> I want to present kind of "demo" for QL on the retro-computing > competition called Forever see: http://forever.zeroteam.sk > I did some graphics already on PC and it looks good (looks cool in > fact > :-). But, I need to write special screen hadler with following > conditions: > > 1) I need to use both screens of the QL without affecting of the 2nd > screen by system variables. 1. Standard QDOS cannot handle the second screen area, system variables have to stay at address decimal 163840
2. Minerva version of QDOS can handle second screen. Am I missing something here, or could you just set up a 32K buffer area in memory and write an assembler routine to fast copy graphics to the standard screen? Or is it essential to be able to build up a graphic on one screen and switch "instantly"? The display control register address on a QL is hex 18063, where bit 1 blanks the display (used by some screen savers in the past), bit 3 sets 256 pixel mode 8, and bit 7 sets screen base (I thinkit is 0 for standard, 1 for second screen, although I can't remember from memory). There are some useful routines in Quanta's software library, including a nice little routine which sets a mixed mode display - allowing part of the screen to be in mode 4 for 85 column text and another part in mode 8 to have 8 colours. I can't remember how it works, presumably using interrupts of some kind to ensure switching of modes at the right time in the frame. The QL's display hardware is pretty primitive, but various people over the years have achieved a surprising amount with it. -- Dilwyn Jones _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
