[Freeciv-Dev] Re: (PR#3936) introducing native coordinates

[Ross Wetmore <rwetmore@xxxxxxxxxxxx>]

Jason Dorje Short wrote:
> Raimar Falke wrote:
> > On Thu, Apr 24, 2003 at 08:58:16AM -0500, Jason Dorje Short wrote:
[...]
> Something truly simple could be written with basic wrapping, ignoring 
> the iso nature of the mapview.  This is what the current code does, but 
> it has a signficant bug: even if you make the canvas infinitely large 
> some tiles will never be shown.
I don't think the "infinitely large" condition is cited correctly here.
Once you pass the bounding box size, all coordinates will be shown.

Making things infinitely large in only one dimension may lop off positions
that could be shown at some multiply wrapped location in that dimension.

But such candycane maps, while an interesting possiblity, would be so
confusing to interpret that outlawing them is a good thing. And whether
or not candycane maps will ever cover all of a map is subtly dependent
on the map dimensions and size of the stripe. For example, the stripe
might be just in sync and repaint the same area over and over in
subsequent loops, never to overlap with neighbouring points. Or it may
repeat the same coordinates many times adding only a small extra band
on each revolution. Changing the canvas window dimensions or the map
dimensions in minor ways would of course change such "beat" paterns.

The summary, is don't ever think of going there.

> For full correctness, unnormalize_map_pos should take a width and height 
> parameter.  This also potentially allows multiple drawing of tiles. 
> However, this makes it even more complicated and only helps in a few 
> pathological cases.
No. Wrong approach that misses the underlying invariants of the system.

> jason
Cheers,
RossW
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