NAME¶
vga_getmodeinfo - returns pointer to mode information structure for a mode
SYNOPSIS¶
#include <vga.h>
vga_modeinfo *vga_getmodeinfo(int mode );
DESCRIPTION¶
The function returns a pointer to a statical allocated mode information
structure which is filled out with details for a video mode
mode.
#include <vga.h> defines
vga_modeinfo as
typedef struct {
int width;
int height;
int bytesperpixel;
int colors;
int linewidth;
int maxlogicalwidth;
int startaddressrange;
int maxpixels;
int haveblit;
int flags;
/* Extended fields, not always available: */
int chiptype;
int memory;
int linewidth_unit;
char *linear_aperture;
int aperture_size;
void (*set_aperture_page) (int page);
void *extensions;
} vga_modeinfo;
If the given
mode is out of range,
NULL is returned.
Beware, even when
vga_getmodeinfo() returns details about a
certain mode, you must check if it is currently available (may depend on
memory size and other details) with
vga_hasmode (3).
The fields meaning in detail:
Basic mode details¶
- width
- Width of mode in pixels.
- height
- Height of mode in pixel lines.
- bytesperpixel
- Bytes per pixel. This is 1, 2, 3, or 4 (for 256, 32K &
64K, 16M, 16M$ modes) and 0 for planar VGA modes.
- linewidth
- Logical scanline width in bytes. This is the memory offset
between two pixels above each other in two adjacent screen lines. It is
not valid to assume that linewidth == width *
bytesperpixel in general!
- colors
- The number of colors which you can display simultaneously
2, 16, 256, 32768, 65536, or 16777216. Generally 16 and 256 mean that a
color lookup table is used. 2 means that only black/white is used and the
others use some high/true color mode.
Possible modifications of the memory layout¶
- maxlogicalwidth
- The maximum logical scanline width (in bytes) which you can
set for this mode with vga_setlogicalwidth(3) while still expecting
a perfect screen image.
- startaddressrange
- Mask of changeable bits of start address (in pixels). All
bits zero in startaddressrange must also be zero in a call to
vga_setdisplaystart(3) when you want to avoid noisy video
signals.
Memory size¶
- maxpixels
- Maximum number of pixels that will fit in a logical screen
(depends on video memory).
Further, advanced capabilities¶
- haveblit
- Indicates whether the following bitblit functions are
available. It is a logical or of the following predefined values (which
each have only one bit set).
- flags
- Miscellaneous flags. It is a logical or of the following
predefined values (which each have only one bit set).
- HAVE_RWPAGE
- vga_setreadpage(3) and vga_setwritepage(3)
are available in this mode.
- IS_INTERLACED
- Mode is interlaced, which means it will tend to flicker and
the user might be happier if the application chooses another mode.
- IS_MODEX
- Mode user mode X like memory layout (planar 256 colors VGA
mode). See vga_setmodeX(3) for some explanations.
- IS_DYNAMICMODE
- Dynamically loaded mode. This mode was defined in
/etc/vga/libvga.conf by the user. He will probably prefer its
usage. However, usually this should be of no interest to the user.
- CAPABLE_LINEAR
- Mode can be set to linear addressing with
vga_setlinearaddressing(3).
- IS_LINEAR
- Linear addressing is already enabled for this mode.
- EXT_INFO_AVAILABLE
- The extended fields in this information structure are set
to sensible information. If EXT_INFO_AVAILABLE is not set you should even
not access these fields as you might have encountered an old version of
svgalib and the fields migth actually not have been allocated at all.
- RGB_MISORDERED
- For 16M4 modes it means that the 4 bytes per pixel actually
mean 0BGR rather than BGR0 as per default. For 16M mode it means that the
3 bytes actually mean RGB instead of BGR.
The first is a general limitation of Mach32, the latter one of Mach32 with a
ramdac of type 4. The vga_ drawing functions takes this into
account.
- HAVE_EXT_SET
- A vga_ext_set(3) is available and can be
called.
You must check for
EXT_INFO_AVAILABLE in
flags before trying to
access these values.
- chiptype
- the chiptype that was detected/set. This specifies a
subtype of the current vga_getchipset(3) setting whose value
depends on the chipset. It should be only used for debugging or
internally.
- memory
- memory available on the SVGA card in KB.
- linewidth_unit
- use only a multiple of this value for
set_logicalwidth(3) or set_displaystart(3) to ensure
graceful alignment of lines onto the vga memory in this mode and for
noiseless video signals.
- linear_aperture
- ptr to a mmaped secondary linear framebuffer (not related
to the use of vga_setlinearaddressing(3)) (NULL if
unavailable)
- aperture_size
- size of the secondary framebuffer in KB. 0 if
unavailable.
- set_aperture_page
- a function taking an int as parameter to select a page in
the framebuffer addressed by read/writes to this memory arey (if
aperture_size < memory.
- extensions
- pointer to additional, internal, chipset specific info
(contents of the EEPROM for Mach32 driver.)
The
vgatest(6) demo displays most of this info for all supported modes.
SEE ALSO¶
svgalib(7),
vgagl(7),
libvga.config(5),
vgatest(6),
vga_hasmode(3),
vga_init(3),
vga_setmode(3),
vga_getcurrentmode(3),
vga_getdefaultmode(3),
vga_lastmodenumber(3),
vga_getmodename(3),
vga_getmodenumber(3),
vga_setlogicalwidth(3),
vga_bitblt(3),
vga_fillblt(3),
vga_imageblt(3),
vga_hlinelistblt(3),
vga_blitwait(3),
vga_setmodeX(3),
vga_getchipset(3),
vga_ext_set(3),
vga_setlinearaddressing(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 extent are due to Harm
Hanemaayer <H.Hanemaayer@inter.nl.net>.
Occasionally this might be wrong. I hereby asked to be excused by the original
author and will happily accept any additions or corrections to this first
version of the svgalib manual.