Interactor - base class for interactive objects
In 2.6, Interactor was the base class for all interactive objects. It is currently provided for backward compatibility.
Every interactor has a shape member variable that defines the desired characteristics of screen space in terms of size, shrinkability, and
stretchability. This information is used to allocate display space for the interactor and the interactor's canvas member variable is set
to the actual space obtained. The lower left corner of the canvas is addressed by (0, 0); the upper right by the member variables
The input member variable is the normal sensor for reading events. The output member variable is the standard painter for performing
graphics operations. Interactors generally should not set output; it will either be inherited (and shared) from the interactor's parent or
set by user customization attributes.
An interactor may optionally define the perspective member variable to represent the portion of total area that the interactor is display-
ing. Perspectives allow interactors to coordinate with other interactors, such as scrollers, that want to control the display area.
An interactor also may specify certain characteristics of the interactor's canvas, such as whether it is read-only or read/write, whether
its contents should be saved when not visible. Interactors also may specify the visual format and interpretation of the input pointing
device (e.g., mouse cursor) when it is inside the interactor's canvas.
To be mapped to some portion of the display, an interactor must have been inserted into a scene, called its parent. The interactor will be
mapped when its parent is mapped. The root scene for the display can be accessed through a World(3I) object.
Construct an interactor. The input sensor and output painters are initialized to nil.
Interactor(const char* name)
Construct an interactor associated with the string name. The string is used to customize the behavior of the interactor according
to user preferences. Behavior can also be customized on a per-class basis using the subclass name. Although not explicitly docu-
mented, an instance of any object inheriting from interactor may be constructed with an additional argument (appearing first) con-
taining the string name. For example, both ``HGlue(natural, stretch)'' and ``HGlue("somename", natural, stretch)'' are valid.
The base destructor automatically deletes the base fields, including shape, canvas, input, and output.
void Align(Alignment, int w, int h, Coord& l, Coord& b)
Return the coordinates at which an object with the given width and height will have the given alignment within the interactor's can-
void SetClassName(const char*)
const char* GetClassName()
void SetInstance(const char*)
const char* GetInstance()
Set/get the class or instance name for an interactor. The names are used to determine user style preferences. SetClassName and
SetInstance can only be performed by subclasses.
void Config(Scene* s)
Configure this interactor and its descendants according to user preferences. The scene s is assumed to be the interactor's parent
and is used to inherit attribute values. This operation need not be called explicitly; it is called automatically when the ances-
tors of an interactor become known (e.g., when the interactor or an ancestor is inserted into a world).
Configuration involves a traversal of the interactor hierarchy. For each interactor in the hierarchy, the output painter is either inher-
ited from its parent or copied from its parent if there are user preferences specific to the interactor for painter attributes such as col-
ors, font, and brush. For example, suppose the user preference is ``A*B*font:9x15'' and the interactor hierarchy is ``A.B.C.D'' (each
``.'' representing a nesting level in the hierarchy). Interactors A and B will share the same output painter, C will copy B's output and
change the font to ``9x15'', and D will share C's output.
After assigning the output painter, configuration is performed recursively on any children interactors. The final step at each node in the
traversal is to call the virtual Reconfig operation.
virtual void Reconfig()
Perform any configuration specific to a particular interactor. This operation should minimally compute the interactor's shape based
on the shape of its children and/or the characteristics of its output painter (e.g., font). It can also retrieve user preferences
specific to this interactor's class or instance name using GetAttribute.
const char* GetAttribute(const char*)
Retrieve the value of a user preference with the given name. GetAttribute searches for the most specific match to the current con-
virtual void Reshape(Shape&)
Set/get the shape of an interactor. Reshape is a a suggestion that an interactor's shape should change to the given one. The
default operation sets the interactor's shape to the new shape and calls Scene::Change on the interactor's parent. Suggested shape
information may be lost when an interactor is configured; thus, it is best to avoid use of Reshape. The same affect can usually be
achieved by putting the interactor in a box along with a particular shape of glue.
Set/get the cursor that will be displayed when the pointing device is inside the interactor's canvas. If the interactor does not
explicitly set its cursor, it will use its parent's cursor. GetCursor returns nil in this case.
Return the interactor's parent or nil if the interactor has not been inserted into a scene.
Return a pointer to the world the interactor has been inserted into or nil if the interactor's root ancestor is not mapped.
void GetRelative(Coord& x, Coord& y, Interactor* = nil)
Map coordinates that are relative to this interactor's canvas to be relative to another interactor's canvas. If the other interac-
tor is nil, then the coordinates are made relative to the world.
virtual void GetComponents(Interactor**, int, Interactor**&, int&)
Construct an array of pointers to the interactors contained within this interactor. The first and second parameters specify an
array of interactors that is already allocated. This array is used if it is large enough, otherwise a new array is allocated from
free store. The third and fourth parameters return the which array was used and the actual number of components. This operation is
only defined by scenes; the default operation sets the number of elements to zero.
