183 lines
5.7 KiB
Groff
183 lines
5.7 KiB
Groff
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.TH vga_setmode 3 "28 Jul 1999" "Svgalib 1.4.1" "Svgalib User Manual"
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.SH NAME
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vga_setmode \- sets a video mode
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.SH SYNOPSIS
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.B "#include <vga.h>"
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.BI "int vga_setmode(int " mode );
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.SH DESCRIPTION
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.BI "vga_setmode(int " mode )
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selects the video
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.I mode
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given and clears the screen (if it was a graphics mode).
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Basically this should be the first action of your application after calling
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.BR vga_init (3)
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and finding out which mode to use.
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Prior to exiting your application should call
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.B vga_setmode(TEXT).
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.B vga_setmode()
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returns 0 on success and -1 if this mode is not available.
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From svgalib-1.4.1, if
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.I mode
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is -1 then vga_setmode() returns the current svgalib version, in BCD format, so
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svgalib 1.4.1 returns 0x1410.
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.I mode
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should be one of the following, predefined values, or generally a value in range
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.B 1 <=
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.I mode
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.B <= vga_lastmodenumber()
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where
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.BR vga_modeinfo (3)
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returned details about this mode. Instead of trying to set the mode,
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.BR vga_hasmode (3)
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determines if the mode would actually be supported. It is also possible to use
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the numeric values given below though this is discouraged. They are commonly used as values
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for the
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.B SVGALIB_DEFAULT_MODE
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environment variable to set the
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.BR vga_getdefaultmode (3).
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Here are the predefined values for
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.IR mode .
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.SS Text mode
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.BR TEXT (0)
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restores textmode and falls back to ordinary text console handling. All other calls switch to a
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graphics mode. You should set this mode prior to exiting an svgalib application.
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.SS VGA compatible graphics modes
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In general, for all modes following, the first number is the amount of x pixels, the second
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the amount of y pixels, the third the number of colors, with shortcuts 32K, 64K, 16M, 16M4
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for 32768, 65536, and 1677721. Those with 2 or more than 256 colors use fixed color mappings
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(either black and white or some RGB true/high color) the others make use of a color lookup
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table.
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Memory layout for the VGA modes is weird. Too weird to be explained here, but you can check
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the usual VGA literature.
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.BR vga_setmodeX (3)
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has a short explanation which is valid for all 256 color modes.
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.BR G320x200x16 (1),
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.BR G640x200x16 (2),
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.BR G640x350x16 (3),
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.BR G640x480x16 (4),
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.BR G320x200x256 (5),
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.BR G320x240x256 (6),
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.BR G320x400x256 (7),
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.BR G360x480x256 "(8), and "
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.BR G640x480x2 (9)
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.SS Basic SVGA modes
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These use linear 256 color memory layouts similar to
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.BR G320x200x256 .
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.BR G640x480x256 (10),
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.BR G800x600x256 (11),
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.BR G1024x768x256 "(12), and "
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.BR G1280x1024x256 (13)
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.SS High color SVGA modes
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These also use linear memory layouts, but for 32K & 64K each pixel occupies two bytes and
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three for 16M. For 32K, each 16 bit word is divided into 555 bit portions refering to 5
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bit red, green, blue part. The most significant bit is ignored by the card. For 64K the
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division is 565 allowing to specify green in a little bit more detail (Human eyes are more
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sensitive to green. People joke this is because our ancestors lived in trees where light was
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filtered through green leaves).
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For the 16M modes, from low to high addresses the 3 bytes are named BGR and specify the
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blue, green, red parts of the pixel value.
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.BR G320x200x32K (14),
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.BR G320x200x64K (15),
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.BR G320x200x16M (16),
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.BR G640x480x32K (17),
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.BR G640x480x64K (18),
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.BR G640x480x16M (19),
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.BR G800x600x32K (20),
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.BR G800x600x64K (21),
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.BR G800x600x16M (22),
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.BR G1024x768x32K (23),
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.BR G1024x768x64K (24),
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.BR G1024x768x16M (25),
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.BR G1280x1024x32K (26),
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.BR G1280x1024x64K "(27), and "
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.BR G1280x1024x16M (28)
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.SS High resolutions with less color numbers.
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Memory layout is probably one nibble per pixel, two pixels per byte in a linear fashion where
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the most significant nibble is the left most pixel.
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.BR G800x600x16 (29),
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.BR G1024x768x16 "(30), and "
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.BR G1280x1024x16 (31)
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.SS Hercules emulation mode
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Again check out the ordinary VGA literature for the memory layout.
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.BR G720x348x2 (32)
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.SS 32-bit per pixel modes
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These are similar to 16M but each pixel uses four bytes. The first three are similar to
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16M but the fourth is left empty and ignored by the VGA card (you can store own status there).
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This eases pixel address calculations on the screen and drawing operations. However, 1/3 more
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data has to be moved to the screen. Experiments show that usually the higher memory bandwidth
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used outweighs the effects of the simplified algorithms by far.
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.BR G320x200x16M32 (33),
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.BR G640x480x16M32 (34),
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.BR G800x600x16M32 (35),
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.BR G1024x768x16M32 "(36), and "
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.BR G1280x1024x16M32 (37)
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.SS Some more resolutions
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It should by now be clear how the modes will look.
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.BR G1152x864x16 (38),
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.BR G1152x864x256 (39),
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.BR G1152x864x32K (40),
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.BR G1152x864x64K (41),
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.BR G1152x864x16M (42),
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.BR G1152x864x16M32 (43),
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.BR G1600x1200x16 (44),
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.BR G1600x1200x256 (45),
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.BR G1600x1200x32K (46),
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.BR G1600x1200x64K (47),
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.BR G1600x1200x16M "(48), and "
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.BR G1600x1200x16M32 (49)
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.PP
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The
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.BR vgatest (6)
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produces a list of supported modes for your hardware, prints some info on the modes and
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allows you to try each of them.
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.SH SEE ALSO
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.BR svgalib (7),
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.BR vgagl (7),
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.BR libvga.config (5),
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.BR vgatest (6),
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.BR vga_hasmode (3),
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.BR vga_init (3),
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.BR vga_modeinfo (3),
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.BR vga_getcurrentmode (3),
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.BR vga_getdefaultmode (3),
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.BR vga_lastmodenumber (3),
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.BR vga_getmodename (3),
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.BR vga_getmodenumber (3)
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.SH AUTHOR
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This manual page was edited by Michael Weller <eowmob@exp-math.uni-essen.de>. The
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exact source of the referenced function as well as of the original documentation is
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unknown.
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It is very likely that both are at least to some extent are due to
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Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.
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Occasionally this might be wrong. I hereby
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asked to be excused by the original author and will happily accept any additions or corrections
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to this first version of the svgalib manual.
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