[gnumeric] gnm_xml_out_add_gocolor: handle alpha.

[Morten Welinder <mortenw src gnome org>]

commit ca20fbec82952c1a36d02fe4aa94b77405df093a
Author: Morten Welinder <terra gnome org>
Date:   Mon Jun 18 11:06:11 2012 -0400

    gnm_xml_out_add_gocolor: handle alpha.
    
    More work towards using alpha correctly.  Not sure if it'll be useful,
    but the lower levels of code shouldn't be making that decision.

 ChangeLog           |    4 ++++
 src/xml-sax-write.c |   17 ++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 22a1a35..b7d9adb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2012-06-18  Morten Welinder  <terra gnome org>
+
+	* src/xml-sax-write.c (gnm_xml_out_add_gocolor): Handle alpha.
+
 2012-06-16  Andreas J. Guelzow <aguelzow pyrshep ca>
 
 	* src/sheet-filter.c (gnm_filter_set_range): new
diff --git a/src/xml-sax-write.c b/src/xml-sax-write.c
index d1a4467..3babac4 100644
--- a/src/xml-sax-write.c
+++ b/src/xml-sax-write.c
@@ -83,9 +83,24 @@ typedef struct {
 void
 gnm_xml_out_add_gocolor (GsfXMLOut *o, char const *id, GOColor c)
 {
+	/*
+	 * This uses format "rrrr:gggg:bbbb" or "rrrr:gggg:bbbb:aaaa"
+	 * using hex numbers, i.e., the numbers are in the range from
+	 * 0 to FFFF.
+	 *
+	 * Note, that while go_xml_out_add_color exists, we cannot use
+	 * it as it using a 0-255 scaling and always includes alpha.
+	 */
 	unsigned r, g, b, a;
+	char buf[4 * 4 * sizeof (unsigned int) + 1];
+
 	GO_COLOR_TO_RGBA (c, &r, &g, &b, &a);
-	gsf_xml_out_add_color (o, id, r * 0x101, g * 0x101, b * 0x101);
+
+	sprintf (buf, "%X:%X:%X%c%X",
+		 r * 0x101, g * 0x101, b * 0x101,
+		 (a == 0xff ? 0 : ':'),
+		 a * 0x101);
+	gsf_xml_out_add_cstr_unchecked (o, id, buf);
 }
 
 static void