diff --git a/AABB_tree/demo/AABB_tree/CMakeLists.txt b/AABB_tree/demo/AABB_tree/CMakeLists.txt
index eb4f6a96fca..cec72a6421c 100644
--- a/AABB_tree/demo/AABB_tree/CMakeLists.txt
+++ b/AABB_tree/demo/AABB_tree/CMakeLists.txt
@@ -14,7 +14,7 @@ endif()
 # Include this package's headers first
 include_directories( BEFORE ./ ./include ../../include )
 # Find CGAL and CGAL Qt5
-find_package(CGAL REQUIRED COMPONENTS Qt5 )
+find_package(CGAL COMPONENTS Qt5 )
 include( ${CGAL_USE_FILE} )
 
 # Find Qt5 itself
diff --git a/AABB_tree/demo/AABB_tree/Scene.cpp b/AABB_tree/demo/AABB_tree/Scene.cpp
index c9efc60a573..08665e5f5ba 100644
--- a/AABB_tree/demo/AABB_tree/Scene.cpp
+++ b/AABB_tree/demo/AABB_tree/Scene.cpp
@@ -1311,6 +1311,7 @@ void Scene::deactivate_cutting_plane()
 }
 void Scene::initGL()
 {
+    qDebug()<<"context from scene is valid :"<<context->isValid();
     initializeOpenGLFunctions();
     glGenTextures(1, &textureId);
     compile_shaders();
diff --git a/AABB_tree/demo/AABB_tree/Viewer.cpp b/AABB_tree/demo/AABB_tree/Viewer.cpp
index 7a72edb85df..34c9cffe106 100644
--- a/AABB_tree/demo/AABB_tree/Viewer.cpp
+++ b/AABB_tree/demo/AABB_tree/Viewer.cpp
@@ -31,6 +31,7 @@ void Viewer::initializeGL()
   QGLViewer::initializeGL();
   setBackgroundColor(::Qt::white);
   m_pScene->context = this->context();
+  qDebug()<<"context from viewer is valid :"<<this->context()->isValid();
   m_pScene->initGL();
 }
 
diff --git a/Algebraic_kernel_d/test/Algebraic_kernel_d/CMakeLists.txt b/Algebraic_kernel_d/test/Algebraic_kernel_d/CMakeLists.txt
index 7349cd12e46..a548cd61e69 100644
--- a/Algebraic_kernel_d/test/Algebraic_kernel_d/CMakeLists.txt
+++ b/Algebraic_kernel_d/test/Algebraic_kernel_d/CMakeLists.txt
@@ -26,7 +26,7 @@ include( ${CGAL_USE_FILE} )
 include( CGAL_CreateSingleSourceCGALProgram )
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
 
diff --git a/Alpha_shapes_3/demo/Alpha_shapes_3/CMakeLists.txt b/Alpha_shapes_3/demo/Alpha_shapes_3/CMakeLists.txt
index 668afba7b39..6161c34ca8f 100644
--- a/Alpha_shapes_3/demo/Alpha_shapes_3/CMakeLists.txt
+++ b/Alpha_shapes_3/demo/Alpha_shapes_3/CMakeLists.txt
@@ -11,7 +11,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include(${CGAL_USE_FILE})
 
 find_package(Qt5 COMPONENTS Xml Script OpenGL)
diff --git a/BGL/test/BGL/CMakeLists.txt b/BGL/test/BGL/CMakeLists.txt
index 7ac8cf18194..9b420b7a3af 100644
--- a/BGL/test/BGL/CMakeLists.txt
+++ b/BGL/test/BGL/CMakeLists.txt
@@ -36,7 +36,7 @@ include( ${CGAL_USE_FILE} )
 
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
   message(STATUS "This project requires the Boost library, and will not be compiled.")
diff --git a/CGAL_Core/examples/Core/CMakeLists.txt b/CGAL_Core/examples/Core/CMakeLists.txt
index e3fbde5cdfd..3a56a0ac573 100644
--- a/CGAL_Core/examples/Core/CMakeLists.txt
+++ b/CGAL_Core/examples/Core/CMakeLists.txt
@@ -33,7 +33,7 @@ include( ${CGAL_USE_FILE} )
 
