PK
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.
2.0 Introduction
3.0 Background
3.1 Design Philosophy 3.2 Conventions 3.3 Terminology 3.4 Differences from GLUT 3.7
4.0 Initialization Functions
4.1 glutInit 4.2 glutInitWindowPosition, glutInitWindowSize 4.3 glutInitDisplayMode 4.4 glutInitDisplayString
5.0 Event Processing Functions
5.1 glutMainLoop 5.2 glutMainLoopEvent 5.3 glutLeaveMainLoop
6.0 Window Functions
6.1 glutCreateWindow 6.2 glutCreateSubwindow 6.3 glutDestroyWindow 6.4 glutSetWindow, glutGetWindow 6.5 glutSetWindowTitle, glutSetIconTitle 6.6 glutReshapeWindow 6.7 glutPositionWindow 6.8 glutShowWindow, glutHideWindow, glutIconifyWindow 6.9 glutPushWindow, glutPopWindow 6.10 glutFullScreen
7.0 Display Functions
7.1 glutPostRedisplay 7.2 glutPostWindowRedisplay 7.3 glutSwapBuffers
8.0 Mouse Cursor Functions
8.1 glutSetCursor 8.2 glutWarpPointer
9.0 Overlay Functions
9.1 glutEstablishOverlay 9.2 glutRemoveOverlay 9.3 glutUseLayer 9.4 glutPostOverlayRedisplay 9.5 glutPostWindowOverlayRedisplay 9.6 glutShowOverlay, glutHideOverlay
10.0 Menu Functions
10.1 glutCreateMenu 10.2 glutDestroyMenu 10.3 glutGetMenu, glutSetMenu 10.4 glutAddMenuEntry 10.5 glutAddSubMenu 10.6 glutChangeToMenuEntry 10.7 glutChangeToSubMenu 10.8 glutRemoveMenuItem 10.9 glutAttachMenu, glutDetachMenu
11.0 Global Callback Registration Functions
11.1 glutTimerFunc 11.2 glutIdleFunc
12.0 Window-Specific Callback Registration Functions
12.1 glutDisplayFunc 12.2 glutOverlayDisplayFunc 12.3 glutReshapeFunc 12.4 glutCloseFunc 12.5 glutKeyboardFunc 12.6 glutSpecialFunc 12.7 glutKeyboardUpFunc 12.8 glutSpecialUpFunc 12.9 glutMouseFunc 12.10 glutMotionFunc, glutPassiveMotionFunc 12.11 glutVisibilityFunc 12.12 glutEntryFunc 12.13 glutJoystickFunc 12.14 glutSpaceballMotionFunc 12.15 glutSpaceballRotateFunc 12.16 glutSpaceballButtonFunc 12.17 glutButtonBoxFunc 12.18 glutDialsFunc 12.19 glutTabletMotionFunc 12.20 glutTabletButtonFunc 12.21 glutMenuStatusFunc 12.22 glutWindowStatusFunc
12.21 glutMenuStatusFunc 12.22 glutWindowStatusFunc
13.0 State Setting and Retrieval Functions
13.1 glutSetOption 13.2 glutGet 13.3 glutDeviceGet 13.4 glutGetModifiers 13.5 glutLayerGet 13.6 glutExtensionSupported 13.7 glutGetProcAddress
14.0 Font Rendering Functions
14.1 glutBitmapCharacter 14.2 glutBitmapString 14.3 glutBitmapWidth 14.4 glutBitmapLength 14.5 glutBitmapHeight 14.6 glutStrokeCharacter 14.7 glutStrokeString 14.8 glutStrokeWidth 14.9 glutStrokeLength 14.10 glutStrokeHeight
15.0 Geometric Object Rendering Functions
15.1 glutWireSphere, glutSolidSphere 15.2 glutWireTorus, glutSolidTorus 15.3 glutWireCone, glutSolidCone 15.4 glutWireCube, glutSolidCube 15.5 glutWireTetrahedron, glutSolidTetrahedron 15.6 glutWireOctahedron, glutSolidOctahedron 15.7 glutWireDodecahedron, glutSolidDodecahedron 15.8 glutWireIcosahedron, glutSolidIcosahedron 15.9 glutWireRhombicDodecahedron, glutSolidRhombicDodecahedron 15.10 glutWireTeapot, glutSolidTeapot
16.0 Game Mode Functions
16.1 glutGameModeString 16.2 glutEnterGameMode, glutLeaveGameMode 16.3 glutGameModeGet
17.0 Video Resize Functions
17.1 glutVideoResizeGet 17.2 glutSetupVideoResizing, glutStopVideoResizing 17.3 glutVideoResize 17.4 glutVideoPan
18.0 Color Map Functions
18.1 glutSetColor, glutGetColor 18.2 glutCopyColormap
19.0 Miscellaneous Functions
19.1 glutIgnoreKeyRepeat, glutSetKeyRepeat 19.2 glutForceJoystickFunc 19.3 glutReportErrors
20.0 Usage Notes
21.0 Implementation Notes
22.0 GLUT State
23.0 "freeglut.h" Header File
24.0 References
