Fix Visual Studio compiler warnings, make output visible...

on Windows w/o a console device ("DOS"/Debug window) if OpenGL3 is
not available.

1 files changed, 7 insertions, 2 deletions

diff --git a/examples/OpenGL3-glut-test.cxx b/examples/OpenGL3-glut-test.cxx
index a5060feee..311a02603 100644
--- a/examples/OpenGL3-glut-test.cxx
+++ b/examples/OpenGL3-glut-test.cxx
@@ -1,7 +1,7 @@
 //
 // Tiny OpenGL v3 + glut demo program for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2022 by Bill Spitzak and others.
+// Copyright 1998-2024 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -25,6 +25,7 @@
 #  include <GL/glew.h>
 #endif
 #include <FL/glut.H>
+#include <FL/fl_ask.H>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -207,10 +208,14 @@ int main (int argc, char* argv[])
 #endif
   int gl_version_major;
   const char *glv = (const char*)glGetString(GL_VERSION);
-  fprintf(stderr, "OpenGL version %s supported\n", glv);
   sscanf(glv, "%d", &gl_version_major);
+  fprintf(stderr, "OpenGL version %s supported\n", glv);
   if (gl_version_major < 3) {
     fprintf(stderr, "\nThis platform does not support OpenGL V3\n\n");
+    fflush(stderr);
+    // ensure that users see a message on Windows w/o console output:
+    fl_alert("OpenGL version %s supported.\n"
+             "This platform does not support OpenGL V3!",glv);
     exit(1);
   }
   initShaders();