Re: Problem with "limited with" in a *real* application

["Lucretia" <lucretia9@lycos.co.uk>]

Inside the Sizer package I have an Add procedure which adds a
Window_Type (e.g. Button_Type, Check_Box_Type, etc) into the derived
type to Self, which is a Sizer_Type derived type. So, I want (ideally)
to minimize the casting, so I changed the Window type to take a
Window_Type'Class so that any type can be accepted. Now, this forces me
to cast the Self type in the New_Minimal_Frame procedure (See the
Add's) to the base Sizer_Type. Now in C++ the Add function can be
overridden (as in the case of wxGridBagSizer and they're not virtuals)
so in the case of mapping to Ada in this current form, the programmer
must know which Add to use, i.e. which cast to use, which is fair
enough, but surely it would be easier to let the compiler decide?
Should I use a 'Class type here?

So, with this in mind, it's a possibility that all of the wxAda
primitives could take 'Class types so that no casting is ever needed,
but surely this is wrong, Ada-wise?

The format of the following code might get a bit screwed by Google:

<wx.Core.Sizer>
package wx.Core.Sizer is

  -- This is the actual type (wxSizer) we are creating here.
  type Sizer_Type is new Object_Type with private;

  procedure Add(
    Self       : in out Sizer_Type;
    Window     : in Window_Type'Class;
    Proportion : in Sizer_Proportion_Type := 0;
    Flags      : in Sizer_Flag_Type := 0;
    Border     : in Integer := 0);

end wx.Core.Sizer;
</wx.Core.Sizer>

<Minimal_Frame>
package body Minimal_Frame is

  procedure New_Minimal_Frame(Self : in out Minimal_Frame_Type) is

    procedure Button_Connect is new
wxEvtHandler.Connect(Command_Event_Function);
    procedure Check_Box_Connect is new
wxEvtHandler.Connect(Command_Event_Function);
    procedure My_Test_Connect is new
wxEvtHandler.Connect(On_My_Test_Function);
    procedure Slider_Connect is new
wxEvtHandler.Connect(Scroll_Event_Function);
    procedure Size_Connect is new
wxEvtHandler.Connect(Size_Event_Function);
    procedure Paint_Connect is new
wxEvtHandler.Connect(Paint_Event_Function);

    Field_Widths : Field_Widths_Array(0 .. 1) := (-3, -1);

    package Address_To_Object is new
System.Address_To_Access_Conversions(Minimal_Frame_Type);
    use Address_To_Object;

  begin

    New_Frame(Self, ID_ANY, "Minimal wxAda App", Point_Type'(400,
300));
    Text_IO.Put_Line("Self'Access : " &
System.Address_Image(To_Address(Self'Access)));

    New_Panel(Self.Panel, Window_Type(Self), Id_Any);

    New_Validator(Self.Validator);

    New_Button(Self.Button, Window_Type(Self.Panel),
Id_Type(Id_Test_Button), "Test &Button", Default_Position,
Default_Size, 0);
    Set_Validator(Window_Type(Self.Button), Self.Validator);

    New_Check_Box(Self.Check_Box, Window_Type(Self.Panel), Id_Any,
"Test &Check Box", Style => Check_Box_Align_Right);
    New_Slider(Self.Slider, Window_Type(Self.Panel), Id_Any, 50, 0,
100, Style => Slider_Horizontal or Slider_Labels);
    New_Spin(Self.Spin, Window_Type(Self.Panel), Id_Any, "0", Style =>
Spin_Wrap or Spin_Arrow_Keys);
    New_Scroll_Bar(Self.Scroll_Bar, Window_Type(Self.Panel),
Id_Type(Id_Test_Slider));
    Set_Scroll_Bar(Self.Scroll_Bar, 20, 10, 100, 1000);

    New_Static_Box(Self.Box, Window_Type(Self.Panel), Id_Any,
"Testing...");
    New_Static_Box_Sizer(Self.Sizer, Self.Box'Unchecked_Access,
Box_Sizer_Orientation_Vertical);
    --New_Box_Sizer(Self.Sizer, Box_Sizer_Orientation_Vertical);
    Add(Sizer_Type(Self.Sizer), Self.Button, 1, Sizer_Expand or
Sizer_Border_All, 5);
    Add(Sizer_Type(Self.Sizer), Self.Check_Box, 1, Sizer_Expand or
Sizer_Border_All, 5);
    Add(Sizer_Type(Self.Sizer), Self.Slider, 1, Sizer_Expand or
Sizer_Border_All, 5);
    Add(Sizer_Type(Self.Sizer), Self.Spin, 1, Sizer_Expand or
Sizer_Border_All, 5);
    Add(Sizer_Type(Self.Sizer), Self.Scroll_Bar, 1, Sizer_Expand or
Sizer_Border_All, 5);

    New_Status_Bar(Self.Status_Bar, Window_Type(Self), Id_Any);
    Set_Fields_Count(Self.Status_Bar, Field_Widths);
    Set_Status_Bar(Self, Self.Status_Bar);
    Set_Status_Text(Self.Status_Bar, "Welcome to wxAda!");
--    Set_Status_Widths(Test_Status_Bar, Field_Widths'Length,
Field_Widths);

    Set_Size_Hints(Sizer_Type(Self.Sizer),
Self.Panel'Unchecked_Access);
--    Set_Sizer(Window_Type(Self.Panel), Self.Sizer'Unchecked_Access);
    Set_Sizer(Window_Type(Self.Panel), Sizer_Type(Self.Sizer)'Access);
--    Set_Sizer(Self.Panel, Sizer_Type(Self.Sizer));

    Test_Event.New_Test_Event(Self.My_Test);

    --Button_Connect(Self, Id_Type(ID_TEST_BUTTON), Id_Any,
wx.Base.Event.Command.Button_Clicked, On_Quit'Access);
    Button_Connect(Self, Id_Type(Id_Test_Button), Id_Any,
Evt_Button_Clicked, On_Quit'Access);
    --Check_Box_Connect(Self, Id_Type(ID_TEST_BUTTON), Id_Any,
wx.Base.Event.Command.Check_Box_Clicked, On_Quit'Access);
    Slider_Connect(Self, Id_Type(Id_Test_Slider), Id_Any,
Evt_Scroll_Thumb_Track, On_Scroll_Top'Access);
    Size_Connect(Self, Id_Any, Id_Any, Evt_Size, On_Size'Access);
    --Paint_Connect(Self.Panel, Id_Any, Id_Any, Evt_Paint,
On_Paint'Access);
    Dump(Self);
    My_Test_Connect(Self, Id_Any, Id_Any, Test_Event.My_Test_Event,
On_My_Test'Access);
    
  end New_Minimal_Frame;

end Minimal_Frame;
</Minimal_Frame>