Store files and objects as BMP files.
Recall BMP files as graphical objects.
Also adjust `Show` to not add a border to input graphical objects.
Fixes: #867
Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>
Make sure that we capture consistent pixmaps, which we can do on the
RPL thread, and only defer the transfer of the pixmap to the main
thread, which is fast.
Additionally, optimize updates by doing a byte-by-byte xor comparison
in order to see which bytes actually changed. This minimizes the cost
on the RPL thread to update the pixmap.
This makes it possible to have a much better screen behaviour for the
`CBench` benchmark, where it updates it regularly on the screen while
not slowing things down too much.
Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>
