Make it easier to use HB_BUFFER_FLAG_BOT/EOT
Previously, we expected users to provide BOT/EOT flags when the text *segment* was at paragraph boundaries. This meant that for clients that provide full paragraph to HarfBuzz (eg. Pango), they had code like this: hb_buffer_set_flags (hb_buffer, (item_offset == 0 ? HB_BUFFER_FLAG_BOT : 0) | (item_offset + item_length == paragraph_length ? HB_BUFFER_FLAG_EOT : 0)); hb_buffer_add_utf8 (hb_buffer, paragraph_text, paragraph_length, item_offset, item_length); After this change such clients can simply say: hb_buffer_set_flags (hb_buffer, HB_BUFFER_FLAG_BOT | HB_BUFFER_FLAG_EOT); hb_buffer_add_utf8 (hb_buffer, paragraph_text, paragraph_length, item_offset, item_length); Ie, HarfBuzz itself checks whether the segment is at the beginning/end of the paragraph. Clients that only pass item-at-a-time to HarfBuzz continue not setting any flags whatsoever. Another way to put it is: if there's pre-context text in the buffer, HarfBuzz ignores the BOT flag. If there's post-context, it ignores EOT flag.
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