[Freeciv-Dev] drawing tiles multiple times

[Jason Dorje Short <jdorje@xxxxxxxxxxxx>]

In the past it's been suggested that a tile could be drawn multiple times.

For instance if you have a 40x25 map and your mapview is 50 tiles wide, 
currently the extra 10 tiles are drawn black (at least they are supposed 
to be: it's easy to get bugs where junk gets drawn here).  But if tiles 
were drawn multiple times then the 10 tiles on the left of the mapview 
would be shown in duplicate on the right.
In the above example there are no big advantages to drawing tiles 
multiple times.  The only advantage is that you don't have the big black 
area on ths screen (which is ugly).
The main disadvantage to drawing multiple times is that it's hard to do 
right.  In the past we'd have situations where the tile would be drawn 
multiple times, but only partially.  Thus you'd get two copies of a unit 
but only one woudl blink.  This was confusing.  To do it correctly, both 
copies of the unit have to blink, and if you animate a unit both units 
need to be animated.  If done properly, I think the main argument 
against doing this (that it is confusing to the player) will be moot.
So the question is, why would you want to draw tiles multiple times? 
With current topologies there's no reason why you need to do so.  As 
long as you center properly on the current unit it will always be 
surrounded by a lot of properly drawn tiles.  In almost all cases the 
mapview is much smaller than the map, so there is no issue whatsoever.
But consider an exotic topology in Marcelo's PR#7287 patch.  In a 
quincuncial topology, there are tiles that are adjacent to themselves! 
That is, if you go northeast from (40,0) you wrap around to 
reach...(40,0).  (These "singularities" are generally hidden in remote 
locations like the north and south poles.)  If you only draw a tile once 
this gives you big problems.  Imagine what happens if it *looks* like 
the map ends one tile north of your unit, but when you move north you 
end up being animated to the east.  Very bizarre.  I've looked at these 
maps, and it's incredibly confusing.  But if you draw tiles multiple 
times everything becomes clear.  Hopefully.
Marcelo's PR#7287 patch includes a full implementation for drawing tiles 
multiple times (actually only 1 extra wrap in each direction, so only up 
to 9 times AFAICT).
So I'd like to reopen the discussion on whether drawing tiles multiple 
times is forbidden.
jason