Further reduction of include dependencies

rtengine/diagonalcurvetypes.h

@@ -0,0 +1,31 @@
+/*
+ *  This file is part of RawTherapee.
+ *
+ *  Copyright (c) 2004-2019 Gabor Horvath <hgabor@rawtherapee.com>
+ *
+ *  RawTherapee is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  RawTherapee is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#pragma once
+
+// For compatibility and simplicity reason, order shouldn't change, and must be identical to the order specified in the curveType widget
+enum DiagonalCurveType {
+    DCT_Empty = -1,     // Also used for identity curves
+    DCT_Linear,         // 0
+    DCT_Spline,         // 1
+    DCT_Parametric,     // 2
+    DCT_NURBS,          // 3
+    DCT_CatumullRom,    // 4
+    // Insert new curve type above this line
+    DCT_Unchanged       // Must remain the last of the enum
+};