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
 
diff --git a/Circular_kernel_3/demo/Circular_kernel_3/CMakeLists.txt b/Circular_kernel_3/demo/Circular_kernel_3/CMakeLists.txt
index 904cdf884d5..5cd80fabca5 100644
--- a/Circular_kernel_3/demo/Circular_kernel_3/CMakeLists.txt
+++ b/Circular_kernel_3/demo/Circular_kernel_3/CMakeLists.txt
@@ -5,7 +5,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include(${CGAL_USE_FILE})
 
 find_package(Qt5 COMPONENTS Xml Script OpenGL)
diff --git a/GraphicsView/demo/Apollonius_graph_2/CMakeLists.txt b/GraphicsView/demo/Apollonius_graph_2/CMakeLists.txt
index 19cedbca651..40e1b7aaa50 100644
--- a/GraphicsView/demo/Apollonius_graph_2/CMakeLists.txt
+++ b/GraphicsView/demo/Apollonius_graph_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Bounding_volumes/CMakeLists.txt b/GraphicsView/demo/Bounding_volumes/CMakeLists.txt
index 49030e5c161..e814d5f1df5 100644
--- a/GraphicsView/demo/Bounding_volumes/CMakeLists.txt
+++ b/GraphicsView/demo/Bounding_volumes/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Circular_kernel_2/CMakeLists.txt b/GraphicsView/demo/Circular_kernel_2/CMakeLists.txt
index 6fa65edc26a..658bb01c7f8 100644
--- a/GraphicsView/demo/Circular_kernel_2/CMakeLists.txt
+++ b/GraphicsView/demo/Circular_kernel_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Generator/CMakeLists.txt b/GraphicsView/demo/Generator/CMakeLists.txt
index c66f47ee65a..ea06203df7d 100644
--- a/GraphicsView/demo/Generator/CMakeLists.txt
+++ b/GraphicsView/demo/Generator/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/GraphicsView/CMakeLists.txt b/GraphicsView/demo/GraphicsView/CMakeLists.txt
index 99cdba4a4aa..84e4dbbf4df 100644
--- a/GraphicsView/demo/GraphicsView/CMakeLists.txt
+++ b/GraphicsView/demo/GraphicsView/CMakeLists.txt
@@ -7,7 +7,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/L1_Voronoi_diagram_2/CMakeLists.txt b/GraphicsView/demo/L1_Voronoi_diagram_2/CMakeLists.txt
index fe8c0ce03ac..1d321d45047 100644
--- a/GraphicsView/demo/L1_Voronoi_diagram_2/CMakeLists.txt
+++ b/GraphicsView/demo/L1_Voronoi_diagram_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Largest_empty_rect_2/CMakeLists.txt b/GraphicsView/demo/Largest_empty_rect_2/CMakeLists.txt
index 797a9ff5c41..371082b344e 100644
--- a/GraphicsView/demo/Largest_empty_rect_2/CMakeLists.txt
+++ b/GraphicsView/demo/Largest_empty_rect_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Periodic_2_triangulation_2/CMakeLists.txt b/GraphicsView/demo/Periodic_2_triangulation_2/CMakeLists.txt
index 5c626904950..6644b70d530 100644
--- a/GraphicsView/demo/Periodic_2_triangulation_2/CMakeLists.txt
+++ b/GraphicsView/demo/Periodic_2_triangulation_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if ( COMMAND cmake_policy )
   cmake_policy( SET CMP0003 NEW )
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5 REQUIRED)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Polygon/CMakeLists.txt b/GraphicsView/demo/Polygon/CMakeLists.txt
index 4480b885075..20fc3dc2fd0 100644
--- a/GraphicsView/demo/Polygon/CMakeLists.txt
+++ b/GraphicsView/demo/Polygon/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5 Core)
+find_package(CGAL COMPONENTS Qt5 Core)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Snap_rounding_2/CMakeLists.txt b/GraphicsView/demo/Snap_rounding_2/CMakeLists.txt
index 93b316d290c..ba03c2f1e0b 100644
--- a/GraphicsView/demo/Snap_rounding_2/CMakeLists.txt
+++ b/GraphicsView/demo/Snap_rounding_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Spatial_searching_2/CMakeLists.txt b/GraphicsView/demo/Spatial_searching_2/CMakeLists.txt
index e7a8a0099e0..e541182aa5e 100644
--- a/GraphicsView/demo/Spatial_searching_2/CMakeLists.txt
+++ b/GraphicsView/demo/Spatial_searching_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Stream_lines_2/CMakeLists.txt b/GraphicsView/demo/Stream_lines_2/CMakeLists.txt
index f5c81caacd6..bf778783aa0 100644
--- a/GraphicsView/demo/Stream_lines_2/CMakeLists.txt
+++ b/GraphicsView/demo/Stream_lines_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/GraphicsView/demo/Triangulation_2/CMakeLists.txt b/GraphicsView/demo/Triangulation_2/CMakeLists.txt
index 7f83e32453d..30a921133ae 100644
--- a/GraphicsView/demo/Triangulation_2/CMakeLists.txt
+++ b/GraphicsView/demo/Triangulation_2/CMakeLists.txt
@@ -8,7 +8,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 
 include(${CGAL_USE_FILE})
 
