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Chapter 3
Initializing the
Video Environment
44 Fastgraph User's Guide
Overview
Before Fastgraph can perform any text or graphics video operations, you
must select a video mode in which your program will run. An important part
of this selection depends on whether your program will run in a text mode, a
graphics mode, or both. The first two sections in this chapter discuss the
necessary video initialization for standard text and graphics modes, while
the last section addresses the additional setup needed for SuperVGA (SVGA)
graphics modes.
Establishing a Text Mode
When you write a program that only uses text modes, you must determine
if the program will run on monochrome systems, color systems, or both. In
general, there is no reason to exclude one type of system, because the
additional programming required to support both is rather trivial.
The Fastgraph routine fg_setmode establishes a video mode and
initializes Fastgraph's internal parameters for that mode. This routine has
a single integer argument whose value is a video mode number between 0 and
29. Its value can also be -1, which tells Fastgraph to use the current video
mode. Specifying an fg_setmode argument of -1 is often useful in programs
that only use text video modes.
When you establish a text video mode, the ROM BIOS text cursor is made
visible, and this is often undesirable. The Fastgraph routine fg_cursor
controls the visibility of the text cursor. The fg_cursor routine has a
single integer argument that specifies the cursor visibility. If its value
is 0, the cursor is made invisible; if its value is 1, the cursor is made
visible.
At this point, an example may help to clarify things. The following
program shows how to initialize Fastgraph for the 80-column color text mode
(mode 3) and turn off the text mode cursor. It uses two Fastgraph routines
that we have not yet discussed, fg_setcolor and fg_text. These routines will
be discussed in later sections of this document. For now, it should suffice
to know the call to fg_setcolor makes subsequent text appear in white, and
the call to fg_text displays the characters passed to it.
Example 3-1.
#include <fastgraf.h>
void main(void);
void main()
{
fg_setmode(3);
fg_cursor(0);
fg_setcolor(15);
fg_text("Hello, world.",13);
}
Chapter 3: Initializing the Video Environment 45
If you run example 3-1, notice the text displayed by the program appears
in the upper left corner of the screen. On the line below this, the DOS
prompt appears, waiting for your next DOS command. Furthermore, if your
system uses the ANSI.SYS driver to set screen attributes (such as with
Norton's SA program), you should also notice only the DOS prompt appears in
the colors defined by the screen attributes -- the rest of the screen is
blank.
A more graceful return to DOS is needed. In example 3-2, we'll use the
Fastgraph routine fg_reset. This routine erases the screen, and if the
ANSI.SYS driver is loaded, fg_reset also restores any previously set screen
attributes. We've also included a call to the Fastgraph routine fg_waitkey
to wait for a keystroke before exiting. If we didn't do this, we would never
see the program's output.
Example 3-2.
#include <fastgraf.h>
void main(void);
void main()
{
fg_setmode(3);
fg_cursor(0);
fg_setcolor(15);
fg_text("Hello, world.",13);
fg_waitkey();
fg_reset();
}
Since examples 3-1 and 3-2 specifically used video mode 3, they would
not work on a monochrome system. Ideally, we'd like to use fg_setmode(3) for
color systems and fg_setmode(7) for monochrome systems. To do this, we need
a way to determine whether the program is being run on a color system or on a
monochrome system. The next example illustrates an easy way to do this.
Example 3-3 uses the Fastgraph routine fg_testmode to determine if the
user's system will support the video mode number specified as its first
argument (the second argument is the number of video pages required, which
will be 1 for all examples in this section). The fg_testmode routine returns
a value of 1 (as its function value) if the requested video mode can be used,
and it returns 0 if not. The program first sees if an 80-column color text
mode is available (mode 3), and if so, it selects that mode. If the color
mode is not available, it checks if the monochrome text mode is available
(mode 7), and if so, it chooses the monochrome mode. If neither mode is
available, then the program assumes the user's system has a 40-column
display, issues a message indicating the program requires an 80-column
display, and then exits.
