create placeholder object for void results

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
fix path coloring when zoomed out

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
use buffered rendering for paths

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
implement layers in the rendering engine

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
generate random colors

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>