dropping-outline

Class

The class of the dropping-outline control. This is a special subclass of outline that can drop the outline itself down from a single-line widget that simply displays the current value, similar to a drop-down list widget or combo-box.

A dropping outline does not change its selection when its pixmaps are clicked to expand or collapse items. This feature allows users to expand or condense the outline hierarchy without making a selection, since making a selection un-drops the outline.

Control

An instance of the dropping-outline class. This control is similar to a combo-box, only when you open it, you expose an outline rather than a list. It is a special subclass of the outline class.

Users can only see one outline item at a time in the dropping-outline display, but when the down-arrow portion of the control is clicked the outline will drop (open up) to the size you define when sizing the control. Note that the outline may be clipped by the boundaries of the dialog containing the dropping-outline control. Whether of not it is clipped is controlled by the top-level-dropper property. (The default value for top-level-dropper changed in release 7.0 from nil to t.)

Once dropped, arrow keys can be used to navigate in the outline.

Adding a dropping-outline control to your form

Click the dropping-outline tool on of the Component toolbar. Move the mouse cursor to the part of the form where you want to place the control, and click again. The control will appear with colored resizing handles.

Resizing and moving the control

Controls can only be resized and moved on forms during the design stage; the size and location of everything is fixed on a running form.

Resize the control by clicking the mouse cursor and dragging one of the handles to the new size-point. Release the mouse key when you are satisfied with the new size.

Resizing this control horizontally changes the size of the un-dropped form of the control.

Resizing the control vertically defines the full size of the window displaying the dropped version of the control. If you need a taller window to display the dropped-outline items in a running form, go back to the layout and resize the control vertically.

Resizing the dropping-outline won't mean proportional changes in the size of the characters inside the list. Change the font property if you want to change the size of the actual characters displayed.

Move the control by clicking anywhere on it except a resizing handle and dragging it to a new location on the form. Release the mouse key when you are ready to place the control.

Creating an instance of a dropping-outline control

See the example form creating an outline widget in the description of the outline class. Replace the first five lines with

(make-window 'dropping-outline-dialog  ;; new name for window
  :class 'dialog
  :interior (make-box-relative 100 200 240 140)
  :dialog-items
  (list (make-instance 'dropping-outline  ;; instead of 'outline
  ...
  )))

The example will now create a dropping outline rather than an outline.

See About how to get sample code for creating controls in cgide.htm, which explains how to use the IDE to create such code.

A diagram of window and widget classes is shown in Widget and window classes in cgide.htm.

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This page was not revised from the 10.0 page.
Created 2019.8.20.