Canvas* GetCanvas() const
Return the interactor's canvas, which may be nil if the interactor is not mapped to a display.
ManagedWindow* GetTopLevelWindow() const
Return the top-level window associated with the interactor, if it is mapped and top-level.
virtual void Draw()
Draw is used to display the contents of an interactor, including the contents of any interior interactors. The default Draw opera-
tion calls Redraw(0, 0, xmax, ymax). Interactors usually don't need to redefine Draw unless they contain interior interactors
(i.e., scene subclasses); most simple interactors redefine only Redraw.
virtual void Highlight(boolean)
Turn highlighting on or off, depending on whether the parameter is true or false. The default operation is a nop.
Set/get the type of canvas desired for an interactor. This operation must be performed before an interactor is mapped. The possi-
ble canvas types are CanvasShapeOnly, meaning the interactor performs no input or output (e.g., glue), CanvasInputOnly, meaning the
interactor performs no output, CanvasInputOutput, which is the default, CanvasSaveUnder, which suggests that the interactor will be
mapped for a short time (e.g., a popup menu) and that the information under the canvas should be saved, CanvasSaveContents, which
suggests that Redraw calls are expensive and should be avoided by caching the display, and CanvasSaveBoth, which requests both Can-
vasSaveUnder and CanvasSaveContents.
Sync waits until any pending operations have completed. Flush makes sure the local buffer of pending operations (if any) is sent to
the display. An input operation will do a Sync automatically if it would block; thus, applications generally need not call Sync or
When an interactor is mapped onto a display, its input interest is determined by its input sensor. A different sensor can be speci-
fied with the Listen operation. To switch back to input, call Listen(input).
boolean Read(long sec, long usec, Event&)
Each application has a single input queue of events. Any interactor can use Read to take the next event from the queue. Redraw and
Resize operations may be called as a side effect of a Read (or any input operation). The target field of the event specifies the
interactor for which the event is intended, which is not necessarily the same as the interactor that performed the Read. The target
is normally the interactor whose canvas is under the pointing device. The second form of Read behaves differently if there are no
events to read in that it times out after the given number of seconds and microseconds have elapsed and returns false to the calling
UnRead puts an event back on the input queue as if it had never been read.
virtual void Handle(Event&)
When an interactor wishes to pass an event to another interactor, it calls the other interactor's Handle operation. Thus, input
flow control can be either procedural with Read or event-driven with Handle.
Run implements a simple event dispatching loop. It calls Read to get the next event and passes the event to the target interactor
via Handle. The loop terminates if the Handle operation sets the event's target to nil.
QuitRunning sets the event's target to nil. A Handle operation can call it to make Run exit its event dispatching loop.
Check determines whether an event of interest has occurred.
Poll sets an event to reflect the current input state. Input polling can be wasteful of cycles and should be avoided if possible.
CheckQueue returns the number of input packets that have been queued within the application. The event queue manager always reads
as much information as possible from input; thus, a single Read might store many events in a local buffer. Subsequent reads can
simply access the buffer. This buffer can include out-of-band packets, such as those requiring a Redraw. The number returned by
CheckQueue does not correspond, therefore, to the actual number of input events.
virtual void Adjust(Perspective&)
Adjust suggests to an interactor that its perspective should change to the given perspective; the interactor may choose to accept
any part of the new perspective and must ensure that the parameter matches its (new) perspective before returning. Adjust can be
used by another interactor to scroll, pan, or zoom an interactor.
GetPerspective returns the perspective associated with an interactor or nil if the interactor has not assigned one.
virtual void Update()
Change the display to reflect some change in state that the interactor depends on. This operation is used in a number of contexts.
One example is in managing perspectives. If an interactor changes its perspective (e.g., the total of size of what it is displaying
changes), it must notify its perspective, which in turn calls Update on the interactors that access the perspective (such as a
virtual void Redraw(Coord l, Coord b, Coord r, Coord t)
The Redraw operation is called when some portion of the Interactor needs to be redrawn, presumably because it was previously
obscured. The Redraw operation should NOT redraw interior interactors; the Interviews library or the Draw operation will call their
Redraw operations automatically. The default Redraw operation does nothing.
virtual void RedrawList(int n, Coord l, Coord b, Coord r, Coord t)
RedrawList notifies an interactor that several areas of its canvas need to be redrawn, presumably because it was raised to the top
of other canvases. The default RedrawList operation redraws each area separately with Redraw.
virtual void Resize()
Resize notifies an interactor that its canvas has been created or modified. Only scenes are typically concerned with Resize, as
they must place their component interactors within the new or resized canvas. The default Resize operation does nothing.
InterViews Reference Manual, Perspective(3I), Scene(3I), Sensor(3I), Shape(3I), World(3I)
InterViews Reference Manual Interactor(3I)