Login or Register to Ask a Question and Join Our Community

Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

glutpostoverlayredisplay(3glut) [redhat man page]

glutPostOverlayRedisplay(3GLUT) 				       GLUT					   glutPostOverlayRedisplay(3GLUT)

NAME

       glutPostOverlayRedisplay,  glutPostWindowOverlayRedisplay  -  marks  the overlay of the current or specified window as needing to be redis-
       played.

SYNTAX

       void glutPostOverlayRedisplay(void);
       void glutPostWindowOverlayRedisplay(int win);

DESCRIPTION

       Mark the overlay of current window as needing to be redisplayed.  The next iteration through glutMainLoop,  the	window's  overlay  display
       callback  (or  simply  the  display callback if no overlay display callback is registered) will be called to redisplay the window's overlay
       plane. Multiple calls to glutPostOverlayRedisplay before the next display callback opportunity (or overlay display callback opportunity	if
       one  is	registered)  generate only a single redisplay. glutPostOverlayRedisplay may be called within a window's display or overlay display
       callback to re-mark that window for redisplay.

       Logically, overlay damage notification for a window is treated as a glutPostOverlayRedisplay on the damaged window. Unlike damage  reported
       by  the	window	system,  glutPostOverlayRedisplay  will  not set to true the overlay's damaged status (returned by glutLayerGet(GLUT_OVER-
       LAY_DAMAGED).

       If the window you want to post an overlay redisplay on is not already current (and you do not require it to be immediately  made  current),
       using glutPostWindowOverlayRedisplay is more efficient that calling glutSetWindow to the desired window and then calling glutPostOverlayRe-
       display.

EXAMPLE

       If you are doing an interactive effect like rubberbanding in the overlay, it is a good idea to structure your rendering to minimize flicker
       (most  overlays are single-buffered).  Only clear the overlay if you know that the window has been damaged.  Otherwise, try to simply erase
       what you last drew and redraw it in an updated position.  Here is an example overlay display callback used to implement overlay rubberband-
       ing:

	 void
	 redrawOverlay(void)
	 {
	   static int prevStretchX, prevStretchY;

	   if (glutLayerGet(GLUT_OVERLAY_DAMAGED)) {
	     /* Damage means we need a full clear. */
	     glClear(GL_COLOR_BUFFER_BIT);
	   } else {
	     /* Undraw last rubber-band. */
	     glIndexi(transparent);
	     glBegin(GL_LINE_LOOP);
	     glVertex2i(anchorX, anchorY);
	     glVertex2i(anchorX, prevStretchY);
	     glVertex2i(prevStretchX, prevStretchY);
	     glVertex2i(prevStretchX, anchorY);
	     glEnd();
	   }
	   glIndexi(red);
	   glBegin(GL_LINE_LOOP);
	   glVertex2i(anchorX, anchorY);
	   glVertex2i(anchorX, stretchY);
	   glVertex2i(stretchX, stretchY);
	   glVertex2i(stretchX, anchorY);
	   glEnd();
	   prevStretchX = stretchX;
	   prevStretchY = stretchY;
	 }

       Notice how glutLayerGet(GLUT_OVERLAY_DAMAGED) is used to determine if a clear needs to take place because of damage; if a clear is unneces-
       sary, it is faster to just draw the last rubberband using the transparent pixel.

       When the application is through with the rubberbanding effect, the best way to get ride of the rubberband is to simply hide the overlay	by
       calling glutHideOverlay.

SEE ALSO

       glutPostRedisplay, glutEstablishOverlay, glutLayerGet

AUTHOR

       Mark J. Kilgard (mjk@nvidia.com)

GLUT
									3.7					   glutPostOverlayRedisplay(3GLUT)

Check Out this Related Man Page

glutDisplayFunc(3GLUT)						       GLUT						    glutDisplayFunc(3GLUT)

NAME

       glutDisplayFunc - sets the display callback for the current window.

SYNTAX

       void glutDisplayFunc(void (*func)(void));

ARGUMENTS

       func	 The new display callback function.

DESCRIPTION

       glutDisplayFunc	sets  the  display callback for the current window.  When GLUT determines that the normal plane for the window needs to be
       redisplayed, the display callback for the window is called. Before the callback, the current window is set to  the  window  needing  to	be
       redisplayed  and (if no overlay display callback is registered) the layer in use is set to the normal plane. The display callback is called
       with no parameters. The entire normal plane region should be redisplayed in response to the callback (this includes  ancillary  buffers	if
       your program depends on their state).

       GLUT  determines  when the display callback should be triggered based on the window's redisplay state. The redisplay state for a window can
       be either set explicitly by calling glutPostRedisplay or implicitly as the result of window damage reported by the window system.  Multiple
       posted redisplays for a window are coalesced by GLUT to minimize the number of display callbacks called.

       When  an  overlay is established for a window, but there is no overlay display callback registered, the display callback is used for redis-
       playing both the overlay and normal plane (that is, it will be called if either the redisplay state or overlay redisplay state is set).	In
       this case, the layer in use is not implicitly changed on entry to the display callback.

       See glutOverlayDisplayFunc to understand how distinct callbacks for the overlay and normal plane of a window may be established.

       When  a window is created, no display callback exists for the window. It is the responsibility of the programmer to install a display call-
       back for the window before the window is shown. A display callback must be registered for any window that is shown.  If	a  window  becomes
       displayed  without  a  display  callback being registered, a fatal error occurs. Passing NULL to glutDisplayFunc is illegal as of GLUT 3.0;
       there is no way to ``deregister'' a display callback (though another callback routine can always be registered).

       Upon return from the display callback, the normal damaged state of the window (returned	by  calling  glutLayerGet(GLUT_NORMAL_DAMAGED)	is
       cleared.  If  there  is	no  overlay  display  callback	registered the overlay damaged state of the window (returned by calling glutLayer-
       Get(GLUT_OVERLAY_DAMAGED) is also cleared.

SEE ALSO

       glutCreateMenu, glutPostRedisplay, glutOverlayDisplayFunc

AUTHOR

       Mark J. Kilgard (mjk@nvidia.com)

GLUT
									3.7						    glutDisplayFunc(3GLUT)
Man Page