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[CoreText] Ensure cluster indices in output buffer are non-decreasing. 

Does not provide Uniscribe-compatible results, but should at least avoid
breaking hb-view due to out-of-order cluster values.

For RTL runs, ensure cluster values are non-increasing (instead of
non-decreasing).
This commit is contained in:
Jonathan Kew 2012-07-26 15:58:45 -04:00 committed by Behdad Esfahbod
parent 441d3bb7de
commit ac2085d4b3
1 changed files with 37 additions and 0 deletions
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37
src/hb-coretext.cc
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@ -319,5 +319,42 @@ _hb_coretext_shape (hb_font_t *font,
pos->y_offset = info->var2.u32;
}
// Fix up clusters so that we never return out-of-order indices;
// if core text has reordered glyphs, we'll merge them to the
// beginning of the reordered cluster.
// This does *not* mean we'll form the same clusters as Uniscribe
// or the native OT backend, only that the cluster indices will be
// non-decreasing in the output buffer.
if (HB_DIRECTION_IS_FORWARD (buffer->props.direction)) {
unsigned int prev_cluster = 0;
for (unsigned int i = 0; i < count; i++) {
unsigned int curr_cluster = buffer->info[i].cluster;
if (curr_cluster < prev_cluster) {
for (unsigned int j = i; j > 0; j--) {
if (buffer->info[j - 1].cluster > curr_cluster)
buffer->info[j - 1].cluster = curr_cluster;
else
break;
}
}
prev_cluster = curr_cluster;
}
} else {
// For RTL runs, we make them non-increasing instead.
unsigned int prev_cluster = (unsigned int)-1;
for (unsigned int i = 0; i < count; i++) {
unsigned int curr_cluster = buffer->info[i].cluster;
if (curr_cluster > prev_cluster) {
for (unsigned int j = i; j > 0; j--) {
if (buffer->info[j - 1].cluster < curr_cluster)
buffer->info[j - 1].cluster = curr_cluster;
else
break;
}
}
prev_cluster = curr_cluster;
}
}
return true;
}