;;; pie.skb  --  Pie charts.
;;; -*- coding: iso-8859-1 -*-
;;;
;;; Copyright 2006, 2009  Ludovic Courtès <ludovic.courtes@laas.fr>
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;;; FIXME: This is a stub and must be completed!

(chapter :title [Pie Charts] :ident "pie-charts"

   (p [Skribilo contains a pie-chart formatting package, located in the
,(tt [(skribilo package pie)]) module.  It allows users to produces
represent numeric data as pie charts as in the following example:]

	(disp (pie :title [Use of Document Formatting Systems]
	           :fingers? #t :labels 'outside
	           :initial-angle 90
	           :ident "pie-skribilo-rulez"
                 (slice :weight 10 :color "red" :detach? #t
                   (bold [Skribilo]))
                 (slice :weight  6 :color "green"     "Skribe")
                 (slice :weight  6 :color "blue"      "Lout")
                 (slice :weight  4 :color "lightgrey" "LaTeX")
                 (slice :weight  2 :color "yellow"    "Docbook")
                 (slice :weight  1 :color "black"     "others"))))

   (p [A default implementation, which uses ,(ref :text [Ploticus] :url
"http://ploticus.sf.net") as an external program, is available for all
engines.  There is also a specific implementation for the Lout engine
which relies on Lout's own pie-chart package.  In the latter case, you
don't need to have Ploticus installed, but you need it in the former.])
   (p [Currently it only supports slice-coloring, but support for
textures (particularly useful for black & white printouts) could be
added in the future.])
   
   (section :title [Syntax]
            :info-node [Pie Syntax]
      
      (p [Let us start with a simple example:]
	
	(example-produce
	  (example :legend "Example of a pie chart"
	     (prgm :file "src/pie1.skb"))
	  (disp (include "src/pie1.skb"))))
      
      (p [This illustrates the three markups provided by the ,(tt [pie])
package, namely ,(tt [pie]), ,(tt [slice]), and ,(tt [sliceweight]).
This last markup returns the weight of the slice it is used in, be it as
a percentage or an absolute value.  Note that the ,(tt [:total]) option
of ,(tt [pie]) can be used to create pie charts no entirely filled.])
      (p [Various options allow the pie layout to be controlled:]
	
	(example-produce
	  (example :legend "Specifying the layout of a pie chart"
	     (prgm :file "src/pie2.skb"))
	  (disp (include "src/pie2.skb"))))
   
      (p [The available markups and their options are described below.])
      
      (doc-markup 'pie
      		  `((:title         ,[The title of the pie chart.])
		    (:initial-angle ,[The initial angle of the pie, in degrees.])
		    (:total         ,[If a number, specifies the
"weight" of the whole pie; in this case, if the pie's slices don't add
up to that number, then part of the pie is shown as empty.  If ,(code
[#f]), the total that is used is the sum of the weight of each slice.])
                    (:radius        ,[The pie's radius.  How this value
is interpreted depends on the engine used.])
                    (:fingers?      ,[Indicates whether to add "fingers"
(arrows) from labels to slices when labels are outside of slices.])
	            (:labels        ,[A symbol indicating where slice
labels are rendered: ,(code [outside]) to have them appear outside of
the pie, ,(code [inside]) to have them appear inside the pie, and ,(code
[legend]) to have them appear in a separate legend.]))
	           :source "skribilo/package/pie.scm"
		   :see-also '(slice))
      
      (doc-markup 'slice
      		  `((#!rest label ,[The label of the node.  It can
contain arbitrary markup, notably instances of ,(markup-ref
"sliceweight").  However, some engines, such as the Ploticus-based
rendering, are not able to render markup other than ,(markup-ref
"sliceweight"); consequently, they render the label as though it were
markup-free.])
		    (:weight      ,[An integer indicating the weight of this
slice.])
	            (:color       ,[The background color of the slice.])
		    (:detach?     ,[Indicates whether the slice should be
detached from the pie.]))
	           :source "skribilo/package/pie.scm"
		   :see-also '(pie sliceweight))
      
      (p [As seen in the examples above, the body of a ,(markup-ref
"slice") markup can contain instances of ,(markup-ref "sliceweight") to
represent the weight of the slice:])
      
      (doc-markup 'sliceweight
            	  `((:percentage? ,[Indicates whether the slice's weight
should be shown as a percentage of the total pie weight or as a raw
weight.]))
	           :see-also '(slice)
		   :source "skribilo/package/pie.scm")))
      

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