OpenGL is a trademark of Silicon Graphics, Inc. X Window System is a trademark of X Consortium, Inc. Spaceball is a registered trademark of Spatial Systems Inc.
The authors have taken care in preparation of this documentation but make no expressed or implied warranty of any kind and assumes no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising from the use of information or programs contained herein.
Note that the FreeGLUT 3.0 enhancements and additions are already mentioned in this API document. Some of the functions described here will thus not work with the currently available 2.8.1 release.
The OpenGL programming world owes a tremendous debt to Mr. Mark J. Kilgard for writing the OpenGL Utility Toolkit, or GLUT. The GLUT library of functions allows an application programmer to create, control, and manipulate windows independent of what operating system the program is running on. By hiding the dependency on the operating system from the application programmer, he allowed people to write truly portable OpenGL applications.
Mr. Kilgard copyrighted his library and gave it a rather unusual license. Under his license, people are allowed freely to copy and distribute the libraries and the source code, but they are not allowed to modify it. For a long time this did not matter because the GLUT library worked so well and because Mr. Kilgard was releasing updates on a regular basis. But with the passage of time, people started wanting some slightly different behaviours in their windowing system. When Mr. Kilgard stopped supporting the GLUT library in 1999, having moved on to bigger and better things, this started to become a problem.
In December 1999, Mr. Pawel Olzsta started work on an open-source clone of the GLUT library. This open-source clone, which does not use any of the GLUT source code, has evolved into the present freeglut library. This documentation specifies the application program interface to the freeglut library.
In developing the freeglut library, we have taken careful steps to ensure consistency in function operation across the board, in such a manner as to maintain compatibility with GLUT's behavior whenever possible. In this section some of the important conventions of FreeGLUT, and their compatibility with GLUT, are made explicit.
There is considerable confusion about the "right thing to do" concerning
window size and position. GLUT itself is not consistent between
Windows and UNIX/X11; since platform independence is a virtue for
freeglut, we decided to break with GLUT's behaviour.
Under UNIX/X11, it is apparently not possible to get the window border
sizes in order to subtract them off the window's initial position until
some time after the window has been created. Therefore we decided on
the following behavior, both under Windows and under UNIX/X11:
Since the freeglut library was developed in order to update GLUT, it is natural that there will be some differences between the two. Each function in the API notes any differences between the GLUT and the freeglut function behaviours. The important ones are summarized here.
One of the commonest complaints about the GLUT library was that once an application called glutMainLoop, it never got control back. There was no way for an application to loop in GLUT for a while, possibly as a subloop while a specific window was open, and then return to the calling function. A new function, glutMainLoopEvent, has been added to allow this functionality. Another function, glutLeaveMainLoop, has also been added to allow the application to tell freeglut to clean up and close down.
Another difficulty with GLUT, especially with multiple-window programs, is that if the user clicks on the "x" in the window header the application exits immediately. The application programmer can now set an option, GLUT_ACTION_ON_WINDOW_CLOSE, to specify whether execution should continue, whether GLUT should return control to the main program, or whether GLUT should simply exit (the default).
Function to leave fullscreen window mode, glutLeaveFullScreen, or to toggle between fullscreen and normal window mode, glutFullScreenToggle, have been added.
Several new callbacks have been added and several callbacks which were specific to Silicon Graphics hardware have not been implemented. Most or all of the new callbacks are listed in the GLUT Version 4 "glut.h" header file but did not make it into the documentation. The new callbacks consist of regular and special key release callbacks, a joystick callback, a menu state callback (with one argument, distinct from the menu status callback which has three arguments), a window status callback (also with one argument), and a window position callback. Unsupported callbacks are the two Tablet callbacks. If the user has a need for an unsupported callback he should contact the freeglut development team.
New functions have been added to render full character strings (including carriage returns) rather than rendering one character at a time. More functions return the widths of character strings and the font heights, in pixels for bitmapped fonts and in OpenGL units for the stroke fonts.
Two functions have been added to render a wireframe and a solid rhombic dodecahedron. Furthermore, solid and wireframe versions of the original teacup and teaspoon that accompanied the famous Newell teapot. As these geometry functions are often used for teaching purposes, glutSetOption(GLUT_GEOMETRY_VISUALIZE_NORMALS,true/false) can now be used to visualize the normal vectors for each vertex. Lastly, to support drawing these objects with shaders, three functions have been added with which users can provide the addresses of the Coordinate, Normal and Texture Coordinate vertex attribs: glutSetVertexAttribCoord3, glutSetVertexAttribNormal, and glutSetVertexAttribTexCoord2. Texture coordinates are only generated for the teaset.
glutGetProcAddress is a wrapper for the glXGetProcAddressARB and wglGetProcAddress functions.
The glutInitWindowPosition and glutInitWindowSize functions specify a desired position and size for windows that freeglut will create in the future.
Usage
void glutInitWindowPosition ( int x, int y );
void glutInitWindowSize ( int width, int height );
Description
The glutInitWindowPosition and glutInitWindowSize functions specify a desired position and size for windows that freeglut will create in the future. The position is measured in pixels from the upper left hand corner of the screen, with "x" increasing to the right and "y" increasing towards the bottom of the screen. The size is measured in pixels. Freeglut does not promise to follow these specifications in creating its windows, but it certainly makes an attempt to.
The position and size of a window are a matter of some subtlety. Most
windows have a usable area surrounded by a border and with a title bar
on the top. The border and title bar are commonly called "decorations."
The position of the window unfortunately varies with the operating system.
On both Linux and Windows, you specify the coordinates of the upper
left-hand corner of the window's decorations. Also for both operating
systems, the size of the window is the size of the usable interior.
With glutGet information can be acquired about the current
window's size, position and decorations. Note however that according to
FreeGLUT's conventions, the information
returned about the window coordinates does not correspond to the
coordinates used when setting window position.
