Fwd: [Patch 1143563] Place arbitrary rectangles in 2D

[Ethan M. <merritt@u.washington.edu>]

[I'm moving discussion to the mailing list] 

Recent SourceForge Patch #1143563

Initial Comment:
Here is a good start at a new plot element with a
number of uses. The basic syntax is

    set rectangle <id> from <position> to <position>
                   {front|back} {rectcolor <colorspec>}
                   {fillstyle <fillstyle>}

The rectcolor and fillstyle are optional for any
particular rectangle; if you don't give them it will
inherit defaults from a general setting controlled by
    set style rectangle {rectcolor <colorspec>}
               {fs <fillstyle>}

The from/to positions specify diagonal corners of the
rectangle. They may of course be screen coords, graph
coords, or plot coords.  

There is a simple demo file in the patchset, and "help
set rect" or "help set style rect" should get you started.

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>Comment By: Petr Mikulik (mikulik)

>Just my few first ideas: 
>set rect ... {noborder | border} {lt | ls ...} 

Those already work. They are part of the generic
<fillstyle> and <rectcolor> syntax.

>What about, rather for a future 
>set shape rect .... 
>set object rect ... 
>if we want hexagons, circles, ...? 

I originally hoped to implement this without using the
pm3d polygon routines, which meant limiting it to rectangles.
But I ended up using pm3d routines heavily so yes, extending
it to other polygons would not be difficult.

It would be easy to modify the syntax to 
	set polygon from <xy0> to <xy1> to <xy2> ...
for an arbitrary number of vertices.  The only real change
needed is to allocate the vertices dynamically rather than
simply reserved space for the 2 corners of a rectangle.

>Could the rectangle be rotated? 

Not using code that's already in place.
What would you expect to happen if you rotate a polygon
whose vertices are specified in screen or graph coordinates?
 
> Could it support not only "from ... to", but also "at ... size" and maybe 
> "{center|left|right}" -- that would to accommodate labels. 

If you limit it to rectangles, then one could have
	set rect at <coords> width <x> height <y> {center}

Something similar would work for regular polygons (square, pentagon, n-gon).
But it's not obvious how to extend this to a general polygon specified 
by its vertices.  

> Are rect drawn before labels? 

They are supposed to be, but I see there's a bug if the setting is "front".

> Could the above-mentioned size be given as "stringwidth"?
> Then we could give "size" in the "character" units. 
 
Very few drivers can pass back enough information to do this in the
core code.
I was thinking instead that a future bit of work could implement

    set label "foo" ... {box|nobox}

That way drivers (PostScript, gd, pdf) with an internal notion of
textbox size could just stroke the textbox after writing the label text.
The enhanced text code *tries* to keep this information in a generic way,
but it does an imperfect job.


-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195