Patch: Key position information

[Philipp K. J. <ja...@ie...>]

Gnuplot makes a lot of information about the most
recent plot available through GPVAL variables. It
seems reasonable to include information about the
current position of the key.

I prepared a small patch that populates four new
variables for each plot:
	GPVAL_KEY_XCENTER
	GPVAL_KEY_YCENTER
	GPVAL_KEY_WIDTH
	GPVAL_KEY_HEIGHT

Using the information in these variables, one can
recreate the most recent positioning of the key
as follows:

plot sin(x)
set key center at screen \
GPVAL_KEY_XCENTER/GPVAL_TERM_XSIZE,GPVAL_KEY_YCENTER/GPVAL_TERM_YSIZE
replot

For 3dim graphs, there is an additional wrinkle, 
because splot does only honor the horizontal
(right/center/left) positioning commands, but
always uses "top" for vertical positioning.
Hence, one needs to modify the vertical position:

splot sin(x)*cos(y)
set key center at screen \
GPVAL_KEY_XCENTER/GPVAL_TERM_XSIZE, \
(GPVAL_KEY_YCENTER+GPVAL_KEY_HEIGHT/2)/GPVAL_TERM_YSIZE
replot

The commands given above recreate the last position
of the key. By adding/subtracting appropriate values,
one can achieve any desired offset.

The patch is available here, if you want to check
it out:
	http://www.philipp-janert.com/keypos.patch

Best,

		Ph.