| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
A non-instantiable superclass of the instantiable window classes
non-refreshing-window
, bitmap-window
, and
text-edit-window
.
When a frame-with-single-child
subclass is
instantiated by calling make-window, the frame window that
is created directly serves only as a frame (consisting of a title-bar
and/or a border), and a second window is created automatically as
child pane that serves as the interior drawing area.
A frame-with-single-child
window is
most useful when a toolbar or status-bar is to be added to the window,
especially if the window has scrollbars. The reason is that these
auxilliary windows are created as siblings of the automatically-added
child pane, and the scrollbars (if any) are created on the child pane
rather than on the frame. This arrangement allows the application to
draw in the entire page-box of the child pane without
any of the drawing being covered by the toolbar or status-bar, and
allows the drawing to scroll without scrolling the toolbar or
status-bar along with it.
This double-window arrangement is also needed for a text-edit-window
, because a text-edit-pane
is
actually a control internally and cannot have a frame itself. (For
other window classes, frame attributes may be added even when the
class excludes them by default for typical usage as a frameless pane.)
A default-pane-class method that
specializes on the frame-with-single-child
class
determines what class is instantiated to make the child pane. When
subclassing a frame-with-single-child
class for
use in an application, it is typically necessary to subclass both the
frame class and the pane class, and then to define a trivial default-pane-class method
to associate the two with each other. Several of the examples in the
Examples tab of the Navigator dialog, including the
"Custom Windows" example at the top of the list, illustrate this
common technique.
The function frame-child returns the child pane
that was automatically added to a frame-with-single-child
window.
The function owner, as usual, will return the
frame window from the pane.
Note that any drawing that is done must be done on the pane window rather than on the frame window, because the frame's interior is covered by the pane. Until version 6.0, Common Graphics would automatically divert drawing to the pane window, but this is no longer done because it was deemed more confusing than useful. Various other functions must be called on the pane itself when it is the true object of interest, even though the two windows are conceptually a single window.
The frame-child
pane window resizes itself as needed whenever the frame window (or its
interior) is resized by always setting its right-attachment property to
:right
and its bottom-attachment to
:bottom
. Applications may use this techique for
custom child panes that do not use the built-in frame-with-single-child
facility.
This may be necessary, for example, if multiple child panes are
desired or a single child pane is desired that does not fill the frame
window's interior.
A diagram of window and widget classes is shown in Widget and window classes in cgide.htm.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |