From 3409fb1c767118067cf7edfb97068936b6f4b717 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 21 Aug 2013 17:22:21 -0400
Subject: [PATCH] [uniscribe] Ask Uniscribe to return shaping results in
 logical order

See discussion on the list in the thread "Arabic presentation forms
and the uniscribe backend".

Based on patch from Jonathan Kew.
---
 src/hb-uniscribe.cc | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/hb-uniscribe.cc b/src/hb-uniscribe.cc
index 075875046..2bda0bc2e 100644
--- a/src/hb-uniscribe.cc
+++ b/src/hb-uniscribe.cc
@@ -832,9 +832,8 @@ retry:
   unsigned int glyphs_offset = 0;
   unsigned int glyphs_len;
   bool backward = HB_DIRECTION_IS_BACKWARD (buffer->props.direction);
-  for (unsigned int j = 0; j < item_count; j++)
+  for (unsigned int i = 0; i < item_count; i++)
   {
-    unsigned int i = backward ? item_count - 1 - j : j;
     unsigned int chars_offset = items[i].iCharPos;
     unsigned int item_chars_len = items[i + 1].iCharPos - chars_offset;
 
@@ -875,6 +874,10 @@ retry:
       }
     }
 
+    /* Asking for glyphs in logical order circumvents at least
+     * one bug in Uniscribe. */
+    items[i].a.fLogicalOrder = true;
+
   retry_shape:
     hr = funcs->ScriptShapeOpenType (font_data->hdc,
 				     &font_data->script_cache,
@@ -962,15 +965,9 @@ retry:
     uint32_t *p = &vis_clusters[log_clusters[buffer->info[i].utf16_index()]];
     *p = MIN (*p, buffer->info[i].cluster);
   }
-  if (!backward) {
-    for (unsigned int i = 1; i < glyphs_len; i++)
-      if (vis_clusters[i] == -1)
-	vis_clusters[i] = vis_clusters[i - 1];
-  } else {
-    for (int i = glyphs_len - 2; i >= 0; i--)
-      if (vis_clusters[i] == -1)
-	vis_clusters[i] = vis_clusters[i + 1];
-  }
+  for (unsigned int i = 1; i < glyphs_len; i++)
+    if (vis_clusters[i] == -1)
+      vis_clusters[i] = vis_clusters[i - 1];
 
 #undef utf16_index
 
@@ -1004,10 +1001,13 @@ retry:
 
     /* TODO vertical */
     pos->x_advance = info->mask;
-    pos->x_offset = info->var1.u32;
+    pos->x_offset = backward ? -info->var1.u32 : info->var1.u32;
     pos->y_offset = info->var2.u32;
   }
 
+  if (backward)
+    hb_buffer_reverse (buffer);
+
   /* Wow, done! */
   return true;
 }