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Chapter 3 Initializing the Video Environment 42 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 clarify things. We'll start with a variation of Kernighan and Ritchie's famous "Hello, world" program that 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. For now, it should suffice to know that fg_setcolor(15) makes subsequent text appear in white, and fg_text displays the characters passed to it. Example 3-1. #include <fastgraf.h> void main(void); void main() { fg_initpm(); fg_setmode(3); fg_cursor(0); fg_setcolor(15); fg_text("Hello, world.",13); } Chapter 3: Initializing the Video Environment 43 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_initpm(); 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 use 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 stating the program requires an 80-column display, and then exits. Example 3-3. #include <fastgraf.h> #include <stdio.h> #include <stdlib.h> 44 Fastgraph User's Guide void main(void); void main() { int old_mode; fg_initpm(); 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 save the fg_getmode return value and pass it to fg_setmode just 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 80x25 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> #include <stdio.h> Chapter 3: Initializing the Video Environment 45 #include <stdlib.h> void main(void); void main() { int old_mode; int new_mode; fg_initpm(); 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 46 Fastgraph User's Guide available on EGA systems equipped with an enhanced display). Next, the 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; fg_initpm(); 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. Chapter 3: Initializing the Video Environment 47 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 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 320x200 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. 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. 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. 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]; fg_initpm(); old_mode = fg_getmode(); new_mode = fg_automode(); fg_setmode(new_mode); fg_setcolor(15); fg_text("I'm running in mode ",20); 48 Fastgraph User's Guide sprintf(string,"%d.",new_mode); fg_text(string,3); fg_waitkey(); fg_setmode(old_mode); 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 320x200 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 320x200 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 320x200 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]; fg_initpm(); 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(); Chapter 3: Initializing the Video Environment 49 fg_setmode(old_mode); fg_reset(); } 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 320x200 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]; fg_initpm(); 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(); } 50 Fastgraph User's Guide 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 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 minimum amount of video memory required to support each mode and Fastgraph's corresponding video mode numbers. -------- 256 colors -------- -- 16 colors -- SVGA chipset 640x400 640x480 800x6001024x768 800x6001024x768 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 28800/38800/68800/88800 Y Y Y Y Y Y Avance Logic 2000 series Y Y Y Y Y Y Chips & Technologies 82c451 Y N N N Y N Chips & Technologies 82c452 Y Y N N Y Y Chips & Technologies 82c453 Y Y Y Y Y Y Cirrus Logic 5400 series N Y Y Y Y Y Cirrus Logic 6400 series Y Y Y Y Y Y Genoa 6000 series Y Y Y N Y Y NCR 77C22/77C32 Y Y Y Y Y Y Oak OTI-067 N Y Y N Y Y Oak OTI-077 N Y Y Y Y Y Oak OTI-087 Y Y Y N Y Y Paradise PVGA1a Y Y N N Y N Paradise WD90C00/10 Y Y N N Y Y Paradise WD90C11/30/31/33 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 needed 256K 512K 512K 1MB 256K 512K Fastgraph mode number 24 25 26 27 28 29 Chapter 3: Initializing the Video Environment 51 The SVGA kernel maps Fastgraph's video mode numbers (24 to 29) to the chipset- specific mode numbers. For example, the 640x480 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. As we constantly add support for new SVGA chipsets, please refer to Fastgraph's READ.ME file for the current chipset list. The READ.ME file also lists known problems and limitations with the various chipsets. 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) 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 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 SVGA chipset, precedence to chipset-specific code * autodetect the SVGA chipset, precedence to the VESA BIOS * use a designated SVGA chipset The fg_svgainit routine's argument is an integer value between 0 and 27 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 27 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 52 Fastgraph User's Guide 3 Ahead "B" type 4 ATI 18800 5 ATI 18800-1 6 ATI 28800/38800/68800/88800 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/WD90C33 15 Trident 8800 16 Trident 8900/9000 17 Tseng ET3000 18 Tseng ET4000 19 Video7 20 Cirrus Logic 5400 series 21 S3 22 NCR 77C22/77C32 23 Oak OTI-077 24 Oak OTI-087 25 reserved 26 Cirrus Logic 6400 series 27 Avance Logic 2000 series >27 autodetect (with chipset-specific precedence) For autodetect requests, fg_svgainit returns a value between 1 and 27 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 27 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", Chapter 3: Initializing the Video Environment 53 "ATI 18800-1", "ATI 28800/38800/68800/88800", "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/WD90C33", "Trident 8800", "Trident 8900/9000", "Tseng ET3000", "Tseng ET4000", "Video7", "Cirrus Logic 5400 series", "S3", "NCR 77C22/77C32", "Oak OTI-077", "Oak OTI-087", " ", "Cirrus Logic 6400 series", "Avance Logic 2000 series" }; void main() { int id, major, minor; fg_initpm(); 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 detect the user's SVGA chipset automatically. It initializes the SVGA kernel so 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. Another useful function is fg_svgastat, which returns information about the current state of Fastgraph's SVGA kernel. The function returns a bit mask in which bit 0 will be set if the SVGA kernel has been successfully initialized, and bit 1 will be set if the kernel is using the VESA BIOS. Other 54 Fastgraph User's Guide fg_svgastat bits provide information about the availability of extended video pages and whether or not the active chipset supports separate read and write banks. We'll discuss these features in later chapters. 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 (800x600), and finally mode 25 (640x480). 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 have initialized 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]; fg_initpm(); old_mode = fg_getmode(); 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 "); 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(); Chapter 3: Initializing the Video Environment 55 fg_setmode(old_mode); fg_reset(); } While the VESA specification defines a common programming interface for chipset-specific SVGA functions, we must remember that VESA is just that -- a specification. Some manufacturers provide VESA drivers or BIOS implementations that realize the full VESA specification with only slight performance degradations. Others aren't as good, having problems with anything beyond the rudimentary functions of mode initialization and bank switching, not to mention performance issues. Other problems can occur with the few SVGA cards that do not completely follow the chipset manufacturer's predefined video mode numbers and register definitions. While the SVGA kernel allows for these problems when known, it's just not possible to support every problematic SVGA card. To complicate matters, some of these troublesome video cards only exhibit problems in certain revisions, meaning two apparently identical cards will behave differently. Fortunately, such problematic cards are by far the exception. If you're developing an SVGA product for general distribution, we recommend using Fastgraph's chipset-specific code by default, but also providing a way to override the chipset-specific code and use VESA support. Most often this is done by recognizing a command line switch or using an application-specific configuration file. Some programmers even take this one step farther by including a way to avoid the SVGA autodetection procedure and initialize Fastgraph's SVGA kernel for a specific chipset. This might be important if your product will run on laptop systems, which sometimes have SVGA video subsystems that don't respond to autodetection requests as reliably as their desktop counterparts. 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 800x600 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. FG_BESTMODE is similar to fg_automode, but it excludes video modes that do not offer the specified resolution and video page requirements. 56 Fastgraph User's Guide 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 used 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_SVGASTAT returns information about the current state of Fastgraph's SVGA kernel. FG_SVGAVER returns the SVGA kernel's 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.