/****************************************************************************
*
* MegaGraph Graphics Library
*
* Copyright (C) 1993 Kendall Bennett.
* All rights reserved.
*
* Filename: $RCSfile: modes.c $
* Version: $Revision: 1.2 $
*
* Language: ANSI C
* Environment: IBM PC (MS DOS)
*
* Description: Routine to determine the available video modes for a
* specified video card, given memory restrictions.
*
* $Id: modes.c 1.2 1993/03/07 04:04:13 kjb Exp $
*
* Revision History:
* -----------------
*
* $Log: modes.c $
* Revision 1.2 1993/03/07 04:04:13 kjb
* Bug fixes.
*
* Revision 1.1 1993/03/03 10:46:00 kjb
* Initial revision
*
****************************************************************************/
#include "drivers.h"
/*--------------------------- Global Variables ----------------------------*/
int __modeTable[grMAXMODE+1]; /* Internal table of video modes */
/*------------------------- Implementation --------------------------------*/
/* Routines in 'detectgr.asm' for returning the list of possible video
* modes for this adapter and display pages.
*/
char far * _getSuperVGAModes(void);
int _getSuperVGAPages(int mode,int memory,long *pagesize);
PRIVATE int loadVGAModes(int i)
/****************************************************************************
*
* Function: loadVGAModes
* Parameters: i - Index to start loading modes at
* Returns: Index of next available space in mode table.
*
* Description: Fills in all of the standard VGA video modes in the mode
* table.
*
****************************************************************************/
{
__modeTable[i++] = grEGA_320x200x16;
__modeTable[i++] = grEGA_640x200x16;
__modeTable[i++] = grEGA_640x350x16;
__modeTable[i++] = grVGA_640x400x16;
__modeTable[i++] = grVGA_640x480x16;
__modeTable[i++] = grVGA_320x200x256;
__modeTable[i++] = grVGAX_320x200x256;
__modeTable[i++] = grVGAX_320x240x256;
__modeTable[i++] = grVGAX_320x400x256;
__modeTable[i++] = grVGAX_320x480x256;
__modeTable[i++] = grVGAX_360x200x256;
__modeTable[i++] = grVGAX_360x240x256;
__modeTable[i++] = grVGAX_360x400x256;
__modeTable[i++] = grVGAX_360x480x256;
return i;
}
PUBLIC int * MGL_availableModes(int driver,int memory)
/****************************************************************************
*
* Function: MGL_availableModes
* Parameters: driver - Graphics device driver to check.
* memory - Amount of memory on video card
*
* Returns: Returns a pointer to a list of all the video modes that are
* currently available. This routine can be called before
* MGL_init() is called to determine the video modes available.
* The list of video modes is terminated by a -1, but you
* will have to call MGL_detectGraph() to determine the
* currently installed video card.
*
****************************************************************************/
{
int i;
long pagesize;
char far *modes;
switch(driver) {
case grMCGA:
__modeTable[0] = grVGA_320x200x256;
__modeTable[1] = -1; /* Terminate the table */
memory = 64;
break;
case grEGA:
__modeTable[0] = grEGA_320x200x16;
__modeTable[1] = grEGA_640x200x16;
__modeTable[2] = grEGA_640x350x16;
__modeTable[3] = -1; /* Terminate the table */
memory = 256;
break;
case grVGA:
i = loadVGAModes(0);
__modeTable[i] = -1; /* Terminate the table */
memory = 256;
break;
default:
if (driver >= __FIRST_SVGA && driver <= __LAST_SVGA) {
/* We have a Super VGA video card. We know that we can use
* all of the standard VGA video modes, but we must also
* determine what SuperVGA video modes are available. We
* obtain this information from the DetectGraph module.
*/
i = loadVGAModes(0);
/* Install all detected SuperVGA modes, filtering
* those not supported with the memory installed
*/
modes = _getSuperVGAModes();
if (memory >= 4096) /* Fix strange memory sizes */
memory = 4096;
else if (memory >= 3072)
memory = 3072;
else if (memory >= 2048)
memory = 2048;
else if (memory >= 1024)
memory = 1024;
else if (memory >= 512)
memory = 512;
else if (memory >= 256)
memory = 256;
while (*modes != -1) {
/* Compute the size of the video page for the mode, and
* if we have enough memory for one page then include
* it in the mode list
*/
if (*modes != 0) {
if (_getSuperVGAPages(*modes | 0x80,memory,&pagesize) > 0) {
if ((pagesize / 1024) <= memory)
__modeTable[i++] = *modes;
}
}
modes++;
}
__modeTable[i] = -1; /* Terminate the table */
}
else {
/* No video modes are supported for this adapter */
__modeTable[0] = -1; /* Terminate the table */
}
}
return __modeTable;
}
PUBLIC int MGL_availablePages(int driver,int memory,int mode)
/****************************************************************************
*
* Function: MGL_availablePages
* Parameters: driver - Graphics device driver to check.
* memory - Amount of memory on video card.
* mode - Video mode to check
* Returns: Number of available video pages for the mode, -1 on error.
*
* Description: Determines the number of available video pages for a
* specific video mode and driver. This routine assumes that
* the MGL_detectGraph() routine has already been called
* to obtain the video device driver ID.
*
* If the video mode specified is invalid, a -1 is returned.
*
****************************************************************************/
{
int *modes;
long pagesize;
/* Get list of available video modes and check that the mode specified
* is currently valid
*/
modes = MGL_availableModes(driver,memory);
while (*modes != -1) {
if (mode == *modes)
break;
modes++;
}
if (*modes == -1)
return -1;
switch(driver) {
case grMCGA:
return 1;
case grEGA:
case grVGA:
switch (mode) {
case grEGA_320x200x16:
return 8;
case grEGA_640x200x16:
return 4;
case grEGA_640x350x16:
return 2;
case grVGA_640x400x16:
return 2;
case grVGA_640x480x16:
return 1;
case grVGA_320x200x256:
return 1;
}
return -1;
default:
if (driver >= __FIRST_SVGA && driver <= __LAST_SVGA) {
/* We have a Super VGA video card. We simply call the
* assembly language routine to compute the number
* of video pages.
*/
return _getSuperVGAPages(mode,memory,&pagesize);
}
else {
/* No video modes are supported for this adapter */
return -1;
}
}
}
