Inquire True Markersize and Linewidth

[EmDash00]

Hi, been working on a project and was wondering if there was a way to get the true markersize or linewidth in NDC. Right now the setlinewidth and setmarkersize functions return a scale factor and I'd like more fine grained control if possible.

[jheinen]

The attributes are scaling factors according to the GKS definition. However, we have ensured that the results are the same in all logical device drivers. Perhaps this (Julia) example illustrates how the factors could be handled:

using GR

const LINEWIDTH_TO_NDC = 1/500
const MARKERSIZE_TO_NDC =  500/6

function lines()
    y = 0.4
    for w in (1, 2, 5, 10, 20, 50)
        setlinewidth(w)
        polyline([0, 0.25], [y + w*0.5*LINEWIDTH_TO_NDC, y + w*0.5*LINEWIDTH_TO_NDC])
        y += 0.1
    end
end

function markers()
    setmarkertype(-1)
    setmarkercolorind(983)
    setbordercolorind(1)
    x = y = 0
    for s = (0.1, 0.2, 0.3, 0.4)
        x += s
        y = x
        setmarkersize(s * MARKERSIZE_TO_NDC)
        polymarker([x - 0.5*s], [y - 0.5*s])
   end
end

selntran(0)
grid(0.01, 0.01, 0, 0, 10, 10)

markers()
lines()

updatews()

The conversion factors may seem unusual at first glance - but we had to define a nominal size for marker symbols and line widths (internally) at an early stage of development in order to achieve comparable results (even with other GKS implementations) on different output devices.

[EmDash00]

That makes sense. If they're constant across all device drivers, it might be convenient to include these as constants. I wasn't aware of these factors' existence until now.