[PATCH gtk-3-16] GtkComboBox wrong menu_ypos

[Leslie Zhai <xiang zhai i-soft com cn>]

Hi Gtk developers,

I pay more attention to the gtk_combo_box_menu_position, the user 
supplied function used to position the menu, when pressed the combobox 
button 
https://git.gnome.org/browse/gtk+/tree/gtk/gtkcombobox.c?h=gtk-3-16#n2268

I argue that it ignore the relationship between DisplayHeight (use X11 
style), GdkEventButton`s y_root and popup menu`s allocation height 
https://twitter.com/xiangzhai/status/605902462189314048

If DisplayHeight minus y_root is smaller than menu_alloc_height, the 
menu_ypos should be minus menu_alloc_height, then my workaround patch 
shown as below, not a monkey patch any more ;) 
https://mail.gnome.org/archives/gtk-devel-list/2015-June/msg00000.html


diff --git a/gtk/gtkcombobox.c b/gtk/gtkcombobox.c
index ccda6ad..ce60473 100644
--- a/gtk/gtkcombobox.c
+++ b/gtk/gtkcombobox.c
@@ -159,6 +159,7 @@ struct _GtkComboBoxPrivate
   GdkDevice *grab_keyboard;

   gchar *tearoff_title;
+  guint y_root;
 };

 /* While debugging this evil code, I have learned that
@@ -1125,6 +1126,8 @@ gtk_combo_box_init (GtkComboBox *combo_box)
   priv->text_column = -1;
   priv->text_renderer = NULL;
   priv->id_column = -1;
+
+  priv->y_root = 0;
 }

 static void
@@ -1898,6 +1901,18 @@ gtk_combo_box_menu_position_below (GtkMenu *menu,
    *push_in = FALSE;
 }

+static GdkRectangle m_get_monitor_geo()
+{
+  GdkRectangle r;
+  GdkDisplay *display = gdk_display_get_default();
+  GdkScreen *screen = gdk_display_get_default_screen(display);
+  gint mon_id = gdk_screen_get_primary_monitor(screen);
+
+  gdk_screen_get_monitor_geometry(screen, mon_id, &r);
+
+  return r;
+}
+
 static void
 gtk_combo_box_menu_position_over (GtkMenu  *menu,
                                   gint     *x,
@@ -1938,6 +1953,13 @@ gtk_combo_box_menu_position_over (GtkMenu *menu,
       menu_ypos -= child_allocation.height / 2;
     }

+  gtk_widget_get_allocation(GTK_WIDGET(menu), &allocation);
+  GdkRectangle display_rect = m_get_monitor_geo();
+  if (display_rect.height - combo_box->priv->y_root < allocation.height) {
+    menu_ypos -= allocation.height;
+  }
+
   children = GTK_MENU_SHELL 
(combo_box->priv->popup_widget)->priv->children;
   while (children)
     {
@@ -3237,6 +3261,7 @@ gtk_combo_box_menu_button_press (GtkWidget      
*widget,
           !gtk_widget_has_focus (priv->button))
         gtk_widget_grab_focus (priv->button);

+      priv->y_root = event->y_root;
       gtk_combo_box_menu_popup (combo_box, event->button, event->time);

       return TRUE;


What about ***unimplented*** part? menu_ypos minus popup menu`s 
allocation height is not enough when popup menu ***active*** item is, 
for example, last one not the first, then menu_ypos should be plus the 
height of active item to the first one, sorry for my poor English ;P

--
Regards,
Leslie Zhai