Element: window.scroll { }

Type

callback

Description

The command procedure to be executed when window is scrolled by a user operation on the window’s scrollbars. It is invoked in three cases:

• When the mouse button is released at the end of a scroll operation, known as "new-position".

• When the top (or left) arrow button is pressed while the CONTROL key is depressed, known as "get-previous".

• When the bottom (or right) arrow button is pressed while the CONTROL key is depressed, known as "get-next".

The "get-previous" operation also scrolls to the top (or left) of the window. "get-next" also scrolls to the bottom (or right).

When a scroll procedure is defined for a window and is invoked, three parameters are passed to the procedure:

• 1. The window identifier.

• 2. Which scrollbar was used (a numeric value);

• 0 Indicates horizontal.

• 1 Indicates vertical.

• 3. Which user action invoked the procedure (a numeric value);

• 0 New-position.

• -1 Get-previous.

• 1 Get-next.

The procedure is executed after the scroll operation and thus after any necessary window repaint. A window without scrollbars never invokes this procedure.

New windows have a scroll procedure of null.

Parameters

window.scroll (<window>,<num>,<num>)

Examples

window mywin = wgraphic -wk=<2,2>
mywin.scroll = {
    args w=window, v=numeric, mode=numeric
    tell <'Scroll operation:',w>
    if (v) !Vertical scrollbar
    else !Horizontal scrollbar
    switch mode {
        case -1: !Get previous
        case 1: !Get next
        default: !New position
    }
}

See Also