[gtk/wip/chergert/faster-comparison] textlayout: remove use of GtkTextIter in line comparison

[Christian Hergert <chergert src gnome org>]

commit 7cea21043ea33ab7db5fa2cdfc8bd2834285dd04
Author: Christian Hergert <chergert redhat com>
Date:   Wed Sep 4 09:12:54 2019 -0700

    textlayout: remove use of GtkTextIter in line comparison
    
    We do not need to create a GtkTextIter to perform the comparison here as
    that will require a number of validation steps that are extra work
    compared to just discovering the GtkTextLine number directly.

 gtk/gtktextlayout.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtktextlayout.c b/gtk/gtktextlayout.c
index 5e4b5975a3..fee6d59a4a 100644
--- a/gtk/gtktextlayout.c
+++ b/gtk/gtktextlayout.c
@@ -4197,11 +4197,16 @@ gtk_text_line_display_compare (const GtkTextLineDisplay *display1,
                                const GtkTextLineDisplay *display2,
                                GtkTextLayout            *layout)
 {
-  GtkTextIter iter1;
-  GtkTextIter iter2;
+  gint line1;
+  gint line2;
 
-  gtk_text_layout_get_iter_at_line (layout, &iter1, display1->line, 0);
-  gtk_text_layout_get_iter_at_line (layout, &iter2, display2->line, 0);
+  line1 = _gtk_text_line_get_number (display1->line);
+  line2 = _gtk_text_line_get_number (display2->line);
 
-  return gtk_text_iter_compare (&iter1, &iter2);
+  if (line1 < line2)
+    return -1;
+  else if (line1 > line2)
+    return 1;
+  else
+    return 0;
 }