Event Control

nmtkcontrol is an alternative to using coventional UI components.

nmtkcontrol is better than xmanager because it has better support for multiple controls within the same UI.Each control is responsible for:

1. Managing and rendering top level graphics atoms

   1. It is possible to add the same top level graphics atom to many different controls. This allows for specialised aspects of rendering and managment of a graphics tree to be performed by different controls. For example, one control might handle an image, whilst the other might control a plot on the same window.

2. Registering and handling events

• 1. It is also possible to register the same WIDGET_DRAW to many different controls. This allows for specialised event processing to be performed by different controls. For example one control might handle mouse motion events, whilst the other might handle WIDGET_BUTTON events.

3. Interacting with the data model

• 1. Controls may need to notify other subsystems of changes to the UI. The exact architecture of these systems are not a core concern at present. I have included a method for notifying a change to a specified nmtkactivity, however, I am yet to decide upon an officially supported data model.

The difference between xmanager is nmtkcontrol can be shown schematically (below). Each UI component is disentangled because there can be a many to many relationship between components.

Managing and rendering top level graphics atoms

It is possible to add top level graphics atoms to be managed by nmtkcontrol. In each case, a realized WIDGET_DRAW must be specified as the target window.

Initialise the control object

oControl = obj_new("nmtkcontrol")

Add a top level view to be managed by this control

oControl -> AddView, widget_draw_id, oView

Add a view which belongs to a top level scene to be managed by this control

oControl -> AddScene, widget_draw_id, oScene, oView

Once the views or scenes have been added, it is possible to render them by calling

oControl -> Redraw

Registering and handling events

It is possible to register widgets for event processing. The events are handled by the nmtkcontrol::event procedure.

Initialise the control object and enable event processing

oControl = obj_new("nmtkcontrol",ENABLED=1)

Register a widget for event processing (without blocking)

oControl -> Register, widget_id, /JUST_REG

Specify a cursor to be set upon next redraw of a WIDGET_DRAW

oControl -> SetProperty, CURSOR_NAME="CROSSHAIR"

Writing an event handler for a control is achieved by overriding nmtkcontrol::event. If the event occured within a graphics atom, then it is possible to find the location of the event with respect to the units of the specified atom.

pro mycontrol::event, ev

 location = self -> conv_coord(ev,oAtom)

 print, "X:",location[0], "Y:",location[1]

end

Interacting with the data model

nmtkcontrol is generic and not designed for any particular data model. However, nmtkcontrol does include a signalling mechanism which is compatible withIDLitIMessage. This mechanism useful for synchronising controls. It is possible to send signals to multiple Observers after each event is processed.