When working in high contrast mode, we want to be able to select a
footprint with only elements in, e.g. silk and fab layers.
The previous design for footprint IsOnLayer had one behavior of every
other element and a different behavior for footprints. This leads to
multiple bugs as new features use the overloaded IsOnLayer expecting it
to report if the element exists on a layer or not.
For footprints, we need a different routine to determine whether or not
to select the footprint when clicking on it. IsOnLayer will report if
the footprint has any elements on a specific layer but we don't want to
use the bbox for a hittest because large footprints with through hole
pads will exist on every layer and have an enormous bbox. Instead, we
filter footprints based on the hittest of each element. This behaves in
a more logical fashion, allowing you to select a footprint by clicking
on a visible element of that footprint.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/15284
* Add compare method to COLOR4D object.
* Add unit test to validate COLOR4D comparison method.
* Add missing color test in text attribute comparison method.
* Add unit test for text attribute object.
* Remove unnecessary headers from text attribute header.
* Move text attribute code into separate source file.
Seth Hillbrand
Jeff Young
Mike Williams
Wayne Stambaugh
Jon Evans