Pie charts with Lout + separate subject: html2lout improved

[Mark Summerfield]

Pie charts with Lout + separate subject: html2lout improved
(html2lout is covered at the very end)

Pie charts with Lout: are they implementable?

I've got an idea for expressing pie charts with Lout - but I still don't
understand Lout well enough to know how or even if this is possible. The
syntax idea goes like this:

@Pie {
    @Segment 
        size { 20 }  colour { red }    olabel { Tomato } pullout { yes } 
    @Segment 
        size { 70 }  colour { green }  olabel { Kiwi }  
    @Segment 
        size { 220 } colour { yellow } olabel { Banana }
}

size - only the size option would be mandatory and is a number which is 
relative to
the other sizes, i.e. its your data, integer or real any +ve number. 

colour or color - optional, the colour of the segment.

olabel - optional, outer label, appears outside the segment.

ilabel - optional, inner label, appears on the segment.

pullout - optional, default no, but if yes the segment is 'pulled out' of the
pie.

Probably needs other options, e.g. outlinecolour.


A simple algorithm to do this:

# Calculate how many degrees wide each unit size is 
totalsize = 0
foreach Segment
    totalsize += size
sizeangle = 360 / totalsize # In this example 1.161 degrees.

# For the example given the angle of each would be
# 23, 81 and 255 degrees respectively.

# Now draw the arcs
startoffset = 0
foreach Segment
    angle = size * sizeangle
    drawarc( startoffset, angle, colour )
    startoffset += angle


Although I can't write it in Lout (and don't know if its expressible), here's
an example in Perl/Tk. 
The data at the end can be changed, added to or reduced so long as each line 
is in the form:
<size>,<colour>

#!/usr/bin/perl -w

use strict ;
use Tk ;

my @Pie ;
while( <DATA> ) {
    chomp ;
    last unless $_ ;
    my( $size, $colour ) = split /,/ ;
    push @Pie, { -size => $size, -colour => $colour } ;
}

my $Win    = new MainWindow ;
my $Canvas = $Win->Canvas->pack ;
&draw_pie ;
MainLoop ;


sub draw_pie {
    my $totalsize  = 0 ;
    foreach my $ref ( @Pie ) {
        my $size   = $ref->{-size} ;
        $totalsize += $size ;
    }
    my $sizeangle  = 360 / $totalsize ;

    my $offset     = 0 ;
    foreach my $ref ( @Pie ) {
        my $colour = $ref->{-colour} ;
        my $size   = $ref->{-size} ;
        my $angle  = $size * $sizeangle ;
        $Canvas->createArc( 0, 0, 200, 200,
            -fill    => $colour,
            -outline => $colour,
            -start   => $offset + 90,
            -extent  => $angle,
            ) ;
        $offset += $angle ;
        print "$colour * $size * $angle\n" ;
    }
    print "$totalsize $sizeangle $offset\n" ;
}

__DATA__
30,white
70,violet
100,red
15,blue
150,yellow
40,black
120,green


html2lout in xxx2lout-1.00.tar.gz has been uploaded and should 
appear within 24hrs. A link has now been added from the Lout Home Page.

html2lout has been significantly fixed:
* No longer puts @LP's all over the place - this was a bug, now fixed.
* Table handling improved - but still basic and will require hand tweaking.
* List handling improved (mainly due to @LP bugfix).
* New tags supported and some minor fixes implemented.
* Now does full and proper &entity; to address@hidden entity} conversions.
* Provides full control of commented output of handled and unhandled tags.
* For Perl programmers Lout.pm offers txt2lout and htmlentity2lout; and
  HTML::LoutParser now gives proper objects (without the scoping bug I started
  out with:) 

Regards.
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