Hello;
I have always wanted to see a good framework to port certain graphic
libraries from the PC world to unix and GGI seems to be that framework.
There are several interesting libraries out there; jlib, gfx, the EMX
SVGA library..however the most interesting toolkit is probably Vogle.
Vogle is also the base for vogl, an implementation similar to the IrisGL
API (yes, I know MesaGGI exists :-).
ftp://gondwana.ecr.mu.oz.au/pub/
The port is probably trivial for someone that knows GGI well;
unfortunately I don't. Check out the attached file for the driver
requirements, it should be really easy if a kind soul wants to help out.
cheers,
Pedro.
This directory contains the general device drivers and their makefiles
The directory ibmpc contains the files specific to ibm pc's, see the pc
makefiles in the src directory for more details on these.
-------------------------------------------------------------------------
The Structure of a Device Driver.
Vogle device entries are structured as follows:
three character pointers giving:
the name of the device,
the name for the small hardware font,
and the name for the large hardware font.
seventeen function pointers giving the functionality of the device.
If a device is not capable of some things (eg. colour
changing) a no-op function should be provided which
has a return value of -1.
A function must also be specified in the device driver which copies
the device entry into the global device entry vdevice.dev. This
function call should be included conditionally in the file drivers.c,
as should the device name in the code printing the list of available
devices - also found in drivers.c.
The twelve functions required for a complete device driver are:
DEV_char
a routine which prints a character of hardware text. This routine must
doing any neccessary moving to make sure the current drawing position
on the device is correct, and it must leave the device in graphics
mode.
DEV_clear
a routine which clears the "screen" to the current background colour.
DEV_color
a routine to change the current color on the device. The default
colors are in the man page in the docs directory.
DEV_draw
a routine which draws from the current device position to a point (x, y)
in vogle device coords - note these assume that (0, 0) is the bottom
left hand corner. This routine must doing any neccessary moving to make
sure the current drawing position on the device is correct.
DEV_exit
a routine which does the necessary cleaning up to allow vogle to exit
leaving the device in a usable form.
DEV_fill
a routine for doing filled polygons, devices which do not support this
should just do an outline.
DEV_font
a routine which sets up a hardware font. This should also set
vdevice.hwidth and vdevice.hheight, which are the width and height
of the current hardware font in pixels. VOGLE assumes that hardware
text is of a fixed width.
DEV_getkey
a routine which gets a single character of input from a device capable
of providing it.
DEV_init
a routine which enables graphics on the device, sets the default
colour map, and sets vdevice.maxS{x,y} and vdevice.minS{x,y} to the
window size in pixels.
DEV_locator
a routine finds the mouse position for the device in vogle device
coordinates (returned in the arguments) and returns a bit pattern
giving which buttons were down at the time of the call.
DEV_mapcolor
a routine for changing a colormap index to a given rgb value.
DEV_string
a routine for printing a string of hardware text. This routine must
doing any neccessary moving to make sure the current drawing position
on the device is correct, and it must leave the device in graphics
mode.
DEV_backbuf
a routine to initialise double buffering by selecting the back
drawing buffer and performing any other initialisations. If there
are any hassles with all this then it should return -1.
Lot's of this double buffering isn't really double buffering at
all. It's kind of a pseudo double buffering in that drawing is
done off screen and copied to the screen when needed.
DEV_frontbuf
a routine to switch drawing into the front drawing buffer
DEV_swapbuf
a routine to make the back buffer visible and notionally switch
the roles of the front and back drawing buffers.
DEV_sync
a routine to syncronize the display with what we think has been
output. This function can be noop. It is used with drivers such
as X11 which don't necesarily display things as soon as a call
has been made to a drawing routine. Because of buffering withing
the system, a considerable speed up may be obtained by only syncing
the display when necesary. Cases in point are:
When drawing objects
When drawing arcs
When drawing Splines and patches
where the whole lot can be "sent down the line" with a single "sync"
at the end.