Example 3-3.
#include <fastgraf.h>
#include <stdio.h>
#include <stdlib.h>
46 Fastgraph User's Guide
void main(void);
void main()
{
int old_mode;
old_mode = fg_getmode();
if (fg_testmode(3,1))
fg_setmode(3);
else if (fg_testmode(7,1))
fg_setmode(7);
else {
printf("This program requires\n");
printf("an 80-column display.\n");
exit(1);
}
fg_cursor(0);
fg_setcolor(15);
fg_text("Hello, world.",13);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
Example 3-3 also illustrates another useful procedure. It is
recommended, especially in graphics modes, to restore the original video mode
and screen attributes before a program returns to DOS. We've already seen
how the fg_reset routine restores the screen attributes, but how do we
restore the original video mode? The Fastgraph routine fg_getmode returns
the current video mode as its function value. If we call fg_getmode before
calling fg_setmode, we can use the return value from fg_getmode and again
call fg_setmode before the program exits.
You also can use another Fastgraph routine, fg_bestmode, to determine if
a video mode with a specific resolution is available on the user's system.
The fg_bestmode routine requires three integer arguments: a horizontal
resolution, a vertical resolution, and the number of video pages required.
As its function value, fg_bestmode returns the video mode number that offers
the most capabilities for the resolution and number of pages requested. It
returns a value of -1 if no available video mode offers the requested
criteria.
For example, if we require an 80 by 25 text mode, we can use the
function call fg_bestmode(80,25,1) to pick the "best" video mode available
that offers this capability. In text modes, the term best means to give
preference to a color text mode over a monochrome text mode. Example 3-4
performs the same function as example 3-3, but it uses fg_bestmode rather
than fg_testmode.
Example 3-4.
#include <fastgraf.h>
Chapter 3: Initializing the Video Environment 47
#include <stdio.h>
#include <stdlib.h>
void main(void);
void main()
{
int old_mode;
int new_mode;
old_mode = fg_getmode();
new_mode = fg_bestmode(80,25,1);
if (new_mode < 0) {
printf("This program requires\n");
printf("an 80-column display.\n");
exit(1);
}
fg_setmode(new_mode);
fg_cursor(0);
fg_setcolor(15);
fg_text("Hello, world.",13);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
43-line and 50-line Text Modes
When using an 80-column text mode on a system equipped with an EGA, VGA,
MCGA, or SVGA video display and adapter, you can extend the screen size from
25 lines to 43 or 50 lines. While all systems offer 25-line text modes, EGA
systems also offer 43-line modes, MCGA systems also offer 50-line modes, and
VGA and SVGA systems offer both 43-line and 50-line modes. The 43-line mode
is not available on EGA systems equipped with an RGB display. If you extend
the screen size to 43 or 50 lines, the physical character size is reduced
proportionally so all lines appear on the screen.
The fg_setlines routine defines the number of text rows per screen. It
has a single integer argument whose value must be 25, 43, or 50. If you pass
any other value to fg_setlines, or pass a value not supported by the host
system's video configuration, fg_setlines does nothing. In addition, calling
fg_setlines makes the text cursor visible. Another Fastgraph routine,
fg_getlines, returns as its function value the number of text rows currently
in effect. You also can use fg_getlines in graphics video modes.
Example 3-5 illustrates the use of the fg_setlines and fg_getlines
routines. The program first establishes the 80-column color text mode (this
sets the screen size to its 25-line default) and makes the text cursor
invisible. It then displays the words "first line" in the upper left corner
of the screen. Next, the program checks if an EGA with enhanced display is
available, and if so, changes the screen to 43 lines (video mode 16 is only
available on EGA systems equipped with an enhanced display). Next, the
48 Fastgraph User's Guide
program checks if a VGA, MCGA, or SVGA is available, and if so changes the
screen to 50 lines (video mode 17 is only available on these systems).
Finally, the program restores the original video mode, restores the number of
lines per screen to its original setting, and restores the original screen
attributes before exiting.
