Intent of NavigatableComponent$isVisibleOnScreen()

[Paul Hartmann]

On 20.11.2017 00:09, Robert Scott wrote:
> Hi,
> 
> Just trying to decode some of the reasoning behind bits of
> NavigatableComponent - was wondering what case exactly NavigatableComponent
> $isVisibleOnScreen() is intended to protect updateLocationState() from.
> 
> I'm looking at it thinking whether it's possible to make it more granular with
> a view to being able to use MapView more fully in tests, and its presence
> confuses me - if it's possible to patch it out with just a constant true (e.g.
> in gui.mappaint.RenderingHelper, even in headless mode, what is its purpose?
> 
> Is it an optimization? Is it for cases when it might get called before a
> NavigatableComponent's added to a visible window? Is it for the CLI mode?
> 
> If I knew I'd be able to see whether it can be replaced with something more
> specific.

This code is by Michael Zangl, so he would know much more about it. From 
my understanding, isVisibleOnScreen() prevents the recalculation of the 
location state when the component has not been added to the visible window.
At the same time, the method is intended to be overridden with constant 
true in a situation where the NavigatableComponent is handled completely 
off-screen (RenderingHelper and unit tests, see also [10405]).

It would be good if RenderingHelper could be compiled without any 
dependency on Swing classes (i.e. JComponent as super class of 
NavigatableComponent). Michael has achieved a lot in this direction, but 
there is still more to be done. :)

Paul