9.23  snip%

A direct instance of snip% is uninteresting. Useful snips are defined by instantiating derived subclasses, but this class defines the basic functionality.

In deriving a new snip class, these methods must be overridden to create a useful snip:

• get-extent

• draw

• resize if the snip can be resized by the user

• partial-offset if the snip can contain more than one item

• split if the snip can contain more than one item

• size-cache-invalid if the snip caches the result to get-extent

• get-text (not required)

• find-scroll-step, get-num-scroll-steps, and get-scroll-step-offset if the snip can contain more than one scroll position

• set-unmodified if the snip's internal state can be modified by the user, and call modified in the snip's administrator when the state changes the first time

If a snip can contain more than one item, then the snip's count must be maintained as well.

To define a class of snips that can be saved or cut-and-pasted:

• Create an instance of snip-class%, implementing the read method.

• For each instance of the snip class, set the snip's class object with set-snipclass.

• Override the copy method.

• Override the write method.

To define a class of snips that read specially with open-input-text-editor:

• Make your snip% class implement readable-snip<%>.

• Implement the read-special method.

• (make-object snip%) -> snip% object

  Creates a plain snip of length 1 with the "Basic" style of the-style-list.

  
  

Methods
    adjust-cursor
    blink-caret
    can-do-edit-operation? (augmentable only)
    copy
    do-edit-operation
    draw
    find-scroll-step
    get-admin
    get-count
    get-extent
    get-flags
    get-num-scroll-steps
    get-scroll-step-offset
    get-snipclass
    get-style
    get-text
    get-text!
    is-owned?
    match?
    merge-with
    next
    on-char
    on-event
    own-caret
    partial-offset
    previous
    release-from-owner
    resize
    set-admin
    set-count
    set-flags
    set-snipclass
    set-style
    set-unmodified
    size-cache-invalid
    split
    write