Re: [AD] new GUI focus selection algorithm

[Sven Sandberg <svens@xxxxxxxxxx>]

Eric Botcazou wrote:
> - I think that using the Euclidean distance is too costly in terms of ratio 
> benefit/overhead.

But this computation is not going to be done more often than the user 
presses a key! I think we can (and should) ignore the computation time. 
(Remember that we have to redraw the objects we move from and to anyway, 
normally a much more costly operation!)

That said, we can avoid square roots by comparing the _squares_ of the 
(Euclidean) distances. It will be faster and not change the behavior.

> After all, all distances are (mathematically) equivalent 

Well, they are all metrics, but that is an abstract algebraic notion not 
related to the geometric interpretation. So it doesn't mean all metrics 
feel the same way to the user.

> and we don't care if our circles look like squares :-)

If our circles look like squares, then A and B have the same distance to 
C in this example:

 A B


     C

So moving up from C could equally well move to A or B (or always to A, 
if it ends one pixel below B).

> - You should introduce a compile-time parameter in the distance formula so 
> that we can tweak the relative weight of the two axes.

That could make sense, although it will be tedious to implement because 
we want to swap the weights when moving horizontally vs vertically.

Sven