Independent TaskPane/Popup-based widgets

[jng]

The measure widget and any TaskPane-based widget have really bad usability with regards to what happens when the Task Pane is hidden.

When the Task Pane that the widget resides in is hidden, the widget itself is still internally active and the viewer is still accepting mouse input for digitization.

We need a mechanism by which such widgets can be notified when the Task Pane is hidden and shown, so that such widgets can then act appropriately.

Current thinking is when the Task Pane is hidden, such widgets are notified and their default action is to instruct the Task Pane to go home and to activate the default widget (Zoom?). Will need some more discussion on this matter.

[jng]

Discussion thread: ​http://osgeo-org.1560.n6.nabble.com/Usability-of-Redline-Query-Theme-Measure-Buffer-FeatureInfo-td5041641.html

Affected widgets: Redline, Query, Theme, Measure, Buffer, FeatureInfo

What I propose as a solution is the following:

• Make the aforementioned widgets *not* mutually exclusive (ie. isExclusive is false). There is no concept of enabled/disabled for these widgets. If you can see their UI, they're active. This frees said widgets from active state.
• Tweak the respective widget UIs to be independent from the rest of the Fusion system, regardless of active widget state. To be specific:
  • Measure: Modify it to be more like its AJAX viewer counterpart. Have buttons to explicitly start/stop the measuring process instead of auto-start on widget activation.
  • FeatureInfo: Add a button/link to refresh the layer list dropdown
  • Query: Make use of the MapMessage component to relay digitization prompts for tracing the spatial filter geometry. Add a button to manually stop digitization.
  • Theme: No changes
  • Buffer: No changes

With these changes, the UX should be much more bullet-proof. No longer will you have situations like panning with an active dangling geometry digitizer, tracing shapes as you're panning as a result. Such situations are all to easy to trigger under the current behaviour of these widgets.

[jng]

Redline: No changes either