The width of the chart in viewport space. This is only used when drawing in screenspace via DrawScreenspace(), but ignored when drawing via Draw(). Viewport space goes from lower-left (= 0,0) to upper-right (= 1,1).
The name "*_relToCamViewport" is ambiguous, because it leaves open if the width is relative to the camera viewport height or the the camera viewport width. This decision is made via the optional "chartWidth_isDefinedRelTo_cameraWidth_notCameraHeight" parameter of the DrawScreenspace() function. The default is "relative to viewport width".