Versione attuale delle 16:09, 1 mag 2023

Con alcune risorse della libreria di X11 è possibile, premendo la combinazione del tasto "Ctrl" e un altro tasto della tastiera, uscire da un'applicazione Gambas.

E' necessario richiamare nell'applicazione Gambas la libreria condivisa del sistema X11: "libX11.so.6.4.0 ".

Mostriamo un semplice esempio pratico, nel quale, premendo la combinazione dei tasti Ctrl e "q ", si determinerà la chiusura dell'applicazione Gambas che contiene il codice:

Library "libX11:6.4.0"

Private Enum KeyPress = 2, KeyRelease, ButtonPress, ButtonRelease, MotionNotify, EnterNotify, LeaveNotify,
                           FocusIn, FocusOut, KeymapNotify, Expose, GraphicsExpose, NoExpose
Private Const GrabModeAsync As Integer = 1
Private KeyPressMask As Integer = 1 * CInt(2 ^ 0)
Private ControlMask As Integer = 1 * CInt(2 ^ 2)
Private ShiftMask As Integer = 1 * CInt(2 ^ 0)

' Display *XOpenDisplay(char *display_name)
' Opens a connection to the X server that controls a display.
Private Extern XOpenDisplay(display_name As Pointer) As Pointer

' Window XDefaultRootWindow(Display *display)
' Returns the root window for the default screen.
Private Extern XDefaultRootWindow(display As Pointer) As Integer

' KeyCode XKeysymToKeycode(Display *display, KeySym keysym)
' Obtains a KeyCode for a key having a specific KeySym.
Private Extern XKeysymToKeycode(display As Pointer, keysym As Integer) As Integer

' XGrabKey(Display *display, int keycode, unsigned int modifiers, Window grab_window, Bool owner_events, int pointer_mode, int keyboard_mode)
' Passively grabs a single key of the keyboard.
Private Extern XGrabKey(display As Pointer, keycode As Integer, modifiers As Integer, grab_window As Integer, owner_events As Boolean, pointermode As Integer, keyboard_mode As Integer)

' XSelectInput(Display *display, Window w, long event_mask)
' Requests that the X server report the events associated with the specified event mask.
Private Extern XSelectInput(display As Pointer, w As Integer, event_mask As Long)

' XNextEvent(Display *display, XEvent *event_return)
' Gets the next event and remove it from the queue.
Private Extern XNextEvent(display As Pointer, event_return As Pointer)

' XUngrabKey(Display *display, int keycode, unsigned int modifiers, Window grab_window)
' Ungrabs a key.
Private Extern XUngrabKey(display As Pointer, keycode As Integer, modifiers As Integer, Window As Pointer)

' XCloseDisplay(Display *display)
' Closes a display or disconnects from the X server.
Private Extern XCloseDisplay(display As Pointer)


Public Sub Main()

 Dim dpy, ev As Pointer
 Dim root, keycode As Integer
    
 ev = Alloc(SizeOf(gb.Byte), 192)
  
 dpy = XOpenDisplay(0)
 If dpy == 0 Then Error.Raise("Errore !")  
 
 root = XDefaultRootWindow(dpy)
  
 keycode = XKeysymToKeycode(dpy, Asc("q"))
  
 XGrabKey(dpy, keycode, ControlMask Or ShiftMask, root, False, GrabModeAsync, GrabModeAsync)
   
 XSelectInput(dpy, root, KeyPressMask)
  
 While True
   XNextEvent(dpy, ev)
   Select Case Int@(ev)
     Case KeyPress
       Print "Premuto il tasto 'q' !"
       XUngrabKey(dpy, keycode, ControlMask Or ShiftMask, root)
       Break
   End Select
 Wend
  
 Free(ev)
 XCloseDisplay(dpy)
  
End

Riferimenti

• https://tronche.com/gui/x/
• http://www.x.org/archive/X11R7.5/doc/libX11/libX11.html