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casa::DisplayEH Class Reference

class for handling any type of DisplayEvent. More...

#include <DisplayEH.h>

Inheritance diagram for casa::DisplayEH:
casa::DisplayData casa::WCRefreshEH casa::WorldCanvas casa::CachingDisplayData casa::NBody casa::PrincipalAxesDD casa::AnimatorRefEH casa::Annotations casa::DDDObject casa::LinkedCursorEH casa::MultiWCTool casa::viewer::RegionToolManager casa::WCToolRefEH casa::WorldCanvasHolder

Public Member Functions

virtual void handleEvent (DisplayEvent &)
 Classes that contain this interface (i.e., derive from it) can override this method to implement actions for whatever types of DisplayEvent they're interested in. More...
virtual ~DisplayEH ()

Detailed Description

class for handling any type of DisplayEvent.



DisplayEH : generic display event handler–A handler for any type of display library event.


DisplayEH has an overridable callback that allows it to handle any type of base class DisplayEvent. It is intended to allow different types of handlers (for different types of event) to reside on the same callback list.


Different types of events (and event-handling routines) are needed in the display library, and more are likely to be needed in future. However, creating still more specialized handler lists in places like WC for each new type of event seems impractical. WorldCanvas and PixelCanvas already maintain 3 such lists each. This generic event handler interface will allow more general use of existing event dispatching lists.

The immediate use for DisplayEH will be to enable more general exchange of control messages between objects already attached (directly or indirectly) to WorldCanvas as handlers, in particular between DisplayDatas and MultiWCTools. WorldCanvas and WorldCanvasHolder will add this simple interface in order to distribute the new events; DisplayData will inherit it in order to handle them. WCRefreshEH will also be altered to inherit from this class, and WorldCanvas's existing refresh event handler list will be altered to accept any DisplayEH (not just WCRefreshEH objects).

To listen for an event on this new WC 'channel', an object derived from this interface would be attached to the WC's RefreshEHList (as the MultiWCTools are) or WCH's DD list (in the DD case). The object would then implement handleEvent() to respond (only) to the events of interest. A sender would create a new DisplayEvent type (or use an existing one for its intended purpose), and send the event by calling WC::handleEvent(event).

Except for the accommodations mentioned above, the current interface and functionality of WCRefreshEHs and all other existing event handlers is left as is. Note especially that the older events (Position, Motion, Refresh) are still sent using the old 'operator()' interface, which remains in place, at least for now.

In the future, it may be useful to derive all existing handlers from DisplayEH, to consolidate to just one generic EH list each in PC, WC and WCH (and anywhere else event dispatching is needed), and to distinguish handler and event types only during event dispatching or processing. Then any object which inherits this interface could be placed on any such dispatching list in order to respond to events of interest.

Definition at line 100 of file DisplayEH.h.

Constructor & Destructor Documentation

virtual casa::DisplayEH::~DisplayEH ( )

Definition at line 112 of file DisplayEH.h.

Member Function Documentation

virtual void casa::DisplayEH::handleEvent ( DisplayEvent )

Classes that contain this interface (i.e., derive from it) can override this method to implement actions for whatever types of DisplayEvent they're interested in.

It was thought best at this point to move away from the old 'operator()' style of handling interface, for clarity.

Reimplemented in casa::DisplayData, casa::WorldCanvas, casa::MSAsRaster, casa::WorldCanvasHolder, casa::Profile2dDD, casa::MWCCrosshairTool, casa::MultiEllipseToolImpl, casa::MultiPointToolImpl, casa::MultiRectToolImpl, casa::MultiPVToolImpl, casa::MWCRTRegion, and casa::MWCETRegion.

Definition at line 110 of file DisplayEH.h.

The documentation for this class was generated from the following file: