DisplayEvents

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Detailed Description

A module providing event handling for the DisplayCanvases.

See below for an overview of the classes in this module.

Intended use:

Part of API

Review Status

Reviewed By:

None yet

Date Reviewed:

yyyy/mm/dd

Prerequisite

• DisplayCanvas

Etymology

The module provides various classes that are responsible for "handling" "events"

Synopsis

This module contains classes which are used to handle position, motion and refresh events that occur on PixelCanvases and WorldCanvases. Position events occur when the user presses or releases a keyboard key or a mouse button when the window input focus is over a PixelCanvas or WorldCanvas. Motion events occur when the user moves the mouse over a PixelCanvas or a WorldCanvas. Refresh events occur for a variety of reasons, and arise when PixelCanvases or WorldCanvases need to redraw their contents.

The lowest level of event classes are those which describe the various events on the PixelCanvas. These comprise PCPositionEvent, PCMotionEvent and PCRefreshEvent. All of the information pertaining to a particular event will be stored in one of these classes. To receive these type of events, the programmer must register a class derived from PCPositionEH, PCMotionEH or PCRefreshEH (where the "EH" stands for Event Handler) with the appropriate PixelCanvas. Then any events of that type (Position, Motion or Refresh) will be distributed to the class that the programmer registered. The WorldCanvas has equivalent event storage classes in WCPositionEvent, WCMotionEvent and WCRefreshEvent, and equivalent event handling classes in WCPositionEH, WCMotionEH and WCRefreshEH.

It is important to note that none of the event handlers "consume" events. This means that all PixelCanvas events occuring on a particular PixelCanvas wil be distributed to all the event handlers registered on that PixelCanvas. Likewise, all WorldCanvas events for a particular WorldCanvas are distributed to all WorldCanvas event handlers registered on that WorldCanvas.

It is also critical for the programmer to be aware that in general, the WorldCanvas registers one instance of each of the PCPositionEH, PCMotionEH and PCRefreshEH type handler classes for its own use. These event handlers are responsible for constructing WorldCanvas event information objects (WCPositionEvent, WCMotionEvent and WCRefreshEvent) from the corresponding PixelCanvas events, and then call the appropriate handlers on the WorldCanvas. So the programmer must be careful that they handle each event once and only once - either on the PixelCanvas, or on the WorldCanvas, but not on both. There will be rare instances where handling events on both the WorldCanvas and its underlying PixelCanvas is necessary.

Example

Motivation

Any interactive display library must provide methods for the programmer to respond to user input. That is the reason for this module.

To Do

• None known

Modules
	DisplayEvents_internal_classes
	Internal DisplayEvents classes and functions.
Classes
class	casa::AnimatorRefEH
	WorldCanvas refresh event handler for Animator class. More...
class	casa::Animator
	Animation controller for WorldCanvasHolders. More...
class	casa::AniPosEH
	WorldCanvas position event handler for Animator. More...
class	casa::CrosshairEvent
	WorldCanvasEvent:contains info on the WC point selected by MWCCrosshairTool. More...
class	casa::DisplayEH
	class for handling any type of DisplayEvent. More...
class	casa::MultiWCTool
	Base class for MultiWorldCanvas event-based tools. More...
class	casa::MWCAnimator
	Animator for MultiWCHolder class. More...
class	casa::MWCCrosshairTool
	Base class for MultiWorldCanvas event-based crosshair tools. More...
class	casa::ResetCrosshairEvent
	Event sent to tell MWCCrosshairTool to reset. More...
class	casa::ResetRTRegionEvent
	Event sent to tell MWCRTRegionTool to reset. More...
class	casa::MWCPannerTool
class	casa::MWCPolylineTool
	Base class for WorldCanvas event-based polyline tools. More...
class	casa::MWCPolyTool
	Base class for WorldCanvas event-based polygon tools. More...
class	casa::MWCPTRegion
	WorldCanvas event-based polygon region drawer. More...
class	casa::MWCRectTool
	Base class for MultiWorldCanvas event-based rectangle tools. More...
class	casa::MWCRTRegion
	WorldCanvas event-based rectangle region drawer. More...
class	casa::MWCRTZoomer
	Multi WorldCanvas event-based zoomer. More...
class	casa::PCInvisTool
	Base implementation of PCTool for invisible (non-drawing) tools. More...
class	casa::PCITFiddler
	Colormap fiddling on the PixelCanvas. More...
class	casa::PCMotionEH
	PixelCanvas Event Handler for managing pointer motion events. More...
class	casa::PCMotionEvent
	Class which stores PixelCanvas motion event information. More...
class	casa::PCPositionEH
	PixelCanvas Event Handler for managing keyboard and mouse button events. More...
class	casa::PCPositionEvent
	Class which stores PixelCanvas position event information. More...
class	casa::PCRefreshEH
	WorldCanvas Event Handler for managing events. More...
class	casa::PCRefreshEvent
	Class which stores PixelCanvas refresh event information. More...
class	casa::PCTestPattern
	PixelCanvas test pattern display refresh event handler. More...
class	casa::PCToolPosEH
	PixelCanvas position event handler for PCTool. More...
class	casa::PCToolMotEH
	PixelCanvas motion event handler for PCTool. More...
class	casa::PCToolRefEH
	PixelCanvas refresh event handler for PCTool. More...
class	casa::PCTool
	Base class for PixelCanvas event-based tools. More...
class	casa::RectRegionEvent
	Contains info on the WC rectanglar area selected by MWCRTRegion mouse tool. More...
class	casa::WCCrosshairTool
	Base class for WorldCanvas event-based crosshair tools. More...
class	casa::WCInvisTool
	Base implementation of WCTool for invisible (non-drawing) tools. More...
class	casa::WCMotionEH
	Base class for handling WorldCanvas motion events. More...
class	casa::WCMotionEvent
	Class which stores WorldCanvas motion event information. More...
class	casa::WCPolyTool
	Base class for WorldCanvas event-based polygon tools. More...
class	casa::WCPositionEH
	Base class for handling WorldCanvas position events. More...
class	casa::WCPositionEvent
	Class which stores WorldCanvas position event information. More...
class	casa::WCPTRegion
	WorldCanvas event-based polygon region drawer. More...
class	casa::WCRectTool
	Base class for WorldCanvas event-based rectangle tools. More...
class	casa::WCRefreshEH
	Base class for handling WorldCanvas refresh events. More...
class	casa::WCRefreshEvent
	Class which stores WorldCanvas refresh event information. More...
class	casa::WCRTRegion
	WorldCanvas event-based rectangle region drawer. More...
class	casa::WCRTZoomer
	WorldCanvas event-based zoomer. More...
class	casa::WCToolPosEH
	WorldCanvas position event handler for WCTool. More...
class	casa::WCToolMotEH
	WorldCanvas motion event handler for WCTool. More...
class	casa::WCToolRefEH
	WorldCanvas refresh event handler for WCTool. More...
class	casa::WCTool
	Base class for WorldCanvas event-based tools. More...

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