Again: canvas size

[Harald H. <h.h...@tu...>]

In the last days, I have thought about the canvas size discussion we had
in this mailing list.

At the moment, there are two different possibilities to change
the canvas size (partly depending on the terminal):

- Use 'set size xcan,ycan' before using 'set terminal'.
  This leads to screen coordinates 0,0 in the lower left corner and
  xcan,ycan in the upper right corner.

- Use 'set terminal <term> size xterm,yterm'.
  This leads to screen coordinates 0,0 in the lower left corner and
  1,1 in the upper right corner.

In my opinion, both possibilities are necessary.

Of course, it is a good thing to specify the canvas size in
terminal-dependent, absolute values, using 'set terminal <term> size'. And
in many cases, it is good to reach a canvas that has the screen
coordinates 0,0 and 1,1 for the lower left and upper right corner,
respectively.

But there are also cases, where a screen coordinate unequal to 1,1 for the
upper right corner is useful:
Say, you want to have many plots in one document with identical size. If
one of these plots is a multiplot, it is useful to have a canvas with
maximal screen coordinates 1,2.

I propose following structure:

- The canvas size is defined exclusively by the 'set terminal' commands,
  e.g., 'set terminal png size 640,480' or 'set term post size 6in,4in'.
- Inside the bounds of the canvas, the screen coordinate system can be set
  by another command, e.g.,
  'set screen-coordinate min <xmin>,<ymin> max <xmax>,<ymax>'
  where defaults are xmin=0, ymin=0, xmax=1, ymax=1.
  This command does not change the canvas size, e.g., Bounding Box (in
  contrast to the current 'set size' command before 'set terminal').

In the case mentioned above, you could use for a single plot:

set screen-coordinate max 1,1
set terminal postscript size 5in,3in

And for a multiplot, you can use

set screen-coordinate max 1,2
set terminal postscript size 5in,6in

This would lead to identical absolute screen coordinate lengths in both
cases.

What do you think of this structure?

Best regards
Harald

-- 
Harald Harders
h.h...@tu...
http://www.harald-harders.de