Yeah , looking at it again OpenVG does not concern itself with such things.
Have you looked at readymade solutions like info-beamer or PiPresents ?
I guess without HW acceleration slideshows might be stuttery on the single-core Pi models , which will limit you to hardcore C programming.
• Don't like the board ? Missing features ? Change to the prosilver theme ! You can find it in your settings.
• Don't like to search the forum BEFORE posting 'cos it's useless ? Try googling : yoursearchtermshere site:raspberrypi.org