将附加参数传递给gtk函数 [英] Passing additional arguments to gtk function

问题描述

我想学习如何使用gtk + 3.0制作GUI。我想传递一个简单的参数，一个整数，到一个回调函数，这样当我按下按钮的参数的值改变。这是我的代码：

I'm trying to learn how to make GUIs using gtk+ 3.0. I want to pass a simple argument, an integer, to a callback function, so that when I press the button the value of the argument changes. Here's my code:

#include <gtk/gtk.h>

void buttonFunction(GtkWidget * widget, gpointer data, int & n){
    n = 1;
}

int main(int argc, char ** argv){
    int n = 0;
    GtkWidget * window;
    GtkWidget * button; 

    gtk_init(&argc,&argv);

    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    button = gtk_button_new_with_label("Osss");

    gtk_container_add(GTK_CONTAINER(window),button);
    gtk_widget_show_all(window);

    g_signal_connect(G_OBJECT(window), "destroy",G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), n);

    gtk_main();

    return 0;
}

我发现传递参数的唯一方法是作为指针：

The only way I found to pass the argument was as a pointer:

void buttonFunction(GtkWidget * widget, gpointer * data);
g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), &n);

如何以这种方式传递多个参数？

How do I pass multiple arguments this way tho?

推荐答案

要传递多个参数，可以定义一个结构，填充它，然后传递一个指向结构的指针，如 gpointer user_data g_signal_connect 的参数，这是最后一个参数。然后在您的回调中，您只需将 user_data 参数转换为指向您的结构的指针。

To pass multiple arguments, you define a structure, fill it, and pass a pointer to the structure as the gpointer user_data parameter of the g_signal_connect, which is the last parameter. Then in your callback, you just cast the user_data parameter to a pointer to your structure.

int main (int argc, char **argv)
{
    int n = 0;
    GtkWidget *window;
    GtkWidget *button; 

    gtk_init (&argc,&argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    button = gtk_button_new_with_label ("Osss");

    gtk_container_add (GTK_CONTAINER(window), button);
    gtk_widget_show_all (window);

    g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);

    /* Here's the magic: you pass a pointer to the variable you'd like to modify
     * in the callback, be it a simple variable or a struct */
    g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(buttonFunction), &n);

    gtk_main();

    return 0;
}

void on_button_clicked (GtkButton *button, gpointer user_data) /* No extra parameter here ! */
{
    /* you cast to the type of what you passed as last argument of g_signal_connect */ 
    int *pn = user_data; 
    *pn = 1;
}

您必须使用文档中定义的回调的签名信号部分的文档的GtkButton），你不能做的东西。 BTW，你不能通过 n 作为引用而不是指针。如果你想在C ++中使用GTK，看看GTKmm。

You MUST use the signature of the callback defined in the documentation (look at the "signals" section of the documentation for GtkButton), you can't make things up. BTW, you can't pass n as a reference instead of a pointer. If you want to use GTK in C++, give a look at GTKmm.

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