Example 3-5.
#include <fastgraf.h>
void main(void);
void main()
{
int lines;
int old_lines;
int old_mode;
old_lines = fg_getlines();
old_mode = fg_getmode();
fg_setmode(3);
fg_cursor(0);
fg_setcolor(15);
fg_text("first line",10);
fg_waitkey();
if (fg_testmode(16,0)) {
fg_setlines(43);
fg_cursor(0);
fg_waitkey();
}
if (fg_testmode(17,0)) {
fg_setlines(50);
fg_cursor(0);
fg_waitkey();
}
fg_setmode(old_mode);
fg_setlines(old_lines);
fg_reset();
}
Establishing a Graphics Mode
The steps for establishing a graphics mode are similar to establishing a
text mode. However, there are more restrictions since some systems may not
support all the graphics video modes. For example, a program could not run
in mode 13 on a CGA system, nor could a program run in mode 9 on anything
except a Tandy 1000 or PCjr system.
For graphics programs, it may suffice to write a program to run in a
specific video mode, but it is often more desirable to write a program that
will run in any of several video modes. This is especially true for
Chapter 3: Initializing the Video Environment 49
commercial products, since they should ideally run on as many different video
configurations as possible.
Fastgraph includes a routine named fg_automode that determines the
graphics video mode that offers the most functionality for the user's video
hardware configuration. For example, the Tandy 1000 series computers support
all three CGA modes (4, 5, and 6) and the 320 by 200 16-color Tandy 1000 mode
(9). Of these modes, mode 9 offers the most features from a graphics
standpoint, so fg_automode will return a value of 9 when run on a Tandy 1000
computer. The following table summarizes the video mode numbers returned by
fg_automode for given adapter-display combinations.
display
adapter mono RGB ECD VGA
MDA 7 0 7 7
HGC 11 0 0 11
CGA 0 4 0 0
EGA 15 13 16 0
VGA 17 17 17 18
MCGA 17 17 17 19
Tandy 7 9 0 0
PCjr 7 9 0 0
Example 3-6 shows how to use fg_automode to determine the "best"
graphics mode for the user's video hardware. In graphics modes, the term
best means the highest resolution, followed by the number of available
colors. To maintain compatibility with earlier versions of Fastgraph,
fg_automode does not consider the extended VGA graphics modes (modes 20 to
23) or SVGA graphics modes (modes 24 to 29) when selecting a video mode. The
program displays a message that includes the selected video mode number.
Example 3-6.
#include <fastgraf.h>
#include <stdio.h>
void main(void);
void main()
{
int old_mode;
int new_mode;
char string[4];
old_mode = fg_getmode();
new_mode = fg_automode();
fg_setmode(new_mode);
fg_setcolor(15);
fg_text("I'm running in mode ",20);
sprintf(string,"%d.",new_mode);
fg_text(string,3);
fg_waitkey();
fg_setmode(old_mode);
50 Fastgraph User's Guide
fg_reset();
}
For simple programs such as example 3-6, different screen resolutions
may not be an issue. However, in more complex graphics programs it is often
desirable to write a program for a fixed screen resolution. A common
practice is to develop graphics programs to run in modes 4 (for CGA), 9
(Tandy 1000 or PCjr), 12 (Hercules), 13 (EGA, VGA, or SVGA), and 19 or 20
(MCGA, VGA, or SVGA). The reason for selecting these five modes is they all
use the same 320 by 200 resolution and will run on any IBM PC or PS/2 with
graphics capabilities.
Example 3-7 performs the same function as example 3-6, but it uses
fg_bestmode instead of fg_automode to restrict the program to 320 by 200
graphics modes. For this resolution, the fg_bestmode routine will first
check the availability of mode 20, followed by modes 19, 13, 9, 4, and 12.
If fg_bestmode determines no 320 by 200 graphics mode is available (indicated
by a return value of -1), the program prints an informational message and
exits. Otherwise it selects the video mode fg_bestmode proposes and
continues.
