On_Button_Press_Event in Text_View

On_Button_Press_Event in Text_View

[Gavin McCord]

Using gtkada (gtk3), is it possible to use a custom handler to
deal with a button-press-event (or other events if necessary)
inside a widget such as a Text_View?

For example I create a Text_View with buffer. To process a
button-press within that view I have this code in my main
procedure:

  The_View.On_Button_Press_Event (Press_CB'Access);
  The_View.Set_Events (The_View.Get_Events or Button_Press_Mask);

The callback looks like this:

  function Press_CB (Self  : access Gtk_Widget_Record'Class;
                     Event : Gdk_Event_Button)
                     return Boolean is
   begin
      Put_Line ("Mouse click in text view");
      return True;
   end Press_CB;

So far, so good.

But I'd like to pass additional data to the callback,
without using global variables/records if it can be
avoided.

I have a custom handler used when I update the Text_Buffer:

 Button_Callback.Connect
   (Update_Button, "clicked", Update_Clicked'Access,
    Buffer_To_Pass);

That works fine so I was imagining something similar might
be possible, but I've run through various permuations of
records and access types but not yet got a working callback.

Any help gratefully received (I can post the full code if
that's useful).

Kind regards,

Gavin McCord

Re: On_Button_Press_Event in Text_View

[Dmitry A. Kazakov]

On 2024-08-13 13:37, Gavin McCord wrote:

> I have a custom handler used when I update the Text_Buffer:
> 
>   Button_Callback.Connect
>     (Update_Button, "clicked", Update_Clicked'Access,
>      Buffer_To_Pass);
> 
> That works fine so I was imagining something similar might
> be possible, but I've run through various permuations of
> records and access types but not yet got a working callback.
> 
> Any help gratefully received (I can post the full code if
> that's useful).

Something like this:

    package Event_Handlers is
       new Gtk.Handlers.User_Return_Callback
           (  GObject_Record,
              Boolean,
              User_Data_Type
           );


    function On_Button_Press
             (  Object : access GObject_Record'Class;
                Event  : Gdk_Event;
                Data   : User_Data_Type
             )  return Boolean;


    View.Set_Events (View.Get_Events or Button_Press_Mask);
    Event_Handlers.Connect
    (  View,
       "button-press-event",
       Event_Handlers.To_Marshaller (On_Button_Press'Access),
       Data
    );

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: On_Button_Press_Event in Text_View

[Gavin McCord]

On Tue, 13 Aug 2024 22:29:59 +0200, Dmitry A. Kazakov wrote:

> On 2024-08-13 13:37, Gavin McCord wrote:
> 
>> I have a custom handler used when I update the Text_Buffer:
>> 
>>   Button_Callback.Connect
>>     (Update_Button, "clicked", Update_Clicked'Access,
>>      Buffer_To_Pass);
>> 
>> That works fine so I was imagining something similar might be possible,
>> but I've run through various permuations of records and access types
>> but not yet got a working callback.
>> 
>> Any help gratefully received (I can post the full code if that's
>> useful).
> 
> Something like this:
> 
>     package Event_Handlers is
>        new Gtk.Handlers.User_Return_Callback
>            (  GObject_Record,
>               Boolean, User_Data_Type
>            );
> 
> 
>     function On_Button_Press
>              (  Object : access GObject_Record'Class;
>                 Event  : Gdk_Event; Data   : User_Data_Type
>              )  return Boolean;
> 
> 
>     View.Set_Events (View.Get_Events or Button_Press_Mask);
>     Event_Handlers.Connect (  View,
>        "button-press-event",
>        Event_Handlers.To_Marshaller (On_Button_Press'Access),
>        Data
>     );

Thank you. That allows me to pass a record of the buffer.

There's only one other thing.

If I try to check the Event I get another error, such as

 function On_Button_Press
 [skipped lines]

    if Event.The_Type = Gdk_2button_Press then
       Put_Line ("double-click");
    end if;

Attempting to compile that gives me

   error: cannot reference discriminant of unchecked union


Gavin McCord

Re: On_Button_Press_Event in Text_View

[Dmitry A. Kazakov]

On 2024-08-14 13:42, Gavin McCord wrote:
> On Tue, 13 Aug 2024 22:29:59 +0200, Dmitry A. Kazakov wrote:
> 
>> On 2024-08-13 13:37, Gavin McCord wrote:
>>
>>> I have a custom handler used when I update the Text_Buffer:
>>>
>>>    Button_Callback.Connect
>>>      (Update_Button, "clicked", Update_Clicked'Access,
>>>       Buffer_To_Pass);
>>>
>>> That works fine so I was imagining something similar might be possible,
>>> but I've run through various permuations of records and access types
>>> but not yet got a working callback.
>>>
>>> Any help gratefully received (I can post the full code if that's
>>> useful).
>>
>> Something like this:
>>
>>      package Event_Handlers is
>>         new Gtk.Handlers.User_Return_Callback
>>             (  GObject_Record,
>>                Boolean, User_Data_Type
>>             );
>>
>>
>>      function On_Button_Press
>>               (  Object : access GObject_Record'Class;
>>                  Event  : Gdk_Event; Data   : User_Data_Type
>>               )  return Boolean;
>>
>>
>>      View.Set_Events (View.Get_Events or Button_Press_Mask);
>>      Event_Handlers.Connect (  View,
>>         "button-press-event",
>>         Event_Handlers.To_Marshaller (On_Button_Press'Access),
>>         Data
>>      );
> 
> Thank you. That allows me to pass a record of the buffer.

