According to MS docs, psDot style must give nice looking 1 pixel dots. https://docs.microsoft.com/en-us/windows/desktop/gdi/pen-style

Lazarus creates pen via Widgetset's ExtCreatePen which calls Win32 ExtCreatePen.

reality: If I set psDot to StringGrid.GridLineStyle, I get ugly dots: each of about 3 pixels fragments. psDash is ugly too: dashes are very long.

Why?

Line styles are dependent on the ‘Cosmetic’ and ‘EndCap’ settings. For Cosmetic pens with 1-pixel wide lines the dots are elongated. For wider lines it is possible to get round dots by using the ‘pecRound’ cap style.

If you want to get 1 pixel dots followed by 1 pixel spaces then this works for dotted Geometric (Cosmetic = false) pen but only looks OK for horizontal and vertical lines. Guess this is good for grid cell borders.

Regard,
Nigel

Thanks for this info, made a patch for Grids.

1 pixel dots followed by 1 pixel spaces then this works for dotted

Geometric (Cosmetic = false) pen