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ÝinstalluserdriverÞ <GRAPHICS.H>
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Installs a vendor-added device driver to the BGI device driver table
Declaration:
int far installuserdriver(char far *name, int huge (*detect)(void));
Remarks:
With installuserdriver, you can add a vendor-added device driver to
the BGI internal table.
Argument³ What It Is/Does
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name ³ Name of the new device driver file (filename.BGI)
detect ³ Points to an optional autodetect function that can accompany the
³ new driver. This autodetect function takes no parameters and
³ returns an integer value.
You can install up to 10 drivers at one time.
There are two ways to use the vendor-supplied driver:
1) passing the driver number directly to
initgraph, or
2) linking in an autodetect function.
Passing driver number directly to initgraph
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Assume you have a new video card called the Spiffy Graphics Array
(SpGA) and that the SpGA manufacturer provided you with a BGI device
driver (SPGA.BGI).
The easiest way to use this driver is to install it by calling
installuserdriver and then passing the return value (the assigned
driver number) directly to initgraph.
Linking in an autodetect function
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The more general way to use this hypothetical SpGA driver is to link
in an autodetect function that will be called by initgraph as part of
its hardware-detection logic. (Presumably, the manufacturer of the
SpGA gave you this autodetect function).
When you install the driver (by calling installuserdriver), you pass
the address of this autodetect function, along with the device
driver's file name.
After you install the device driver's file name and the SpGA
autodetect function, call initgraph and let it go through its normal
autodetection process.
Before initgraph calls its own built-in autodetection function
(detectgraph), it first calls the SpGA autodetect function.
þ If the SpGA autodetect function doesn't find the SpGA hardware, it
returns a value of -11 (grError), and initgraph proceeds with its
normal hardware detection logic.
(This can include calling any other vendor-supplied autodetection
functions in the order in which they were "installed").
þ If, however, the autodetect function determines that an SpGA is
present, it returns a non-negative mode number.
initgraph then:
1) locates and loads SPGA.BGI
2) puts the hardware into the default
graphics mode recommended by the
autodetect function
3) returns control to your program.
Return Value:
Returns the driver number you pass to initgraph to manually select the
newly installed driver.
Portability:
É DOS Ñ UNIX Ñ ANSI C Ñ C++ Only »
º Yes ³ ³ ³ º
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See Also:
initgraph registerbgidriver
Example:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
/* function prototypes */
int huge detectEGA(void);
void checkerrors(void);
int main(void)
{
int gdriver, gmode;
/* install a user written device driver */
gdriver = installuserdriver("EGA", detectEGA);
/* must force use of detection routine */
gdriver = DETECT;
/* check for any installation errors */
checkerrors();
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* check for any initialization errors */
checkerrors();
/* draw a line */
line(0, 0, getmaxx(), getmaxy());
/* clean up */
getch();
closegraph();
return 0;
}
/* detects EGA or VGA cards */
int huge detectEGA(void)
{
int driver, mode, sugmode = 0;
detectgraph(&driver, &mode);
if ((driver == EGA) || (driver == VGA))
/* return suggested video mode number */
return sugmode;
else
/* return an error code */
return grError;
}
/* check for and report any graphics errors */
void checkerrors(void)
{
int errorcode;
/* read result of last graphics operation */
errorcode = graphresult();
if (errorcode != grOk)
{
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1);
}
}
.... neways...thanx for all the help.....will try out wat u pple said....thanx