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NAME
Interactor - base class for interactive objects
SYNOPSIS
#include <InterViews/interactor.h>
DESCRIPTION
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
(xmax, ymax).
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 displaying. 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.
CONSTRUCTORS
Interactor()
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 documented, an instance of any
object inheriting from interactor may be constructed with an additional argument (appearing first)
containing the string name. For example, both ``HGlue(natural, stretch)'' and ``HGlue("somename",
natural, stretch)'' are valid.
~Interactor()
The base destructor automatically deletes the base fields, including shape, canvas, input, and
output.
CONFIGURATION
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 canvas.
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 ancestors 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 inherited from its parent or copied from its parent if there are user
preferences specific to the interactor for painter attributes such as colors, 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 context.
virtual void Reshape(Shape&)
Shape* GetShape()
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.
void SetCursor(Cursor*)
Cursor* GetCursor()
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.
INTERACTOR HIERARCHY
Scene* Parent()
Return the interactor's parent or nil if the interactor has not been inserted into a scene.
World* GetWorld()
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 interactor 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.
OUTPUT
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 operation 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.
void SetCanvasType(CanvasType)
CanvasType GetCanvasType()
Set/get the type of canvas desired for an interactor. This operation must be performed before an
interactor is mapped. The possible 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 CanvasSaveUnder
and CanvasSaveContents.
void Sync()
void Flush()
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 Flush
explicitly.
INPUT
void Listen(Sensor*)
When an interactor is mapped onto a display, its input interest is determined by its input sensor.
A different sensor can be specified with the Listen operation. To switch back to input, call
Listen(input).
void Read(Event&)
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 program.
void UnRead(Event&)
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.
void Run()
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.
void QuitRunning(Event&)
QuitRunning sets the event's target to nil. A Handle operation can call it to make Run exit its
event dispatching loop.
boolean Check()
Check determines whether an event of interest has occurred.
void Poll(Event&)
Poll sets an event to reflect the current input state. Input polling can be wasteful of cycles
and should be avoided if possible.
int CheckQueue()
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.
VIEWS
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.
Perspective* GetPerspective()
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 scroller).
PROTECTED OPERATIONS
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.
SEE ALSO
InterViews Reference Manual, Perspective(3I), Scene(3I), Sensor(3I), Shape(3I), World(3I)