GTK keypress event propagation either causes recursion or does not work

问题

I have a simple GTK program containing a single webkit2 widget in a window and nothing else. I want to be able to filter the keypresses going to the webkit2 widget. At first I added a key mask to the webkit widget and added a callback function, however after propogating the event in the callback function it just calls itself recursively which results in a crash. To resolve this I attached my key mask to the main-window, which is parent to my webkit widget, however this no longer prevents input from getting stopped and sometimes key release events recursively call each other. I was wondering how to achieve my goal? (I've used all different types of propogation mentioned on the GTK+ input event handeling documentation page.)

current key mask:

    gtk_widget_add_events(GTK_WIDGET(main_window), GDK_KEY_PRESS_MASK);
    g_signal_connect(G_OBJECT(GTK_WIDGET(main_window)), "key_press_event", G_CALLBACK(keypressHandeler), NULL);
    g_signal_connect(G_OBJECT(GTK_WIDGET(main_window)), "key_release_event", G_CALLBACK(keypressHandeler), NULL);

current callback function (the return is just to see if the propogation worked at the moment)

gboolean keypressHandeler(GtkWidget *widget, GdkEventKey *event, gpointer data){
    if(event->type == GDK_KEY_PRESS)
        printf("Key press\n");
    if(event->type == GDK_KEY_RELEASE)
        printf("Key release\n");
    return gtk_widget_event(GTK_WIDGET(webView), event);
}

回答1:

The problem in your code is that you're manually simulating the signal through gtk_widget_event() (https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-event)

so after the first time keypressHandeler gets called gtk_widget_event will simulate the same event again so it will run in an endless loop.

if you return false or true in "keypressHandeler" your code will work

#include <gtk/gtk.h>
#include <webkit2/webkit2.h>



WebKitWebView *webView;

gboolean keypressHandeler(GtkWidget *widget, GdkEventKey *event, gpointer data)
{
    if (event->type == GDK_KEY_PRESS)
        printf("Key press from mainwindow\n");
    if (event->type == GDK_KEY_RELEASE)
        printf("Key release\n");

    //for the key use want to propogate 
       if (dont wanna propogate )
        {
          return TRUE;
         } else {
          return FALSE;
        }

}

gboolean keypressHandeler2(GtkWidget *widget, GdkEventKey *event, gpointer data)
{
    if (event->type == GDK_KEY_PRESS)
        printf("Key press from webkit\n");
    if (event->type == GDK_KEY_RELEASE)
        printf("Key release\n");
    // set it as TRUE to stop porpogation.. (for some reason it propogating to mainwindow once)
    return TRUE;
}

static void destroyWindowCb(GtkWidget* widget, GtkWidget* window);
static gboolean closeWebViewCb(WebKitWebView* webView, GtkWidget* window);

int main(int argc, char* argv[])
{
    // Initialize GTK+
    gtk_init(&argc, &argv);

    // Create an 800x600 window that will contain the browser instance
    GtkWidget *main_window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(main_window), 800, 600);

    // Create a browser instance
    webView = WEBKIT_WEB_VIEW(webkit_web_view_new());

    // Put the browser area into the main window
    gtk_container_add(GTK_CONTAINER(main_window), GTK_WIDGET(webView));

    // Set up callbacks so that if either the main window or the browser instance is
    // closed, the program will exit
    gtk_widget_add_events(GTK_WIDGET(main_window), GDK_KEY_PRESS_MASK);
   g_signal_connect(G_OBJECT(GTK_WIDGET(main_window)), "key_press_event", G_CALLBACK(keypressHandeler), NULL);
    g_signal_connect(G_OBJECT(GTK_WIDGET(webView)), "key_press_event", G_CALLBACK(keypressHandeler2), NULL);
   g_signal_connect(G_OBJECT(GTK_WIDGET(main_window)), "key_release_event", G_CALLBACK(keypressHandeler), NULL);
    g_signal_connect(G_OBJECT(GTK_WIDGET(webView)), "key_release_event", G_CALLBACK(keypressHandeler2), NULL);

    g_signal_connect(main_window, "destroy", G_CALLBACK(destroyWindowCb), NULL);
    g_signal_connect(webView, "close", G_CALLBACK(closeWebViewCb), main_window);

    // Load a web page into the browser instance
    webkit_web_view_load_uri(webView, "http://www.webkitgtk.org/");

    // Make sure that when the browser area becomes visible, it will get mouse
    // and keyboard events
    gtk_widget_grab_focus(GTK_WIDGET(webView));

    // Make sure the main window and all its contents are visible
    gtk_widget_show_all(main_window);

    // Run the main GTK+ event loop
    gtk_main();

    return 0;
}


static void destroyWindowCb(GtkWidget* widget, GtkWidget* window)
{
    gtk_main_quit();
}

static gboolean closeWebViewCb(WebKitWebView* webView, GtkWidget* window)
{
    gtk_widget_destroy(window);
    return TRUE;
}

If this what your trying.. whats happening is that when you set GDK_KEY_PRESS_MASK it is also being reflected on the webkit.

so if you comment " g_signal_connect(G_OBJECT(GTK_WIDGET(main_window)), "key_press_event", G_CALLBACK(keypressHandeler), NULL);" the program should work fine

returning true for mainwindow handler will stop the propagation to the webview and returning false will allow propagation.

来源：https://stackoverflow.com/questions/58981660/gtk-keypress-event-propagation-either-causes-recursion-or-does-not-work

标签

gtk

keypress