Re: Questions on Key-Press Event

[Bob Caryl <bob fis-cal com>]

Hello,

I have several applications that use more than one window.  I 
implemented context sensitive help by using the following in the 
constructor for the main application window:

// code snippet
Gtk::Main::signal_key_snooper().connect(sigc::mem_fun(*this,&<your 
window class name::your callback slot>));
///////////////////////

where "your window class name" is what it describes, as well as "your 
callback slot."  In the callback slot connected to this signal, you can 
intercept any keystroke you like, then return 1 so the regular keystroke 
handlers will ignore the keystroke, or 0 to allow this event to be 
passed along to them.

The callback syntax is like this:

// code snippet
sigc::slot< int, Widget *, GdkEventKey * >
/////////////////////////////////////////////

or:

// code snippet
int <your widget class name>::<your callback slot name>(Gtk::Widget 
*,GdkEventKey *)
{
   ... your code goes here
}
///////////////////////////////////////////

The widget pointer passed to your function points to the widget that had 
focus when the key was pressed.
GdkEventKey is as follows:

// code snippet
typedef struct {
 GdkEventType type;
 GdkWindow *window;
 gint8 send_event;
 guint32 time;
 guint state;
 guint keyval;
 gint length;
 gchar *string;
 guint16 hardware_keycode;
 guint8 group;
} GdkEventKey;
///////////////////////////////////////////

Describes a key press or key release event.

GdkEventType <cid:part1.01000202.04020205@fis-cal.com> /type/; 	the type 
of the event (GDK_KEY_PRESS or GDK_KEY_RELEASE).
GdkWindow <cid:part2.04000809.05080203@fis-cal.com> */window/; 	the 
window which received the event.
gint8 <cid:part3.09050804.02010101@fis-cal.com> /send_event/; 	TRUE if 
the event was sent explicitly (e.g. using XSendEvent).
guint32 <cid:part4.04020206.09030901@fis-cal.com> /time/; 	the time of 
the event in milliseconds.
guint <cid:part5.06070804.09090804@fis-cal.com> /state/; 	a bit-mask 
representing the state of the modifier keys (e.g. Control, Shift and 
Alt) and the pointer buttons. See GdkModifierType 
<cid:part6.01030209.08030201@fis-cal.com>.
guint <cid:part5.06070804.09090804@fis-cal.com> /keyval/; 	the key that 
was pressed or released. See the <gdk/gdkkeysyms.h> header file for a 
complete list of GDK key codes.
gint <cid:part8.05050907.05060706@fis-cal.com> /length/; 	the length of 
/string/.
gchar <cid:part9.07020608.06070005@fis-cal.com> */string/; 	a string 
containing the an approximation of the text that would result from this 
keypress. The only correct way to handle text input of text is using 
input methods (see GtkIMContext 
<cid:part10.05080800.07080200@fis-cal.com>), so this field is deprecated 
and should never be used. (gdk_unicode_to_keyval() 
<cid:part11.08050709.03050102@fis-cal.com> provides a non-deprecated way 
of getting an approximate translation for a key.) The string is encoded 
in the encoding of the current locale (Note: this for backwards 
compatibility: strings in GTK+ and GDK are typically in UTF-8.) and 
NUL-terminated. In some cases, the translation of the key code will be a 
single NUL byte, in which case looking at /length/ is necessary to 
distinguish it from the an empty translation.
guint16 <cid:part12.00000809.07050707@fis-cal.com> /hardware_keycode/; 
the raw code of the key that was pressed or released.
guint8 <cid:part13.01050009.09090503@fis-cal.com> /group/; 	the keyboard 
group.


I use the "keyval" field of this structure in my application.  The above 
information tells you which include file has all the key values defined.

I hope this helps a little bit.

Bob

Efrat Regev wrote:

>  Hello,
>
>  I'm having some difficulty with key-press events,
> and haven't been able to find answers in the mailing
> list, docs, faqs, etc. I'd very much appreciate any
> help.
>
>  My main window has a menu-bar, tool-bar, and other
> widget children. I'm trying to capture the events of
> the keyboard's arrows being pressed (since the
> application is a simple game). My main window
> overrides
> virtual bool
> my_main_wnd::on_key_press_event(GdkEventKey *p_event).
> This doesn't work (for me), due to two reasons:
> A. When my main window overrides on_key_press_event, I
> get notified of these events, but the keyboard has no
> effect on the window's menu. When I erase the
> override, however, the menu works fine with the
> keyboard. Is there a way to both get the key-press
> event and have the menu working properly?
> B. In on_key_press_event, I switch(){} on
> p_event->keyval. I'm checking for cases such as case
> GDK_leftarrow:, but when I press the left key I get a
> different value (65361), not the one I expect
> (GDK_leftarrow). What should I write in the case _:,
> therefore?
>
>  Again, many thanks for you time. Additionally,
> thanks to all those who contributed to this awesome
> ass-kicking library!
>
>  
>
>
>
>
> 		
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