As a general advice. Usually you have a custom widget derived from 
Gtk_Grid_Record servicing as the main window.

    type Main_Window_Record is new Gtk_Grid_Record with record
       Button    : Gtk_Button;
       Text_View : Gtk_Text_View;
       Buffer    : Gtk_Text_Buffer;
       ...
    type Main_Window is access all Main_Window_Record'Class;

Main_Window you pass to all handlers, so that you always have a full 
context in any of them.

> There's only one other thing.
> 
> If I try to check the Event I get another error, such as
> 
>   function On_Button_Press
>   [skipped lines]
> 
>      if Event.The_Type = Gdk_2button_Press then
>         Put_Line ("double-click");
>      end if;
> 
> Attempting to compile that gives me
> 
>     error: cannot reference discriminant of unchecked union

    case Get_Event_Type (Event) is
       when Button_Press =>
          ...
       when Gdk_2Button_Press | Gdk_3Button_Press =>
          ...
       when Key_Press =>
          case Get_Key_Val (Event) is
             when GDK_Up | GDK_KP_Up =>
                ...
             when GDK_Down | GDK_KP_Down =>
                ...
          end case;
          ...
       when others =>
          ...
    end case;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: On_Button_Press_Event in Text_View

[Gavin McCord]

On Wed, 14 Aug 2024 14:03:24 +0200, Dmitry A. Kazakov wrote:

> On 2024-08-14 13:42, Gavin McCord wrote:
>> On Tue, 13 Aug 2024 22:29:59 +0200, Dmitry A. Kazakov wrote:
>> 
>>> On 2024-08-13 13:37, Gavin McCord wrote:
>>>
>>>> I have a custom handler used when I update the Text_Buffer:
>>>>
>>>>    Button_Callback.Connect
>>>>      (Update_Button, "clicked", Update_Clicked'Access,
>>>>       Buffer_To_Pass);
>>>>
>>>> That works fine so I was imagining something similar might be
>>>> possible,
>>>> but I've run through various permuations of records and access types
>>>> but not yet got a working callback.
>>>>
>>>> Any help gratefully received (I can post the full code if that's
>>>> useful).
>>>
>>> Something like this:
>>>
>>>      package Event_Handlers is
>>>         new Gtk.Handlers.User_Return_Callback
>>>             (  GObject_Record,
>>>                Boolean, User_Data_Type
>>>             );
>>>
>>>
>>>      function On_Button_Press
>>>               (  Object : access GObject_Record'Class;
>>>                  Event  : Gdk_Event; Data   : User_Data_Type
>>>               )  return Boolean;
>>>
>>>
>>>      View.Set_Events (View.Get_Events or Button_Press_Mask);
>>>      Event_Handlers.Connect (  View,
>>>         "button-press-event",
>>>         Event_Handlers.To_Marshaller (On_Button_Press'Access),
>>>         Data
>>>      );
>> 
>> Thank you. That allows me to pass a record of the buffer.
> 
> As a general advice. Usually you have a custom widget derived from
> Gtk_Grid_Record servicing as the main window.
> 
>     type Main_Window_Record is new Gtk_Grid_Record with record
>        Button    : Gtk_Button;
>        Text_View : Gtk_Text_View;
>        Buffer    : Gtk_Text_Buffer;
>        ...
>     type Main_Window is access all Main_Window_Record'Class;
> 
> Main_Window you pass to all handlers, so that you always have a full
> context in any of them.
> 
>> There's only one other thing.
>> 
>> If I try to check the Event I get another error, such as
>> 
>>   function On_Button_Press [skipped lines]
>> 
>>      if Event.The_Type = Gdk_2button_Press then
>>         Put_Line ("double-click");
>>      end if;
>> 
>> Attempting to compile that gives me
>> 
>>     error: cannot reference discriminant of unchecked union
> 
>     case Get_Event_Type (Event) is
>        when Button_Press =>
>           ...
>        when Gdk_2Button_Press | Gdk_3Button_Press =>
>           ...
>        when Key_Press =>
>           case Get_Key_Val (Event) is
>              when GDK_Up | GDK_KP_Up =>
>                 ...
>              when GDK_Down | GDK_KP_Down =>
>                 ...
>           end case;
>           ...
>        when others =>
>           ...
>     end case;

I've got it working now. Get_Event_Type (Event) is what I needed.

Thank you again for all your help.

Gavin