Line Blitter and DMACON::BZERO flag

[dirkwhoffmann]

Test case:
https://github.com/dirkwhoffmann/vAmigaTS/tree/master/Blitter/line/zero1

From the README:

This test runs 12 line blits. Each blit draws a horizontal line with varying line patterns and 
multiple combinations of the SING and USEC bit. After each blit, the value of the Blitter zero 
bit is read and visualized in form of a blue or yellow line.

Amiga 500 8A:

UAE (cycle exact mode):

UAE (immediate blits):

The test fails in UAE because the zero bit is written inside function blitter_line_write() and not outside:

WinUAE/blitter.cpp

Line 682 in 849ed34

blt_info.blitzero = 0;

On the real machine, the bit gets cleared even if nothing is written into memory.

[tonioni]

Thanks, fixed. Unfortunately no one have done weird things with line mode or I would have noticed these kinds of bugs long time ago. Non-line mode on the other hand..