Windows has some additional quirks which the application programmer should know about. First, the minimum y-coordinate of a window decoration is zero. (This is a feature of freeglut and can be adjusted if so desired.) Second, there appears to be a minimum window width on Windows which is 104 pixels. The user may specify a smaller width, but the Windows system calls ignore it. It is also impossible to make a window narrower than this by dragging on its corner.
Changes From GLUT
For some reason, GLUT is not affected by the 104-pixel minimum window width. If the user clicks on the corner of a window which is narrower than this amount, the window will immediately snap out to this width, but the application can call glutReshapeWindow and make a window narrower again.
Changes From GLUT
glutInitDisplayString support is limited: any of the tokens recognized by GLUT are also recognized by FreeGLUT, but any statements with comparators cannot (yet: do help develop this!) be handled. Any spec (comparator and value) after the token is ignored. However, many of these values can be set with glutSetOption for now...
The glutInitErrorFunc and glutInitWarningFunc functions specify callbacks that will be called upon warnings and errors issued from within FreeGLUT so that the user can deal with these. Useful for rerouting to another output sink (e.g., logging) and also to avoid exit(1) being called upon error. As with other glutInit* functions, these can be set before glutInit is called, so any output from the library can be handled by the user.
Usage
void glutInitErrorFunc ( void (* callback)( const char *fmt, va_list ap) );
void glutInitWarningFunc ( void (* callback)( const char *fmt, va_list ap) );
Description
The users callback is passed a format string and a variable argument
list that can be passed to functions such as printf.
Note that there are the preprocessor definitions
FREEGLUT_PRINT_ERRORS and FREEGLUT_PRINT_WARNINGS,
which affect FreeGLUT's warning and error behavior when no user
callback is defined. If defined at library (not client app!) compile
time--by default it is, warnings and errors are printed to
stderr. If not defined, warnings and errors are muted (not
printed to stderr), though errors still trigger deinitialization and
exit. Whether FREEGLUT_PRINT_ERRORS and
FREEGLUT_PRINT_WARNINGS is defined does not affect whether the
client callback is called, it only affects whether warnings and errors
are printed to stderr when no callback is defined.
Changes From GLUT
GLUT does not provide these functions.
After an application has finished initializing its windows and menus, it enters an event loop. Within this loop, freeglut polls the data entry devices (keyboard, mouse, etc.) and calls the application's appropriate callbacks.
In GLUT, control never returned from the event loop (as invoked by the glutMainLoop function) to the calling function. This prevented an application from having re-entrant code, in which GLUT could be invoked from within a callback, and it prevented the application from doing any post-processing (such as freeing allocated memory) after GLUT had closed down. Freeglut allows the application programmer to specify more direct control over the event loop by means of two new functions. The first, glutMainLoopEvent, processes a single iteration of the event loop and allows the application to use a different event loop controller or to contain re-entrant code. The second, glutLeaveMainLoop, causes the event loop to exit nicely; this is preferable to the application's calling exit from within a GLUT callback.
The glutMainLoop function enters the event loop.
Usage
void glutMainLoop ( void );
Description
The glutMainLoop function causes the program to enter the window event loop. An application should call this function at most once. It will call any application callback functions as required to process mouse clicks, mouse motion, key presses, and so on.
Changes From GLUT
In GLUT, there was absolutely no way for the application programmer to have control return from the glutMainLoop function to the calling function. Freeglut allows the programmer to force this by setting the GLUT_ACTION_ON_WINDOW_CLOSE option and invoking the glutLeaveMainLoop function from one of the callbacks. Stopping the program this way is preferable to simply calling exit from within a callback because this allows freeglut to free allocated memory and otherwise clean up after itself. (I know I just said this, but I think it is important enough that it bears repeating.)
The glutMainLoopEvent function processes a single iteration in the freeglut event loop.
Usage
void glutMainLoopEvent ( void );
Description
The glutMainLoopEvent function causes freeglut to process one iteration's worth of events in its event loop. This allows the application to control its own event loop and still use the freeglut windowing system.
Changes From GLUT
GLUT does not include this function.
The glutLeaveMainLoop function causes freeglut to stop its event loop.
Usage
void glutLeaveMainLoop ( void );
Description
The glutLeaveMainLoop function causes freeglut to stop the event loop. If the GLUT_ACTION_ON_WINDOW_CLOSE option has been set to GLUT_ACTION_GLUTMAINLOOP_RETURNS or GLUT_ACTION_CONTINUE_EXECUTION, control will return to the function which called glutMainLoop; otherwise the application will exit.
If the application has two nested calls to glutMainLoop and calls glutLeaveMainLoop, the behaviour of freeglut is undefined. It may leave only the inner nested loop or it may leave both loops. If the reader has a strong preference for one behaviour over the other he should contact the freeglut Programming Consortium and ask for the code to be fixed.
Changes From GLUT
GLUT does not include this function.
The glutSetWindowTitle, glutSetIconTitle set the window title for when the window is in a visible state and when it is in an iconified state respectively.
Usage
glutSetWindowTitle(const char* title);
glutSetIconTitle(const char* title);
Description
Normally a window system displays a title for every top-level window in
the system. The initial title is set when you call glutCreateWindow().
By means of the glutSetWindowTitle function you can set the
titles for your top-level FreeGLUT windows. If you just want one
title for the window over the window's entire life, you should set it
when you open the window with glutCreateWindow().
glutSetIconTitle sets the title to be displayed for the window
when it is in iconified (minimized) state.
Changes From GLUT
glutSetIconTitle does nothing in GLUT on Windows, but is emulated on Windows by FreeGLUT.
The glutFullScreen, glutLeaveFullScreen and glutFullScreenToggle functions are used to transition the current window between fullscreen and normal mode.
