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Jan 23rd, 2018, 7:10pm

Cross-platform BBC BASIC (Win32, Linux x86, Android, Mac OS-X, Raspberry Pi)

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 thread  Author  Topic: 'Omit last point' plotting (SDL bug)  (Read 121 times)
Richard Russell

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xx 'Omit last point' plotting (SDL bug)
« Thread started on: Jan 12th, 2017, 8:51pm »

If you've tried BBCSDL you may have noticed an anomaly: the 'omit last point' (more correctly 'plot last point twice') PLOT codes 8-15 work correctly in Linux but not in MacOS (or Windows, or Android) - effectively the effect of codes 0-7 and 8-15 are reversed.

This is strange, because in every case the underlying renderer is OpenGL (OpenGLES on Android) so why should plotting work differently? The answer seems to be because there is code in SDL2 specifically to make it behave differently in Linux! It's pretty clear that this code shouldn't be there (maybe it was to workaround a bug in OpenGL which has since been fixed) but there's nothing I can do about that - at least until SDL is next updated.

So I am going to have to incorporate a workaround in the next release of BBCSDL. It's annoying, and it may not be a complete cure, but it's better than what we have now. It will also mean that BBCSDL will then fail if SDL is later updated to fix the bug. Grrr!

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