ruby-****@sourc*****
ruby-****@sourc*****
2009年 2月 23日 (月) 08:26:51 JST
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REMOTE_ADDR = 74.15.84.244
REMOTE_HOST =
URL = http://ruby-gnome2.sourceforge.jp/hiki.cgi?tut-gtk2-mnstbs-statb
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@@ -169,3 +169,10 @@
eventbox.realize
window.show_all
Gtk.main
+
+
+When implementing status bar hints, you first need to figure out what signals are necessary. We want to be able to add a message to the status bar when the mouse cursor moves over the menu item, and remove it when the cursor leaves. For this scenario the ((*enter-notify-event*)) and ((*leave-notify-event*)) seem like a reasonable choice.
+
+When working with signals we usually have to be concerned about the callback block parameters that are passed along when a callback is invoked. Namely if we use a single callback method for two different signals, like our ((*statusbar_hint*)) method, we should rely on these parameters to identify which event occurred, and most likely which device (in our case menu item) emitted it. Both ((*'enter-notify-event'*)) and ((*'leave-notify-event'*)) pass the signal emitting widget, and the Gtk::EventCrossing object which is a descendant of Gtk::Event object that will provide us with the needed info, namely whether we are dealing with an entering or leaving cursor. For that we use the Gtk::Event#event_type accessor method retrieving either Gdk::Event::ENTER_NOTIFY or Gdk::Event::LEAVE_NOTIFY event id value.
+
+To identify the menu item, we had to do some preparation work at the time when menu items were created. We assigned them the name by calling Gtk::Widget#name=. We use this name in two places: (1) to store status messages in a hash where this widget's (menu item's) name is the key, and (2) in callback method where we use this menu item's name as a key to retrieve the appropriate message.