Usage
void glutFullScreen ( void );
void glutLeaveFullScreen ( void );
void glutFullScreenToggle ( void );
Description
The glutFullScreen function causes the current window to enter
fullscreen mode, glutLeaveFullScreen to go back to the window
size and position as it was before entering fullscreen mode, and
glutFullScreenToggle toggles between fullscreen and normal
mode.
In multi-monitor setups on Windows 2000 and newer, the window will
become fullscreen on the monitor that it overlaps the most.
Calls to these functions are ignored for gamemode and child windows.
Use glutGet(GLUT_FULL_SCREEN) to query fullscreen state of
current window.
Changes From GLUT
GLUT does not include the glutLeaveFullScreen and glutFullScreenToggle functions.
Freeglut does not allow overlays, although it does "answer the mail" with function stubs so that GLUT-based programs can compile and link against freeglut without modification.
If the reader needs overlays, he should contact the freeglut Programming Consortium and ask for them to be implemented. He should also be prepared to assist in the implementation.
The glutEstablishOverlay function is not implemented in freeglut.
Usage
void glutEstablishOverlay ( void );
Description
The glutEstablishOverlay function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutRemoveOverlay function is not implemented in freeglut.
Usage
void glutRemoveOverlay ( void );
Description
The glutRemoveOverlay function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutUseLayer function is not implemented in freeglut.
Usage
void glutUseLayer ( GLenum layer );
Description
The glutUseLayer function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutPostOverlayRedisplay function is not implemented in freeglut.
Usage
void glutPostOverlayRedisplay ( void );
Description
The glutPostOverlayRedisplay function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutPostWindowOverlayRedisplay function is not implemented in freeglut.
Usage
void glutPostWindowOverlayRedisplay ( int window );
Description
The glutPostWindowOverlayRedisplay function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutShowOverlay and glutHideOverlay functions are not implemented in freeglut.
Usage
void glutShowOverlay( void );
void glutHideOverlay( void );
Description
The glutShowOverlay and glutHideOverlay functions are not implemented in freeglut.
Changes From GLUT
GLUT implements these functions.
glutSetMenuFont sets the (bitmap) font to be used for drawing the specified menu.
Usage
void glutSetMenuFont( int menuID, void* fontID );
Description
Only bitmap fonts (GLUT_BITMAP_xxx, see here for a list) can be used as menu fonts. A warning is issued and the request is ignored if the supplied font is a stroke font, or an unknown font.
Changes From GLUT
GLUT does not provide this function.
The glutIdleFunc function sets the global idle callback. Freeglut calls the idle callback when there are no inputs from the user.
Usage
void glutIdleFunc ( void (*func) ( void ) );
funcThe new global idle callback function
Description
The glutIdleFunc function
specifies the function that freeglut will call to perform background
processing tasks such as continuous animation when window system events are
not being received. If enabled, this function is called continuously
from freeglut while no events are received. The callback function
has no parameters and returns no value. Freeglut does not change
the current window or the current menu before invoking the idle
callback; programs with multiple windows or menus must explicitly set the
current window and current menu
and not rely on its current setting.
The amount of computation and rendering done in an idle
callback should be minimized to avoid affecting the program's interactive
response. In general, no more than a single frame of rendering should
be done in a single invocation of an idle callback. Note that no actual
drawing to the framebuffer should be done from the idle callback, this
is not supported. While it might work on some platforms, it will not on
others or might stop working in the future. Drawing should be done in
the glutDisplayFunc callback.
Calling glutIdleFunc with a NULL argument
disables the call to an idle callback.
Changes From GLUT
Application programmers should note that if they have specified the "continue execution" action on window closure, freeglut will continue to call the idle callback after the user has closed a window by clicking on the "x" in the window header bar. If the idle callback renders a particular window (this is considered bad form but is frequently done anyway), the programmer should supply a window closure callback for that window which changes or disables the idle callback.
The glutPositionFunc function sets the window's position callback. Freeglut calls the position callback when the window is repositioned/moved programatically or by the user.
Usage
void glutPositionFunc ( void (* func)( int x, int y) );
Description
When FreeGLUT calls this callback, it provides the new position on the screen of the top-left of the non-client area, that is, the same coordinates used by glutInitPosition and glutPositionWindow. To get the position on the screen of the top-left of the client area, use glutGet(GLUT_WINDOW_X) and glutGet(GLUT_WINDOW_Y). See FreeGLUT's conventions for more information.
Changes From GLUT
This function is not implemented in GLUT.
The glutCloseFunc function sets the window's close callback. Freeglut calls the close callback when the window is about to be destroyed.
Usage
void glutCloseFunc ( void (*func) ( void ) );
func The window's new closure callback function
Description
The glutCloseFunc function specifies the function
that freeglut will call to notify the application that a window
is about to be closed, either because it is requested using
glutDestroyWindow, because the user clicked on the "x" in the
window header (for top-level windows only), or due to a pending closure
of a subwindow's parent window. In the first case, the closure callback
is not invoked from the glutDestroyWindow call, but at a
later time point.
Freeglut sets the current window to the window
which is about to be closed when the callback is invoked. The window can
thus be retrieved in the callback using glutGetWindow.
Users looking to prevent FreeGLUT from exiting when a window is
closed, should look into using glutSetOption to set
GLUT_ACTION_ON_WINDOW_CLOSE. Some settings will prevent the
application from exiting when a window is closed.
Please note that glutWMCloseFunc, a deprecated function, is an
alias to glutCloseFunc.
Changes From GLUT
This function is not implemented in GLUT.
The glutSpecialFunc function sets the window's special key press callback. Freeglut calls the special key press callback when the user presses a special key.
