Initial implementation of C++ supports,

some documentation of the existing code.

xs/src/libslic3r/Surface.hpp

@@ -6,11 +6,29 @@
 
 namespace Slic3r {
 
-enum SurfaceType { stTop, stBottom, stBottomBridge, stInternal, stInternalSolid, stInternalBridge, stInternalVoid, stPerimeter };
+enum SurfaceType { 
+    // Top horizontal surface, visible from the top.
+    stTop,
+    // Bottom horizontal surface, visible from the bottom, printed with a normal extrusion flow.
+    stBottom,
+    // Bottom horizontal surface, visible from the bottom, unsupported, printed with a bridging extrusion flow.
+    stBottomBridge,
+    // Normal sparse infill.
+    stInternal,
+    // Full infill, supporting the top surfaces and/or defining the verticall wall thickness.
+    stInternalSolid,
+    // 1st layer of dense infill over sparse infill, printed with a bridging extrusion flow.
+    stInternalBridge,
+    // stInternal turns into void surfaces if the sparse infill is used for supports only,
+    // or if sparse infill layers get combined into a single layer.
+    stInternalVoid,
+    // Inner/outer perimeters.
+    stPerimeter
+};
 
 class Surface
 {
-    public:
+public:
     SurfaceType     surface_type;
     ExPolygon       expolygon;
     double          thickness;          // in mm