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Revised documentation files.
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Michael R Sweet
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<HTML>
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<BODY>
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<H1 ALIGN=RIGHT><A NAME="glut">D - GLUT Compatibility</A></H1>
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You should be able to compile existing Glut source code by
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including <FL/glut.H> instead of <GL/glut.h>. This can be done by
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editing the source, by changing the -I switches to the compiler, or by
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providing a symbolic link from GL/glut.h to FL/glut.H.
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<p>All files calling glut procedures must be compiled with C++. You may
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have to alter them slightly to get them to compile without warnings,
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and you may have to rename them to get make to use the C++ compiler.
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I was unable to get some calls to glu to compile without adding some
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casts, apparently due to errors in the glu header files.
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<p>You must link with -lFl. If you call any glut drawing functions
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that fltk does not emulate (<code>glutExtensionsSupported(), glutWire*(),
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glutSolid*(), and glutStroke*()</code>), you will also have to link with
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-lglut, <i>after</i> -lFl.
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<p>Most of glut.H is inline functions. You should take a look at it
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(and maybe at glut.C in the fltk source) if you are having trouble
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porting your Glut program.
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<p>This has been tested with most of the demo programs that come with
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the Glut 3.3 distribution.
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<h2>Known Problems</h2>
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<ul>
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<li>The following functions and/or arguments to functions are missing,
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and you will have to replace them or comment them out for your code to
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compile:<ul>
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<li><code>glutLayerGet(GLUT_LAYER_IN_USE)</code>
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<li><code>glutLayerGet(GLUT_HAS_OVERLAY)</code>
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<li><code>glutSetColor(), glutGetColor(), glutCopyColormap()</code>
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<li><code>glutInitDisplayMode(GLUT_STEREO)</code>
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<li><code>glutInitDisplayMode(GLUT_LUMINANCE)</code>
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<li><code>glutPushWindow()</code>
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<li><code>glutWarpPointer()</code>
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<li>Spaceball, buttonbox, dials, tablet functions, <code>glutDeviceGet()</code>
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<li><code>glutWindowStatusFunc()</code>
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<li><code>glutGet(GLUT_WINDOW_NUM_CHILDREN)</code>
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<li><code>glutGet(GLUT_SCREEN_WIDTH_MM)</code>
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<li><code>glutGet(GLUT_SCREEN_HEIGHT_MM)</code>
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<li><code>glutGet(GLUT_ELAPSED_TIME)</code>
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<li><code>glutVideoResize()</code> missing.
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</ul>
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<li>Most of the symbols/enumerations have different values than
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Glut uses. This will break code that relies on the actual values.
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The only symbols guaranteed to have the same values are true/false
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pairs like <code>GLUT_DOWN</code> and <code>GLUT_UP</code>, mouse
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buttons <code>GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON,
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GLUT_RIGHT_BUTTON</code>, and <code>GLUT_KEY_F1</code> thru
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<code>F12</code>.
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<li><i>The strings passed as menu labels are not copied</i>.
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<li><code>glutPostRedisplay()</code> does not work if called from
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inside a display function. You must use <code>glutIdleFunc()</code>
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if you want your display to update continuously.
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<li><code>glutSwapBuffers()</code> does not work from inside a display
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function. This is on purpose, because fltk swaps the buffers for you.
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<li><code>glutUseLayer()</code> does not work well, and should only be
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used to initialize transformations inside a resize callback. You
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should redraw overlays by using <code>glutOverlayDisplayFunc()</code>.
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<li>Overlays are cleared before the overlay display function is
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called. <code>glutLayerGet(GLUT_OVERLAY_DAMAGED)</code> always
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returns true, this fixed some glut overlay programs. You must rewrite
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your code so that gl_color() is used to choose colors in an overlay,
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or you will get random overlay colors.
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<li><code>glutSetCursor(GLUT_CURSOR_FULL_CROSSHAIR)</code> just
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results in a small crosshair.
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<li>The fonts used by <code>glutBitmapCharacter() and
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glutBitmapWidth()</code> may be different.
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<li><code>glutInit(argc,argv)</code> will consume different switches than glut
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does. It accepts the switches recognized by <a
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href=Fl.html>Fl_Window::arg()</a>, and will accept any
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abbreviation of these switches (such as -d for -display).
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</ul>
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<h2>Mixing Glut code and Fltk code</h2>
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You can make your Glut window a child of a Fl_Window with the
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following scheme. The biggest trick is that Glut insists on
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show()'ing the window at the point it is created, which means the
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Fl_Window parent window must already be show()n.
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<p>Don't call glutInit().
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<p>Create your Fl_Window, and any fltk widgets. Leave a blank area in
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the window for your glut window.
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<p>show() the Fl_Window. Perhaps call show(argc,argv).
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<p>Call window->begin() so the glut window will be automatically added
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to it.
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<p>Use glutInitWindowSize() and glutInitWindowPosition() to set the
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location in the parent window to put the glut window.
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<p>Put your glut code next. It probably does not need many changes.
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Call window->end() immediately after the glutCreateWindow()!
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<p>You can call either glutMainLoop() or Fl::run() or loop calling
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Fl::wait() to run the program.
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<h2>class Fl_Glut_Window : public <a href=Fl_Gl_Window.html>Fl_Gl_Window</a></h2>
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Each Glut window is an instance of this class, which is a subclass of
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<a href=Fl_Gl_Window.html>Fl_Gl_Window</a>. You may find it useful to
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manipulate instances directly rather than use glut window id's. These
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may be created without opening the display, and thus can fit better
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into FL's method of creating windows.
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<p>The current glut window is available in <code>Fl_Glut_Window
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*glut_window</code>.
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<p><code>new Fl_Glut_Window(...)</code> is the same as
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<code>glutCreateWindow()</code> except it does not show() the window
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or make the window current.
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<p><code>window->make_current()</code> is the same as
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<code>glutSetWindow(number)</code>. If the window has not had show()
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called on it yet, some functions that assumme a gl context will not
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work. If you do show() the window, call make_current() again to set
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the context.
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<p><code>~Fl_Glut_Window()</code> is the same as
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<code>glutDestroyWindow()</code>.
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</BODY>
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</HTML>
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