Fix STR 3458: "GLUT compatibility mode segfaults"

... "when there's no current window".

Silently ignore GLUT function calls that need a current window if the
current window is NULL, return 0 from functions that return an 'int'.

Check if window is shown in Fl_X11_Gl_Window_Driver::swap_buffers().
This would issue "XRequest.nnn: GLXBadDrawable 0x0" on X11 otherwise.

Note: the chosen implementation to ignore GLUT calls silently appears
to be compatible with GLUT (3.7) whereas FreeGLUT 3.0 would issue error
messages and exit. The latter could be implemented as well but would
be much more work.

1 files changed, 172 insertions, 0 deletions

diff --git a/test/glut_test.cxx b/test/glut_test.cxx
new file mode 100644
index 000000000..0a7facc86
--- /dev/null
+++ b/test/glut_test.cxx
@@ -0,0 +1,172 @@
+//
+// GLUT test program for the Fast Light Tool Kit (FLTK).
+//
+// Provided by Brian Schack (STR #3458, see "big.cxx").
+// Copyright 2023 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
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+// Thanks to the original author Brian Schack for this test program.
+// This program has been extended to test several GLUT functions with
+// (1) a valid and (2) an invalid (destroyed) GLUT window.
+// The test program opens two GLUT windows, runs the tests, prints
+// diagnostics on stdout, and exits immediately. This is intended.
+
+// To compile (examples with different GLUT implementations)
+// as of Apr 03, 2018 provided Brian Schack, slightly modified
+//
+// macOS GLUT:
+//   g++ -o glut_test glut_test.cxx -framework OpenGL -framework GLUT
+//
+// FreeGLUT (on macOS, with Macport's FreeGLUT):
+//   g++ -o glut_test glut_test.cxx -framework OpenGL -I/opt/local/include -L/opt/local/lib -lglut
+//
+// FLTK
+//   fltk-config --use-gl --compile glut_test.cxx
+
+// Enable one of the following two #include's depending on the GLUT implementation
+
+// #include <GLUT/glut.h>		// GLUT and FreeGLUT version
+#include <FL/glut.H>        // FLTK version
+
+#include <stdio.h>
+
+// Empty callback functions for testing.
+void displayFunc() {}
+void reshapeFunc(int w, int h) {}
+void keyboardFunc(unsigned char key, int x, int y) {}
+void mouseFunc(int b, int state, int x, int y) {}
+void motionFunc(int x, int y) {}
+void passiveMotionFunc(int x, int y) {}
+void entryFunc(int s) {}
+void visibilityFunc(int s) {}
+void idleFunc() {}
+void timerFunc(int value) {}
+void menuStateFunc(int state) {}
+void menuStatusFunc(int status, int x, int y) {}
+void specialFunc(int key, int x, int y) {}
+void overlayDisplayFunc() {}
+
+int main(int argc, char **argv) {
+  glutInit(&argc, argv);
+
+  // Create 2 windows.
+  int win1 = glutCreateWindow("Window 1");
+  int win2 = glutCreateWindow("Window 2");
+  printf("Window 1 created, number = %d\n", win1);
+  printf("Window 2 created, number = %d\n", win2);
+
+  // Run tests twice, with (1) a valid and (2) an invalid current window
+
+  for (int i = 0; i < 2; i++) {
+
+    // Find out which window is current.
+    int current = glutGetWindow();
+    printf("Window %d is current\n", current);
+
+    // Ask GLUT to redisplay things.
+    glutPostRedisplay();
+
+    // Set window title
+    glutSetWindowTitle((char *)"Non-existent");
+
+    // Set icon title
+    glutSetIconTitle((char *)"Non-existent");
+
+    // Position window
+    glutPositionWindow(10, 20);
+
+    // Reshape window
+    glutReshapeWindow(100, 200);
+
+    // Pop window
+    glutPopWindow();
+
+    // Iconify window
+    glutIconifyWindow();
+
+    // Show window
+    glutShowWindow();
+
+    // Hide window
+    glutHideWindow();
+
+    // Go to full screen mode
+    glutFullScreen();
+
+    // Set the cursor
+    glutSetCursor(GLUT_CURSOR_INFO);
+
+    // Establish an overlay
+    glutEstablishOverlay();
+
+    // Remove overlay
+    glutRemoveOverlay();
+
+    // Choose a layer
+    glutUseLayer(GLUT_NORMAL);
+    glutUseLayer(GLUT_OVERLAY);
+
+    // Post display on a layer
+    glutPostOverlayRedisplay();
+
+    // Show overlay
+    glutShowOverlay();
+
+    // Hide overlay
+    glutHideOverlay();
+
+    // Attach a menu
+    glutAttachMenu(0);
+
+    // Detach a menu
+    glutDetachMenu(0);
+
+    // Specify callbacks
+    glutDisplayFunc(displayFunc);
+    glutReshapeFunc(reshapeFunc);
+    glutKeyboardFunc(keyboardFunc);
+    glutMouseFunc(mouseFunc);
+    glutMotionFunc(motionFunc);
+    glutPassiveMotionFunc(passiveMotionFunc);
+    glutEntryFunc(entryFunc);
+    glutVisibilityFunc(visibilityFunc);
+    glutIdleFunc(idleFunc);
+    glutTimerFunc(1000, timerFunc, 42);
+    glutMenuStateFunc(menuStateFunc);
+    glutMenuStatusFunc(menuStatusFunc);
+    glutSpecialFunc(specialFunc);
+    glutOverlayDisplayFunc(overlayDisplayFunc);
+
+    // Swap buffers
+    glutSwapBuffers();
+
+    // GLUT gets
+    printf("GLUT_WINDOW_X = %d\n", glutGet(GLUT_WINDOW_X));
+    printf("GLUT_WINDOW_Y = %d\n", glutGet(GLUT_WINDOW_Y));
+    printf("GLUT_WINDOW_WIDTH = %d\n", glutGet(GLUT_WINDOW_WIDTH));
+    printf("GLUT_WINDOW_HEIGHT = %d\n", glutGet(GLUT_WINDOW_HEIGHT));
+    printf("GLUT_WINDOW_PARENT = %d\n", glutGet(GLUT_WINDOW_PARENT));
+
+    // GLUT layer gets
+    printf("GLUT_OVERLAY_POSSIBLE = %d\n", glutLayerGet(GLUT_OVERLAY_POSSIBLE));
+    printf("GLUT_NORMAL_DAMAGED = %d\n", glutLayerGet(GLUT_NORMAL_DAMAGED));
+
+    // Destroy the current window - this sets glut_window to NULL
+    printf("Destroy the current window (%d)\n\n", glutGetWindow());
+    glutDestroyWindow(current);
+
+  } // loop with current window
+
+  printf("All tests done, exiting.\n");
+  return 0;
+}