This appendix describes the GLUT compatibility header file supplied with FLTK. FLTK's GLUT compatibility is based on the original GLUT 3.7 and the follow-on FreeGLUT 2.4.0 libraries.
You should be able to compile existing GLUT source code by including <FL/glut.H> instead of <GL/glut.h>. This can be done by editing the source, by changing the -I switches to the compiler, or by providing a symbolic link from GL/glut.h to FL/glut.H.
All files calling GLUT procedures must be compiled with C++. You may have to alter them slightly to get them to compile without warnings, and you may have to rename them to get make to use the C++ compiler.
You must link with the FLTK library. Most of FL/glut.H is inline functions. You should take a look at it (and maybe at test/glpuzzle.cxx in the FLTK source) if you are having trouble porting your GLUT program.
This has been tested with most of the demo programs that come with the GLUT and FreeGLUT distributions.
The following functions and/or arguments to functions are missing, and you will have to replace them or comment them out for your code to compile:
The strings passed as menu labels are not copied.
glutPostRedisplay() does not work if called from inside a display function. You must use glutIdleFunc() if you want your display to update continuously.
glutSwapBuffers() does not work from inside a display function. This is on purpose, because FLTK swaps the buffers for you.
glutUseLayer() does not work well, and should only be used to initialize transformations inside a resize callback. You should redraw overlays by using glutOverlayDisplayFunc().
Overlays are cleared before the overlay display function is called. glutLayerGet(GLUT_OVERLAY_DAMAGED) always returns true for compatibility with some GLUT overlay programs. You must rewrite your code so that gl_color() is used to choose colors in an overlay, or you will get random overlay colors.
glutSetCursor(GLUT_CURSOR_FULL_CROSSHAIR) just results in a small crosshair.
The fonts used by glutBitmapCharacter() and glutBitmapWidth() may be different.
glutInit(argc,argv) will consume different switches than GLUT does. It accepts the switches recognized by Fl::args(), and will accept any abbreviation of these switches (such as "-di" for "-display").
Fl_Gl_Window | +----Fl_Glut_Window
The current GLUT window is available in the global variable glut_window.
new Fl_Glut_Window(...) is the same as glutCreateWindow() except it does not show() the window or make the window current.
window->make_current() is the same as glutSetWindow(number). If the window has not had show() called on it yet, some functions that assumme an OpenGL context will not work. If you do show() the window, call make_current() again to set the context.
~Fl_Glut_Window() is the same as glutDestroyWindow() .
|display||A pointer to the function to call to draw the normal planes.|
|entry||A pointer to the function to call when the mouse moves into or out of the window.|
|keyboard||A pointer to the function to call when a regular key is pressed.|
|menu||The menu to post when one of the mouse buttons is pressed.|
|mouse||A pointer to the function to call when a button is pressed or released.|
|motion||A pointer to the function to call when the mouse is moved with a button down.|
|overlaydisplay||A pointer to the function to call to draw the overlay planes.|
|passivemotion||A pointer to the function to call when the mouse is moved with no buttons down.|
|reshape||A pointer to the function to call when the window is resized.|
|special||A pointer to the function to call when a special key is pressed.|
|visibility||A pointer to the function to call when the window is iconified or restored (made visible.)|