grants@usage.csd.unsw.oz (Grant Sayer) (01/23/89)
I am trying to draw two images one on an offscreen pixelmap and then quickly swap the images, testing if a subject can detect the colour changes. The problem is that with the vertical retrace the subject will see part of the scan line which interrupts the picture. Does the method of placing the code which swaps the images, basically a copybits operation, into the VBL task queue seem a viable solution. If this is the casethen is it true that Turbo Pascal failsto allow procedures to be passed using the @ operator on the procedure name thereby preventing installation of the drawing procedure into VBInstall Any comments or suggestions would be appreciated Thanks in advance Grant Sayer (grants%usage.csd.unsw.oz@munnari.oz)
vincent@ditsyda.oz (David A. Vincent) (01/24/89)
in article <243@usage.csd.unsw.oz>, grants@usage.csd.unsw.oz (Grant Sayer) says: > Xref: ditsyda aus.mac:414 comp.sys.mac.programmer:2784 comp.sys.mac:18246 > > > I am trying to draw two images one on an offscreen pixelmap and then [...] >code which swaps the images, basically a copybits operation, into the VBL >task queue seem a viable solution. If this is the casethen is it true This seems viable provided that the copybits can be completed during the VBL period. >that Turbo Pascal failsto allow procedures to be passed using the @ >operator on the procedure name thereby preventing installation of the >drawing procedure into VBInstall TP allows you to apply @ to proc. or func. and pass the resulting pointer to an assembly-language routine (which I think is all you need to do). TP does not allow you to use such a pointer except to pass it around as a parameter. > > Any comments or suggestions would be appreciated > > Thanks in advance You're welcome. > Grant Sayer (grants%usage.csd.unsw.oz@munnari.oz) David A. Vincent vacation student, CSIRO Division of IT ACSnet: vincent@ditsyda.oz Post: GPO Box 1710-T Phone (w): +61 2 887 9383 Hobart TAS 7001 FidoNet: 3:670/700 Australia ---------------------------------------------------------------- Common sense is not all that common. -- Bertrand Russell.