Control Discussion

Tom, Bruno, Fred and I discussed the control/interaction architecture yesterday (Jan 15th, 2013). Quick report on the discussion.

Control

Currently a Control is an object wrapping a DOM element and including a reference to the map. A control can be given a target DOM element (container). If no target is provided the map's "overlay container" is used as the target.

Current Issue

The map currently maintains a collection of controls, and provides a getControls method for accessing the collection. The current design is flawed. In particular the following use-case doesn't work:

map1.getControls().push(aControl);
aControl.setMap(map2);

In this case the control is still in map1's controls collection, but it now includes a reference to map2.

Interaction

The map has a collection of Interactions. The map listen to browser events, wrap these browser events in "map browser events" and pass them to the interactions by calling handleMapBrowserEvent on every interaction of the collection. The interaction may handle or ignore the received map browser event, based on its role. The interaction reacts to the event by changing the view (calling view.setCenter for example).

The order of interactions in the collection matters. If an interaction calls preventDefault() on the map browser event other the interactions at lower indexes in the collection won't receive the event.

Control Classification

In OL2 everything is a Control. In particular the notion of Interactions does not exist. A control in OL2 may have no relationship with the DOM.

We have attempted to categorize each OL2 control and handler, to see where they fit in the OL3 architecture. See below. The result is that there are OL2 controls that are neither controls nor interactions in the OL3 architecture. Solutions must be found for those.

OL3 CONTROL
Attribution
LayerSwitcher
MousePosition
OverviewMap
Pan
PanZoomBar
Scale
ScaleLine
Zoom
ZoomToMaxExtent

OL3 INTERACTION
DragPan
GetFeature
KeyboardDefaults
PinchZoom
UTFGrid
WMSGetFeatureInfo
WMTSGetFeatureInfo
ZoomBox
Feature Handler (low level)

OL3 WE DON'T KNOW YET
ArgParser
Geolocate
NavigationHistory
Permalink

OL3 GEOMETRY MANIPULATION
DragFeature
DrawFeature
Measure
ModifyFeature
SLDSelect
SelectFeature
Snapping
Split
TransformFeature
Box
Path Handler
Point Handler
Polygon Handler
RegularPolygon Handler

OL3 NOT RELEVANT
Button
EditingToolbar
NavToolbar
Panel
ZoomIn
ZoomOut
ZoomPanel

OL3 SOURCE WRAPPER
CacheRead
CacheWrite

OL3 LAYER
Graticule

SHORTCUTS
Navigation
PanPanel
PanZoom
TouchNavigation

OL3 MAP BROWSER EVENT
Click Handler
Drag Handler
Hover Handler
Keyboard Handler
MouseWheel Handler
Pinch Handler

OL3 IDEAS
tree of controls
modifiers to listen to different events