147 lines
3.4 KiB
Racket
147 lines
3.4 KiB
Racket
#lang scribble/doc
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@(require "common.ss")
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@defclass/title[snip-class% object% ()]{
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Useful snip classes are defined by instantiating derived subclasses of
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@scheme[snip-class%]. A class derived from @scheme[snip-class%]
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serves as a kind of ``meta-class'' for snips; each snip is associated
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with an instance of @scheme[snip-class%] as its snip class.
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In deriving a new @scheme[snip-class%] class, override the
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@method[snip-class% read] method. Then, for each instance of the
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derived class (where each instance corresponds to a single snip
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class):
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@itemize[
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@item{Set the classname using @method[snip-class% set-classname].}
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@item{Set the version using
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@method[snip-class% set-version].}
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@item{Install the class into the list returned by
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@scheme[get-the-snip-class-list] using the
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@method[snip-class-list<%> add] method. Note that if the same
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name is inserted into the same class list multiple times, all
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but the first insertion is ignored.}
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]
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See also @|snipclassdiscuss|.
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@defconstructor[()]{
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Creates a (useless) snip class.
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}
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@defmethod[(get-classname)
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string?]{
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Returns the class's name, a string uniquely designating this snip
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class. For example, the standard text snip classname is
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@scheme["wxtext"]. Names beginning with @litchar{wx} are reserved.
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A snip class name should usually have the form @scheme["((lib ...)
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(lib ...))"] to enable on-demand loading of the class. See
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@|snipclassdiscuss| for details.
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}
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@defmethod[(get-version)
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exact-integer?]{
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Returns the version of this snip class. When attempting to load a file
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containing a snip with the same class name but a different version,
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the user is warned.
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}
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@defmethod[(read [f (is-a?/c editor-stream-in%)])
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(or/c (is-a?/c snip%) false/c)]{
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@methspec{
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Reads a snip from a given stream, returning a newly created snip as
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the result or @scheme[#f] if there is an error.
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}
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@methimpl{
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Returns @scheme[#f].
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}}
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@defmethod[(read-header [f (is-a?/c editor-stream-in%)])
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boolean?]{
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@methspec{
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Called to read header information that may be useful for every snip
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read in this class. This method is only called once per editor read
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session, and only if the stream contains header information for this
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class.
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The return value is @scheme[#f] if a read error occurs or anything else
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otherwise.
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See also @method[snip-class% write-header].
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}
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@methimpl{
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Returns @scheme[#t].
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}}
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@defmethod[(reading-version [stream (is-a?/c editor-stream-in%)])
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exact-integer?]{
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Returns the version number specified for this snip class for snips
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currently being read from the given stream.
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}
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@defmethod[(set-classname [name string?])
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void?]{
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Sets the class's name. See also @method[snip-class% get-classname].
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}
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@defmethod[(set-version [v exact-integer?])
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void?]{
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Sets the version of this class. See @method[snip-class% get-version].
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}
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@defmethod[(write-header [stream (is-a?/c editor-stream-out%)])
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boolean?]{
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@methspec{
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Called to write header information that may be useful for every snip
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written for this class. This method is only called once per editor
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write session, and only if the editor contains snips in this class.
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When reading the snips back in, @method[snip-class% read-header] will
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only be called if @method[snip-class% write-header] writes some data
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to the stream.
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The return value is @scheme[#f] if a write error occurs or anything else
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otherwise.
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}
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@methimpl{
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Returns @scheme[#t].
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}}
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}
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