[josm-dev] MapMode Button State

[Holger Mappt]

Hi,

I created a map mode based on MapMode and an IconToggleButton that is 
added to the MapFrame.  The map mode works with objects on an overlay 
layer (photos of the GeoImageLayer).  The goal is to enable the button 
if there is at least one GeoImageLayer with at least one photo loaded 
and to disable/hide it otherwise.  The button method 
setAutoHideDisabledButton(true) is called to hide the button if there is 
nothing to do for my map mode.  Depending on the MapMode methods that I 
implement the button state can be enabled, disabled but visible, or hidden.

Question: How can I implement the intended map mode button behavior?  Is 
there a good example?

MapMode.layerIsSupported() seems to be the only method that JOSM 
supports to set the button state.  But it doesn't work in my case 
because the active layer doesn't matter.  MapMode.updateEnabledState() 
is implemented by some other MapModes, but I don't understand how it is 
connected to the button.  The MapMode is the button action, but I want 
to disable the button, not the action.  I can call 
IconToggleButton.setEnabled(), but MapView.setActiveLayer() overwrites 
it if the layer is switched.  What else can I do?

Thanks,
Holger