GPencil: Add option to draw new strokes on back of layer

For artist point of view is very useful to have an option to draw by
default the new strokes on back of all strokes in the layer.

1 files changed, 11 insertions, 2 deletions

diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index d637affe79d..cebcbfe9317 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -692,6 +692,7 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 	bGPDspoint *pt;
 	tGPspoint *ptc;
 	bGPDbrush *brush = p->brush;
+	ToolSettings *ts = p->scene->toolsettings;
 	
 	int i, totelem;
 	/* since strokes are so fine, when using their depth we need a margin otherwise they might get missed */
@@ -925,8 +926,16 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 	gps->palcolor = palcolor;
 	strcpy(gps->colorname, palcolor->info);
 
-	/* add stroke to frame */
-	BLI_addtail(&p->gpf->strokes, gps);
+	/* add stroke to frame, usually on tail of the listbase, but if on back is enabled the stroke is added on listbase head 
+	* because the drawing order is inverse and the head stroke is the first to draw. This is very useful for artist
+	* when drawing the background
+	*/
+	if (ts->gpencil_flags & GP_TOOL_FLAG_PAINT_ONBACK) {
+		BLI_addhead(&p->gpf->strokes, gps);
+	}
+	else {
+		BLI_addtail(&p->gpf->strokes, gps);
+	}
 	gp_stroke_added_enable(p);
 }