Class interface seems not to add axes

[MrMoose]

Bug category

• bug - compilation error
• bug - compilation warning
• bug - runtime error
• bug - runtime warning
• bug - logic error

Describe the bug

I was attempting to plot two scatter plots in one figure. I am trying to use the "class interface" which doesn't rely on global data in order to be more in-line with the rest of the code and potentially thread in the future.

According to how I understand some examples, this should work:

namespace plt = matplot;
plt::figure_handle figure = plt::figure();
plt::title("Points");
figure->size(1920, 1080);

plt::axes_handle axes_red = figure->add_axes();
plt::line_handle lh1 = axes_red->scatter(x, y, 10);
lh1->marker_face_color(plt::string_to_color("red"));

plt::axes_handle axes_blue = figure->add_axes();
plt::line_handle lh2 = axes_blue->scatter(h, y, 10);
lh2->marker_face(true);
lh2->marker_face_color(plt::string_to_color("blue"));

figure->save(...);

However, if I do it like this, the second axes (plot) will always replace the first and only one plot is drawn. If I insert this (which as I understand is meant to be for global data interface):

...
plt::axes_handle axes_red = figure->add_axes();
plt::line_handle lh1 = axes_red->scatter(x, y, 10);
lh1->marker_face_color(plt::string_to_color("red"));
plt::hold(true);
plt::axes_handle axes_blue = figure->add_axes();
plt::line_handle lh2 = axes_blue->scatter(h, y, 10);
...

It works. Am I misusing this? Because I was under the impression hold() is only needed for global data interface and add_axes() is pretty clear in it's meaning to add an axes, right?

Steps to Reproduce

Try above code sample.

Output

One scatter plot without hold(), two scatter plots with hold().

Platform

• cross-platform issue - linux
• cross-platform issue - windows
• cross-platform issue - macos

Environment Details:

• OS: Win 10
• OS Version:
• Compiler: MSVC143
• Compiler version:

Additional context

Latest gnuplot installed, matplot++ built from sources with JPEG dependency but without anything else.