Add faces perpendicular and parallel constraints.

src/constraint.cpp

@@ -721,7 +721,11 @@ void Constraint::MenuConstrain(Command id) {
         }
 
         case Command::PARALLEL:
-            if(gs.vectors == 2 && gs.n == 2) {
+            if(gs.faces == 2 && gs.n == 2) {
+                c.type = Type::PARALLEL;
+                c.entityA = gs.face[0];
+                c.entityB = gs.face[1];            
+            } else if(gs.vectors == 2 && gs.n == 2) {
                 c.type = Type::PARALLEL;
                 c.entityA = gs.vector[0];
                 c.entityB = gs.vector[1];
@@ -765,6 +769,7 @@ void Constraint::MenuConstrain(Command id) {
             } else {
                 Error(_("Bad selection for parallel / tangent constraint. This "
                         "constraint can apply to:\n\n"
+                        "    * two faces\n"
                         "    * two line segments (parallel)\n"
                         "    * a line segment and a normal (parallel)\n"
                         "    * two normals (parallel)\n"
@@ -776,13 +781,18 @@ void Constraint::MenuConstrain(Command id) {
             break;
 
         case Command::PERPENDICULAR:
-            if(gs.vectors == 2 && gs.n == 2) {
+            if(gs.faces == 2 && gs.n == 2) {
+                c.type = Type::PERPENDICULAR;
+                c.entityA = gs.face[0];
+                c.entityB = gs.face[1];            
+            } else if(gs.vectors == 2 && gs.n == 2) {
                 c.type = Type::PERPENDICULAR;
                 c.entityA = gs.vector[0];
                 c.entityB = gs.vector[1];
             } else {
                 Error(_("Bad selection for perpendicular constraint. This "
                         "constraint can apply to:\n\n"
+                        "    * two faces\n"
                         "    * two line segments\n"
                         "    * a line segment and a normal\n"
                         "    * two normals\n"));

src/entity.cpp

@@ -26,6 +26,9 @@ bool EntityBase::HasVector() const {
 }
 
 ExprVector EntityBase::VectorGetExprsInWorkplane(hEntity wrkpl) const {
+    if(IsFace()) {
+        return FaceGetNormalExprs();
+    }
     switch(type) {
         case Type::LINE_SEGMENT:
             return (SK.GetEntity(point[0])->PointGetExprsInWorkplane(wrkpl)).Minus(
@@ -62,6 +65,9 @@ ExprVector EntityBase::VectorGetExprs() const {
 }
 
 Vector EntityBase::VectorGetNum() const {
+    if(IsFace()) {
+        return FaceGetNormalNum();
+    }
     switch(type) {
         case Type::LINE_SEGMENT:
             return (SK.GetEntity(point[0])->PointGetNum()).Minus(
@@ -79,6 +85,9 @@ Vector EntityBase::VectorGetNum() const {
 }
 
 Vector EntityBase::VectorGetRefPoint() const {
+    if(IsFace()) {
+        return FaceGetPointNum();
+    }
     switch(type) {
         case Type::LINE_SEGMENT:
             return ((SK.GetEntity(point[0])->PointGetNum()).Plus(