[perl-Gtk2] Gtk2::Gdk::Region::spans_intersect_foreach(): allow empty spans list

[Torsten Schönfeld <tsch src gnome org>]

commit 931dd526e025bd3e3970959179606aefe8543a5d
Author: Kevin Ryde <user42 zip com au>
Date:   Sun Nov 28 08:12:26 2010 +1100

    Gtk2::Gdk::Region::spans_intersect_foreach(): allow empty spans list
    
    Don't pass spans==NULL for an empty input array, but instead explicitly do
    nothing in that case. Avoids a g_log if the Perl level spans array is empty.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=635950

 t/GdkRegion.t   |    8 +++++++-
 xs/GdkRegion.xs |   49 ++++++++++++++++++++++++++++---------------------
 2 files changed, 35 insertions(+), 22 deletions(-)
---
diff --git a/t/GdkRegion.t b/t/GdkRegion.t
index a142fd1..dae8c15 100644
--- a/t/GdkRegion.t
+++ b/t/GdkRegion.t
@@ -1,6 +1,6 @@
 #!/usr/bin/perl -w
 use strict;
-use Gtk2::TestHelper tests => 29, noinit => 1;
+use Gtk2::TestHelper tests => 30, noinit => 1;
 
 # $Id$
 
@@ -51,6 +51,12 @@ $region -> spans_intersect_foreach([24, 43, 5,
   is($data, "bla");
 }, "bla");
 
+{
+  my $callback = 0;
+  $region -> spans_intersect_foreach([], 1, sub { $callback = 1; });
+  is($callback, 0, 'spans_intersect_foreach() 0 coords - no callback');
+}
+
 ok (! eval { $region->spans_intersect_foreach([1], 1, sub {}); 1 },
       'spans_intersect_foreach() 1 coord - expect error');
 ok (! eval { $region->spans_intersect_foreach([1,2], 1, sub {}); 1 },
diff --git a/xs/GdkRegion.xs b/xs/GdkRegion.xs
index 54ec46c..1b5aaeb 100644
--- a/xs/GdkRegion.xs
+++ b/xs/GdkRegion.xs
@@ -260,28 +260,35 @@ gdk_region_spans_intersect_foreach (region, spans_ref, sorted, func, data=NULL)
 	if ((n_spans % 3) != 0)
 		croak ("span list not a multiple of 3");
 	n_spans /= 3;
-	spans = g_new0 (GdkSpan, n_spans);
-
-	for (i = 0; i < n_spans; i++) {
-		if ((value = av_fetch (array, 3*i, 0)) && gperl_sv_is_defined (*value))
-			spans[i].x = SvIV (*value);
-		if ((value = av_fetch (array, 3*i + 1, 0)) && gperl_sv_is_defined (*value))
-			spans[i].y = SvIV (*value);
-		if ((value = av_fetch (array, 3*i + 2, 0)) && gperl_sv_is_defined (*value))
-			spans[i].width = SvIV (*value);
-	}
-
-	callback = gperl_callback_new (func, data, 0, NULL, 0);
 
-	gdk_region_spans_intersect_foreach (region,
-	                                    spans,
-	                                    n_spans,
-	                                    sorted,
-	                                    (GdkSpanFunc) gtk2perl_gdk_span_func,
-	                                    callback);
-
-	gperl_callback_destroy (callback);
-	g_free (spans);
+	/* gdk_region_spans_intersect_foreach() is happy to take n_spans==0
+	   and do nothing, but it doesn't like spans==NULL (as of Gtk 2.20),
+	   and NULL is what g_new0() gives for a count of 0.  So explicit
+	   skip if n_spans==0.  */
+	if (n_spans != 0) {
+		spans = g_new0 (GdkSpan, n_spans);
+
+		for (i = 0; i < n_spans; i++) {
+			if ((value = av_fetch (array, 3*i, 0)) && gperl_sv_is_defined (*value))
+				spans[i].x = SvIV (*value);
+			if ((value = av_fetch (array, 3*i + 1, 0)) && gperl_sv_is_defined (*value))
+				spans[i].y = SvIV (*value);
+			if ((value = av_fetch (array, 3*i + 2, 0)) && gperl_sv_is_defined (*value))
+				spans[i].width = SvIV (*value);
+		}
+
+		callback = gperl_callback_new (func, data, 0, NULL, 0);
+
+		gdk_region_spans_intersect_foreach (region,
+		                                    spans,
+		                                    n_spans,
+		                                    sorted,
+		                                    (GdkSpanFunc) gtk2perl_gdk_span_func,
+		                                    callback);
+
+		gperl_callback_destroy (callback);
+		g_free (spans);
+	}
 
 #if GTK_CHECK_VERSION (2, 18, 0)