Usage
void glutSpecialFunc ( void (*func) ( int key, int x, int y ) );
func The window's
new special key press callback function
key The
key whose press triggers the callback
x
The x-coordinate of the mouse relative
to the window at the time the key is pressed
y
The y-coordinate of the mouse relative
to the window at the time the key is pressed
Description
The glutSpecialFunc function specifies the function
that freeglut will call when the user
presses a special key on the keyboard. The callback function has one
argument: the name of the function to be invoked ("called back") at
the time at which the special key is pressed. The function returns no
value. Freeglut sets the current window to the window
which is active when the callback is invoked. "Special keys" are the
function keys, the arrow keys, the Page Up and Page Down keys, and the Insert
key. The Delete key is considered to be a regular key.
Calling glutSpecialUpFunc with a NULL argument
disables the call to the window's special key press callback.
The key argument may take one of the following defined constant values:
Changes From GLUT
None.
The glutKeyboardUpFunc function sets the window's key release callback. Freeglut calls the key release callback when the user releases a key.
Usage
void glutKeyboardUpFunc ( void (*func) ( unsigned char key, int x, int y ) );
func The window's
new key release callback function
key The
key whose release triggers the callback
x
The x-coordinate of the mouse relative
to the window at the time the key is released
y
The y-coordinate of the mouse relative
to the window at the time the key is released
Description
The glutKeyboardUpFunc
function specifies the function that freeglut will call when the
user releases a key from the keyboard. The callback function has one
argument: the name of the function to be invoked ("called back") at
the time at which the key is released. The function returns no value.
Freeglut sets the current window to the window which is
active when the callback is invoked.
While freeglut checks
for upper or lower case letters, it does not do so for non-alphabetical
characters. Nor does it account for the Caps-Lock key being on.
The operating system may send some unexpected characters to
freeglut, such as "8" when the user is pressing the Shift
key. Freeglut also invokes the callback when the user
releases the Control, Alt, or Shift keys, among others. Releasing
the Delete key causes this function to be invoked with a value of
127 for key.
Calling glutKeyboardUpFunc with
a NULL argument disables the call to the window's key release callback.
Changes From GLUT
This function is not implemented in GLUT versions before Version 4. It has been designed to be as close to GLUT as possible. Users who find differences should contact the freeglut Programming Consortium to have them fixed.
The glutSpecialUpFunc function sets the window's special key release callback. Freeglut calls the special key release callback when the user releases a special key.
Usage
void glutSpecialUpFunc ( void (*func) ( int key, int x, int y ) );
func The window's
new special key release callback function
key The
key whose release triggers the callback
x
The x-coordinate of the mouse relative
to the window at the time the key is released
y
The y-coordinate of the mouse relative
to the window at the time the key is released
Description
The glutSpecialUpFuncfunction specifies the function that freeglut will call when the
user releases a special key from the keyboard. The callback function
has one argument: the name of the function to be invoked ("called back")
at the time at which the special key is released. The function returns
no value. Freeglut sets the current window to the window
which is active when the callback is invoked. "Special keys" are the
function keys, the arrow keys, the Page Up and Page Down keys, and the Insert
key. The Delete key is considered to be a regular key.
Calling glutSpecialUpFunc with a NULL argument
disables the call to the window's special key release callback.
The key argument may take one of the following defined constant values:
Changes From GLUT
This function is not implemented in GLUT versions before Version 4. It has been designed to be as close to GLUT as possible. Users who find differences should contact the freeglut Programming Consortium to have them fixed.
The glutMouseWheelFunc function sets the window's mouse wheel callback. Freeglut calls the mouse wheel callback when the user spins the mouse wheel.
Usage
void glutMouseWheelFunc ( void( *callback )( int wheel, int direction, int x, int y ));
Description
If the mouse wheel is spun over your (sub)window, FreeGLUT
will report this via the MouseWheel callback. wheel is the wheel
number, direction is +/- 1, and x and y are
the mouse coordinates.
If you do not register a wheel callback, wheel events will be reported
as mouse buttons.
Changes From GLUT
This function is not implemented in GLUT.
The glutSpaceballMotionFunc function is implemented in freeglut on X11 only. On other platforms, function stubs are provided so that GLUT-based programs can compile and link against freeglut without modification.
Usage
void glutSpaceballMotionFunc ( void (* callback)( int x, int y, int z ) );
Description
TODO
The glutSpaceballRotateFunc function is implemented in freeglut on X11 only. On other platforms, function stubs are provided so that GLUT-based programs can compile and link against freeglut without modification.
Usage
void glutSpaceballRotateFunc ( void (* callback)( int x, int y, int z ) );
Description
TODO
The glutSpaceballButtonFunc function is implemented in freeglut on X11 only. On other platforms, function stubs are provided so that GLUT-based programs can compile and link against freeglut without modification.
Usage
void glutSpaceballButtonFunc ( void (* callback)( int button, int updown ) );
Description
TODO
The glutDialsFunc function sets the global dials&buttons box callback. Freeglut calls the callback when there is input from the box buttons.
Usage
void glutButtonBoxFunc ( void (* callback)( int button, int updown ) );
Description
The Dials&Buttons box is an ancient device presenting several pushable
or rotatable buttons, sending the events to the computer via serial
I/O.
See http://www.reputable.com/sgipix/sgi-dialnbutton1.jpg
[1]
for instance.
The glutDialsFunc function sets the global dials&buttons box callback. Freeglut calls the callback when there is input from the box dials.
Usage
void glutDialsFunc ( void (* callback)( int dial, int value ) );
Description
The Dials&Buttons box is an ancient device presenting several pushable
or rotatable buttons, sending the events to the computer via serial
I/O.
See http://www.reputable.com/sgipix/sgi-dialnbutton1.jpg
[1]
for instance.
The glutTabletMotionFunc function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..
Usage
void glutTabletMotionFunc ( void (* callback)( int x, int y ) );
Description
The glutTabletMotionFunc function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutTabletButtonFunc function is not implemented in freeglut, although the library does "answer the mail" to the extent that a call to the function will not produce an error..
Usage
void glutTabletButtonFunc ( void (* callback)( int button, int updown, int x, int y ) );
Description
The glutTabletButtonFunc function is not implemented in freeglut.
