Improve grease pencil stroke quality

Improve the quality of current grease pencil strokes adding a new dynamic smooth and subdivision. The level of smooth and subdivide can be adjusted using UI parameters. These options are disabled by default in order to keep the grease pencil stroke compatible with any existing add-on.

Both parameters are defined at layer level.

Reviewers: aligorith

Differential Revision: https://developer.blender.org/D1866

release/scripts/startup/bl_ui/properties_grease_pencil_common.py

@@ -622,6 +622,14 @@ class GreasePencilDataPanel:
         row.prop(gpl, "after_color", text="")
         sub.prop(gpl, "ghost_after_range", text="After")
 
+        # Smooth and subdivide new strokes
+        layout.separator()
+        col = layout.column(align=True)
+        col.label(text="New Stroke Quality:")
+        split = col.split()
+        split.prop(gpl, "smooth_drawfac")
+        split.prop(gpl, "subdivision")
+
 
 class GreasePencilToolsPanel:
     # subclass must set