Example 3-7.
#include <fastgraf.h>
#include <stdio.h>
#include <stdlib.h>
void main(void);
void main()
{
int old_mode;
int new_mode;
char string[4];
old_mode = fg_getmode();
new_mode = fg_bestmode(320,200,1);
if (new_mode < 0) {
printf("This program requires a 320 by 200 graphics mode.\n");
exit(1);
}
fg_setmode(new_mode);
fg_setcolor(15);
fg_text("I'm running in mode ",20);
sprintf(string,"%d.",new_mode);
fg_text(string,3);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
Chapter 3: Initializing the Video Environment 51
If a program will run in specific video modes, you may want to consider
using the fg_testmode routine instead of fg_bestmode to check for
availability of these video modes. You also may want to use fg_testmode to
change the video mode precedence used by fg_bestmode. For example, mode 13
(EGA) is faster than mode 19 (MCGA), so you may want to consider giving EGA
precedence over MCGA, especially if your program does not use more than 16
colors.
Example 3-8 is similar to example 3-7, but it will only run in the 320
by 200 EGA, MCGA, and CGA graphics modes (video modes 13, 19, and 4,
respectively). The program uses fg_testmode to select its video mode. Note
the order of calls to fg_testmode gives EGA precedence over MCGA, and MCGA
precedence over CGA.
Example 3-8.
#include <fastgraf.h>
#include <stdio.h>
#include <stdlib.h>
void main(void);
void main()
{
int old_mode;
char string[4];
old_mode = fg_getmode();
if (fg_testmode(13,1))
fg_setmode(13);
else if (fg_testmode(19,1))
fg_setmode(19);
else if (fg_testmode(4,1))
fg_setmode(4);
else {
printf("This program requires an EGA, MCGA, or CGA.\n");
exit(1);
}
fg_setcolor(15);
fg_text("I'm running in mode ",20);
sprintf(string,"%d.",getmode());
fg_text(string,3);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
SuperVGA Graphics Modes
Unlike previous generations of graphics cards, there was no video
standard in place when different companies began developing SVGA cards. As
a result, they implemented enhanced SVGA features according to their own
specifications based upon different video controller chips. Each such
52 Fastgraph User's Guide
implementation is called a chipset. While each chipset generally offers the
same video memory organization and common screen resolutions, the SVGA-
specific features such as mode initialization, bank switching, and setting
the display start address differ radically between chipsets. In other words,
code written for one specific SVGA chipset will not run on another chipset,
even at the same resolution. This is why many software vendors provide
different SVGA drivers for their products.
Fastgraph's integrated SVGA kernel makes these obscure differences
between SVGA chipsets transparent, without the need for external drivers.
This means, for instance, if you write an application for the 1024 by 768
256-color SVGA graphics mode, it will run without changes on any supported
SVGA chipset which offers that resolution. The SVGA kernel supports the
chipsets listed in the table below. A "Y" entry means the chipset supports
the video mode, and an "N" means it doesn't. The last two rows of the table
show the amount of video memory required to support each mode and Fastgraph's
corresponding video mode numbers.