Changes From GLUT
GLUT implements this function.
The glutVisibilityFunc and the glutWindowStatusFunc functions set the window's visibility and windowStatus callbacks for the current window. Setting one overwrites the other. Freeglut calls these callbacks when the visibility status of a window changes.
Usage
void glutVisibilityFunc ( void( *callback )( int state ));
void glutWindowStatusFunc ( void( *callback )( int state ));
Description
glutVisibilityFunc is deprecated and superseded by the more
informative glutWindowStatusFunc.
For glutWindowStatusFunc, the state callback parameter is one
of GLUT_HIDDEN, GLUT_FULLY_RETAINED, GLUT_PARTIALLY_RETAINED, or
GLUT_FULLY_COVERED depending on the current window status of the window.
GLUT_HIDDEN means that the window is not shown (often meaning that the
window is iconified). GLUT_FULLY_RETAINED means that the window is fully
retained (no pixels belonging to the window are covered by other
windows). GLUT_PARTIALLY_RETAINED means that the window is partially
retained (some but not all pixels belonging to the window are covered by
other windows). GLUT_FULLY_COVERED means the window is shown but no part
of the window is visible, i.e., until the window's status changes, all
further rendering to the window is discarded.
GLUT considers a window visible if any pixel of the window is visible or
any pixel of any descendant window is visible on the screen.
GLUT applications are encouraged to disable rendering and/or animation
when windows have a status of either GLUT_HIDDEN or
GLUT_FULLY_COVERED.
If the window status callback for a window is disabled and later
re-enabled, the window status of the window is undefined; any change in
window window status will be reported, that is if you disable a window
status callback and re-enable the callback, you are guaranteed the next
window status change will be reported.
Setting the window status callback for a window disables the visibility
callback set for the window (and vice versa). The visibility callback is
set with glutVisibilityFunc, and its
state callback parameter is either GLUT_NOT_VISIBLE or GLUT_VISIBLE
depending on the current visibility of the window. GLUT_VISIBLE does not
distinguish a window being totally versus partially visible.
GLUT_NOT_VISIBLE means no part of the window is visible, i.e., until the
window's visibility changes, all further rendering to the window is
discarded.
Not all window managers support such finegrained callback messages or
can even ensure basic correctness. On Windows, there are no
notifications if the visibility status of a window changes and
FreeGLUT might be in visible state even if the window is fully
obscured by other windows.
Changes From GLUT
None.
Allows you to set some general state/option variables.
Usage
void glutSetOption ( GLenum eWhat, int value );
Description
Stores the value into a state variable named by eWhat.
The following state variables can be set:
Changes From GLUT
This function is not implemented in GLUT.
The following state variables may be queried with glutGet. The returned value is an integer.
example:
int windowLeft = glutGet(GLUT_WINDOW_X);
These queries are with respect to the current window:
These queries do not depend on the current window.
glutGetProcAddress returns a pointer to a named GL or freeglut function.
Usage
void *glutGetProcAddress ( const char *procName );
procName Name of an OpenGL or GLUT function.
Description
glutGetProcAddress is useful for dealing with OpenGL extensions. If an application calls OpenGL extension functions directly, that application will only link/run with an OpenGL library that supports the extension. By using a function pointer returned from glutGetProcAddress(), the application will avoid this hard dependency and be more portable and interoperate better with various implementations of OpenGL.
Both OpenGL functions and freeglut functions can be queried with this function.
Changes From GLUT
GLUT does not include this function.
Freeglut supports two types of font rendering: bitmap fonts, which are rendered using the glBitmap function call, and stroke fonts, which are rendered as sequences of OpenGL line segments. Because they are rendered as bitmaps, the bitmap fonts tend to render more quickly than stroke fonts, but they are less flexible in terms of scaling and rendering. Bitmap font characters are positioned with calls to the glRasterPos* functions while stroke font characters use the OpenGL transformations to position characters.
It should be noted that freeglut fonts are similar but not identical to GLUT fonts. At the moment, freeglut fonts do not support the "`" (backquote) and "|" (vertical line) characters; in their place it renders asterisks.
Freeglut supports the following bitmap fonts:
Freeglut calls glRasterPos4v to advance the cursor by the width of a character and to render carriage returns when appropriate. It does not use any display lists in it rendering in bitmap fonts.
Freeglut supports the following stroke fonts:
Freeglut does not use any display lists in its rendering of stroke fonts. It calls glTranslatef to advance the cursor by the width of a character and to render carriage returns when appropriate.
The glutBitmapCharacter function renders a single bitmapped character in the current window using the specified font.
Usage
void glutBitmapCharacter ( void *font, int character );
font
The bitmapped font to use in rendering
the character
character The ASCII
code of the character to be rendered
Description
The glutBitmapCharacter function renders the given character in the specified bitmap font. Freeglut automatically sets the necessary pixel unpack storage modes and restores the existing modes when it has finished. Before the first call to glutBitMapCharacter the application program should call glRasterPos* to set the position of the character in the window. The glutBitmapCharacter function advances the cursor position as part of its call to glBitmap and so the application does not need to call glRasterPos* again for successive characters on the same line.
Changes From GLUT
Nonexistent characters are rendered as asterisks. The rendering position in freeglut is apparently off from GLUT's position by a few pixels vertically and one or two pixels horizontally.
The glutBitmapString function renders a string of bitmapped characters in the current window using the specified font.
Usage
void glutBitmapString ( void *font, char *string );
font
The bitmapped font to use in rendering
the character string
string String
of characters to be rendered
Description
The glutBitmapString function renders the given character string in the specified bitmap font. Freeglut automatically sets the necessary pixel unpack storage modes and restores the existing modes when it has finished. Before calling glutBitMapString the application program should call glRasterPos* to set the position of the string in the window. The glutBitmapString function handles carriage returns. Nonexistent characters are rendered as asterisks.
