Vmapper:Z requires physical re-mapping and rewiring of panels when switching from odd to even number in height

[marcmerlin]

You can currently wire things so that they work whether you have odd or even, but if you try to add a panel, everything gets flipped around
#1014 still works, but is fairly suboptimal

[marcmerlin]

This is with --led-chain=4

and with --led-chain=5, everything is reversed and all the panels need to be re-wired for the new order.

As per my upcoming PR, the problem and solution

+    // because the panel you plug into ends up being the "bottom" panel and coordinates
+    // start from the top panel, and you typically don't wire the bottom panel (first in
+    // the chain) upside down, whether each panel gets swapped depends on this.
+    // Without this, if you wire for 4 panels high and add a 5h panel, without this
+    // code everything would get reversed and you'd have to re-layout all the panels
+    bool is_height_even_panels = ( matrix_width / panel_width) % 2;

[marcmerlin]

this is now fixed in #1664