25.0 Index
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.
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, 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 Linux, it is the coordinates of the upper left-hand corner of its decorations. On Windows, it is the coordinates of the upper left hand corner of its usable interior. For both operating systems, the size of the window is the size of the usable interior.
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.
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.
void glutMainLoop ( void ) ;
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.
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.)
void glutMainLoopEvent ( void ) ;
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.
GLUT does not include this function.
void glutLeaveMainLoop ( void ) ;
The "glutLeaveMainLoop " function causes freeglut to stop the event loop. If the " GLUT_ACTION_ON_WINDOW_CLOSE" option has been set to "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.
void glutEstablishOverlay ( void ) ;
The "glutEstablishOverlay" function is not implemented in freeglut.
GLUT implements this function.
void glutRemoveOverlay ( void ) ;
The "glutRemoveOverlay" function is not implemented in freeglut.
void glutUseLayer ( GLenum layer ) ;
The "glutUseLayer" function is not implemented in freeglut.
void glutPostOverlayRedisplay ( void ) ;
The "glutPostOverlayRedisplay " function is not implemented in freeglut.
void glutPostWindowOverlayRedisplay ( int window ) ;
The "glutPostWindowOverlayRedisplay " function is not implemented in freeglut.
void glutShowOverlay( void ) ; void glutHideOverlay( void ) ;
The "glutShowOverlay" and " glutHideOverlay" functions are not implemented in freeglut .
GLUT implements these functions.
void glutIdleFunc ( void (*func) ( void ) ) ;
func The new global idle callback function
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. Calling "glutIdleFunc" with a NULL argument disables the call to an idle callback.
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.
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
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:
None.
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
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.
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.
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
The "glutSpecialUpFunc " function 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.
void glutSpaceballMotionFunc ( void (* callback)( int x, int y, int z ) ) ;
The "glutSpaceballMotionFunc " function is not implemented in freeglut.
void glutSpaceballRotateFunc ( void (* callback)( int x, int y, int z ) ) ;
The "glutSpaceballRotateFunc " function is not implemented in freeglut.
void glutSpaceballButtonFunc ( void (* callback)( int button, int updown ) ) ;
The "glutSpaceballButtonFunc " function is not implemented in freeglut.
void glutSpaceballButtonBoxFunc ( void (* callback)( int button, int updown ) ) ;
The "glutSpaceballButtonBoxFunc " function is not implemented in freeglut.
void glutDialsFunc ( void (* callback)( int dial, int value ) ) ;
The "glutDialsFunc" function is not implemented in freeglut.
void glutTabletMotionFunc ( void (* callback)( int x, int y ) ) ;
The "glutTabletMotionFunc" function is not implemented in freeglut.
void glutTabletButtonFunc ( void (* callback)( int button, int updown, int x, int y ) ) ;
The "glutTabletButtonFunc" function is not implemented in freeglut.
