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List:       gtkmm
Subject:    [gtkmm] How to notify the parent?
From:       "Chan Siu On" <siuonchan () hotmail ! com>
Date:       2001-06-23 9:58:40
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Hello,

Assume that there is a class MyDrawingArea inherited from Gtk::DrawingArea, 
and a class MyWindow inherited from Gtk::Window.

If MyWindow has a child of class MyDrawingArea and the child has received 
certain signals, says the user has pressed and then released a mouse 
button, how can the child notify the parent that it has received such a 
signal?

Sometimes I have to do some processing in 
MyDrawingArea::button_release_event_impl(). It would be nice if I do not 
connect MyDrawingArea::button_release_event directly to a method of 
MyWindow, but instead I create a new signal member field for MyDrawingArea, 
says MyDrawingArea::special_event, and connect this field to a method of 
MyWindow.

I've tried to do so with SigC++ but failed. When the program is running, 
error messages appear saying something like 'cannot find a name "null"' or 
'cannot find <handle_id>'.

Here is part of my source code:

void mydrawingarea_special_event(GtkDrawingArea *drawingarea);

class MyDrawingArea : public Gtk::DrawingArea
{
...
public:
  union
    {
        // I've tried to set this field to 'this' in the constructor
      CppObjectType *drawingarea_self;
        // In the line below, the fourth field in <void, ...> may be the 
cause of the error - I don't know how to fill this field properly or what 
should be done if it is filled with 0
      EmitProxySignal0<void, CppObjectType, BaseObjectType, 0, 
&mydrawingarea_special_event> special_event;
    };
};

What's wrong with the class MyDrawingArea? Or is there any simpler method 
to notify the parent?
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