item: Add a char offset

Add a char_offset field to PangoItem, compute it as part of
itemization and update it when splitting items. Keeping this
number around cuts down on the amount of list and utf8 walking
we need to do later.

We have to do some extra shenanigans to preserve abi in the
face of pango's open-coded structs, so we introduce a
PangoItemPrivate type that is used internally. On 64bit,
PangoItem has a 4 byte whole, so we can keep the size of
PangoItemPrivate the same. No such luck on 32bit.

1 files changed, 14 insertions, 5 deletions

diff --git a/pango/pango-item.c b/pango/pango-item.c
index ce38e6d2..484d5f1f 100644
--- a/pango/pango-item.c
+++ b/pango/pango-item.c
@@ -21,7 +21,7 @@
 
 #include "config.h"
 #include "pango-attributes.h"
-#include "pango-item.h"
+#include "pango-item-private.h"
 #include "pango-impl-utils.h"
 
 /**
@@ -35,9 +35,11 @@
 PangoItem *
 pango_item_new (void)
 {
-  PangoItem *result = g_slice_new0 (PangoItem);
+  PangoItemPrivate *result = g_slice_new0 (PangoItemPrivate);
 
-  return result;
+  result->analysis.flags |= PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET;
+
+  return (PangoItem *)result;
 }
 
 /**
@@ -57,11 +59,13 @@ pango_item_copy (PangoItem *item)
   if (item == NULL)
     return NULL;
 
-  result = g_slice_new (PangoItem);
+  result = pango_item_new ();
 
   result->offset = item->offset;
   result->length = item->length;
   result->num_chars = item->num_chars;
+  if (item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    ((PangoItemPrivate *)result)->char_offset = ((PangoItemPrivate *)item)->char_offset;
 
   result->analysis = item->analysis;
   if (result->analysis.font)
@@ -101,7 +105,10 @@ pango_item_free (PangoItem *item)
   if (item->analysis.font)
     g_object_unref (item->analysis.font);
 
-  g_slice_free (PangoItem, item);
+  if (item->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    g_slice_free (PangoItemPrivate, (PangoItemPrivate *)item);
+  else
+    g_slice_free (PangoItem, item);
 }
 
 G_DEFINE_BOXED_TYPE (PangoItem, pango_item,
@@ -151,6 +158,8 @@ pango_item_split (PangoItem *orig,
   orig->offset += split_index;
   orig->length -= split_index;
   orig->num_chars -= split_offset;
+  if (orig->analysis.flags & PANGO_ANALYSIS_FLAG_HAS_CHAR_OFFSET)
+    ((PangoItemPrivate *)orig)->char_offset += split_offset;
 
   return new_item;
 }