| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
The class of a hotspot object. Hotspots are invisible regions on a window that can receive and respond to mouse events just as actual windows do. They can be used to overlay images drawn on a window in order to make the images behave as graphical objects without using a separate child window that would obscure overlapping images on the main window.
The mouse-in,
mouse-out, and
various mouse click methods such as mouse-left-down are invoked for
hotspot instances just as it is for windows. If you define mouse click
methods for hotspots, the methods should return nil
if you want the click to be further processed by
the hotspot's parent window, or non-nil
to
prevent further processing of the click by the window.
basic-pane
(or one of its subclasses) that has
hotspot-mixin
as another
superclass. (It is best to specify hotspot-mixin
as the first superclass, so that
its methods will take precedence over those of the parent window
class.) Instances of this window class may contain hotspots. For
example: (defclass my-hotspot-window (hotspot-mixin
frame-window)())
hotspot
class so that you can specialize methods
for your hotspots only.
hotspot
that call highlight-hotspot, so do not override these
methods unless you want to bypass highlight-hotspot.)
hotspot-mixin
subclass. Create hotspot
instances by calling make-instance on your hotspot subclass, and add
the instances to the window by calling add-hotspot.
A hotspot's highlight-style
may optionally be set to :invert
or
:outline
to make the hotspot highlight itself
whenever the mouse is inside its hotspot-region. If these two built-in highlight
styles are not adequate, you can override the default highlight-hotspot method to highlight
the hotspot however you like.
Other than highlighting themselves when under the mouse cursor, hotspots do not draw anything on their parent window. Typically a hotspot covers the same region where something is drawn, allowing the user to click on that thing. But since an application could draw any sort of graphic where the hotspot lies, the hotspot does not attempt to do this drawing itself; instead, the window's redisplay-window method should draw the "real" object that the hotspot is making active. For a polygon hotspot, for example, the redisplay-window method could pass the same vector of positions to draw-polygon to draw the "real" polygon as the corresponding hotspot uses to define its hotspot-region.
Here are some other properties that hotspots can be given, either by
passing the keyword initarg such as :name
to
make-instance, or by calling
the setf function such as
(setf name) any
time later.
The function hotspots returns a list of all of the hotspots that are currently on a window, and current-hotspot returns the one that is currently under the mouse, if any. Calling parent on a hotspot returns the window that it is on, if any.
The IDE's Navigator Dialog includes a complete example of using hotspots. Look for Hotspots: mouse-active highlighting regions.
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 |