U++

It seems that LabelBox colors is not emulated when GTK styling is on.

This is my solution (well tested - please reed comment - CtrlLib/ChGtk.cpp):

        GtkWidget *label = gtk_label_new("Ch");
        Setup(label);
        Color labelColor = ChGtkColor(0, label);
        SColorLabel_Write(labelColor);
        gtk_widget_destroy(label);

                GtkWidget *frame = gtk_frame_new("");
        Setup(frame);
        /*
        GtkWidget *frameLabel = gtk_frame_get_label_widget((GtkFrame*)frame); // <- Default GTK label (We don't need this). We will use label color to emulate this!!!
        Setup(frameLabel); // <- For some reason it causes IDE crash, but without calling this emulation will failed (Text always black).
        */
        Color frameColor = ChGtkColor(4, frame); // <- Why "4"? I don't know, but it works perfect on light/dark theme. "1, 2, 3" doesn’t work at all!
        LabelBoxColor_Write(frameColor);
        LabelBoxTextColor_Write(labelColor); // <- We are using labelColor from labelWidget.
        gtk_widget_destroy(frame);

To apply patch please use diff version (without unnecessary comments). Of course I enclose several examples. Final version is similar to Windows version.