The following state variables may be queried with "glutGet". The returned value is an integer.
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.
void *glutGetProcAddress ( const char *procName ) ;
procName Name of an OpenGL or GLUT function.
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.
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 supports the following stroke fonts:
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
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.
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.
void glutBitmapString ( void *font, char *string ) ;
font The bitmapped font to use in rendering the character string string String of characters to be rendered
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.
int glutBitmapWidth ( void *font, int character ) ;
font The bitmapped font to use in calculating the character width character The ASCII code of the character
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.
Nonexistent characters return the width of an asterisk.
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
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.
int glutBitmapHeight ( void *font ) ;
font The bitmapped font to use in calculating the character height
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.
void glutStrokeCharacter ( void *font, int character ) ;
font The stroke font to use in rendering the character character The ASCII code of the character to be rendered
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.
Nonexistent characters are rendered as asterisks.
void glutStrokeString ( void *font, char *string ) ;
font The stroke font to use in rendering the character string string String of characters to be rendered
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.
int glutStrokeWidth ( void *font, int character ) ;
font The stroke font to use in calculating the character width character The ASCII code of the character
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.
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
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.
GLfloat glutStrokeHeight ( void *font ) ;
font The stroke font to use in calculating the character height
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.
void glutWireSphere ( GLdouble dRadius, GLint slices, GLint stacks ) ;
void glutSolidSphere ( GLdouble dRadius, GLint slices, GLint stacks ) ;
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
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.
None that we know of.
void glutWireTorus ( GLdouble dInnerRadius, GLdouble dOuterRadius, GLint nSides, GLint nRings ) ;
void glutSolidTorus ( GLdouble dInnerRadius, GLdouble dOuterRadius, GLint nSides, GLint nRings ) ;
dInnerRadius The desired inner radius of the torus, from the origin to the circle defining the centers of the outer circles
dOuterRadius The desired outer radius of the torus, from the center of the outer circle to the actual surface of the torus
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
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.
void glutWireCone ( GLdouble base, GLdouble height, GLint slices, GLint stacks ) ;
void glutSolidCone ( GLdouble base, GLdouble height, GLint slices, GLint stacks ) ;
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)
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.
void glutWireCube ( GLdouble dSize ) ;
void glutSolidCube ( GLdouble dSize ) ;
dSize The desired length of an edge of the cube
The "glutWireCube" and " glutSolidCube" functions render a cube of the desired size, centered at the origin. Its faces are normal to the coordinate directions.
void glutWireTetrahedron ( void ) ;
void glutSolidTetrahedron ( void ) ;
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.
void glutWireOctahedron ( void ) ;
void glutSolidOctahedron ( void ) ;
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.
void glutWireDodecahedron ( void ) ;
void glutSolidDodecahedron ( void ) ;
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.
void glutWireIcosahedron ( void ) ;
void glutSolidIcosahedron ( void ) ;
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.
void glutWireRhombicDodecahedron ( void ) ;
void glutSolidRhombicDodecahedron ( void ) ;
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).
GLUT does not include these functions.
void glutWireTeapot ( GLdouble dSize ) ;
void glutSolidTeapot ( GLdouble dSize ) ;
dSize The desired size of the teapot
The "glutWireTeapot" and " glutSolidTeapot" functions render a teapot of the desired size, centered at the origin. This is the famous OpenGL teapot [add reference].
The following environment variables are recognized by freeglut:
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_ext.h> #else #include <GL/glut.h> #endif
Compile-time freeglut version testing can be done as follows:
#ifdef FREEGLUT_VERSION_2_0 code specific to freeglut 2.0 or later here #endif
In future releases, FREEGLUT_VERSION_2_1, FREEGLUT_VERSION_2_2, etc will be defined. This scheme mimics OpenGL conventions.
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); }