Changes From GLUT
GLUT does not include this function.
The glutBitmapWidth function returns the width in pixels of a single bitmapped character in the specified font.
Usage
int glutBitmapWidth ( void *font, int character );
font
The bitmapped font to use in calculating
the character width
character The ASCII
code of the character
Description
The glutBitmapWidth function returns the width of the given character in the specified bitmap font. Because the font is bitmapped, the width is an exact integer.
Changes From GLUT
Nonexistent characters return the width of an asterisk.
The glutBitmapLength function returns the width in pixels of a string of bitmapped characters in the specified font.
Usage
int glutBitmapLength ( void *font, char *string );
font The bitmapped
font to use in calculating the character width
string String of characters
whose width is to be calculated
Description
The glutBitmapLength function returns the width in pixels of the given character string in the specified bitmap font. Because the font is bitmapped, the width is an exact integer: the return value is identical to the sum of the character widths returned by a series of calls to glutBitmapWidth. The width of nonexistent characters is counted to be the width of an asterisk.
If the string contains one or more carriage returns, freeglut calculates the widths in pixels of the lines separately and returns the largest width.
Changes From GLUT
GLUT does not include this function.
The glutBitmapHeight function returns the height in pixels of the specified font.
Usage
int glutBitmapHeight ( void *font );
font The bitmapped font to use in calculating the character height
Description
The glutBitmapHeight function returns the height of a character in the specified bitmap font. Because the font is bitmapped, the height is an exact integer. The fonts are designed such that all characters have (nominally) the same height.
Changes From GLUT
GLUT does not include this function.
The glutStrokeCharacter function renders a single stroke character in the current window using the specified font.
Usage
void glutStrokeCharacter ( void *font, int character );
fontThe stroke font to use in rendering the character
characterThe ASCII code of the character to be rendered
Description
The glutStrokeCharacter function renders the given character in the specified stroke font. Before the first call to glutStrokeCharacter the application program should call the OpenGL transformation (positioning and scaling) functions to set the position of the character in the window. The glutStrokeCharacter function advances the cursor position by a call to glTranslatef and so the application does not need to call the OpenGL positioning functions again for successive characters on the same line.
Changes From GLUT
Nonexistent characters are rendered as asterisks.
The glutStrokeString function renders a string of characters in the current window using the specified stroke font.
Usage
void glutStrokeString ( void *font, char *string );
font
The stroke font to use in rendering
the character string
string String
of characters to be rendered
Description
The glutStrokeString function renders the given character string in the specified stroke font. Before calling glutStrokeString the application program should call the OpenGL transformation (positioning and scaling) functions to set the position of the string in the window. The glutStrokeString function handles carriage returns. Nonexistent characters are rendered as asterisks.
Changes From GLUT
GLUT does not include this function.
The glutStrokeWidth function returns the width in pixels of a single character in the specified stroke font.
Usage
int glutStrokeWidth ( void *font, int character );
font
The stroke font to use in calculating
the character width
character The ASCII
code of the character
Description
The glutStrokeWidth function returns the width of the given character in the specified stroke font. Because the font is a stroke font, the width is actually a floating-point number; the function rounds it to the nearest integer for the return value.
Changes From GLUT
Nonexistent characters return the width of an asterisk.
The glutStrokeLength function returns the width in pixels of a string of characters in the specified stroke font.
Usage
int glutStrokeLength ( void *font, char *string );
font The stroke
font to use in calculating the character width
string String of characters
whose width is to be calculated
Description
The glutStrokeLength function returns the width in pixels of the given character string in the specified stroke font. Because the font is a stroke font, the width of an individual character is a floating-point number. Freeglut adds the floating-point widths and rounds the funal result to return the integer value. Thus the return value may differ from the sum of the character widths returned by a series of calls to glutStrokeWidth. The width of nonexistent characters is counted to be the width of an asterisk.
If the string contains one or more carriage returns, freeglut calculates the widths in pixels of the lines separately and returns the largest width.
Changes From GLUT
GLUT does not include this function.
The glutStrokeHeight function returns the height in pixels of the specified font.
Usage
GLfloat glutStrokeHeight ( void *font );
font The stroke font to use in calculating the character height
Description
The glutStrokeHeight function returns the height of a character in the specified stroke font. The application programmer should note that, unlike the other freeglut font functions, this one returns a floating-point number. The fonts are designed such that all characters have (nominally) the same height.
Changes From GLUT
GLUT does not include this function.
Freeglut includes twenty two routines for generating
easily-recognizable 3-d geometric objects. These routines are
effectively the same ones that are included in the GLUT library, and
reflect the functionality available in the aux toolkit described
in the OpenGL Programmer's Guide. They are included to allow
programmers to create with a single line of code a three-dimensional
object which can be used to test a variety of OpenGL functionality.
None of the routines generates a display list for the object which it
draws. The functions generate normals appropriate for lighting but,
except for the teapot functions, do not generate texture coordinates. Do
note that depth testing (GL_LESS) should be enabled for the correct
drawing of the nonconvex objects, i.e., the glutTorus,
glutSierpinskiSponge, glutTeapot, glutTeacup and glutTeaspoon.
Also see the GLUT_GEOMETRY_VISUALIZE_NORMALS option that can be
set with glutSetOption. Lastly, see
glutSetVertexAttribCoord3, glutSetVertexAttribNormal,
and glutSetVertexAttribTexCoord2 if you wish to use these
objects with shaders.
The glutWireSphere and glutSolidSphere functions draw a wireframe and solid sphere respectively.
