[libgis] Add z-index to tiles

[Andy Spencer <andys src gnome org>]

commit 14c34a746fc94a9e5477d081275f04bd1c8b5d6d
Author: Andy Spencer <andy753421 gmail com>
Date:   Mon Apr 19 06:27:17 2010 +0000

    Add z-index to tiles
    
    Tiles are still drawn on the ground, Z-indexes are used as polygon
    offsets so that you can draw things like composite radar images above
    the satellite imagery.

 src/gis-opengl.c       |    2 ++
 src/objects/gis-tile.h |    3 +++
 src/plugins/sat.c      |    2 +-
 3 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/src/gis-opengl.c b/src/gis-opengl.c
index 9f1940b..57cfb47 100644
--- a/src/gis-opengl.c
+++ b/src/gis-opengl.c
@@ -178,7 +178,9 @@ static void _draw_tile(GisOpenGL *opengl, GisTile *tile, GList *triangles)
 		if (lat[2] == 90 || lat[2] == -90) xy[2][0] = 0.5;
 
 		glEnable(GL_TEXTURE_2D);
+		glEnable(GL_POLYGON_OFFSET_FILL);
 		glBindTexture(GL_TEXTURE_2D, *(guint*)tile->data);
+		glPolygonOffset(0, -tile->zindex);
 		glBegin(GL_TRIANGLES);
 		glNormal3dv(tri->p.r->norm); glTexCoord2dv(xy[0]); glVertex3dv((double*)tri->p.r);
 		glNormal3dv(tri->p.m->norm); glTexCoord2dv(xy[1]); glVertex3dv((double*)tri->p.m);
diff --git a/src/objects/gis-tile.h b/src/objects/gis-tile.h
index 4ebf7ef..e2b7252 100644
--- a/src/objects/gis-tile.h
+++ b/src/objects/gis-tile.h
@@ -38,6 +38,9 @@ struct _GisTile {
 	/* Pointer to the tile data */
 	gpointer data;
 
+	/* Pointer to the tile data */
+	gint zindex;
+
 	/* North,South,East,West limits */
 	GisBBox edge;
 
diff --git a/src/plugins/sat.c b/src/plugins/sat.c
index 66150be..9e1af30 100644
--- a/src/plugins/sat.c
+++ b/src/plugins/sat.c
@@ -179,7 +179,7 @@ GisPluginSat *gis_plugin_sat_new(GisViewer *viewer)
 			G_CALLBACK(_on_location_changed), sat);
 
 	/* Add renderers */
-	gis_viewer_add(viewer, GIS_OBJECT(sat->tiles), GIS_LEVEL_WORLD, 0);
+	gis_viewer_add(viewer, GIS_OBJECT(sat->tiles), GIS_LEVEL_WORLD, FALSE);
 
 	return sat;
 }