The more I think about this, it seems the best and perhaps only viable
solution is to move the controller out of the checkboxes, back a step
to the array of layers. That way, every time a layer option is changed
(apart from opacity) the array can have its rules re-evaluated to make
sure no further changes need to be made (e.g. displaying or hiding a
merged-layer). The checkboxes would then be adjusted to simply reflect
whatever settings the array currently holds.

But after about 72 hours of trying I'm really hitting a wall with how
to actually make it work.


On Aug 7, 6:48 pm, Kesuke <[email protected]> wrote:
> Continued 
> from:http://groups.google.com/group/google-maps-js-api-v3/browse_thread/th...
> (can't bump the old thread for some reason).
>
> A year on the project is very nearly complete, but I have a final
> problem;
>
> Each diagram uses about ~130 layers/overlays. To improve performance,
> when large numbers of layers are visible, there need to be special
> layers (which I’ll call “merged-layers”). These are basically just
> flattened versions of several layers, designed to decrease load time
> and bandwidth.
>
> So in the example at:http://www.chiasm.co.uk under the layers tab
> you will see one called “Abdominal MERGED”. This is just a flattened
> version of the 4 layers above it (plus one hidden layer).
>
> But I’m having trouble finding a way to implement this smoothly. There
> are several problematic areas;
>
> 1.) As far as the user is aware, these special layers don’t exist. So,
> the checkboxes of those subordinate layers must remain ticked, even
> though they aren’t really being displayed. If the user unchecks one of
> them, the merged layer must be removed and the remaining ticked layers
> added.
>
> 2.) There need to be several ‘tiers’ of merged layer. So for example
> “Abdominal MERGED” is made up of those 4 muscles. But there might be a
> ‘higher’ (in zIndex) merged-layer which covers the entire thorax, and
> maybe one above that that covers all muscles. The system must pick the
> ‘best/highest’ merged-layer to show.
>
> 3.) These merged layers will mess up any layer opacity settings, so if
> layer opacity is < 100% they must not be used.
>
> Some of these problems arise because currently layer visibility is
> directly derived from the checkboxes. I wonder whether we could shift
> control back to the layers array? So we make changes to the array
> rather than checkboxes (which merely ‘emulate’ the parts of the array
> we want them to).

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