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