Definition
void glutWireSphere (double dRadius, GLint slices, GLint stacks);
void glutSolidSphere(double dRadius, GLint slices, GLint stacks);
Arguments
dRadius The desired radius of the sphere
slices The desired number of slices (divisions in the longitudinal direction) in the sphere
stacks The desired number of stacks (divisions in the latitudinal direction) in the sphere. The number of points in this direction, including the north and south poles, is stacks+1
Description
The glutWireSphere and glutSolidSphere functions render a sphere centered at the origin of the modeling coordinate system. The north and south poles of the sphere are on the positive and negative Z-axes respectively and the prime meridian crosses the positive X-axis.
Changes From GLUT
None that we know of.
The glutWireTorus and glutSolidTorus functions draw a wireframe and solid torus (donut shape) respectively.
Definition
void glutWireTorus (double dInnerRadius, double dOuterRadius, GLint
nSides, GLint nRings);
void glutSolidTorus(double dInnerRadius, double dOuterRadius, GLint
nSides, GLint nRings);
Arguments
dInnerRadius The radius of the tube.
dOuterRadius The distance from the center of the Torus to the center of the tube.
nSides The desired number of segments in a single outer circle of the torus
nRings The desired number of outer circles around the origin of the torus
Description
The glutWireTorus and glutSolidTorus functions render a torus centered at the origin of the modeling coordinate system. The torus is circularly symmetric about the Z-axis and starts at the positive X-axis.
Changes From GLUT
None that we know of.
The glutWireCylinder and glutSolidCylinder functions draw a wireframe and solid cone respectively.
Definition
void glutWireCylinder (double base, double height, GLint slices, GLint
stacks);
void glutSolidCylinder(double base, double height, GLint slices, GLint
stacks);
Arguments
radius The desired radius of the cylinder
height The desired height of the cylinder
slices The desired number of slices around the cylinder
stacks The desired number of segments between the base and the top of the cylinder (the number of points, including the tip, is stacks + 1)
The glutWireCone and glutSolidCone functions draw a wireframe and solid cone respectively.
Definition
void glutWireCone (double base, double height, GLint slices, GLint
stacks);
void glutSolidCone(double base, double height, GLint slices, GLint
stacks);
Arguments
base The desired radius of the base of the cone
height The desired height of the cone
slices The desired number of slices around the base of the cone
stacks The desired number of segments between the base and the tip of the cone (the number of points, including the tip, is stacks + 1)
Description
The glutWireCone and glutSolidCone functions render a right circular cone with a base centered at the origin and in the X-Y plane and its tip on the positive Z-axis. The wire cone is rendered with triangular elements.
Changes From GLUT
None that we know of.
The glutWireCube and glutSolidCube functions draw a wireframe and solid cube respectively.
Definition
void glutWireCube (double dSize);
void glutSolidCube(double dSize);
Arguments
dSize The desired length of an edge of the cube
Description
The glutWireCube and glutSolidCube functions render a cube of the desired size, centered at the origin. Its faces are normal to the coordinate directions.
Changes From GLUT
None that we know of.
The glutWireTetrahedron and glutSolidTetrahedron functions draw a wireframe and solid tetrahedron (four-sided Platonic solid) respectively.
Definition
void glutWireTetrahedron (void);
void glutSolidTetrahedron(void);
Description
The glutWireTetrahedron and glutSolidTetrahedron functions render a tetrahedron whose corners are each a distance of one from the origin. The length of each side is 2/3 sqrt(6). One corner is on the positive X-axis and another is in the X-Y plane with a positive Y-coordinate.
Changes From GLUT
None that we know of.
The glutWireOctahedron and glutSolidOctahedron functions draw a wireframe and solid octahedron (eight-sided Platonic solid) respectively.
Definition
void glutWireOctahedron (void);
void glutSolidOctahedron(void);
Description
The glutWireOctahedron and glutSolidOctahedron functions render an octahedron whose corners are each a distance of one from the origin. The length of each side is sqrt(2). The corners are on the positive and negative coordinate axes.
Changes From GLUT
None that we know of.
The glutWireDodecahedron and glutSolidDodecahedron functions draw a wireframe and solid dodecahedron (twelve-sided Platonic solid) respectively.
Definition
void glutWireDodecahedron (void);
void glutSolidDodecahedron(void);
Description
The glutWireDodecahedron and glutSolidDodecahedron functions render a dodecahedron whose corners are each a distance of sqrt(3) from the origin. The length of each side is sqrt(5)-1. There are twenty corners; interestingly enough, eight of them coincide with the corners of a cube with sizes of length 2.
Changes From GLUT
None that we know of.
The glutWireIcosahedron and glutSolidIcosahedron functions draw a wireframe and solid icosahedron (twenty-sided Platonic solid) respectively.
Definition
void glutWireIcosahedron (void);
void glutSolidIcosahedron(void);
Description
The glutWireIcosahedron and glutSolidIcosahedron functions render an icosahedron whose corners are each a unit distance from the origin. The length of each side is slightly greater than one. Two of the corners lie on the positive and negative X-axes.
Changes From GLUT
None that we know of.
The glutWireRhombicDodecahedron and glutSolidRhombicDodecahedron functions draw a wireframe and solid rhombic dodecahedron (twelve-sided semi-regular solid) respectively.
Definition
void glutWireRhombicDodecahedron (void);
void glutSolidRhombicDodecahedron(void);
Description
The glutWireRhombicDodecahedron and glutSolidRhombicDodecahedron functions render a rhombic dodecahedron whose corners are at most a distance of one from the origin. The rhombic dodecahedron has faces which are identical rhombuses (rhombi?) but which have some vertices at which three faces meet and some vertices at which four faces meet. The length of each side is sqrt(3)/2. Vertices at which four faces meet are found at (0, 0, +/- 1) and (+/- sqrt(2)/2, +/- sqrt(2)/2, 0).
Changes From GLUT
GLUT does not include these functions.
The glutWireTeapot and glutSolidTeapot functions draw a wireframe and solid teapot respectively, the glutWireTeacup and glutSolidTeacup functions a wireframe and solid teacup, and the glutWireTeaspoon and glutSolidTeaspoon functions a wireframe and solid teaspoon.
