Section: GGI (7)
: Display on buffer in main memory
display-memory: [-input] [-noblank]
[ [shmid:<sid> ] | [keyfile:<size>:<id>:<fname>] | pointer ]
Emulates a linear framebuffer in main memory. The framebuffer can be a
shared memory segment, an area specified by the application, or an
area allocated by display-memory
If the -input option is set, an input buffer of INPBUFSIZE
(default is 8192 bytes) as #define'd in ggi/display/memory.h is
allocated at the start of the requested memory area.
When running on shared memory, this option enables you to give
input (using giiEventSend(3)) to other processes sharing
that segment. This technique is demonstrated in cube3d(1)
and can be used for things like GGI multiplexers.
If the -noblank option is set, the framebuffer will not be
filled with solid black when the mode of the visual is set. This
is useful for preserving data from other sources when using a
preallocated area of memory as a framebuffer.
This option will provide a physical screen size for applications
which wish to remain resolution independent. sizex,
sizey are the x,y size of the screen in millimeters, unless
the optional dpi string is affixed, in which case, they
represent resolution in dots-per-inch.
This option will provide a non-default pixel format explicitly.
Currently the accepted format of format_string is something
like "r5b5g5p1", which would specify a pixel where the low bit
of the pixel is unused padding, followed by 5 bits of green, then
5 bits of blue and finally 5 bits of red, with the remaining high
bits, if any, being unused pad. A more formal description of this
format string will be provided (and more strings accepted) in
future LibGGI releases.
This option will provide a non-default framebuffer layout
explicitly. The fstride parameter denotes the number of
bytes between frames in the framebuffer, and will default to the
size of the virtual screen in bytes if nonpresent or set to 0.
Following fstride, the string plb denotes a linear
packed-pixel framebuffer, or the string plan instead denotes a
planar framebuffer. The packed-pixel framebuffer layout is the
default. If the string plb is present, a horizontal stride
lstride may appear, denoting the number of bytes that elapse
between the beginning of one line and the next. This will default
to the size of a horizontal line in bytes if nonpresent or set to
zero. If the string "plan" is present, up to two numbers, comma
separated, may appear after the string. The first number,
pstride denotes the number of bytes which elapse between the
beginning of one plane and the next. This will default to the
minimum integral number of bytes that may contain one bitplane of
the virtual screen if nonpresent or set to zero. The second
number, plstride denotes the number of bytes that elapse
between the beginning of one bitplane-line and the next. This
will default to the minimum integral number of bytes which may
contain one bitplane-line of the virtual screen if nonpresent or
set to zero.
More strings and format parameters may accepted in future LibGGI
use existing shared memory ID sid
On win32, sid is the HANDLE returned by a call to
CreateFileMapping in decimal form.
create a new shm segment with id ftok(fname,id) of size
size (preferred method !). See ftok(3).
On win32, the newly created shared memory mapping has the object
name: ggi-display-memory-shm:<fname>:<ascid>, where all
backslashes have been converted to forward slashes in fname
and ascid is the ascii value of id in decimal form.
If this object does already exist (and is a file mapping) it will
be used, so two apps can share memory by using the same
keyfile arguments on win32.
use the memory pointed to by argptr (only available to
applications calling ggiOpen(3)).
If you specify a memory area to use - be sure it's big enough as
no checks can or will be made that a certain mode fits into it.
DirectBuffer support always available.