
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.

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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.
	twelve 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.