Definition
void glutWireTeapot (double dSize);
void glutSolidTeapot (double dSize);
void glutWireTeacup (double dSize);
void glutSolidTeacup (double dSize);
void glutWireTeaspoon (double dSize);
void glutSolidTeaspoon(double dSize);
Arguments
dSize The desired size of the teapot, teacup and teaspoon - relative to a "standard" size
Description
The glutWireTeapot and glutSolidTeapot functions render a teapot of the desired size, centered at the origin. This is the famous teapot created by Martin Newell. The other functions render the teacup and teaspoon he used in the table scene figure in his PhD thesis. Vertex data retrieved from: ftp://ftp.funet.fi/pub/sci/graphics/packages/objects/teasetorig.gz.
Bugs
OpenGL's default glFrontFace state assumes that front facing polygons (for the purpose of face culling) have vertices that wind counter clockwise when projected into window space. This teapot, teacup and teaspoon are rendered with their front facing polygon vertices winding clockwise. For OpenGL's default back face culling to work, you should use:
glFrontFace(GL_CW);
glutSolidTeapot(size);
glFrontFace(GL_CCW);
This bug reflect issues in the original teaset's vertex data (and is thus present in GLUT too).
Changes From GLUT
GLUT only has the teapot and misses the rest of the teaset.
To draw shapes with shaders (OpenGL 2 and later), one need to upload vertices and associated normal vectors and texture coordinates to vertex attributes of your shaders. Use these functions to set the indices (addresses) of the vertex attributes in your currently active shaders before calling the above geometry functions, and FreeGLUT will upload the object geometry there. Texture coordinates are only generated for the teapot, teacup and teaspoon.
Definition
void glutSetVertexAttribCoord3 (GLint attrib);
void glutSetVertexAttribNormal (GLint attrib);
void glutSetVertexAttribTexCoord2(GLint attrib);
Arguments
attrib The index (address) of the vertex attribute
Changes From GLUT
GLUT does not include these functions.
Specify the display mode that should be entered when GameMode is entered. Default is the current display mode of the monitor on which the GameMode screen will be opened.
Usage
A string is passed to this function that specifies a combination of
resolution, pixel depth (ignored on Linux) and refresh rate. Valid
formats are:
Attempt to change to the requested display mode and open the GameMode window, or close the GameMode window and return to the original display mode. For multi-monitor display setups, freeglut can be told on which monitor the gamemode window should be opened by providing the -display command line option to glutInit.
The following state variables may be queried with glutGet. The returned value is an integer.
example:
int windowLeft = glutGet(GLUT_WINDOW_X);
These queries return information about the current display mode if in GameMode, or about the requested display mode before entering GameMode:
These functions are not implemented in freeglut.
Since this extra support comes at the cost of extra complexity, we're considering whether/how to implement it.
These new callbacks were added:
glutInitContextFunc ← void : called when the context
is initialized or re-initialized (e.g. after a pause)glutAppStatusFunc ← event : called when the
application's status changes, with event identifying the state entered.
Possible states:
glutInitContextFunc callback.Supported mobile platforms
The glutSetKeyRepeat and glutIgnoreKeyRepeat functions set whether repeated key presses (generated by keeping a key depressed) are passed on to the keyboard callbacks. glutSetKeyRepeat allows to globally switch off key repeat, while glutIgnoreKeyRepeat offers control over this behavior on a per-window basis.
Definition
void glutSetKeyRepeat (int repeatMode);
void glutIgnoreKeyRepeat(int ignore);
Arguments
glutSetKeyRepeat's repeatMode
GLUT_KEY_REPEAT_OFF to globally switch key repeat off, or
GLUT_KEY_REPEAT_ON and GLUT_KEY_REPEAT_DEFAULT to globally switch key
repeat on.
glutIgnoreKeyRepeat's ignore if non-zero, key
repeat is switched off for the current window.
Notes
If key repeat is globally switched off through glutSetKeyRepeat, it cannot be reenabled on a per-window basis with glutIgnoreKeyRepeat. If you want per-window control of key repeat, set glutSetKeyRepeat to GLUT_KEY_REPEAT_ON and use glutIgnoreKeyRepeat(GL_TRUE) to switch off key repeat for the windows for which you don't want it.
Changes From GLUT
Nate Robbins' port of GLUT to win32 did not implement glutSetKeyRepeat, but FreeGLUT's behavior should conform on all platforms to GLUT's behavior on X11.
The following environment variables are recognized by freeglut:
Furthermore, on windows, there is a resource file identifier GLUT_ICON
that you can specify for your executable file. It specifies the icon
that goes in the upper left-hand corner of the freeglut windows.
Your application's resource file should contain the line:
GLUT_ICON ICON DISCARDABLE "icon.ico"
where
icon.ico is the filename of your icon. The One demo includes such an
icon as an example.
Application programmers who are porting their GLUT programs to freeglut may continue to include <GL/glut.h> in their programs. Programs which use the freeglut-specific extensions to GLUT should include <GL/freeglut.h>. One possible arrangement is as follows:
#ifdef FREEGLUT #include <GL/freeglut.h> #else #include <GL/glut.h> #endif
It was initially planned to
define FREEGLUT_VERSION_2_0, FREEGLUT_VERSION_2_1, FREEGLUT_VERSION_2_2,
etc., but this was only done for FREEGLUT_VERSION_2_0.
This constant still exist in current FreeGLUT releases but is
deprecated.
The freeglut version can be queried at runtime by calling glutGet(GLUT_VERSION). The result will be X*10000+Y*100+Z where X is the major version, Y is the minor version and Z is the patch level.
This may be used as follows:
if (glutGet(GLUT_VERSION) < 20001) {
printf("Sorry, you need freeglut version 2.0.1 or later to run this program.\n");
exit(1);
}