----------- 256 colors ----------- -- 16 colors ---
SVGA chipset 640x400 640x480 800x600 1024x768 800x600 1024x768
Ahead "A" type Y Y Y N Y Y
Ahead "B" type Y Y Y Y Y Y
ATI 18800 Y Y Y N Y N
ATI 18800-1 Y Y Y N Y Y
ATI 28800 Y Y Y Y Y Y
Chips&Tech 82c451 Y N N N Y N
Chips&Tech 82c452 Y Y N N Y Y
Chips&Tech 82c453 Y Y Y Y Y Y
Cirrus Logic 54xx N Y Y Y Y Y
Genoa 6000 series Y Y Y N Y Y
Oak OTI-067 N Y Y N Y Y
Paradise PVGA1a Y Y N N Y N
Paradise WD90C00/10 Y Y N N Y Y
Paradise WD90C11/30/31 Y Y Y Y Y Y
S3 N Y Y Y Y Y
Trident 8800 Y Y N N Y Y
Trident 8900/9000 Y Y Y Y Y Y
Tseng ET3000 N Y Y N Y Y
Tseng ET4000 Y Y Y Y Y Y
Video7 Y Y Y Y Y Y
minimum video RAM 256K 512K 512K 1MB 256K 512K
Fastgraph mode number 24 25 26 27 28 29
The SVGA kernel maps Fastgraph's video mode numbers (24 to 29) to the
chipset-specific mode numbers. For example, the 640 by 480 256-color SVGA
mode is 62 hex on an ATI card, 5D hex on a Trident card, and 2E hex on a
Tseng card, but it's always mode 25 from Fastgraph's perspective.
The Video Electronics Standards Association (VESA) has assumed the
complex task of improving software compatibility of SVGA cards from different
companies. Most SVGA cards sold today include VESA compatibility, either
directly in ROM or through loadable software drivers supplied with the card.
Besides supporting specific chipsets, Fastgraph's SVGA kernel supports any
SVGA card with VESA compatibility. Note that VESA is not a chipset, but a
BIOS-level interface between an application (the SVGA kernel in this case)
Chapter 3: Initializing the Video Environment 53
and chipset-specific functions. While the current VESA standard covers all
six SVGA graphics modes that Fastgraph supports, these modes are only
available if the underlying chipset also supports them.
When using VESA compatibility, the VESA BIOS handles all chipset-
specific functions such as bank switching. The overhead imposed by the BIOS
usually makes the VESA modes slightly slower than using chipset-specific
functions directly. For this reason, you can specify if you want to give
precedence to the chipset-specific code or to the VESA BIOS. Chipset-
specific precedence means the SVGA kernel will only use the VESA BIOS if no
supported SVGA chipset is found. Conversely, VESA precedence means the
kernel will only use the chipset-specific functions if no VESA BIOS is found.
Before you use any SVGA graphics mode, you must use the fg_svgainit
routine to initialize the SVGA kernel (fg_svgainit must be called before
fg_setmode, fg_bestmode, or fg_testmode). There are three ways to initialize
the SVGA kernel with fg_svgainit:
- autodetect the user's SVGA chipset, giving precedence to
chipset-specific code
- autodetect the user's SVGA chipset, giving precedence to
the VESA BIOS
- use a designated SVGA chipset
The fg_svgainit routine's argument is an integer value between 0 and 19 that
specifies which initialization method to use. Passing 0 to fg_svgainit uses
the first method, in which the SVGA kernel searches for all supported
chipsets before checking if a VESA BIOS is present. This means the SVGA
kernel will only use VESA functions if fg_svgainit doesn't find one of the
supported chipsets. Passing 1 to fg_svgainit also performs a chipset
autodetect, but in this case the SVGA kernel first searches for a VESA BIOS,
then through the list of supported chipsets. This means chipset-specific
code will be used only when no VESA BIOS is found. You can also initialize
the SVGA kernel for a specific chipset by passing a value between 2 and 19 to
fg_svgainit. The following table summarizes the fg_svgainit initialization
codes.
code chipset
0 autodetect (with chipset-specific precedence)
1 autodetect (with VESA precedence)
2 Ahead "A" type
3 Ahead "B" type
4 ATI 18800
5 ATI 18800-1
6 ATI 28800
7 Chips & Technologies 82c451/455/456
8 Chips & Technologies 82c452
9 Chips & Technologies 82c453
10 Genoa 6000 series
11 Oak OTI-067
12 Paradise PVGA1a
13 Paradise WD90C00/WD90C10
14 Paradise WD90C11/WD90C30/WD90C31
15 Trident 8800
16 Trident 8900
17 Tseng ET3000
54 Fastgraph User's Guide
18 Tseng ET4000
19 Video7
20 Cirrus Logic 5400 series
21 S3
22 Trident 8900B/8900C/9000
For autodetect requests, fg_svgainit returns a value between 1 and 19
corresponding to the SVGA chipset found. If the return value is 1, it means
a VESA BIOS will be used. A value between 2 and 22 means a specific SVGA
chipset (as listed in the preceding table) will be used. If no VESA BIOS or
supported SVGA chipset is found, fg_svgainit returns zero. In this case,
Fastgraph's SVGA graphics modes are not available.
