On 5/21/23 13:30, Gonzalo Garramuño wrote:

El 21/5/23 a las 16:07, Manolo escribió:

The example program calls function fl_scale(double x, double y) with null x and y.

Correct, as a side effect of not initializing the values.

    A scale of 0.0 does sound bad, and I might expect that to cause a matrix error.
    If you just add a check in your code so the x,y scale never gets below, for example, 0.1,
    does that fix the app?

    FWIW I was able to get your app to work by adding the above scale check,
    adding colorbar pixels, and drawing dots with fl_begin_complex_polygon() / fl_circle(),
    the attached code gives me:

Pretty close to the old tektronix vectorscopes, but without the NTSC orientations:



I suppose digital vectorscopes don't have to bother with that old
ntsc weirdness, though I thought maybe they'd keep it for consistency (shrug),
with the zero axis being at the far left, representing the "vomit yellow" of
colorburst, and then rotating clockwise through the color circle towards
yellow, red, magenta, etc. This way a grayscale (zero chroma) ended up
as a straight horizontal line going to the left.