How to send data from a static function of other Class to a MainWindow function?

[spirit]

It's an interesting interpretation, but I would make this in other way: make this object as a singleton

class Global: public QObject
{
    Q_OBJECT
 
public:
    static Global *instance();
 
    void send_name(const QString &color_name);
...
 
Q_SIGNALS:
   void send_color(const QString &color_name);
 
private:
   Q_DISABLE_COPY(Global);
};
 
#define myGlobal Global::instance()    //shortcut

class Global: public QObject
{
    Q_OBJECT

public:
    static Global *instance();

    void send_name(const QString &color_name);
...

Q_SIGNALS:
   void send_color(const QString &color_name);

private:
   Q_DISABLE_COPY(Global);
};

#define myGlobal Global::instance()    //shortcut

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Then

...
connect(myGlobal, SIGNAL(send_color(const QString &)), SLOT(applyColor(const QString &)));
...
myGlobal->send_name("lightgray");

...
connect(myGlobal, SIGNAL(send_color(const QString &)), SLOT(applyColor(const QString &)));
...
myGlobal->send_name("lightgray");

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