GPencil: Changes in Fill and new 3D Cursor View Plane

This commit groups several options that were tested in grease pencil branch:

- Changes to fill algorithms and improves, specially in small areas and stroke corners.
  New options has been added in order to define how the fill is working and internally there are optimizations in detect the small areas in the extremes.

  Kudos to @charlie for coding this fill improvements.

- New 3D cursor view plane option.

  Now it's possible to lock the drawing plane to the 3D cursor and use the 3D cursor orientation. This allows more flexibility when you are drawing and reduce the need to create geometry to draw over surfaces.

- Canvas Grid now can be locked to 3D cursor.
- New option to reproject stroke using 3D cursor.
- Small tweaks and fixes.

Changes reviewed by @pepeland and @mendio

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/gpencil_intern.h b/source/blender/editors/gpencil/gpencil_intern.h
index 4fba83a5f02..aa47319e3d9 100644
--- a/source/blender/editors/gpencil/gpencil_intern.h
+++ b/source/blender/editors/gpencil/gpencil_intern.h
@@ -92,6 +92,7 @@ typedef struct tGPDdraw {
 	float tintcolor[4];                 /* tint color */
 	bool onion;                         /* onion flag */
 	bool custonion;                     /* use custom onion colors */
+	bool is_fill_stroke;              /* use fill tool */
 	float diff_mat[4][4];               /* matrix */
 } tGPDdraw;