[pangomm] Layout: Speed up get_log_attrs()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 0da7f36962b9a326a3f83dd8b70ef3b12b5dee14
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Sun Jan 17 15:47:11 2021 +0100

    Layout: Speed up get_log_attrs()
    
    Call pango_layout_get_log_attrs_readonly() instead of
    pango_layout_get_log_attrs(). The PangoLogAttr structs
    will then be copied once instead of twice.

 pango/src/layout.ccg |  6 ++----
 pango/src/layout.hg  | 10 ++++++++--
 2 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/pango/src/layout.ccg b/pango/src/layout.ccg
index 3aa20eb..2e5b3d5 100644
--- a/pango/src/layout.ccg
+++ b/pango/src/layout.ccg
@@ -72,12 +72,10 @@ void Layout::set_markup(const Glib::ustring& markup, gunichar accel_marker, guni
 
 std::vector<PangoLogAttr> Layout::get_log_attrs() const
 {
-  //Get array:
-  PangoLogAttr* pAttrs = nullptr;
   int n_attrs = 0;
-  pango_layout_get_log_attrs(const_cast<PangoLayout*>(gobj()), &pAttrs, &n_attrs);
+  const PangoLogAttr* const pAttrs = pango_layout_get_log_attrs_readonly(const_cast<PangoLayout*>(gobj()), 
&n_attrs);
 
-  return Glib::ArrayHandler<PangoLogAttr>::array_to_vector(pAttrs, n_attrs, Glib::OWNERSHIP_SHALLOW);
+  return Glib::ArrayHandler<PangoLogAttr>::array_to_vector(pAttrs, n_attrs, Glib::OWNERSHIP_NONE);
 }
 
 Rectangle Layout::index_to_pos(int index) const
diff --git a/pango/src/layout.hg b/pango/src/layout.hg
index d73ff15..749f339 100644
--- a/pango/src/layout.hg
+++ b/pango/src/layout.hg
@@ -161,8 +161,14 @@ public:
 
   _WRAP_METHOD(guint get_serial() const, pango_layout_get_serial)
 
-  /** Retrieve an array of logical attributes for each character in the layout.
-   * @return An array of logical attributes.
+  /** Retrieve a vector of logical attributes for each character in the layout.
+   *
+   * The number of attributes returned 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.
+   *
+   * @return A vector of logical attributes.
    */
   std::vector<LogAttr> get_log_attrs() const;