From 90820fe15696d684c622c9a730f22fe57ce38fe1 Mon Sep 17 00:00:00 2001
From: Liam Girdwood <lgirdwood@gmail.com>
Date: Sat, 19 Jul 2008 15:09:00 +0100
Subject: [PATCH] constellation: bounds - fixed problems crossing 0h.

---
 src/sky/constellation.c | 67 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 5 deletions(-)

diff --git a/src/sky/constellation.c b/src/sky/constellation.c
index 3e8b5d3..23351f1 100644
--- a/src/sky/constellation.c
+++ b/src/sky/constellation.c
@@ -2468,13 +2468,70 @@ static inline void equ_dec_line(struct render_object *robject,
 {
 	gint i = 7;
 	gdouble divs = 7.0;//proj->pixels_per_degree
-	gdouble step = (end->ra - pos->ra) / divs;
-
-	if ((pos->ra > 270.0 && end->ra < 90.0) || 
-		(pos->ra < 90.0 && end->ra > 270.0)) {
+	
+	/* we need to do 2 lines if we cross the 0h boundary */
+	if (pos->ra > 330.0 && end->ra < 30.0) {
+		gdouble step = (360.0 - pos->ra) / divs;
+		
+		proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+		cairo_move_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+				
+		for (pos->ra = pos->ra + step; 
+			i > 0; pos->ra += step, i--) {
+			proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+			cairo_line_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		}
+		
+		step = end->ra / divs;
+		pos->ra = 0;
+		proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+		cairo_move_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		for (pos->ra = step; 
+			i > 0; pos->ra += step, i--) {
+			proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+			cairo_line_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		}
+		
+		cairo_move_to(robject->cr, 
+				robject->coord[1].x, robject->coord[1].y);
 		
+	} else if (pos->ra < 30.0 && end->ra > 330.0) {
+		gdouble step = pos->ra / divs;
+		
+		pos->ra = 0;
+		proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+		cairo_move_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		
+		for (pos->ra = step; 
+			i > 0; pos->ra += step, i--) {
+			proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+			cairo_line_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		}
+		
+		step = (360.0 - end->ra) / divs;
+		pos->ra = end->ra;
+		proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+		cairo_move_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+				
+		for (pos->ra = end->ra + step; 
+			i > 0; pos->ra += step, i--) {
+			proj->trans->sky_to_proj_equ(proj, &robject->coord[0]);
+			cairo_line_to(robject->cr, 
+				robject->coord[0].x, robject->coord[0].y);
+		}
+		
+		cairo_move_to(robject->cr, 
+				robject->coord[1].x, robject->coord[1].y);
+				
 	} else { 
-
+		gdouble step = (end->ra - pos->ra) / divs;
 		/* draw to DEC end */
 		for (pos->ra = pos->ra + step; 
 			i > 0; pos->ra += step, i--) {
-- 
2.11.4.GIT