Add a flag to hb_buffer_t to prevent the insertion of dotted circles on incorrect character sequences.

Current behavior unchanged if this flag is not set (and it isn't by default).

src/hb-buffer.h

@@ -284,6 +284,10 @@ hb_buffer_guess_segment_properties (hb_buffer_t *buffer);
  *                      space glyph and zeroing the advance width.)
  *                      @HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES takes
  *                      precedence over this flag. Since: 1.8.0
+ * @HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE:
+ *                      flag indicating that a dotted circle should
+ *                      not be inserted in the rendering of incorrect
+ *                      character sequences (such at <0905 093E>).
  *
  * Since: 0.9.20
  */
@@ -292,7 +296,8 @@ typedef enum { /*< flags >*/
   HB_BUFFER_FLAG_BOT				= 0x00000001u, /* Beginning-of-text */
   HB_BUFFER_FLAG_EOT				= 0x00000002u, /* End-of-text */
   HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES	= 0x00000004u,
-  HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES	= 0x00000008u
+  HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES	= 0x00000008u,
+  HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE	= 0x00000010u
 } hb_buffer_flags_t;
 
 HB_EXTERN void

src/hb-ot-shape-complex-hangul.cc

@@ -214,7 +214,8 @@ preprocess_text_hangul (const hb_ot_shape_plan_t *plan HB_UNUSED,
       else
       {
 	/* No valid syllable as base for tone mark; try to insert dotted circle. */
-	if (font->has_glyph (0x25CCu))
+      if (   !(buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE)
+          && font->has_glyph (0x25CCu))
 	{
 	  hb_codepoint_t chars[2];
 	  if (!is_zero_width_char (font, u)) {

src/hb-ot-shape-complex-indic.cc

@@ -965,6 +965,9 @@ insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   /* Note: This loop is extra overhead, but should not be measurable.
    * TODO Use a buffer scratch flag to remove the loop. */
   bool has_broken_syllables = false;

src/hb-ot-shape-complex-khmer.cc

@@ -365,6 +365,9 @@ insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   /* Note: This loop is extra overhead, but should not be measurable. */
   bool has_broken_syllables = false;
   unsigned int count = buffer->len;

src/hb-ot-shape-complex-myanmar.cc

@@ -298,6 +298,9 @@ insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   /* Note: This loop is extra overhead, but should not be measurable. */
   bool has_broken_syllables = false;
   unsigned int count = buffer->len;

src/hb-ot-shape-complex-use.cc

@@ -523,6 +523,9 @@ insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   /* Note: This loop is extra overhead, but should not be measurable. */
   bool has_broken_syllables = false;
   unsigned int count = buffer->len;

src/hb-ot-shape-complex-vowel-constraints.cc

@@ -34,6 +34,9 @@ _hb_preprocess_text_vowel_constraints (const hb_ot_shape_plan_t *plan HB_UNUSED,
 				       hb_buffer_t              *buffer,
 				       hb_font_t                *font HB_UNUSED)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   /* UGLY UGLY UGLY business of adding dotted-circle in the middle of
    * vowel-sequences that look like another vowel.  Data for each script
    * collected from the USE script development spec.

src/hb-ot-shape.cc

@@ -448,6 +448,9 @@ hb_set_unicode_props (hb_buffer_t *buffer)
 static void
 hb_insert_dotted_circle (hb_buffer_t *buffer, hb_font_t *font)
 {
+  if (unlikely (buffer->flags & HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE))
+    return;
+
   if (!(buffer->flags & HB_BUFFER_FLAG_BOT) ||
       buffer->context_len[0] ||
       !_hb_glyph_info_is_unicode_mark (&buffer->info[0]))