Error 'Invalid argument' when output path contains backslashes on Windows

[w1th0utnam3]

On Windows it's common that paths contain backslashes (although forward slashes are also supported in many places). However, when I pass a path to a save_to_ function that contains backslashes, I get the following error:

gnuplot> set output "Z:\temp\out\energy\energy3d_test\plot.pdf"
                                                               ^
         line 0:          cannot open file; output not changed
system error: Invalid argument

Currently, I use the following workaround in my code

let output_file = output_path.join("plot.pdf");
if cfg!(windows) {
    // On Windows, gnuplot doesn't accept any backslashes in the path
    let output_file = output_file.to_str().unwrap().replace("\\", "/");
    fg.save_to_pdf(&output_file, 12, 8).unwrap();
} else {
    fg.save_to_pdf(&output_file, 12, 8).unwrap();
}

Either the backslashes have to be somehow escaped when passing them to the gnuplot executable or it doesn't support backslashes in the path at all. In any case, I think this should be handled by this library and not by user code. Unfortunately I don't have time at the moment to investigate this further.