vga_setmode(int mode )
selects 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 exiting 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)
determines 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
SVGALIB_DEFAULT_MODE
environment variable to set the
vga_getdefaultmode (3).
Here are the predefined values for
mode .
TEXT (0)
restores textmode and falls 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.
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. Too 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)
These use linear 256 color memory layouts similar to
G320x200x256 .
G640x480x256 (10),
G800x600x256 (11),
G1024x768x256 (12), and
G1280x1024x256 (13)
These also use 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 light 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)
Memory layout is probably one nibble per pixel, two pixels per byte in a linear fashion where
the most significant nibble is the left most pixel.
G800x600x16 (29),
G1024x768x16 (30), and
G1280x1024x16 (31)
Again check out the ordinary VGA literature for the memory layout.
G720x348x2 (32)
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 eases pixel address calculations on the screen and drawing operations. However, 1/3 more
data has to be moved to the screen. Experiments show that usually the higher memory bandwidth
used outweighs the effects of the simplified algorithms by far.
G320x200x16M32 (33),
G640x480x16M32 (34),
G800x600x16M32 (35),
G1024x768x16M32 (36), and
G1280x1024x16M32 (37)
It should by now be clear how the modes will look.
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.