GtkTreeView inconsistent 'row-activated' signal emission before drag'n'drop, 'activate-on-single-click'=TRUE, 'reorderable'=TRUE

gtk-tree-view-row-activated.c

/*
 * Compile with:
 * gcc $(pkg-config --cflags gtk+-3.0 --libs gtk+-3.0) -lm gtk-tree-view-row-activated.c -o gtk-tree-view-row-activated
 */

#include <stdlib.h>
#include <math.h>
#include <glib.h>
#include <gtk/gtk.h>

/*
 * Debug
 */

static const gchar *
time_now(void)
{
        static gchar *now_str;
        GDateTime *now;

        g_free(now_str);

        now = g_date_time_new_now_local();
        now_str = g_strdup_printf("%02d:%02d:%02d.%03d",
                                  g_date_time_get_hour(now),
                                  g_date_time_get_minute(now),
                                  g_date_time_get_second(now),
                                  lround(g_date_time_get_microsecond(now) / 1000.0));
        g_date_time_unref(now);

        return now_str;
}

#define debug(fmt, ...)	\
	printf("%s: " fmt "\n", time_now(), ##__VA_ARGS__);

/*
 * Signal handlers
 */

static gboolean
idle(gpointer user_data)
{
	debug("Idle");

	return FALSE;
}

static void
on_tree_view_row_activated(GtkTreeView       *tree_view,
                           GtkTreePath       *path,
                           GtkTreeViewColumn *column,
                           gpointer           user_data)
{
	debug("Row activated");
	
	g_idle_add(idle, NULL);
}

static void
on_tree_view_drag_begin(GtkWidget      *widget,
                        GdkDragContext *context,
                        gpointer        user_data)
{
	debug("Drag begin");
}

static void
on_tree_view_drag_end(GtkWidget      *widget,
                      GdkDragContext *context,
                      gpointer        user_data)
{
	debug("Drag end");
	printf("----\n");
}

/*
 * Main
 */

static void
station_cell_data_func(GtkTreeViewColumn *tree_column,
                       GtkCellRenderer   *cell,
                       GtkTreeModel      *tree_model,
                       GtkTreeIter       *iter,
                       gpointer           data)
{
	gchar *text;

	gtk_tree_model_get(tree_model, iter,
	                   0, &text,
	                   -1);
	g_object_set(cell,
	             "text", text,
	             NULL);

	g_free(text);
}

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

	/* Create the tree view */
	GtkWidget *tree_view;
	tree_view = gtk_tree_view_new();

	GtkListStore *list_store;
	list_store = gtk_list_store_new(1, G_TYPE_STRING);
	gtk_tree_view_set_model(GTK_TREE_VIEW(tree_view), GTK_TREE_MODEL(list_store));
	g_object_unref(list_store);

	GtkCellRenderer *renderer;
	renderer = gtk_cell_renderer_text_new();

	GtkTreeViewColumn *column;
	column = gtk_tree_view_column_new_with_attributes("Text", renderer, NULL);
	gtk_tree_view_column_set_cell_data_func(column, renderer,
	                                        station_cell_data_func,
	                                        NULL, NULL);

	gtk_tree_view_append_column(GTK_TREE_VIEW(tree_view), column);

	/* Populate the tree view */
	GtkTreeIter tree_iter;
	gtk_list_store_append(list_store, &tree_iter);
	gtk_list_store_set(list_store, &tree_iter,
	                   0, "Yesterday",
	                   -1);
	gtk_list_store_append(list_store, &tree_iter);
	gtk_list_store_set(list_store, &tree_iter,
	                   0, "Today",
	                   -1);
	gtk_list_store_append(list_store, &tree_iter);
	gtk_list_store_set(list_store, &tree_iter,
	                   0, "Tomorrow",
	                   -1);

	/* Configure the tree view */

	/* Activate on single-click */
	gtk_tree_view_set_activate_on_single_click(GTK_TREE_VIEW(tree_view), TRUE);

	/* Set re-orderable, and therefore enable drag'n'drop */
	gtk_tree_view_set_reorderable(GTK_TREE_VIEW(tree_view), TRUE);

	/* Connect signal handlers */
	g_signal_connect(tree_view, "row-activated",
	                 G_CALLBACK(on_tree_view_row_activated), NULL);
	g_signal_connect(tree_view, "drag-begin",
	                 G_CALLBACK(on_tree_view_drag_begin), NULL);
	g_signal_connect(tree_view, "drag-end",
	                 G_CALLBACK(on_tree_view_drag_end), NULL);

	/* Create the window */
	GtkWidget *box;
	box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 8);
	g_object_set(box, "margin", 8, NULL);

	GtkWidget *label;
	label = gtk_label_new("Try re-ordering the items and look\n"
	                      "for the 'row-activated' signal.\n"
	                      "It may or may not be emitted.");

	gtk_box_pack_start(GTK_BOX(box), label, TRUE, FALSE, 0);
	gtk_box_pack_start(GTK_BOX(box), tree_view, TRUE, FALSE, 0);

	GtkWidget *window;
	window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	gtk_container_add(GTK_CONTAINER(window), box);
	gtk_widget_show_all(window);

	/* Main loop */
	gtk_main();

	return EXIT_SUCCESS;
}

Typical output. The signal 'row-activated' is sometimes emitted before the 'drag-begin' signal, sometimes not.

$ ./gtk-tree-view-row-activated 
17:18:19.825: Drag begin
17:18:20.365: Drag end
----
17:18:23.175: Row activated
17:18:23.178: Drag begin
17:18:23.182: Idle
17:18:23.796: Drag end
----
17:18:25.581: Row activated
17:18:25.584: Drag begin
17:18:25.588: Idle
17:18:26.265: Drag end
----
17:18:27.613: Row activated
17:18:27.615: Drag begin
17:18:27.619: Idle
17:18:28.154: Drag end
----
17:18:29.894: Drag begin
17:18:30.719: Drag end
----