Detect click on Gtk::Image?

Question

I've been trying to detect click on a Gtk::Image with gtkmm for over 2 hours, but I couldn't get it to work. It does compile and execute fine, but the event is never triggered.

Some stuff I tried, that compiles, does not crash, but doesn't work:

m_image = manage(new Gtk::Image(Gtk::Stock::APPLY, Gtk::ICON_SIZE_BUTTON));
m_image->add_events(Gdk::ALL_EVENTS_MASK); 
m_hbox->pack_start(*m_image, Gtk::PACK_SHRINK);

m_image->signal_button_release_event()
    .connect(sigc::hide(sigc::mem_fun(*this, &Todo::switchStatus)));

m_image->show();

or

#include <gtkmm/main.h>
#include <gtkmm/window.h>
#include <gtkmm/button.h>
#include <gtkmm/stock.h>
#include <gtkmm/image.h>

#include <iostream>

using namespace std;

class Win : public Gtk::Window
{
    public:
        Win();
        bool link(GdkEventButton* e);

    private:
        Gtk::Image image;
};

Win::Win()
    : image(Gtk::Stock::APPLY, Gtk::ICON_SIZE_BUTTON)
{
    cerr << "created" << endl;

    image.add_events(Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK);
    image.signal_button_release_event().connect(sigc::mem_fun(*this, &Win::link));
    image.show();

    add(image);
}

bool Win::link(GdkEventButton* e)
{
    cerr << "kuh" << endl;
}

int main(int argc, char *argv[])
{
    Gtk::Main   app(argc, argv);

    Gtk::Window window;
    window.resize(300, 500);

    Win win;

    Gtk::Main::run(win);

    return 0;
}

Answer 1

From http://developer.gnome.org/gtkmm/unstable/classGtk_1_1Image.html:

Gtk::Image is a "no window" widget (has no Gdk::Window of its own), so by default does not receive events. If you want to receive events on the image, such as button clicks, place the image inside a Gtk::EventBox, then connect to the event signals on the event box

So I guess try to put a signal on an eventbox after wrapping the image with the EventBox.

Answer 2

This thread is quite old but still popular. I came across the same problem and I coded this code, maybe it can help someone save tim. My code detects the click ONLY if the pointer is hovering the image.

#include <gtk/gtk.h>

//compile with cc `pkg-config --cflags gtk+-3.0` text.c `pkg-config --libs gtk+-3.0` -o text

static void click_callback(GtkWidget *widget, GdkEventButton *event, gpointer );
static gboolean inRange(gint value, gint min, gint max);
static gboolean pointInRect(gint mouseX, gint mouseY, gint wx, gint wy, gint width, gint height);

GtkWidget *image;
GtkWidget *image2;

int main (int argc, char *argv[])
{
  GtkWidget *event_box;
  GtkWidget *window;
  GtkWidget *box;

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  box = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0);

  /* GTK_ALIGN_CENTER is necessary otherwise 
   * the callback triggers from the space on
   * the top and the bottom of the image */

  gtk_widget_set_valign(box, GTK_ALIGN_CENTER);

  image  = gtk_image_new_from_file("image1.png");
  image2 = gtk_image_new_from_file("image2.png");
  gtk_box_pack_start(GTK_BOX(box), image, TRUE, FALSE, 0);
  gtk_box_pack_start(GTK_BOX(box), image2, TRUE, FALSE, 0);

  event_box = gtk_event_box_new ();
  gtk_container_add (GTK_CONTAINER (event_box), box);

  gtk_container_add (GTK_CONTAINER (window), event_box);

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

  g_signal_connect( event_box, "button_press_event", G_CALLBACK( click_callback ), image);

  gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
  gtk_window_set_title(GTK_WINDOW(window), "Image click event");

  gtk_widget_show_all(window);

 gtk_main();

  return 0;
}

static void click_callback(GtkWidget *widget, GdkEventButton *event, gpointer data)
{
    GtkAllocation alloc;
    GtkAllocation alloc2;

    gtk_widget_get_allocation(image, &alloc);
    gtk_widget_get_allocation(image2, &alloc2);

    if (pointInRect(event->x, event->y, alloc.x, alloc.y, alloc.width, alloc.height))
        g_print("You clicked from image\n");

    if (pointInRect(event->x, event->y, alloc2.x, alloc2.y, alloc2.width, alloc2.height))
        g_print("You clicked from image2\n");

}

static gboolean pointInRect(gint mouseX, gint mouseY, gint wx, gint wy, gint width, gint height)
{
    return inRange(mouseX, wx, wx + width) && 
            inRange(mouseY, wy, wy + height);
}

static gboolean inRange(gint value, gint min, gint max)
{
    return (value >= min && value <= max);
}