gEDA-dev: Re: PCB: Graphical bugs

[DJ Delorie]

I don't think we've completely isolated the core from the GUI; we
still have things like ShowSolderSide and Thindraw in the core.

The idea is that EVERYTHING in the core uses plain PCB coordinates.
EVERYTHING.  0,0 is always on the same logic place, you always assume
the whole board, etc.  However, that doesn't stop the core from
knowing *what* to draw.  ShowSolderSide is used to decide which pads
and silk are "on top" and which are "invisible".  Yes, the other use
of ShowSolderSide is suspect, and it turns out that the computed y0
isn't used anyway.

The HIDs are responsible for mapping PCB coordinates onto screen (or
page, or gerber, etc) coordinates, along with any details that
requires (like sorting rectangle coordinates).

Note that lesstif seems to have the same problem, both vertically and
horizontally.

As for the min/max, at the moment they at least keep the grid
computations from placing the crosshairs off the board.  It's also
used to keep buffer items from going off the board.  So, we still need
that, and it's in PCB coordinates anyway.