When you request initialization for a specific chipset, fg_svgainit
always returns the value passed to it. It does not check if that chipset is
actually present, so this feature should be used judiciously.
Example 3-9 is a simple program that checks if an SVGA card is present,
and if so, displays the name of the SVGA chipset. It also displays how much
video memory is present on the SVGA card and the version number of
Fastgraph's SVGA kernel.
Example 3-9.
#include <fastgraf.h>
#include <stdio.h>
void main(void);
char *description[] =
{
"cannot be determined",
"VESA",
"Ahead A",
"Ahead B",
"ATI 18800",
"ATI 18800-1",
"ATI 28800",
"Chips & Technologies 82c451/455/456",
"Chips & Technologies 82c452",
"Chips & Technologies 82c453",
"Genoa 6000 series",
"Oak OTI-067",
"Paradise PVGA1a",
"Paradise WD90C00/WD90C10",
"Paradise WD90C11/WD90C30/WD90C31",
"Trident 8800",
"Trident 8900",
"Tseng ET3000",
"Tseng ET4000",
"Video7",
" ",
"S3",
"Trident 8900B/8900C/9000"
};
void main()
{
Chapter 3: Initializing the Video Environment 55
int id, major, minor;
id = fg_svgainit(0);
printf("SVGA chipset: %s\n",description[id]);
printf("video memory: %d kilobytes\n",fg_memory());
fg_svgaver(&major,&minor);
printf("SVGA version: %d.%2.2d\n",major,minor);
}
This example uses fg_svgainit to automatically detect the user's SVGA
chipset. It initializes the SVGA kernel so that chipset-specific code is
given precedence over VESA (passing 1 instead of 0 to fg_svgainit would give
VESA precedence). Note that the program does not establish an SVGA graphics
mode -- it just uses the fg_svgainit return value to identify which chipset
is present.
Example 3-9 also includes two other Fastgraph routines relevant to the
SVGA kernel. The fg_memory function returns the amount of video memory (in
kilobytes) resident on the user's video card. For example, the fg_memory
return value is 1,024 for a 1MB SVGA card. Another routine, fg_svgaver,
returns the major and minor numbers for the SVGA kernel, similar to the
fg_version routine mentioned in Chapter 1. Note that the SVGA kernel version
number is not the same as the Fastgraph version number.
Our next example, 3-10, is an SVGA version of example 3-8. This program
initializes the SVGA kernel so that VESA will have precedence over chipset-
specific code. It then calls fg_testmode to find a supported 256-color SVGA
graphics mode, first trying mode 27 (1024 by 768), then mode 26 (800 by 600),
and finally mode 25 (640 by 480). Checking the modes in this sequence
insures the program will use the highest resolution available, given the
user's SVGA chipset (not all chipsets support all resolutions) and the amount
of video memory present (mode 27 requires 1MB video RAM; modes 26 and 25 need
512K).
If all three fg_testmode calls fail in example 3-10, the program
displays an appropriate message and exits. This would happen if the program
were run on a non-SVGA system, run on an unsupported SVGA chipset without
VESA compatibility, or if the SVGA card does not have at least 512K video
memory (modes 25, 26, and 27 all require at least 512K). In the first two
cases, the fg_svgainit function wouldn't be able to initialize the SVGA
kernel, so fg_testmode would fail when checking the availability of any SVGA
graphics mode. That's why it's not necessary to check the fg_svgainit return
value in this case.
Example 3-10.
