GLUTINIT

Section: C Library Functions (3)
Updated: LOCAL
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NAME

glutInit - Initialize OpenGLUT data structures.

LIBRARY

OpenGLUT - mainloop

SYNOPSIS

In openglut.h Ft void Fn glutInit int *pargc char **argv

PARAMETERS

Bf Em
pargc Ef
Pointer to something like main()'s Bf Sy
argc. Ef

Bf Em
argv Ef
Something like main()'s Bf Sy
argv. Ef

DESCRIPTION

This function should be called once, near the start of any GLUT, freeglut, or OpenGLUT program. It serves two vital roles:

- It allows OpenGLUT to initialize internal structures.
- It allows OpenGLUT to process command-line arguments to control the initial window position, etc.

You should take note of the interaction between glutInit() and the related functions such as glutInitWindowPosition(). OpenGLUT always uses the most recent configuration information, so if you call glutInit(), then glutInitWindowPosition(), you prevent the user from controlling the initial window position via a command-line parameter.

glutInit() will remove from Bf Sy
pargc, Ef
Bf Sy
argv Ef
any parameters that it recognizes in the command line. The following command-line parameters are suported:

- Bf Sy
-display Ef
Bf Li
display-id Ef
This allows connection to an alternate X server.
- Bf Sy
-geometry Ef
Bf Li
geometry-spec Ef
This takes width, height, and window position. The position is given as a signed value (negative values being distance from the far boundary of the screen). For example, a window geometry of 5x7+11-17 is 5 pixels wide, 7 pixels tall, 11 pixels from the left, and 17 pixels from the bottom edge of the screen.
- Bf Sy
-direct Ef
Insist on only OpenGL direct rendering. Direct rendering is normally requested but indirect is normally accepted. Bf Sy
-direct Ef
is not always available. See Bf Sy
-indirect. Ef

- Bf Sy
-indirect Ef
Attempt only indirect OpenGL rendering. Bf Sy
-indirect Ef
is always available. See Bf Sy
-direct. Ef

- Bf Sy
-iconic Ef
Open the window in iconized form.
- Bf Sy
-gldebug Ef
Print any detected OpenGL errors via glutReportErrors(). Presently done at the bottom of glutMainLoopEvent().
- Bf Sy
-sync Ef
Synchronize the window system communications heavily.

Additionally, this function checks whether the environment variable Bf Sy
GLUT_FPS Ef
is defined (only on UNIX_X11); if so, OpenGLUT will periodically print the average number of times per second that your program calls glutSwapBuffers().

CAVEATS

You really should always call this, even if you are a WIN32 user. It provides a way for the user to directly inform OpenGLUT about preferences without the application needing to explicitly deal with those issues. This is also where OpenGLUT retrieves your program's name to help disambiguate error and warning messages it may be forced to emit.

Option Bf Sy
-sync Ef
sets a flag, but is not actually used at this time.

Lots of code does XFlush() on the X server, regardless of whether Bf Sy
-sync Ef
is specified. Much of that appears to be required in order to support direct client invocation of glutMainLoopEvent(), regrettably. However, if one calls glutMainLoop(), instead, we might avoid gratuitous XFlush() calls. (That last sentence isn't particularly germain to this function, but there's no better place to make this remark at this time.) Even for glutMainLoopEvent(), we may be able to coalesce many XFlush() calls.