diff --git a/Linear_cell_complex/demo/Linear_cell_complex/CMakeLists.txt b/Linear_cell_complex/demo/Linear_cell_complex/CMakeLists.txt
index 13825656b9e..17f59cfcea4 100644
--- a/Linear_cell_complex/demo/Linear_cell_complex/CMakeLists.txt
+++ b/Linear_cell_complex/demo/Linear_cell_complex/CMakeLists.txt
@@ -30,7 +30,7 @@ endif()
 add_definitions(-DCGAL_PROFILE_LCC_DEMO)
 
 ##################
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include(${CGAL_USE_FILE})
 
 find_package(Qt5 COMPONENTS Xml Script OpenGL)
diff --git a/Mesh_3/demo/Mesh_3/implicit_functions/CMakeLists.txt b/Mesh_3/demo/Mesh_3/implicit_functions/CMakeLists.txt
index 8e8f42de751..2e1ab09d1eb 100644
--- a/Mesh_3/demo/Mesh_3/implicit_functions/CMakeLists.txt
+++ b/Mesh_3/demo/Mesh_3/implicit_functions/CMakeLists.txt
@@ -14,7 +14,7 @@ set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}")
 include_directories( BEFORE ${Mesh_3_implicit_functions_BINARY_DIR} ../include )
 
 # Find CGAL and CGAL Qt5
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include( ${CGAL_USE_FILE} )
 
 # Find Qt5 itself
diff --git a/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/CMakeLists.txt b/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/CMakeLists.txt
index 603bbde8ba5..aa45255751d 100644
--- a/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/CMakeLists.txt
+++ b/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/CMakeLists.txt
@@ -10,7 +10,7 @@ if(POLICY CMP0043)
 endif()
 
 # Find CGAL
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include( ${CGAL_USE_FILE} )
 
 # Find Qt5 itself
diff --git a/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/CMakeLists.txt b/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/CMakeLists.txt
index 77ad080102d..a1cc8f4e53d 100644
--- a/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/CMakeLists.txt
+++ b/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/CMakeLists.txt
@@ -12,7 +12,7 @@ if(POLICY CMP0043)
   cmake_policy(SET CMP0043 OLD)
 endif()
 
