give an #error if wxUSE_GLCANVAS == 0 instead of building empty samples

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29830 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/opengl/penguin/penguin.cpp

@@ -25,6 +25,10 @@
 #include "wx/wx.h"
 #endif
 
+#if !wxUSE_GLCANVAS
+    #error "OpenGL required: set wxUSE_GLCANVAS to 1 and rebuild the library"
+#endif
+
 #include "penguin.h"
 #ifdef __WXMAC__
 #  ifdef __DARWIN__
@@ -54,7 +58,6 @@ bool MyApp::OnInit()
     menuBar->Append(fileMenu, wxT("&File"));
     frame->SetMenuBar(menuBar);
 
-#if wxUSE_GLCANVAS
     frame->SetCanvas( new TestGLCanvas(frame, wxID_ANY, wxDefaultPosition,
         wxSize(200, 200), wxSUNKEN_BORDER) );
 
@@ -65,14 +68,6 @@ bool MyApp::OnInit()
     frame->Show(true);
 
     return true;
-#else
-
-    wxMessageBox( _T("This sample has to be compiled with wxUSE_GLCANVAS"),
-        _T("Building error"), wxOK);
-
-    return false;
-
-#endif
 }
 
 IMPLEMENT_APP(MyApp)
@@ -86,9 +81,7 @@ MyFrame::MyFrame(wxFrame *frame, const wxString& title, const wxPoint& pos,
     const wxSize& size, long style)
     : wxFrame(frame, wxID_ANY, title, pos, size, style)
 {
-#if wxUSE_GLCANVAS
     m_canvas = NULL;
-#endif
 }
 
 /* Intercept menu commands */
@@ -98,8 +91,6 @@ void MyFrame::OnExit( wxCommandEvent& WXUNUSED(event) )
     Close(true);
 }
 
-#if wxUSE_GLCANVAS
-
 BEGIN_EVENT_TABLE(TestGLCanvas, wxGLCanvas)
     EVT_SIZE(TestGLCanvas::OnSize)
     EVT_PAINT(TestGLCanvas::OnPaint)
@@ -267,5 +258,3 @@ void TestGLCanvas::InitGL()
     glEnable(GL_COLOR_MATERIAL);
 }
 
-
-#endif // #if wxUSE_GLCANVAS