#include <fastgraf.h>
#include <stdio.h>
#include <stdlib.h>
void main(void);
void main()
{
int old_mode;
char string[4];
old_mode = fg_getmode();
56 Fastgraph User's Guide
fg_svgainit(1);
if (fg_testmode(27,1))
fg_setmode(27);
else if (fg_testmode(26,1))
fg_setmode(26);
else if (fg_testmode(25,1))
fg_setmode(25);
else {
printf("This program requires an SVGA\n");
printf("with at least 512K video memory.\n");
exit(1);
}
fg_setcolor(15);
fg_text("I'm running in mode ",20);
sprintf(string,"%d.",fg_getmode());
fg_text(string,3);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
Some third party SVGA cards based on Fastgraph's supported chipsets do
not completely follow the chipset manufacturer's recommended video mode
numbers and register definitions. While the SVGA kernel tries to compensate
for these problems when known, it's just not possible to support every
problematic SVGA card. For this reason, we recommend SVGA applications that
give precedence to chipset-specific code also provide a way to select VESA
compatibility, such as through a command line switch or configuration file.
The VESA driver supplied with a problem card should work around these
incompatibilities. If it doesn't, you can be assured that most (if not all)
SVGA applications will fail on that card, whether or not they were written
with Fastgraph.
Another important point to consider when writing SVGA applications is
the compatibility between the video card and monitor. Virtually all SVGA
monitors made today have no problems supporting the bandwidth required by any
of Fastgraph's SVGA graphics modes. However, some monitors (most notably
older multisync monitors) cannot support the higher resolution modes such as
800 by 600 and 1024 by 768. The SVGA kernel checks if the SVGA card supports
the requested resolution, but it does not check if the card/monitor
combination does.
Summary of Video Initialization Routines
This section summarizes the functional descriptions of the Fastgraph
routines presented in this chapter. More detailed information about these
routines, including their arguments and return values, may be found in the
Fastgraph Reference Manual.
FG_AUTOMODE determines the graphics video mode that offers the most
features for the user's display and adapter configuration. The value it
returns helps determine a suitable value to pass to the fg_setmode routine.
Chapter 3: Initializing the Video Environment 57
FG_BESTMODE is similar to fg_automode, but it excludes video modes that
do not offer the specified resolution and video page requirements.
FG_CURSOR makes the text mode cursor visible or invisible. This routine
has no effect when used in a graphics mode.
FG_GETLINES returns the number of text rows per screen for the current
video mode.
FG_GETMODE returns the current video mode. It is typically one of the
first Fastgraph routines called in a program. The value returned by
fg_getmode can be retained to restore the original video mode when a program
transfers control back to DOS.
FG_MEMORY returns the amount of video memory present (in kilobytes) on
the user's SVGA card. This routine is meaningful only after successfully
initializing the SVGA kernel with fg_svgainit.
FG_RESET is generally the last Fastgraph routine called in a program.
It only functions in text video modes. When the ANSI.SYS driver is not
loaded, fg_reset merely erases the screen. When ANSI.SYS is loaded, fg_reset
also restores any previously set screen attributes.
FG_SETLINES extends an 80-column text mode to 25, 43, or 50 lines per
screen. This routine is only meaningful when running in 80-column text modes
on EGA, VGA, or MCGA systems (in other cases it does nothing).
FG_SETMODE establishes a video mode and initializes Fastgraph's internal
parameters for that video mode. It must be called before any Fastgraph
routine that performs video output. A program can call fg_setmode as many
times as needed to switch between different video modes.
FG_SVGAINIT initializes Fastgraph's SVGA kernel and performs chipset-
specific SVGA initialization. This routine must be called before
establishing an SVGA graphics mode with fg_setmode.
FG_SVGAVER returns the Fastgraph SVGA kernel major and minor version
numbers.
FG_TESTMODE determines whether or not a specified video mode (with a
given number of video pages) is available on the user's system.
58 Fastgraph User's Guide
