[pango] Add a readonly version of pango_layout_get_log_attrs()

[Matthias Clasen <matthiasc src gnome org>]

commit 4587e5d2231b717dd116253a49badc1ba3aa5db5
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat May 14 08:31:02 2011 -0400

    Add a readonly version of pango_layout_get_log_attrs()
    
    Otherwise, we are forced to either make many unnecessary copies
    or pass the log attrs around alongside the layout in APIs operating
    on the attrs.
    https://bugzilla.gnome.org/show_bug.cgi?id=650170

 docs/pango-sections.txt |    1 +
 pango/pango-layout.c    |   35 +++++++++++++++++++++++++++++++++++
 pango/pango-layout.h    |    3 +++
 pango/pango.def         |    1 +
 4 files changed, 40 insertions(+), 0 deletions(-)
---
diff --git a/docs/pango-sections.txt b/docs/pango-sections.txt
index 61e3f69..d0236a2 100644
--- a/docs/pango-sections.txt
+++ b/docs/pango-sections.txt
@@ -481,6 +481,7 @@ PANGO_TYPE_ALIGNMENT
 
 pango_layout_get_unknown_glyphs_count
 pango_layout_get_log_attrs
+pango_layout_get_log_attrs_readonly
 
 pango_layout_index_to_pos
 pango_layout_index_to_line_x
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index f0dbbcc..0b17ea8 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -1277,6 +1277,41 @@ pango_layout_get_log_attrs (PangoLayout    *layout,
     *n_attrs = layout->n_chars + 1;
 }
 
+/**
+ * pango_layout_get_log_attrs_readonly:
+ * @layout: a #PangoLayout
+ * @n_attrs: location to store the number of the attributes in the array
+ *
+ * Retrieves an array of logical attributes for each character in
+ * the @layout.
+ *
+ * This is a faster alternative to pango_layout_get_log_attrs().
+ * The returned array is part of @layout and must not be modified.
+ * Modifying the layout will invalidate the returned array.
+ *
+ * The number of attributes returned in @n_attrs will be one more
+ * than the total number of characters in the layout, since there
+ * need to be attributes corresponding to both the position before
+ * the first character and the position after the last character.
+ *
+ * Returns: an array of logical attributes
+ *
+ * Since: 1.30
+ */
+PangoLogAttr *
+pango_layout_get_log_attrs_readonly (PangoLayout *layout,
+                                     gint        *n_attrs)
+{
+  g_return_if_fail (layout != NULL);
+
+  pango_layout_check_lines (layout);
+
+  if (n_attrs)
+    *n_attrs = layout->n_chars + 1;
+
+  return layout->log_attrs;
+}
+
 
 /**
  * pango_layout_get_line_count:
diff --git a/pango/pango-layout.h b/pango/pango-layout.h
index 3b769ff..52dc36a 100644
--- a/pango/pango-layout.h
+++ b/pango/pango-layout.h
@@ -166,6 +166,9 @@ void     pango_layout_get_log_attrs (PangoLayout    *layout,
 				     PangoLogAttr  **attrs,
 				     gint           *n_attrs);
 
+PangoLogAttr *pango_layout_get_log_attrs_readonly (PangoLayout *layout,
+                                                   gint        *n_attrs);
+
 void     pango_layout_index_to_pos         (PangoLayout    *layout,
 					    int             index_,
 					    PangoRectangle *pos);
diff --git a/pango/pango.def b/pango/pango.def
index 3b1bc76..70e1a50 100644
--- a/pango/pango.def
+++ b/pango/pango.def
@@ -177,6 +177,7 @@ EXPORTS
 	pango_fontset_simple_size
 	pango_get_lib_subdirectory
 	pango_get_log_attrs
+	pango_get_log_attrs_readonly
 	pango_get_mirror_char
 	pango_get_sysconf_subdirectory
 	pango_glyph_item_apply_attrs