diff --git a/invesalius/constants.py b/invesalius/constants.py
index 37fca9d..cd2616f 100644
--- a/invesalius/constants.py
+++ b/invesalius/constants.py
@@ -293,3 +293,18 @@ VTK_WARNING = 0
 [ID_FILE_IMPORT, ID_FILE_LOAD_INTERNET, ID_FILE_SAVE, ID_FILE_PHOTO,
 ID_FILE_PRINT, ID_FILE_OPEN] = [wx.NewId() for number in range(6)]
 
+
+#---------------------------------------------------------
+SLICE_STATE_DEFAULT = 0
+SLICE_STATE_EDITOR = 1
+SLICE_STATE_WL = 2
+SLICE_STATE_SPIN = 3
+SLICE_STATE_ZOOM = 4
+SLICE_STATE_ZOOM_SL = 5
+
+LEVEL = {SLICE_STATE_DEFAULT: 0,
+         SLICE_STATE_EDITOR: 1,
+         SLICE_STATE_WL: 2,
+         SLICE_STATE_SPIN: 2,
+         SLICE_STATE_ZOOM: 2,
+         SLICE_STATE_ZOOM_SL: 2}
--
libgit2 0.21.2