From: Groepaz (groepaz_at_gmx.net)
Date: 2002-12-11 19:33:49
On Wednesday 11 December 2002 17:23, Ullrich von Bassewitz wrote:
> What do you mean with that? Does writing to the last line lead always to a
> crash, or is it writing some special position? Is this a behaviour of the
> conio implementation of the VIC20 or is this true for all platforms?
writing _beyond_ the last line makes the conio implementation write beyond the
screen memory. (actually, it will write scattered all around random memory
locations... not necessarily resulting in a crash, sometimes tetris runs for
a while, then behaves funny..and then crashes :o)). all targets that use the
PLOT call and write to the resulting pointers like the vic20 implementation
does should be affected by this. (didnt check, just noticed it with the
vic20). problem is, right now the implementation does not check (somewhere
along the newline function) if output goes beyond the last line (which would
cause scrolling normally) so the cursor position gets incremented in Y one to
far and next time any output is done the PLOT function uses bogus values to
calculate the pointers.
however, what it takes to fix is a check in the newline function... if Y
position larger than max Y position, set it to max Y :o)
> There was a bug with this symptoms long ago, but this one is new. In fact,
> I'm still creative enough to create fresh new bugs, there's no need to
> ressort to old and already used ones:-)
LOL :o)
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This archive was generated by hypermail 2.1.3 : 2002-12-11 19:38:03 CET