check-box-column-mixin

A non-instantiable class that can be mixed with the grid-column class to create grid columns whose cells act like check-box 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-check-box-column
  (check-box-column-mixin my-subclass-of-grid-column) ...)

The draw-cell method provided by this mixin will call read-cell-value to determine whether to draw the check mark. If read-cell-value returns nil, it will not draw a check mark, and otherwise it will.

When the user clicks the check-box gadget displayed in the cell, the cell-click method provided by this mixin calls write-cell-value with a value of either t or nil so as to change the domain value represented by the cell. Alternately the user may press the spacebar or the enter key to simulate clicking the check-box.

The title-reader property of the column should be used to determine the string to display in each check-box cell. The click-must-be-on-gadget property may be used to determine where the user must click within the cell to activate the cell's gadget.

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 8.1 page.
Created 2010.1.21.