vdu 25,80,x;y; do wrong triangles about agon-vdp

[lennart-benschop]

1.04 RC2 honours the plot mode, therefore 80 is a relative move (without drawing anything). For a triangle you should now use PLOT 85 instead of PLOT 80.

[breakintoprogram]

@DjPoke have you tried 1.04 RC2? That's got more support for the VDU plot commands than RC1.

[DjPoke]

@DjPoke have you tried 1.04 RC2? That's got more support for the VDU plot commands than RC1.

Under RC2, with my real AgonLight2, triangles are almost entirely black.

[DjPoke]

This is a photography of my Agon Light 2 not drawing triangles.
screenshot

[DjPoke]

Thanks for the information. Just checked on RC2, there is no more the black color issue.
Now, RC2 do like RC1 : a triangle is not drawn exactly at the same place than a line. There is an offset of 1 pixel. (for the same coordinates)

[DjPoke]

If it can help: drawing a line from x1 to x2 is equal to drawing a line from x1+width-1.
I think the bug is something like this, just one pixel of difference.

[stevesims]

there is every chance that there's an off-by-one issue with filled shapes - the underlying graphics system has a concept of "line" and "fill", which doesn't quite fit with what we're doing - so we might need to tweak things slightly

FYI there is now a "rectangle fill" plot command range - they're numbered 0x60-67, so the "absolute plot in current foreground colour" version of that is 0x65 (or 101 in decimal)

[stevesims]

finally looked into this

it's not quite the "off-by-one" issue I thought it might be. my quick test in BASIC of drawing a straight (vertical) line and then plotting a triangle over the top of that left the top and bottom pixels of that original line still visible.

I've raised a PR that fixes. the fix is to call drawPath before fillPath in the triangle plotting routine - this ensures that the triangle corner pixels do get plotted as expected in my tests, and will cover all other triangle plots to ensure they always cover the same pixels as regular line plots