GTK key-press-event

GTK key-press-event

[hreba]

Hi,

I am trying to write a key press handler with user data. I know how to 
connect the handler and that its type is

type Handler is access procedure
	Widget    : access Widget_Type'Class;
         Params    : Glib.Values.GValues;
	User_Data : User_Type);

What I don't know is how to get the key which was pressed.

A few months ago I had a similar problem where I needed a Cairo Graphics 
context, and I got it from the parameter list "Params" , selecting the 
first component with Glib.Values.Nth(), and converting that with 
Cairo.Get_Context.

Does anybody know how to get Gdk_Event_Key (which contains the 
information about the pressed key)?
-- 
Frank Hrebabetzky		+49 / 6355 / 989 5070

Re: GTK key-press-event

[Dmitry A. Kazakov]

On 02/11/2016 10:19, hreba wrote:

> I am trying to write a key press handler with user data. I know how to
> connect the handler and that its type is
>
> type Handler is access procedure
>     Widget    : access Widget_Type'Class;
>         Params    : Glib.Values.GValues;
>     User_Data : User_Type);

There is a typed marshaller for handing this type of events:

    type Handler is access function
         (  Widget    : access Gtk_Widget_Record'Class;
            Event     : Gdk_Event;
            User_Data : User_Type
         )  return Boolean;

> What I don't know is how to get the key which was pressed.

The event parameter contains input event type and if that was a keyboard 
event, the key pressed/released:

    case Get_Event_Type (Event) is
       when Key_Press => -- This a key-press event
          case Get_Key_Val (Event) is
             when GDK_Insert => -- This is INSERT key
                ...

> A few months ago I had a similar problem where I needed a Cairo Graphics
> context, and I got it from the parameter list "Params" , selecting the
> first component with Glib.Values.Nth(), and converting that with
> Cairo.Get_Context.

You could use Nth () but there is no reason doing that. And for this 
type of event there is a return value.

Note that key press events must be unmasked to be emitted. Then some 
widgets never emit these events anyway. They must be wrapped into an 
"event-box" which itself is invisible but emits the events.

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

Re: GTK key-press-event

[hreba]

On 11/02/2016 10:45 AM, Dmitry A. Kazakov wrote:
> On 02/11/2016 10:19, hreba wrote:
>
>> I am trying to write a key press handler with user data. I know how to
>> connect the handler and that its type is
>>
>> type Handler is access procedure
>>     Widget    : access Widget_Type'Class;
>>         Params    : Glib.Values.GValues;
>>     User_Data : User_Type);
>
> There is a typed marshaller for handing this type of events:
>
>    type Handler is access function
>         (  Widget    : access Gtk_Widget_Record'Class;
>            Event     : Gdk_Event;
>            User_Data : User_Type
>         )  return Boolean;
>
>> What I don't know is how to get the key which was pressed.
>
> The event parameter contains input event type and if that was a keyboard
> event, the key pressed/released:
>
>    case Get_Event_Type (Event) is
>       when Key_Press => -- This a key-press event
>          case Get_Key_Val (Event) is
>             when GDK_Insert => -- This is INSERT key
>                ...
>
>> A few months ago I had a similar problem where I needed a Cairo Graphics
>> context, and I got it from the parameter list "Params" , selecting the
>> first component with Glib.Values.Nth(), and converting that with
>> Cairo.Get_Context.
>
> You could use Nth () but there is no reason doing that. And for this
> type of event there is a return value.
>
> Note that key press events must be unmasked to be emitted. Then some
> widgets never emit these events anyway. They must be wrapped into an
> "event-box" which itself is invisible but emits the events.
>

It works now. My widget is a DrawingArea. In addition to unmasking the 
key press event, the "can focus" flag must be set. An event box was not 
necessary.

Thanks for your help.
-- 
Frank Hrebabetzky		+49 / 6355 / 989 5070