted in the comment earlier, we don't try to combine |
+ * ccc=0 chars with their previous Starter. */ |
+ |
+ buffer->clear_output (); |
+ count = buffer->len; |
+ unsigned int starter = 0; |
+ buffer->next_glyph (); |
+ while (buffer->idx < count) |
+ { |
+ if (buffer->info[buffer->idx].combining_class() == 0) { |
+ starter = buffer->out_len; |
+ buffer->next_glyph (); |
+ continue; |
+ } |
+ |
+ hb_codepoint_t composed, glyph; |
+ if ((buffer->out_info[buffer->out_len - 1].combining_class() >= |
+ buffer->info[buffer->idx].combining_class()) || |
+ !hb_unicode_compose (c->buffer->unicode, |
+ buffer->out_info[starter].codepoint, |
+ buffer->info[buffer->idx].codepoint, |
+ &composed) || |
+ !hb_font_get_glyph (c->font, composed, 0, &glyph)) |
+ { |
+ /* Blocked, or doesn't compose. */ |
+ buffer->next_glyph (); |
+ continue; |
+ } |
+ |
+ /* Composes. Modify starter and carry on. */ |
+ buffer->out_info[starter].codepoint = composed; |
+ hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer->unicode); |
+ |
+ buffer->skip_glyph (); |
+ } |
+ buffer->swap_buffers (); |
+ |
+} |
+ |