Fix HarfBuzz Thai character SARA AM handling

This patch is contributed by Thanomsub Noppaburana from libthai. It
added a special thai shaping function to handle SARA AM character
for fonts without OpenType rules to support it, like Nokia Pure Text
AS.

With modification to logClusters assignment to make sure that
QTextLine::glyphRuns(int from, int length) returns correct glyphs.

Task-number: QTBUG-21206
Change-Id: I5a78ee1ab2b4c874c7d0df17d4ee6d264ed5a790
Reviewed-by: Lars Knoll <[email protected]>

Author: Jiang Jiang

src/3rdparty/harfbuzz/src/harfbuzz-shaper-private.h

@@ -111,6 +111,7 @@ extern HB_Bool HB_HangulShape(HB_ShaperItem *shaper_item);
 extern HB_Bool HB_MyanmarShape(HB_ShaperItem *shaper_item);
 extern HB_Bool HB_KhmerShape(HB_ShaperItem *shaper_item);
 extern HB_Bool HB_IndicShape(HB_ShaperItem *shaper_item);
+extern HB_Bool HB_ThaiShape(HB_ShaperItem *shaper_item);
 
 extern void HB_TibetanAttributes(HB_Script script, const HB_UChar16 *string, hb_uint32 from, hb_uint32 len, HB_CharAttributes *attributes);
 

src/3rdparty/harfbuzz/src/harfbuzz-shaper.cpp

@@ -618,7 +618,7 @@ const HB_ScriptEngine HB_ScriptEngines[] = {
     // Sinhala
     { HB_IndicShape, HB_IndicAttributes },
     // Thai
-    { HB_BasicShape, HB_ThaiAttributes },
+    { HB_ThaiShape, HB_ThaiAttributes },
     // Lao
     { HB_BasicShape, 0 },
     // Tibetan
@@ -1308,18 +1308,18 @@ HB_Bool HB_OpenTypePosition(HB_ShaperItem *item, int availableGlyphs, HB_Bool do
 
 #ifdef OT_DEBUG
     if (doLogClusters) {
-        DEBUG("log clusters after shaping:");
-        for (int j = 0; j < length; j++)
-            DEBUG("    log[%d] = %d", j, item->log_clusters[j]);
+        DEBUG("log clusters after shaping:\n");
+        for (unsigned int j = 0; j < item->item.length; j++)
+            DEBUG("    log[%d] = %d\n", j, item->log_clusters[j]);
     }
-    DEBUG("final glyphs:");
-    for (int i = 0; i < (int)hb_buffer->in_length; ++i)
-        DEBUG("   glyph=%4x char_index=%d mark: %d cmp: %d, clusterStart: %d advance=%d/%d offset=%d/%d",
-               glyphs[i].glyph, hb_buffer->in_string[i].cluster, glyphs[i].attributes.mark,
-               glyphs[i].attributes.combiningClass, glyphs[i].attributes.clusterStart,
-               glyphs[i].advance.x.toInt(), glyphs[i].advance.y.toInt(),
-               glyphs[i].offset.x.toInt(), glyphs[i].offset.y.toInt());
-    DEBUG("-----------------------------------------");
+    DEBUG("final glyphs:\n");
+    for (unsigned int i = 0; i < item->num_glyphs; ++i)
+        DEBUG("   glyph=%4x char_index=%d mark: %d cmp: %d, clusterStart: %d advance=%d offset=%d/%d\n",
+               glyphs[i], face->buffer->in_string[i].cluster, attributes[i].mark,
+               attributes[i].combiningClass, attributes[i].clusterStart,
+               item->advances[i] >> 6,
+               item->offsets[i].x >> 6, item->offsets[i].y >> 6);
+    DEBUG("-----------------------------------------\n");
 #endif
     return true;
 }