GPencil Onion Skinning: Setting before/after to -1 will turn off onionskinning in that direction

This is an experimental option that I found would have been useful to have,
when making my earlier anim test. The only contentious point is whether it's
better to use a separate boolean flag (perhaps bound to the labels) instead
of overloading this setting (and describing the usage in the tooltip).

2 files changed, 14 insertions, 8 deletions

diff --git a/source/blender/editors/gpencil/drawgpencil.c b/source/blender/editors/gpencil/drawgpencil.c
index 6ccbd2777b4..7715169cafb 100644
--- a/source/blender/editors/gpencil/drawgpencil.c
+++ b/source/blender/editors/gpencil/drawgpencil.c
@@ -1067,7 +1067,7 @@ static void gp_draw_onionskins(bGPDlayer *gpl, bGPDframe *gpf, int offsx, int of
 		copy_v3_v3(color, gpl->color);
 	}
 	
-	if (gpl->gstep) {
+	if (gpl->gstep > 0) {
 		bGPDframe *gf;
 		float fac;
 		
@@ -1084,13 +1084,16 @@ static void gp_draw_onionskins(bGPDlayer *gpl, bGPDframe *gpf, int offsx, int of
 				break;
 		}
 	}
-	else {
+	else if (gpl->gstep == 0) {
 		/* draw the strokes for the ghost frames (at half of the alpha set by user) */
 		if (gpf->prev) {
 			color[3] = (alpha / 7);
 			gp_draw_strokes(gpf->prev, offsx, offsy, winx, winy, dflag, debug, lthick, color, color);
 		}
 	}
+	else {
+		/* don't draw - disabled */
+	}
 	
 	
 	/* 2) Now draw next frames */
@@ -1101,7 +1104,7 @@ static void gp_draw_onionskins(bGPDlayer *gpl, bGPDframe *gpf, int offsx, int of
 		copy_v3_v3(color, gpl->color);
 	}
 	
-	if (gpl->gstep_next) {
+	if (gpl->gstep_next > 0) {
 		bGPDframe *gf;
 		float fac;
 		
@@ -1118,13 +1121,16 @@ static void gp_draw_onionskins(bGPDlayer *gpl, bGPDframe *gpf, int offsx, int of
 				break;
 		}
 	}
-	else {
+	else if (gpl->gstep_next == 0) {
 		/* draw the strokes for the ghost frames (at half of the alpha set by user) */
 		if (gpf->next) {
 			color[3] = (alpha / 4);
 			gp_draw_strokes(gpf->next, offsx, offsy, winx, winy, dflag, debug, lthick, color, color);
 		}
 	}
+	else {
+		/* don't draw - disabled */
+	}
 	
 	/* 3) restore alpha */
 	glColor4fv(gpl->color);
diff --git a/source/blender/makesrna/intern/rna_gpencil.c b/source/blender/makesrna/intern/rna_gpencil.c
index 82d98d4b199..691eae18d4d 100644
--- a/source/blender/makesrna/intern/rna_gpencil.c
+++ b/source/blender/makesrna/intern/rna_gpencil.c
@@ -770,18 +770,18 @@ static void rna_def_gpencil_layer(BlenderRNA *brna)
 	
 	prop = RNA_def_property(srna, "ghost_before_range", PROP_INT, PROP_NONE);
 	RNA_def_property_int_sdna(prop, NULL, "gstep");
-	RNA_def_property_range(prop, 0, 120);
+	RNA_def_property_range(prop, -1, 120);
 	RNA_def_property_ui_text(prop, "Frames Before",
 	                         "Maximum number of frames to show before current frame "
-	                         "(0 = show only the previous sketch)");
+	                         "(0 = show only the previous sketch,  -1 = Don't show any frames before current)");
 	RNA_def_property_update(prop, NC_GPENCIL | ND_DATA, "rna_GPencil_update");
 	
 	prop = RNA_def_property(srna, "ghost_after_range", PROP_INT, PROP_NONE);
 	RNA_def_property_int_sdna(prop, NULL, "gstep_next");
-	RNA_def_property_range(prop, 0, 120);
+	RNA_def_property_range(prop, -1, 120);
 	RNA_def_property_ui_text(prop, "Frames After",
 	                         "Maximum number of frames to show after current frame "
-	                         "(0 = show only the next sketch)");
+	                         "(0 = show only the next sketch,  -1 = Don't show any frames after current)");
 	RNA_def_property_update(prop, NC_GPENCIL | ND_DATA, "rna_GPencil_update");
 	
 	prop = RNA_def_property(srna, "use_ghost_custom_colors", PROP_BOOLEAN, PROP_NONE);