GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  GLUTESTABLISHOVERLAY (3)

NAME

glutEstablishOverlay - establishes an overlay (if possible) for the current window.

CONTENTS

Syntax
Description
Example
X Implementation Notes
See Also
Author

SYNTAX


void glutEstablishOverlay(void);

DESCRIPTION

glutEstablishOverlay establishes an overlay (if possible) for the current window. The requested display mode for the overlay is determined by the initial display mode. glutLayerGet(GLUT_OVERLAY_POSSIBLE) can be called to determine if an overlay is possible for the current window with the current initial display mode. Do not attempt to establish an overlay when one is not possible; GLUT will terminate the program.
If glutEstablishOverlay is called when an overlay already exists, the existing overlay is first removed, and then a new overlay is established. The state of the old overlay’s OpenGL context is discarded.
The initial display state of an overlay is shown, however the overlay is only actually shown if the overlay’s window is shown.
Implicitly, the window’s layer in use changes to the overlay immediately after the overlay is established.

EXAMPLE

Establishing an overlay is a bit involved, but easy once you get the hang of it. Here is an example:

int overlaySupport; int transparent, red, white; glutInitDisplayMode(GLUT_SINGLE | GLUT_INDEX); overlaySupport = glutLayerGet(GLUT_OVERLAY_POSSIBLE); if (overlaySupport) { glutEstablishOverlay(); glutHideOverlay(); transparent = glutLayerGet(GLUT_TRANSPARENT_INDEX); glClearIndex(transparent); red = (transparent + 1) % glutGet(GLUT_WINDOW_COLORMAP_SIZE); white = (transparent + 2) % glutGet(GLUT_WINDOW_COLORMAP_SIZE); glutSetColor(red, 1.0, 0.0, 0.0); /* Red. */ glutSetColor(white, 1.0, 1.0, 1.0); /* White. */ glutOverlayDisplayFunc(redrawOverlay); glutReshapeFunc(reshape); } else { printf("Sorry, no nifty overlay (try an SGI workstation)!0); }

If you setup an overlay and you install a reshape callback, you need to update the viewports and possibly projection matrices of both the normal plane and the overlay. For example, your reshape callback might look like this:


void reshape(int w, int h) { if (overlaySupport) { glutUseLayer(GLUT_OVERLAY); /* Setup overlay to have X style coordinate system. */ glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0, w, 0, h); glScalef(1, -1, 1); glTranslatef(0, -h, 0); glMatrixMode(GL_MODELVIEW); glutUseLayer(GLUT_NORMAL); } glViewport(0, 0, w, h); }

See the glutOverlayDisplayFunc man page for an example showing one way to write your overlay display callback.

X IMPLEMENTATION NOTES

GLUT for X uses the SERVER_OVERLAY_VISUALS convention is used to determine if overlay visuals are available. While the convention allows for opaque overlays (no transparency) and overlays with the transparency specified as a bitmask, GLUT overlay management only provides access to transparent pixel overlays.
Until RGBA overlays are better understood, GLUT only supports color index overlays.

SEE ALSO

glutUseLayer, glutRemoveLayer, glutCreateWindow, glutPostOverlayRedisplay, glutShowOverlay, glutOverlayDisplayFunc

AUTHOR

Mark J. Kilgard (mjk@nvidia.com)
Search for    or go to Top of page |  Section 3 |  Main Index


GLUT GLUTESTABLISHOVERLAY (3GLUT) 3.7

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.