Remove useless guards

Arrangement_on_surface_2/demo/Arrangement_on_surface_2/ArrangementPainterOstream.cpp

@@ -11,10 +11,7 @@
 
 #include "ArrangementPainterOstream.h"
 #include "ArrangementTypes.h"
-
-#ifdef CGAL_USE_CORE
 #include <CGAL/Curved_kernel_via_analysis_2/Curve_renderer_facade.h>
-#endif
 
 #include <QGraphicsView>
 
@@ -401,7 +398,6 @@ auto ArrangementPainterOstream<CGAL::Arr_algebraic_segment_traits_2<
   Coefficient_>>::getPointsList(const X_monotone_curve_2& curve)
   -> std::vector<Coord_vec_2>
 {
-#ifdef CGAL_USE_CORE
   typedef Curve_renderer_facade<CKvA_2> Facade;
   typedef std::pair<double, double> Coord_2;
   typedef std::vector<Coord_2> Coord_vec_2;
@@ -409,9 +405,6 @@ auto ArrangementPainterOstream<CGAL::Arr_algebraic_segment_traits_2<
   std::vector<Coord_vec_2> points;
   Facade::instance().draw(curve, points);
   return points;
-#else
-  return {};
-#endif
 }
 
 template <typename Coefficient_>
@@ -455,13 +448,11 @@ template <typename Coefficient_>
 void ArrangementPainterOstream<
   CGAL::Arr_algebraic_segment_traits_2<Coefficient_>>::setupFacade()
 {
-#ifdef CGAL_USE_CORE
   typedef Curve_renderer_facade<CKvA_2> Facade;
   QGraphicsView* view = this->getView();
   QRectF viewport = this->viewportRect();
   CGAL::Bbox_2 bbox = this->convert(viewport).bbox();
   Facade::setup(bbox, view->width(), view->height());
-#endif
 }
 
 // Instantiation of Arr_rational_function_traits_2

Arrangement_on_surface_2/demo/Arrangement_on_surface_2/CMakeLists.txt

@@ -2,7 +2,9 @@
 
 cmake_minimum_required(VERSION 3.1...3.15)
 project( Arrangement_on_surface_2_Demo )
+
 set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 
 if(NOT POLICY CMP0070 AND POLICY CMP0053)
   # Only set CMP0053 to OLD with CMake<3.10, otherwise there is a warning.
@@ -13,7 +15,7 @@ if(POLICY CMP0071)
   cmake_policy(SET CMP0071 NEW)
 endif()
 
-find_package(CGAL QUIET COMPONENTS Core Qt5)
+find_package(CGAL QUIET COMPONENTS Qt5 OPTIONAL_COMPONENTS Core)
 find_package(Qt5 QUIET COMPONENTS Gui Widgets)
 
 if (CGAL_FOUND AND CGAL_Qt5_FOUND AND Qt5_FOUND)
@@ -95,5 +97,18 @@ if (CGAL_FOUND AND CGAL_Qt5_FOUND AND Qt5_FOUND)
   cgal_add_compilation_test(arrangement_2)
 
 else()
-  message(STATUS "NOTICE: This demo requires CGAL and Qt5, and will not be compiled.")
+  set(MISSING_DEPS "")
+
+  if(NOT CGAL_FOUND)
+    set(MISSING_DEPS "CGAL, ${MISSING_DEPS}")
+  endif()
+  if(NOT CGAL_Qt5_FOUND)
+    set(MISSING_DEPS "the CGAL Qt5 library, ${MISSING_DEPS}")
+  endif()
+  if(NOT Qt5_FOUND)
+    set(MISSING_DEPS "Qt5, ${MISSING_DEPS}")
+  endif()
+
+  message(STATUS
+          "NOTICE: This demo requires ${MISSING_DEPS} and will not be compiled.")
 endif()