*/
#include "hb-ot-shape-private.hh"
+#include "hb-ot-shape-complex-private.hh"
HB_BEGIN_DECLS
-static bool
-get_glyph (hb_ot_shape_context_t *c, unsigned int i)
+/*
+ * 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 desires,
+ * 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, form use the precomposed character
+ * which typically has better mark positioning.
+ *
+ * - 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 *b = c->buffer;
+ hb_buffer_t *buffer = c->buffer;
- return hb_font_get_glyph (c->font, b->info[i].codepoint, 0, &b->info[i].intermittent_glyph());
+ buffer->output_glyph (glyph);
+ hb_glyph_info_set_unicode_props (&buffer->out_info[buffer->out_len - 1], buffer->unicode);
}
static bool
-handle_single_char_cluster (hb_ot_shape_context_t *c,
- unsigned int i)
+decompose (hb_ot_shape_context_t *c,
+ bool shortest,
+ hb_codepoint_t ab)
{
- if (get_glyph (c, i))
+ 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;
- /* Decompose */
+ 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 bool
-handle_multi_char_cluster (hb_ot_shape_context_t *c,
- unsigned int i,
- unsigned int end)
+static void
+decompose_current_glyph (hb_ot_shape_context_t *c,
+ bool shortest)
{
- /* If there's a variation-selector, give-up, it's just too hard. */
- return FALSE;
+ 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)))
+ return;
+
+ while (c->buffer->idx < end)
+ decompose_current_glyph (c, FALSE);
}
-bool
-_hb_normalize (hb_ot_shape_context_t *c)
+static int
+compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
{
- hb_buffer_t *b = c->buffer;
- bool changed = FALSE;
+ 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.
+ *
+ * TODO: Am I right about Hangul? If I am, we should add a Hangul module
+ * that requests decomposed. */
+
+ 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 count = b->len;
- for (unsigned int i = 0; i < count;) {
unsigned int end;
for (end = i + 1; end < count; end++)
- if (b->info[i].cluster != b->info[end].cluster)
+ if (buffer->info[end].combining_class() == 0)
break;
- if (i + 1 == end)
- changed |= handle_single_char_cluster (c, i);
- else
- changed |= handle_multi_char_cluster (c, i, end);
+
+ /* 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;
}
- return changed;
+
+ 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 ();
+
}
HB_END_DECLS
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