For those interested people,
I have created a testoverlay.c program. you can compile it like any SDL program.
It can be added to the test dir in the SDL source tree. then you can “make testoverlay” or append “testoverlay.c” to the Makefile.am’s noinst_PROGRAMS
The source can be found at http://jcatki.2y.net/files/testoverlay.c
read the source for options… -format and -scale are good ones to play with…
apparently -scale crashes when running this with a software overlay! this is because of display destination coordinates outside of the screen apparently…
is this a bug?–