Styjun

I develop in C a GTK graphical user interface consisting in a main window embedding a GtkImage widget.
I cannot retrieve the correct mouse pointer coordinates with respect to the GtkImage widget inside the click event handler when clicking on my GtkImage widget.

I tried both solutions given by the link given below but none of them work:
How do you find the absolute position of a GTK widget in a window?

See below my code :

static void activate(GtkApplication *app, gpointer user_data)

 GtkWidget *window;
 GtkWidget *grid;

 id.rows = ROWS;
 id.cols = COLS;
 id.stride = COLS * BYTES_PER_PIXEL;
 id.stride += (4 - id.stride % 4) % 4; // ensure multiple of 4

 // Allocate a bitmap
 guchar *pixels = (guchar *)calloc(ROWS * id.stride, 1);
 // Create a GDK Pix buffer from a pre-allocated pixel array
 GdkPixbuf *pixelBuf = gdk_pixbuf_new_from_data(pixels,
 GDK_COLORSPACE_RGB, // colorspace
 0, // has_alpha
 8, // bits-per-sample
 COLS, ROWS, // cols, rows
 id.stride, // rowstride
 free_pixels, // destroy_fn
 NULL // destroy_fn_data
 );

 // Create theGtkImage widget
 GtkImage *image = GTK_IMAGE(gtk_image_new_from_pixbuf(pixelBuf));;
 // Create the main win
 window = gtk_application_window_new(app);
 // Create a grid to automatically place the child widgets
 grid = gtk_grid_new();
 // Stick this grid to the main window
 gtk_container_add(GTK_CONTAINER(window), grid);
 // Create an event box to catch mouse event
 GtkWidget *event_box = gtk_event_box_new();
 // gtk image does'nt handle events, => attach it the event box
 gtk_container_add(GTK_CONTAINER(event_box), GTK_WIDGET(image));
 // Insert the event box into the grid
 gtk_grid_attach(GTK_GRID(grid), GTK_WIDGET(event_box), 0, 0, 1, 1);
 // Connect mouse event to the event box
 g_signal_connect(GTK_WIDGET(event_box), "button-press-event", G_CALLBACK(on_mouse_press),
 pixValEntry);
 // LEt's start the show !
 gtk_widget_show_all(window);



static gboolean on_mouse_press(GtkWidget *widget, GdkEvent *event,
 gpointer user_data)

 GdkEventButton *mouse_click = (GdkEventButton *)event;
 char str[20];

 (void)widget;
 (void)user_data;

 cout << gtk_widget_get_name(widget) << endl;

 if (mouse_click->type == GDK_BUTTON_PRESS)
 
 cout << "mouse_click->x = " << mouse_click->x << endl;
 cout << "mouse_click->y = " << mouse_click->y << endl;
 

(x,y) coordinates shown in the mouse click event handler are shifted and depend on the main window size.
I do not find the way to move from the actual reference system to GtkImage coordinate system.

Many thanks for your help and hints.

Cheers