editable-text-column-mixin

A non-instantiable class that can be mixed with the grid-column class to create grid columns whose cells act like multi-line-editable-text controls. Each cell in the column will implement the pseudo-control if the row of that cell is an instance of a grid-row subclass that mixes in the widget-row-mixin class.

To ensure that this mixin class' methods take precedence over other methods that specialize on grid-column, this mixin class generally should appear first in a defclass expression's list of superclasses, as in:

(defclass my-editable-text-column
  (editable-text-column-mixin my-subclass-of-grid-column) ...)

The edit-start-trigger and edit-end-trigger properties of the column may be used to determine what gesture the user must make to initiate and complete the typing-in of a new value for the cell. The user may press either the spacebar or the enter key to emulate clicking on a cell in this column, and so that will initiate type-in in the same cases that clicking will. This type of column may also be given a template-string to restrict what the user may enter. The scrollbars property determines whether a vertical scrollbar will appear during editing; when true (the default) a scrollbar will appear, and when nil it will not appear (to save space in the cell).

When the user initiates type-in according to the edit-start-trigger property, the user is allowed to edit the string displayed in the cell. The user may then either press the escape key to cancel the edit, or accept the edit by pressing the enter key or by moving the keyboard focus out of the cell. If the edit is accepted and the text has changed, then the column's data-write-converter function is called to convert the typed string to a meaningful data object, which is then written by calling write-cell-value.

The read-cell-value method supplied by this mixin calls the column's data-read-converter to convert the actual domain data value represented by this cell into a string to be drawn in the cell. This string is also the initial string to be edited when the user initiates type-in.

See the section Built-In Grid Cell Widgets on the page for the grid-widget class for an overview of the grid column mixins.

A quicker but less object-oriented alternative to using the widget-column-mixin classes is to write cell-widget methods.

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This page was not revised from the 8.2 page.
Created 2012.5.30.