GTK: set the mouse cursor on the Scintilla view to signal business and on the popup entries

* By default, use the "text" cursor - this is the default Scintilla cursor, but
  inhibited by the GtkEventBox I used to catch all input events.
* When processing input events, the cursor is changed to "wait".
  This is done with a small delay in order to avoid flickering during normal typing.
  The cursor is only changed after 100ms of activity, i.e. only when executing long loops
  or external programs.
* We use the raw GSource API since it's tricky to work with source ids if the
  source could be removed in the meantime.
* The popup entries' cursor is also changed to "pointer" (hand) to give a hint that
  it can be clicked.

3 files changed, 61 insertions, 3 deletions

diff --git a/TODO b/TODO
index 289e724..d297e1b 100644
--- a/TODO
+++ b/TODO
@@ -345,9 +345,7 @@ Features:
    Perhaps blinking or invisible?
    The problem is, this won't work so easily once we use a Scintilla
    minibuffer everywhere.
-   Gtk could at the very least use the hourglass cursor.
- * Gtk: Change the cursor when hovering over popup entries.
-   The text area should have the "I" beam unless we're busy.
+   Gtk already sets the "wait" cursor when busy.
  * Command to free Q-Register (remove from table).
    e.g. FQ (free Q). :FQ could free by QRegister prefix name for
    the common use case of Q-Register subtables and lists.
diff --git a/src/interface-gtk/gtk-info-popup.c b/src/interface-gtk/gtk-info-popup.c
index b9ca41c..aaa0a65 100644
--- a/src/interface-gtk/gtk-info-popup.c
+++ b/src/interface-gtk/gtk-info-popup.c
@@ -47,6 +47,7 @@ struct _TecoGtkInfoPopup {
 	GtkAdjustment *hadjustment, *vadjustment;
 
 	GtkWidget *flow_box;
+	GdkCursor *cursor; /*< pointer/hand cursor */
 	GStringChunk *chunk;
 	teco_stailq_head_t list;
 	guint idle_id;
@@ -74,6 +75,9 @@ teco_gtk_info_popup_finalize(GObject *obj_self)
 	while ((entry = teco_stailq_remove_head(&self->list)))
 		g_free(entry);
 
+	if (self->cursor)
+		g_object_unref(self->cursor);
+
 	/* chain up to parent class */
 	G_OBJECT_CLASS(teco_gtk_info_popup_parent_class)->finalize(obj_self);
 }
@@ -354,6 +358,16 @@ teco_gtk_info_popup_idle_add(TecoGtkInfoPopup *self, teco_popup_entry_type_t typ
 
 	gtk_widget_show_all(hbox);
 	gtk_container_add(GTK_CONTAINER(self->flow_box), hbox);
+
+	GtkWidget *flow_box_child = gtk_widget_get_parent(hbox);
+	g_assert(GTK_IS_FLOW_BOX_CHILD(flow_box_child));
+	GdkWindow *window = gtk_widget_get_window(flow_box_child);
+	g_assert(window != NULL);
+
+	if (G_UNLIKELY(!self->cursor))
+		/* we only initialize it now after guaranteed widget realization */
+		self->cursor = gdk_cursor_new_from_name(gdk_window_get_display(window), "pointer");
+	gdk_window_set_cursor(window, self->cursor);
 }
 
 static gboolean
diff --git a/src/interface-gtk/interface.c b/src/interface-gtk/interface.c
index a41890d..5330bfa 100644
--- a/src/interface-gtk/interface.c
+++ b/src/interface-gtk/interface.c
@@ -60,6 +60,8 @@
 
 //#define DEBUG
 
+static gboolean teco_interface_busy_timeout_cb(gpointer user_data);
+static void teco_interface_event_box_realized_cb(GtkWidget *widget, gpointer user_data);
 static void teco_interface_cmdline_size_allocate_cb(GtkWidget *widget,
                                                     GdkRectangle *allocation,
                                                     gpointer user_data);
@@ -312,6 +314,8 @@ teco_interface_init(void)
 	gtk_box_pack_start(GTK_BOX(overlay_vbox), teco_interface.event_box_widget,
 	                   TRUE, TRUE, 0);
 
+	g_signal_connect(teco_interface.event_box_widget, "realize",
+			 G_CALLBACK(teco_interface_event_box_realized_cb), NULL);
 	g_signal_connect(teco_interface.event_box_widget, "size-allocate",
 			 G_CALLBACK(teco_interface_size_allocate_cb), NULL);
 
@@ -402,6 +406,17 @@ teco_interface_init(void)
 	teco_interface_cmdline_update(&empty_cmdline);
 }
 
+static void
+teco_interface_set_cursor(GtkWidget *widget, const gchar *name)
+{
+	GdkWindow *window = gtk_widget_get_window(widget);
+	g_assert(window != NULL);
+	GdkDisplay *display = gdk_window_get_display(window);
+
+	g_autoptr(GdkCursor) cursor = name ? gdk_cursor_new_from_name(display, name) : NULL;
+	gdk_window_set_cursor(window, cursor);
+}
+
 GOptionGroup *
 teco_interface_get_options(void)
 {
@@ -1332,6 +1347,29 @@ teco_interface_cleanup(void)
  */
 
 /**
+ * Called some time after processing an input event in order to show
+ * business.
+ *
+ * The delay avoids cursor flickering during normal typing.
+ *
+ * @fixme It would be nicer to set the cursor for the entire window,
+ * but that would apparently require another GtkEventBox, spanning everything.
+ */
+static gboolean
+teco_interface_busy_timeout_cb(gpointer user_data)
+{
+	teco_interface_set_cursor(teco_interface.event_box_widget, "wait");
+	return G_SOURCE_REMOVE;
+}
+
+static void
+teco_interface_event_box_realized_cb(GtkWidget *widget, gpointer user_data)
+{
+	/* It's only now safe to get the GdkWindow. */
+	teco_interface_set_cursor(widget, "text");
+}
+
+/**
  * Called when the commandline widget is resized.
  * This should ensure that the caret jumps to the middle of the command line,
  * imitating the behaviour of the current Curses command line.
@@ -1398,6 +1436,10 @@ teco_interface_input_cb(GtkWidget *widget, GdkEvent *event, gpointer user_data)
 
 	recursed = TRUE;
 
+	GSource *busy_timeout = g_timeout_source_new(500); /* ms */
+	g_source_set_callback(busy_timeout, teco_interface_busy_timeout_cb, NULL, NULL);
+	g_source_attach(busy_timeout, NULL);
+
 	teco_memory_start_limiting();
 
 	g_queue_push_tail(teco_interface.event_queue, gdk_event_copy(event));
@@ -1471,6 +1513,10 @@ teco_interface_input_cb(GtkWidget *widget, GdkEvent *event, gpointer user_data)
 
 	teco_memory_stop_limiting();
 
+	g_source_destroy(busy_timeout);
+	g_source_unref(busy_timeout);
+	teco_interface_set_cursor(teco_interface.event_box_widget, "text");
+
 	recursed = FALSE;
 	return TRUE;
 }