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<HEAD>
<TITLE> Macro/Shell Extensions </TITLE>
</HEAD>
<BODY>
<A NAME="Rangesets"></A>
<H2> Rangesets </H2>
<P>
Rangesets are a tool of the macro language to tag parts, or ranges, of the
text, which shall be viewed as a group. A range is merely a contiguous range
of characters between a start and an end position in the document, and a set
of ranges belonging together is called a rangeset. So, a rangeset is nothing
but an in general non-contiguous part of the text.
</P><P>
Rangesets can be assigned a background color to make them visible: characters
within all ranges of a rangeset will have the background color of the
rangeset. (If more than one rangeset includes a given character, its
background color will be that of the most recently created rangeset which has
a color defined.)
</P><P>
Applications of rangesets are for example:
</P><P>
<UL>
<li>Showing differences between two versions of a file. Then, one rangeset would be those parts of the current file that are not in the prior version.</li>
<li>Highlighting all occurrences of a particular pattern, e.g. showing all the strings 'foobar' in the file.</li>
<li>Highlighting spelling mistakes found by a spell-checker.</li>
</UL>
</P><P>
Rangesets are manipulated only through macro routines. Rangesets must be
created first using the rangeset_create() function, which will return an
identifier for the newly-created (empty) rangeset. This identifier is then
passed to the other rangeset functions to manipulate the rangeset. For
example, ranges are added to a rangeset with the rangeset_add() function.
</P><P>
Notice that the ranges inside a rangeset do not have a particular identity.
Only, they are given a (dynamically changing) numeric index, counting from 1,
in the order of appearance in the text buffer. The ranges are adjusted when
modifications are made to the text buffer: they shift around when characters
are added or deleted staying with the original strings of characters.
However, ranges within a set will coalesce if the characters between them are
removed, or a new range is added to the set which bridges or overlaps
others. For more on this, see "How rangesets change with modifications".
</P><P>
There is a limit to the number of rangesets which can exist at any time -
currently up to 63 in each document. Care should be taken to destroy any
rangesets which are no longer needed, by using the rangeset_destroy()
function, if this limit is attained.
</P><P>
Rangesets can be named: this is useful for macros which need a fixed
identification for rangesets which are used for the same purpose in different
documents. Although a new rangeset's number is arbitrary, its name can be
fixed. This is done using the rangeset_set_name() function. Note that
rangeset names within a particular document may not be unique. For this
reason, the rangeset_get_by_name() function returns an array of identifiers,
which will be empty if the name has not been associated with a rangeset.
</P><P>
<H4>How rangesets change with modifications</H4>
</P><P>
When changes are made to the document text, ranges within each set are altered
with it, according to their behavioral mode. If changes are made outside of
the ranges in a rangeset, each range simply maintains its size and adjusts its
position to match the changes. When text within a range is deleted, the
range's length is reduced by the same amount. When changes involving new text
are made within a range of the set, or to one of the extremities of a range,
different behaviours may be desirable. The rangeset_set_mode() function allows
these modes to be chosen.
</P><P>
Note that the precise behaviour of these modes may change in future versions
of NEdit.
</P><P>
The available modes are:
</P><P>
<B>maintain</B> or <B>ins_del</B> -
Both these modes have the same behaviour. New text added at the front of a
range in a set is not added to the range; new text added within the range or
at the end extends the range. Replacement overlapping an extremity of the
set acts as if the new text were added first, then the old text deleted.
This causes curtailment at the front of the range, extension at the end.
Replacement of the full text of the range removes the range from the set.
The default behaviour for a newly created rangeset is <B>maintain</B>.
</P><P>
<B>del_ins</B> -
New text added at the front or end of a range in a set is not added to the
range; new text added within the range extends the range. Replacement
overlapping an extremity of the set acts as if the old text were deleted
first, then the new text added. This causes curtailment at either end.
Replacement of the full text of the range removes the range from the set.
</P><P>
<B>include</B> -
New text added at the front or end of a range in a set extends the range, as
does new text added within the range. Replacement overlapping an extremity
of the set acts as if the new text were added first, then the old text
deleted. This causes curtailment at the front of the range, extension at
the end. Replacement of the full text of the range adds the new text to the
range if the start position of the replacement is at the range's start
point.
</P><P>
<B>exclude</B> -
New text added at the front or end of a range in a set does not extend the
range; new text added within the range extends the range. Replacement
overlapping an extremity causes curtailment of the range. Replacement of
the full text of the range removes the range from the set.
</P><P>
<B>break</B> -
New text added at the front or end of a range in a set does not extend the
range; new text added within the range will split the range. Replacement
overlapping an extremity causes curtailment of the range. Replacement of
the full text of the range removes the range from the set.
