FormElement

FormData FormDataInfo IsFormElement OwningForm SetFormData

Attributes

Class FormElement defines no new attributes.

Fields

Define Class FormElement;
    mixes in with Object;

    // A form element is an object that looks different on each card, even though it is in the form.
    // An example is a text field. The text and text styles are stored in the card.
    // This per-card data for elements of the form is called "form data".

    operation IsFormElement(): Boolean, noMethod;
        // call to test whether object is capable of being a form element
        // return true for viewables that store form data on each card
        // this allows definition of classes where not all instances use form data
        // the value of this only matters when the object is added to a form
        // override when defining a class that stores data in cards

    intrinsic OwningForm(viewable: Viewable): Form;
        // call to get form that this viewable is an element of;
        // returns nilObject if viewable does not implement FormElement,
        // or if viewable is not a form element, or if viewable has no
        // enclosing form. Otherwise returns enclosing form.

    // getting form data from the form element

    operation FormDataInfo(var objectCount: Unsigned; var nonObjectDataSize: Unsigned), noMethod;
        // called by the card before calling FormData to find out how much data is coming
        // occasionally called elsewhere to check number of stored objects
        // override when defining a class that stores data in cards
        // implementation must handle nil for objectCount and nonObjectDataSize
    operation FormData(objects: ObjectList; nonObjectData: Pointer), noMethod;
        // called by the card to get form data to store in the card
        // objects must be an empty list
        // nonObjectData must a buffer sized based on the result from FormDataInfo
        // override when defining a class that stores data in cards

    // changing the form element based on form data

    operation SetFormData(objects: ObjectList; nonObjectData: ReadOnlyPointer; nonObjectDataSize: Unsigned), noMethod;
        // called by the card to set up the form element from data stored in the card
        // (nilObject, nil, 0) is passed when there was no previous data in the card
        // otherwise, the data is what was returned from a previous FormData call
end class;