[Freeciv-Dev] different iso drawing algorithms

[Jason Short <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

When drawing tiles in isometric view, we need to follow the painter's
algorithm.  Since the tiles may overlap, we need to draw a tile in back
before we can draw a tile that may partially cover it.  But if we're
only updating one tile, we can't redraw all the tiles behind it all the
way to the top of the screen, we just want to draw the one row of tiles
above the tile.

There are currently used ways to limit the number of tiles drawn to only
those that are necessary.  I will hence name them partial tile drawing
and tricky buffered drawing.

The attached image describes the basic concepts of the two drawing
systems.

So, the question becomes: which system is better?  Should we support
just one of them, or try to support both?

jason