</P><P>
<H4>Notes</H4>
</P><P>
A rangeset is manipulated <I>only</I> through macro routines. Rangesets
can easily become very large, and may exceed the capacity of the running
process. Coloring relies on proper color names or specifications (such as
the "#rrggbb" hexadecimal digit strings), and appropriate hardware support. If
an invalid color name is given, the default background color is used instead.
Behaviours set using rangeset_set_mode() are subject to change in future
versions.
</P><P>
<H3>Rangeset read-only variables</H3>
</P><P>
<PRE>
<B>$rangeset_list</B>
</PRE>
array of active rangeset identifiers, with integer keys starting at 0,
in the order the rangesets were defined.
</P><P>
<H3>Rangeset functions</H3>
</P><P>
<PRE>
<B>rangeset_create()</B>
<B>rangeset_create( n )</B>
</PRE>
Creates one or more new rangesets. The first form creates a single range
set and returns its identifier; if there are no rangesets available it
returns 0. The second form creates n new rangesets, and returns an array
of the rangeset identifiers with keys beginning at 0. If the requested
number of rangesets is not available it returns an empty array.
</P><P>
<PRE>
<B>rangeset_destroy( r )</B>
<B>rangeset_destroy( array )</B>
</PRE>
Deletes all information about a rangeset or a number of rangesets. The
first form destroys the rangeset identified by r. The second form should
be passed an array of rangeset identifiers with keys beginning at 0 (i.e.
the same form of array returned by rangeset_create(n); it destroys all the
rangesets appearing in the array. If any of the rangesets do not exist,
the function continues without errors. Does not return a value.
</P><P>
<PRE>
<B>rangeset_add( r )</B>
<B>rangeset_add( r, start, end )</B>
<B>rangeset_add( r, r0 )</B>
</PRE>
Adds to the rangeset r. The first form adds the range identified by the
current primary selection to the rangeset, unless the selection is
rectangular. The second form adds the range defined by the start and end
positions given. The third form adds all ranges in the rangeset r0 to the
rangeset r, and returns 0.
</P><P>
Returns the index of the newly-added range within the rangeset.
</P><P>
<PRE>
<B>rangeset_subtract( r, [start, end] )</B>
<B>rangeset_subtract( r, r0 )</B>
</PRE>
Removes from the rangeset r. The first form removes the range identified by
the current primary selection from the rangeset, unless start and end are
defined, in which case the range they define is removed. The second form
removes all ranges in the rangeset r0 from the rangeset r. Does not return
a value.
</P><P>
<PRE>
<B>rangeset_invert( r )</B>
</PRE>
Changes the rangeset r so that it contains all ranges not in r. Does not
return a value.
</P><P>
<PRE>
<B>rangeset_get_by_name( name )</B>
</PRE>
Returns an array of active rangeset identifiers, with integer keys starting at 0,
whose name matches name.
</P><P>
<PRE>
<B>rangeset_info( r )</B>
</PRE>
Returns an array containing information about the rangeset r. The array
has the following keys: <B>defined</B> (whether a rangeset with identifier
r is defined), <B>count</B> (the number of ranges in the rangeset), <B>color</B>
(the current background color of the rangeset, an empty string if the
rangeset has no color), <B>name</B> (the user supplied name of the rangeset,
an empty string if the rangeset has no name), and <B>mode</B> (the name of the
modify-response mode of the rangeset).
</P><P>
<PRE>
<B>rangeset_range( r, [index] )</B>
</PRE>
Returns details of a specific range in the rangeset r. The range is
specified by index, which should be between 1 and n (inclusive), where
n is the number of ranges in the rangeset. The return value is an array
containing the keys <B>start</B> (the start position of the range) and <B>end</B>
(the end position of the range). If index is not supplied, the region
returned is the span of the entire rangeset (the region starting at the
start of the first range and ending at the end of the last). If index
is outside the correct range of values, the function returns an empty array.
</P><P>
<PRE>
<B>rangeset_includes( r, pos )</B>
</PRE>
Returns the index of the range in rangeset r which includes pos; returns
0 if pos is not contained in any of the ranges of r. This can also be used
as a simple true/false function which returns true if pos is contained in
the rangeset.
</P><P>
<PRE>
<B>rangeset_set_color( r, color )</B>
</PRE>
Attempts to apply the color as a background color to the ranges of r. If
color is at empty string, removes the coloring of r. No check is made
regarding the validity of color: if the color is invalid (a bad name,
or not supported by the hardware) this has unpredictable effects.
</P><P>
<PRE>
<B>rangeset_set_name( r, name )</B>
</PRE>
Apply the name to the rangeset r.
</P><P>
<PRE>
<B>rangeset_set_mode( r, type )</B>
</PRE>
Changes the behaviour of the rangeset r when modifications to the text
buffer occur. type can be one of the following: "maintain" (the default),
"break", "include", "exclude", "ins_del" or "del_ins". (These modes are
described above.)
</P><P>
</P>
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