vga_setmode(3)

NAME
vga_setmode - sets a video mode

SYNOPSIS
#include <vga.h> int vga_setmode(int mode);

DESCRIPTION
vga_setmode(int mode) select the video mode given and clears the screen (if it was a graphics mode). Basically this should be the first action of your application after calling vga_init(3) and finding out which mode to use. Prior to exit your application should call vga_setmode(TEXT). vga_setmode() returns 0 on success and -1 if this mode is not available. mode should be one of the following, predefined values, or generally a value in range 1 <= mode <= vga_lastmodenumber() where vga_modeinfo(3) returned details about this mode. Instead of trying to set the mode, vga_hasmode(3) allows to determine if the mode would actually be supported. It is also possible to use the numeric values given below though this is discouraged. They are commonly used as values for the GSVGAMODE environment variable to set the vga_getdefaultmode(3). Here are the predefined values for mode.

  Text mode
TEXT(0) restores textmode and fall back to ordinary text console handling. All other calls switch to a graphics mode. You should set this mode prior to exiting an svgalib application.

  VGA compatible graphics modes
In general, for all modes following, the first number is the amount of x pixels, the second the amount of y pixels, the third the number of colors, with shortcuts 32K, 64K, 16M, 16M4 for 32768, 65536, and 1677721. Those with 2 or more than 256 colors use fixed color mappings (either black and white or some RGB true/high color) the others make use of a color lookup table. Memory layout for the VGA modes is weird. To weird to be explained here, but you can check the usual VGA literature. vga_setmodeX(3) has a short explanation which is valid for all 256 color modes. G320x200x16(1), G640x200x16(2), G640x350x16(3), G640x480x16(4), G320x200x256(5), G320x240x256(6), G320x400x256(7), G360x480x256(8), and G640x480x2(9)

  Basic SVGA modes
These use linear 256 color memory layouts similar to G320x200x256. G640x480x256(10), G800x600x256(11), G1024x768x256(12), and G1280x1024x256(13)

  High color SVGA modes
These use also linear memory layouts, but for 32K & 64K each pixel occupies two bytes and three for 16M. For 32K, each 16 bit word is divided into 555 bit portions refering to 5 bit red, green, blue part. The most significant bit is ignored by the card. For 64K the division is 565 allowing to specify green in a little bit more detail (Human eyes are more sensitive to green. People joke this is because our ancestors lived in trees where ligth was filtered through green leaves). For the 16M modes, from low to high addresses the 3 bytes are named BGR and specify the blue, green, red parts of the pixel value. G320x200x32K(14), G320x200x64K(15), G320x200x16M(16), G640x480x32K(17), G640x480x64K(18), G640x480x16M(19), G800x600x32K(20), G800x600x64K(21), G800x600x16M(22), G1024x768x32K(23), G1024x768x64K(24), G1024x768x16M(25), G1280x1024x32K(26), G1280x1024x64K(27), and G1280x1024x16M(28)

  High resolutions with less color numbers.
Memory layout is probably one nibble per pixel, to pixels per byte in a linear fashion where the most significant nibble is the left most pixel. G800x600x16(29), G1024x768x16(30), and G1280x1024x16(31)

  Hercules emulation mode
Again check out the ordinary VGA literature for the memory layout. G720x348x2(32)

  32-bit per pixel modes
These are similar to 16M but each pixel uses four bytes. The first three are similar to 16M but the fourth is left empty and ignored by the VGA card (you can store own status there). This ease pixel address calculations on the screen and drawin operations. However, 1/3 more data has to be moved to the screen. Experiments show that usually the higher memory bandwidth used outweigh the effects of the simplified algorithms by far. G320x200x16M32(33), G640x480x16M32(34), G800x600x16M32(35), G1024x768x16M32(36), and G1280x1024x16M32(37)

  Some more resolutions
It should by now be clear how the modes will look like. G1152x864x16(38), G1152x864x256(39), G1152x864x32K(40), G1152x864x64K(41), G1152x864x16M(42), G1152x864x16M32(43), G1600x1200x16(44), G1600x1200x256(45), G1600x1200x32K(46), G1600x1200x64K(47), G1600x1200x16M(48), and G1600x1200x16M32(49)

The vgatest(6) produces a list of supported modes for your hardware, prints some info on the modes and allows you to try each of them.

SEE ALSO
svgalib(7), vgagl(7), libvga.config(5), vgatest(6), vga_hasmode(3), vga_init(3), vga_modeinfo(3), vga_getcurrentmode(3), vga_getdefaultmode(3), vga_lastmodenumber(3), vga_getmodename(3), vga_getmodenumber(3)

AUTHOR
This manual page was edited by Michael Weller <eowmob@exp-math.uni-essen.de>. The exact source of the referenced function as well as of the original documentation is unknown. It is very likely that both are at least to some extend are due to Harm Hanemaayer <H.Hanemaayer@inter.nl.net>. Occasionally this might be wrong. I hereby excuse by the correct author and will happily accept any additions or corrections to this first version of the svgalib manual.