PI 3 screen updates & screen banks

Saturday (07 May) I got my PI 3. Installation on SD card was done as follow: R14 PI image written on card, latest firmware files downloaded and installed, latest RISC OS 5.23 image installed. After booting, I also updated the disc with the latest HardDisk archive.

After fixing a few bugs in DigitalCD and the Cthugha plug-in, everything runs except for nasty screen refresh problems in full-screen plug-ins which I couldn’t solve. These involve things like:
- in the TimVis plug-in, the top of the screen tends to flash like mad.
- in other plug-ins it looks like some areas flashes with things that should not be there. For example in Cthugha where a combination of effects displayed an inverted background in white and a central area in the usual black background a not so little part at the bottom of the central area kept flashing in white.

I made a few experiments with swapping the order of screen banks switching and the wait for VSYNC but they made absolutely no difference.

Just after posting, I thought about giving a try to triple buffering. It works, so I have at least a workaround.

Yes, triple buffering is the preferred way of doing things on modern machines. The main problem is that by the time the VSync interrupt has fired, the hardware has already decided what screen bank it’s going to display next (unlike IOMD, where you could change it during the vblank period, and perhaps right up to the start of the first visible scanline?)