DrawImage(D3nfb)

Synopsis

#include "nfbWinStr.h"

void xxxDrawImage (
	BoxPtr pbox,
	void *image,
	unsigned int stride,
	unsigned char alu,
	unsigned long planemask,
	DrawablePtr pDraw);

Description

Arguments

pbox

describes the rectangular area in which the image should appear in the frame buffer. pbox points to an X structure called a BoxRec(D4nfb) where the last pixel of the image should appear.

This means that the pixel width can be determined by subtracting x1 from x2 and the height by subtracting y1 from y2. This is how the X server deals with rectangular coordinates at the lowest level. Your Link Kit driver will never have to deal with situations where the rectangle's width or height are less than or equal to zero so it is not necessary to add code to check these values.

image

points to the actual image data that must be copied into the frame buffer. If you are writing an 8-bits-per-pixel driver, then this void * is actually an unsigned char *. If you are writing a 16-bits-per-pixel driver, then this void * is actually an unsigned short *. If you are writing a 24-bits-per-pixel driver, then this void * is actually an unsigned int *. image points to a contiguous chunk of memory that is stride x pixel width in size.

stride

is the memory offset in bytes between two rows in image memory. See ``stride'' in Developing NFB graphics adapter drivers.

alu

is the raster bit operation that is to be applied when mixing the image with the contents of the frame buffer. See ``alu'' in Developing NFB graphics adapter drivers.

planemask

contains a value that determines which frame buffer planes get modified when drawing this image. If a bit is set, the plane will be modified. If no bits are set, the plane will not be modified. Almost all X drawing operations use a planemask that specifies modification of all planes.

pDraw

pointer to an X structure called DrawableRec. This pointer is used only to access your Screen Private data. The ScreenRec structure is pointed to by pDraw->pScreen. Your Screen Private hangs off the bottom of ScreenRec.

Exit codes

Usage

Note that different functions are required to support depths 1, 2, 4, 8, and 16. Note the following:

• DrawImage( ) needs to be able to draw a rectangular area on the screen, applying the given alu and planemask; see ``alu'' in Developing NFB graphics adapter drivers. You will probably need to set up a static table of size 16 that takes the alu value as an index and returns the actual value required by the hardware. See ``alu'' in Developing NFB graphics adapter drivers.

• The sample driver uses C defines to create a series of macros that will be used extensively to set the planemask value, the alu value, the various drawing command registers, the drawing coordinates, and so forth. You should attempt to use a similar paradigm in your driver to map the alu functions (especially GXcopy, GXxor, and GXinvert to the adapter's operations.

• Once DrawImage( ) has been written, it may be possible to run the X server in an almost usable manner. The cursor code leave tracking on the screen, and expects ReadImage(D3nfb) to be correctly implemented, but otherwise you should be able to start X clients and see their output on your graphics adapter.

Version applicability

Source files

Driver source file

xxxImage.c

Defined in

nfbWinOps structure in xxxData.c

Prototyped in

xxxProcs.h

References

Examples