libstage: add stage_node_[sg]et_origin()

A way to specify how the node's position relates to the node's
AABB rather than always being centered.

An origin of -1,-1 would place position at the bottom left corner
of the node's AABB, and +1,+1 the top right corner.

2 files changed, 18 insertions, 0 deletions

diff --git a/src/stage.c b/src/stage.c
index 7871f8f..35d6835 100644
--- a/src/stage.c
+++ b/src/stage.c
@@ -38,6 +38,7 @@ struct stage_node_t {
 	stage_cached_t		cached;
 	aabb_t			aabb;		/* node coordinates expressed in the space of -1.0...1.0 */
 	v2f_t			position;	/* position of node, optionally used to move aabb as a whole */
+	v2f_t			origin;		/* origin of node, 0,0 being center of aabb (the default) this determines how position relates to aabb.  -1...1 being aabb.min ... aabb.max */
 	float			alpha;		/* alpha for the texture when composited */
 	double			angle;		/* angle for the texture when composited */
 	unsigned		active:1;	/* node is active */
@@ -199,6 +200,21 @@ void stage_node_get_position(const stage_t *stage, const stage_node_t *node, v2f
 }
 
 
+/* set the origin for a node */
+void stage_node_set_origin(const stage_t *stage, stage_node_t *node, v2f_t *origin)
+{
+	node->origin = *origin;
+}
+
+
+/* get the origin for a node */
+void stage_node_get_origin(const stage_t *stage, const stage_node_t *node, v2f_t *res_origin)
+{
+
+	*res_origin = node->origin;
+}
+
+
 /* set a node to active (participates in rendering) */
 void stage_node_set_active(const stage_t *stage, stage_node_t *node)
 {
diff --git a/src/stage.h b/src/stage.h
index e16f917..edb35dd 100644
--- a/src/stage.h
+++ b/src/stage.h
@@ -51,6 +51,8 @@ void stage_node_set_aabb(const stage_t *stage, stage_node_t *node, const aabb_t
 void stage_node_get_aabb(const stage_t *stage, const stage_node_t *node, aabb_t *res_aabb);
 void stage_node_set_position(const stage_t *stage, stage_node_t *node, v2f_t *position);
 void stage_node_get_position(const stage_t *stage, const stage_node_t *node, v2f_t *res_position);
+void stage_node_set_origin(const stage_t *stage, stage_node_t *node, v2f_t *origin);
+void stage_node_get_origin(const stage_t *stage, const stage_node_t *node, v2f_t *res_origin);
 void stage_node_set_active(const stage_t *stage, stage_node_t *node);
 void stage_node_set_inactive(const stage_t *stage, stage_node_t *node);
 void stage_node_set_locked(const stage_t *stage, stage_node_t *node);