fn draw_pointer(g: &mut Graphics, tip: Vec2, half: f32, color: Color)Expand description
Append the arrow-cursor silhouette to g: a classic pointer filled with
color, sized by NDC half-extent half, anchored at its hot-spot tip.
A single convex quad — tip, vertical left edge, tail point, right barb —
because Graphics::draw_polygon fan-triangulates from the first vertex
(a notched arrow would self-overlap) and because the dark-outline-behind
trick (set_cursor draws a larger dark copy then a white one) only stays
registered for a compact shape near the tip: scaling a far-from-tip tail
about the tip would bloat its border out of proportion. The four points
read unmistakably as a pointer while keeping both invariants.