为什么我的GTK +信号回调中出现分段错误？ [英] Why do I get a segmentation fault in my GTK+ signal callback?

问题描述

  #include< gtk / gtk.h>我们正在测量一个GTK标签的大小： 
 
 static void map_event（GtkWidget * window，gpointer lab）{
 g_print（In the callback..\\\
）; 
 GtkWidget * label = GTK_WIDGET（lab）; 
 g_print（一切正常......）; 
 
 
 static void activate（GtkApplication * app，gpointer user_data）
 {
 GtkWidget * window = gtk_application_window_new（app）; 
 gtk_window_set_title（GTK_WINDOW（window），Window1）; 
 gtk_window_set_default_size（GTK_WINDOW（window），200，280）; 
 GtkWidget * grid = gtk_grid_new（）; 
 gtk_container_add（GTK_CONTAINER（window），grid）; 
 GtkWidget * label = gtk_label_new（Hello world！）; 
 gtk_grid_attach（GTK_GRID（grid），label，0,0,1,1）; 
 g_signal_connect（window，map-event，G_CALLBACK（map_event），label）; 
 gtk_widget_show_all（window）; 
 
 
 int main（int argc，char ** argv）{
 GtkApplication * app = gtk_application_new（
org.gtk.example，G_APPLICATION_FLAGS_NONE）; 
 g_signal_connect（app，activate，G_CALLBACK（activate），NULL）; 
 int status = g_application_run（G_APPLICATION（app），argc，argv）; 
 g_object_unref（app）; 
 
返回状态; 
} 
  

这给出了输出：

 在回调中。
分段错误（核心转储）
  

如果我注释掉该行：

  GtkWidget * label = GTK_WIDGET（lab）; 
  

没有分段错误，标签出现并且输出为：

 在回调中.. 
一切正常.. 
  

我在这里错过了什么？

解决方案

map-event 有以下签名，因此您缺少 GdkEvent * 参数：

  gboolean 
 user_function（GtkWidget * widget，
 GdkEvent * event，
 gpointer user_data）
  

<不幸的是，GTK +是用C语言编写的，所以它没有类型安全的回调函数，所以很容易出现这样的错误。

I am trying to measure the size of a GTK label:

#include <gtk/gtk.h>

static void map_event(GtkWidget *window, gpointer lab) {
    g_print( "In the callback..\n" );
    GtkWidget *label = GTK_WIDGET(lab);
    g_print( "Everything is ok..\n" );
}

static void activate (GtkApplication* app, gpointer user_data)
{
    GtkWidget *window = gtk_application_window_new (app);
    gtk_window_set_title (GTK_WINDOW (window), "Window1");
    gtk_window_set_default_size (GTK_WINDOW (window), 200, 280);
    GtkWidget *grid = gtk_grid_new ();
    gtk_container_add (GTK_CONTAINER (window), grid);
    GtkWidget *label = gtk_label_new("Hello world!");
    gtk_grid_attach(GTK_GRID (grid), label, 0,0,1,1);
    g_signal_connect (window, "map-event", G_CALLBACK(map_event), label);
    gtk_widget_show_all (window);
}

int main (int argc, char **argv) {
    GtkApplication *app = gtk_application_new (
        "org.gtk.example", G_APPLICATION_FLAGS_NONE );
    g_signal_connect( app, "activate", G_CALLBACK(activate), NULL);
    int status = g_application_run(G_APPLICATION(app), argc, argv);
    g_object_unref (app);

    return status;
}

This gives output:

In the callback..
Segmentation fault (core dumped)

If I comment out the line:

GtkWidget *label = GTK_WIDGET(lab);

there is no segmentation fault, the label shows up and the output is:

In the callback..
Everything is ok..

What am I missing here?

解决方案

map-event has following signature, so you are missing GdkEvent* argument:

gboolean
user_function (GtkWidget *widget,
               GdkEvent  *event,
               gpointer   user_data)

Unfortunately, GTK+ is written in C, so it lacks type-safe callback functions, so it's easy to make mistakes such as this.

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