ggiDBGetBuffer(3ggi)

NAME
ggiDBGetNumBuffers, ggiDBGetBuffer - Get DirectBuffers from a visual

SYNOPSIS
#include <ggi/ggi.h>

int ggiDBGetNumBuffers(ggi_visual_t vis);

const ggi_directbuffer *ggiDBGetBuffer(ggi_visual_t vis, int bufnum); .SH "DESCRIPTION"

ggiDBGetNumBuffers returns the number of DirectBuffers available to the application. ggiDBGetBuffer obtains the DirectBuffer at the specified position.

Use ggiDBGetBuffer to obtain the DirectBuffers at 0 to n-1, where n is the number returned by ggiDBGetNumBuffers.

Pixel-linear buffers have type==GGI_DB_SIMPLE_PLB | GGI_DB_NORMAL. You're on your own now.

DirectBuffers where ggiResourceMustAcquire(3) is true need to be 'acquired' (i.e. locked) before using. An acquire is done by using ggiResourceAcquire(3) and it is released by calling ggiResourceRelease(3) Beware that the read, write and stride fields of the DirectBuffer may be changed by an acquire, and that they may be NULL or invalid when the DirectBuffer is not acquired.

RETURN VALUE

ggiDBGetNumBuffers returns the number of DirectBuffers available. 0 indicates that no DirectBuffers are available.

ggiDBGetBuffer returns a pointer to a DirectBuffer structure.

EXAMPLES

  HOW TO OBTAIN A DIRECTBUFFER

ggi_visual_t	vis;
ggi_mode	mode;
int		i;
/* Framebuffer info */
unsigned char *fbptr[2];
int stride[2];
int numbufs;
mode.frames = 2;	/* Double-buffering */
mode.visible.x = 640;	/* Screen res */
mode.visible.y = 480;
mode.virt.x = GGI_AUTO;	/* Any virtual resolution.  Will usually be set
mode.virt.y = GGI_AUTO;	   to be the same as visible but some targets may
			   have restrictions on virtual size. */
mode.graphtype = GT_8BIT;		/* Depend on 8-bit palette. */
mode.dpp.x = mode.dpp.y = GGI_AUTO;	/* Always 1x1 but we don't care. */
if(ggiInit())
{
	/* Failed to initialize library. Bomb out. */
}
vis = ggiOpen(NULL);
if(!vis)
{
	/* Opening default visual failed, quit. */
}
if(ggiSetMode(vis, &mode))
{
	/* Set mode has failed, should check if suggested mode
	   is o.k. for us, and try the call again. */
}
numbufs = ggiDBGetNumBuffers(vis);
for(i = 0; i < numbufs; i++)
{
	ggi_directbuffer *db;
	int frameno;
	db = ggiDBGetBuffer(vis, i);
	if(!(db->type & GGI_DB_SIMPLE_PLB))
	{
		/* We don't handle anything but simple pixel-linear buffers.
		   Fall back to ggiPutBox() or something. */
		continue;
	}
	frameno = db->frame;
	if(readptr[frameno] != NULL &&
		(db->buffer.plb.pixelformat->flags & GGI_PF_REVERSE_ENDIAN))
	{
		continue;
	}
	fbptr[frameno] = db->write;	/* read == write for simple plbs */
	/* Stride of framebuffer (in bytes). */
	stride[frameno] = db->buffer.plb.stride;
	/* Check pixel format, be portable.... */