Drawing arrangement (1st rev.) and basic cleanup conic traits

Arrangement_on_surface_2/examples/Arrangement_on_surface_2/CMakeLists.txt

@@ -4,7 +4,7 @@
 cmake_minimum_required(VERSION 3.1...3.23)
 project(Arrangement_on_surface_2_Examples)
 
-find_package(CGAL REQUIRED COMPONENTS Core)
+find_package(CGAL REQUIRED COMPONENTS Core Qt5)
 
 # create a target per cppfile
 file(
@@ -14,3 +14,7 @@ file(
 foreach(cppfile ${cppfiles})
   create_single_source_cgal_program("${cppfile}")
 endforeach()
+
+if(CGAL_Qt5_FOUND)
+  target_link_libraries(draw_arr PUBLIC CGAL::CGAL_Basic_viewer)
+endif()

Arrangement_on_surface_2/examples/Arrangement_on_surface_2/draw_arr.cpp

@@ -0,0 +1,25 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Arrangement_2.h>
+#include <CGAL/Arr_segment_traits_2.h>
+#include <CGAL/draw_arrangement_2.h>
+
+using Kernel = CGAL::Exact_predicates_inexact_constructions_kernel;
+using Traits = CGAL::Arr_segment_traits_2<Kernel>;
+using Point = Traits::Point_2;
+using X_monotone_curve = Traits::X_monotone_curve_2;
+using Arrangement_2 = CGAL::Arrangement_2<Traits>;
+
+int main() {
+  Traits traits;
+  Arrangement_2 arr(&traits);
+  auto ctr_xcv = traits.construct_x_monotone_curve_2_object();
+
+  CGAL::insert(arr, ctr_xcv(Point(-1,-1), Point(1,-1)));
+  CGAL::insert(arr, ctr_xcv(Point(1,-1), Point(1,1)));
+  CGAL::insert(arr, ctr_xcv(Point(1,1), Point(-1,1)));
+  CGAL::insert(arr, ctr_xcv(Point(-1,1), Point(-1,-1)));
+
+  CGAL::draw(arr);
+
+  return EXIT_SUCCESS;
+}

Arrangement_on_surface_2/include/CGAL/draw_arrangement_2.h

@@ -0,0 +1,94 @@
+#ifndef CGAL_DRAW_ARRANGEMENT_2_H
+#define CGAL_DRAW_ARRANGEMENT_2_H
+
+#include <CGAL/Qt/Basic_viewer_qt.h>
+#include <CGAL/Qt/init_ogl_context.h>
+#include <CGAL/Arrangement_2.h>
+
+namespace CGAL {
+
+// Viewer class for Polygon_2
+template <typename Arrangement_2>
+class Arr_2_viewer_qt : public Basic_viewer_qt {
+  typedef Basic_viewer_qt       Base;
+  typedef Arrangement_2         Arr;
+  typedef typename Arr::Point_2 Point;
+
+public:
+  /// Construct the viewer.
+  /// @param arr the arrangement to view
+  /// @param title the title of the window
+  Arr_2_viewer_qt(QWidget* parent, const Arr& arr,
+                  const char* title = "2D Arrangement Basic Viewer") :
+    // First draw: vertices; edges, faces; multi-color; no inverse normal
+    Base(parent, title, true, true, true, false, false),
+    m_arr(arr)
+  { add_elements(); }
+
+protected:
+  void add_ccb(typename Arr::Ccb_halfedge_const_circulator circ) {
+    typename Arr::Ccb_halfedge_const_circulator curr = circ;
+    do {
+      typename Arr::Halfedge_const_handle e = curr;
+      add_segment(e->source()->point(), e->target()->point());
+      add_point(e->source()->point());
+      add_point_in_face(e->source()->point());
+    } while (++curr != circ);
+  }
+
+  void add_face(typename Arr::Face_const_handle f, CGAL::IO::Color c) {
+    if (f->is_unbounded()) return;
+    face_begin(c);
+    add_ccb(f->outer_ccb());
+    for (auto iv = f->isolated_vertices_begin();
+         iv != f->isolated_vertices_end(); ++iv)
+      add_point(iv->point());
+    face_end();
+  }
+
+  void add_elements() {
+    clear();
+    if (m_arr.is_empty()) return;
+    CGAL::IO::Color c(75,160,255);
+    for (auto fit = m_arr.faces_begin(); fit != m_arr.faces_end(); ++fit)
+      add_face(fit, c);
+  }
+
+  virtual void keyPressEvent(QKeyEvent* e) {
+    // Test key pressed:
+    //    const ::Qt::KeyboardModifiers modifiers = e->modifiers();
+    //    if ((e->key()==Qt::Key_PageUp) && (modifiers==Qt::NoButton)) { ... }
+
+    // Call: * add_elements() if the model changed, followed by
+    //       * redraw() if some viewing parameters changed that implies some
+    //                  modifications of the buffers
+    //                  (eg. type of normal, color/mono)
+    //       * update() just to update the drawing
+
+    // Call the base method to process others/classicals key
+    Base::keyPressEvent(e);
+  }
+
+protected:
+  const Arrangement_2& m_arr;
+};
+
+template <typename GeometryTraits_2, typename Dcel>
+void draw(const CGAL::Arrangement_2<GeometryTraits_2, Dcel>& arr,
+          const char* title = "2D Arrangement Basic Viewer") {
+  typedef GeometryTraits_2              Gt;
+  typedef CGAL::Arrangement_2<Gt, Dcel> Arr;
+
+  CGAL::Qt::init_ogl_context(4,3);
+
+  int argc = 1;
+  const char* argv[2] = {"t2_viewer", nullptr};
+  QApplication app(argc, const_cast<char**>(argv));
+  Arr_2_viewer_qt<Arr>mainwindow(app.activeWindow(), arr, title);
+  mainwindow.show();
+  app.exec();
+}
+
+}
+
+#endif