QwtPlotIntervalCurve(3) on Linux
The text de90074ad480, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster) shipped it. The page shows this text now.
QwtPlotIntervalCurve represents a series of samples, where each value is associated with an interval ( $[y1,y2] = f(x)$ ).