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include(${CGAL_USE_FILE})
 
 
diff --git a/Polyhedron/demo/Polyhedron/CMakeLists.txt b/Polyhedron/demo/Polyhedron/CMakeLists.txt
index 971ff57d8bc..1bab8434753 100644
--- a/Polyhedron/demo/Polyhedron/CMakeLists.txt
+++ b/Polyhedron/demo/Polyhedron/CMakeLists.txt
@@ -53,7 +53,7 @@ set( QT_USE_QTOPENGL  TRUE )
 if( POLYHEDRON_QTSCRIPT_DEBUGGER)
   set( QT_USE_QTSCRIPTTOOLS  TRUE )
 endif()
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include( ${CGAL_USE_FILE} )
 find_package(Qt5 COMPONENTS OpenGL Script Svg Xml ScriptTools)
 
diff --git a/Polyline_simplification_2/test/Polyline_simplification_2/CMakeLists.txt b/Polyline_simplification_2/test/Polyline_simplification_2/CMakeLists.txt
index 9d65a2d3099..e451a6ac4d2 100644
--- a/Polyline_simplification_2/test/Polyline_simplification_2/CMakeLists.txt
+++ b/Polyline_simplification_2/test/Polyline_simplification_2/CMakeLists.txt
@@ -36,7 +36,7 @@ include( ${CGAL_USE_FILE} )
 
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
 
diff --git a/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt b/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
index 60d65657f80..dc03be3282f 100644
--- a/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
+++ b/Principal_component_analysis/demo/Principal_component_analysis/CMakeLists.txt
@@ -16,7 +16,7 @@ endforeach()
 include_directories( ./ )
 
 # Find CGAL and CGAL Qt5
-find_package(CGAL REQUIRED COMPONENTS Qt5)
+find_package(CGAL COMPONENTS Qt5)
 include( ${CGAL_USE_FILE} )
 
 # Find Qt5 itself
diff --git a/Surface_mesh_segmentation/examples/Surface_mesh_segmentation/CMakeLists.txt b/Surface_mesh_segmentation/examples/Surface_mesh_segmentation/CMakeLists.txt
index 66401c6d404..e81f3810419 100644
--- a/Surface_mesh_segmentation/examples/Surface_mesh_segmentation/CMakeLists.txt
+++ b/Surface_mesh_segmentation/examples/Surface_mesh_segmentation/CMakeLists.txt
@@ -36,7 +36,7 @@ include( ${CGAL_USE_FILE} )
 
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
 
diff --git a/Surface_mesh_simplification/examples/Surface_mesh_simplification/CMakeLists.txt b/Surface_mesh_simplification/examples/Surface_mesh_simplification/CMakeLists.txt
index bb408d278f5..7848346c654 100644
--- a/Surface_mesh_simplification/examples/Surface_mesh_simplification/CMakeLists.txt
+++ b/Surface_mesh_simplification/examples/Surface_mesh_simplification/CMakeLists.txt
@@ -36,7 +36,7 @@ include( ${CGAL_USE_FILE} )
 
 
 # Boost and its components
-find_package( Boost REQUIRED )
+find_package( Boost )
 
 if ( NOT Boost_FOUND )
 
diff --git a/Surface_mesher/demo/Surface_mesher/CMakeLists.txt b/Surface_mesher/demo/Surface_mesher/CMakeLists.txt
index 864e06fb1a6..a7b4cdfb8bf 100644
--- a/Surface_mesher/demo/Surface_mesher/CMakeLists.txt
+++ b/Surface_mesher/demo/Surface_mesher/CMakeLists.txt
@@ -36,7 +36,7 @@ set( QT_USE_QTXML    TRUE )
 set( QT_USE_QTMAIN   TRUE )
 
 find_package(CGAL COMPONENTS ImageIO Qt5)
-if ( CGAL_FOUND AND CGAL_Qt5_FOUND)
+if ( CGAL_FOUND AND CGAL_Qt5_FOUND AND CGAL_ImageIO_FOUND)
 
   add_definitions(-DQT_NO_KEYWORDS)
   include( ${CGAL_USE_FILE} )
@@ -45,7 +45,7 @@ if ( CGAL_FOUND AND CGAL_Qt5_FOUND)
   find_package(QGLViewer )
   find_package(OpenGL    )
   
-  if ( QGLVIEWER_FOUND )
+  if ( QGLVIEWER_FOUND AND Qt5_FOUND)
 
         
     include_directories( ${QGLVIEWER_INCLUDE_DIR} )