How to handle double-click events in GTK+3? - c

Question

I was wondering how to produce double clicks?
Take the following code that draws lines using single clicks http://zetcode.com/gfx/cairo/basicdrawing/:
#include <cairo.h>
#include <gtk/gtk.h>
static void do_drawing(cairo_t *);
struct {
int count;
double coordx[100];
double coordy[100];
} glob;
static gboolean on_draw_event(GtkWidget *widget, cairo_t *cr,
gpointer user_data)
{
do_drawing(cr);
return FALSE;
}
static void do_drawing(cairo_t *cr)
{
cairo_set_source_rgb(cr, 0, 0, 0);
cairo_set_line_width(cr, 0.5);
int i, j;
for (i = 0; i <= glob.count - 1; i++ ) {
for (j = 0; j <= glob.count - 1; j++ ) {
cairo_move_to(cr, glob.coordx[i], glob.coordy[i]);
cairo_line_to(cr, glob.coordx[j], glob.coordy[j]);
}
}
glob.count = 0;
cairo_stroke(cr);
}
static gboolean clicked(GtkWidget *widget, GdkEventButton *event,
gpointer user_data)
{
if (event->button == 1) {
glob.coordx[glob.count] = event->x;
glob.coordy[glob.count++] = event->y;
}
if (event->button == 3) {
gtk_widget_queue_draw(widget);
}
return TRUE;
}
int main(int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *darea;
glob.count = 0;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
darea = gtk_drawing_area_new();
gtk_container_add(GTK_CONTAINER(window), darea);
gtk_widget_add_events(window, GDK_BUTTON_PRESS_MASK);
g_signal_connect(G_OBJECT(darea), "draw",
G_CALLBACK(on_draw_event), NULL);
g_signal_connect(window, "destroy",
G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(window, "button-press-event",
G_CALLBACK(clicked), NULL);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_window_set_default_size(GTK_WINDOW(window), 400, 300);
gtk_window_set_title(GTK_WINDOW(window), "Lines");
gtk_widget_show_all(window);
gtk_main();
return 0;
}
How do I get this program to respond to double clicks events instead of the single clicks?
I cannot find it in this list https://lazka.github.io/pgi-docs/Gtk-3.0/classes/Button.html#Gtk.Button.signals.clicked.

Answer 1

From GdkEventButton:
For double-clicks the order of events will be:
GDK_BUTTON_PRESS
GDK_BUTTON_RELEASE
GDK_BUTTON_PRESS
GDK_2BUTTON_PRESS
GDK_BUTTON_RELEASE
Note that the first click is received just like a normal button press,
while the second click results in a GDK_2BUTTON_PRESS being received
just after the GDK_BUTTON_PRESS.
(...)
For a double click to occur, the second button press must occur within 1/4 of a second of the first.
Each GdkEvent has a GdkEventType field that you can check for GDK_2BUTTON_PRESS or GDK_DOUBLE_BUTTON_PRESS (alias added in 3.6):
a mouse button has been double-clicked (clicked twice within a short
period of time). Note that each click also generates a
GDK_BUTTON_PRESS event.
in button-press-event callback.
#include <gtk/gtk.h>
gboolean clicked(GtkWidget *widget, GdkEventButton *event, gpointer user_data)
{
if(event->type == GDK_DOUBLE_BUTTON_PRESS)
printf("double\n");
return TRUE;
}
int main (int argc, char *argv[])
{
gtk_init (&argc, &argv);
GtkWidget *window;
GtkWidget *label;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
label = gtk_label_new("label");
gtk_container_add(GTK_CONTAINER(window), label);
g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
gtk_widget_add_events(window, GDK_BUTTON_PRESS_MASK);
g_signal_connect(window, "button-press-event", G_CALLBACK(clicked), NULL);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_window_set_default_size(GTK_WINDOW(window), 400, 300);
gtk_widget_show_all(window);
gtk_main ();
return 0;
}