Multiplot fails if it is the first plot in the script

When a script has a multiplotas it's very first plot, the plot produced it's a regular plot, the second plot overwrites the first one withouth any error indication:

Let's use this small example:

import numpy as np
import gnuplotlib as gp
th = np.linspace(0, 2*np.pi, 100)
x1 = np.cos(th)
y1 = np.sin(th)
x2 = 2*np.cos(th)
y2 = 3*np.sin(th)

gp.plot(
    ((
        x1,
        y1,
        dict(
            legend = "Circle",
            _with = "linespoints dt 4 pt 4",
        )),
     dict(
         title="Circle",
         xlabel="X",
         ylabel="Y",
     )),
    ((
        x2,
        y2,
        dict(
            legend = "Ellipse",
            _with = "linespoints dt 4 pt 4",
        )),
     dict(title="Ellipse",
         xlabel="X",
         ylabel="Y",
     )),
    _wait=True,
    square=True,
    multiplot="layout 2,1"
)

This produces the following output:

As we see, the Ellipse plot has overwritten the Circle plot, totally ignoring the multiplot argument. No warnings, no errors. Just silently ignores the option.

However, if we add a regular plot before the multiplot:

import numpy as np
import gnuplotlib as gp
th = np.linspace(0, 2*np.pi, 100)
x1 = np.cos(th)
y1 = np.sin(th)
x2 = 2*np.cos(th)
y2 = 3*np.sin(th)
# Dummy plot so multiplot doesn't fail
gp.plot(
    np.sin(th),
    np.cos(th),
    _wait=True,
)

gp.plot(
    ((
        x1,
        y1,
        dict(
            legend = "Circle",
            _with = "linespoints dt 4 pt 4",
        )),
     dict(
         title="Circle",
         xlabel="X",
         ylabel="Y",
     )),
    ((
        x2,
        y2,
        dict(
            legend = "Ellipse",
            _with = "linespoints dt 4 pt 4",
        )),
     dict(title="Ellipse",
         xlabel="X",
         ylabel="Y",
     )),
    _wait=True,
    square=True,
    multiplot="layout 2,1"
)

We get the desired output

One curious effect is that this only works if _wait=True is provided in the Dummy Plot

まず issue にある 2 つの Python 再現コードを実行し、プロジェクト内の plot と multiplot の処理を追跡します。最初の plot のケースと、ダミーの plot および _wait=True が前にあるケースを比較します。最初の plot が multiplot="layout 2,1" を使用するスクリプトで、ダミーの plot を必要とせず、最初の plot を暗黙に上書きすることもなく、両方の plot がレンダリングされれば完了です。