Ottenere informazioni sulle applicazioni client in esecuzione su un display con le funzioni del API di X11

La libreria X11 ci consente anche di ottenere alcune informazioni generiche sulle applicazioni client in esecuzione su un display.

Sarà necessario richiamare la libreria del sistema X (nella sua attuale versione): "libX11.so.6.3.0"

Mostriamo di seguito un possibile breve codice al riguardo:

Public Struct XTextProperty
  value As Pointer
  encoding As Long
  formatI As Integer
  nitems As Long
End Struct

Public Struct XClassHint
  res_name As Pointer
  res_class As Pointer
End Struct


Library "libX11:6.3.0"

Private Const XA_STRING As Integer = 31

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

' Window XDefaultRootWindow(display)
' Return the root window for the default screen.
Private Extern XDefaultRootWindow(displayP As Pointer) As Integer

' Status XGetWMClientMachine(Display *display, Window w, XTextProperty *text_prop_return)
' Performs an XGetTextProperty() on the WM_CLIENT_MACHINE property.
Private Extern XGetWMClientMachine(display As Pointer, w As Long, text_prop_return As XTextProperty) As Integer

' Status XGetCommand(Display *display, Window w, char ***argv_return, int *argc_return)
' Reads the WM_COMMAND property from the specified window and returns a string list.
Private Extern XGetCommand(display As Pointer, w As Long, argv_return As Pointer, argc_return As Pointer) As Integer

' int XFree(void *)
' It's a general-purpose Xlib routine that frees the specified data.
Private Extern XFree(po As Pointer) As Integer

' char * XGetAtomName(Display *display, Atom atom) as pointer
' Returns the name associated with the specified atom.
Private Extern XGetAtomName(display As Pointer, atom As Long)

' XGetWMName(Display *display, Window w, XTextProperty *text_prop_return)
' Calls XGetTextProperty() to obtain the WM_NAME property.
Private Extern XGetWMName(displayP As Pointer, w As Long, text_prop_return As XTextProperty) As Integer

' Status XGetWMIconName(Display *display, Window w, XTextProperty *text_prop_return)
' Calls XGetTextProperty() to obtain the WM_ICON_NAME property.
Private Extern XGetWMIconName(displayP As Pointer, w As Long, text_prop_return As XTextProperty) As Integer

' Status XQueryTree(Display *display, Window w, Window *root_return, Window *parent_return, Window **children_return, unsigned int *nchildren_return)
' Returns the root ID, the parent window ID, a pointer to the list of children windows (NULL when there are no children), and the number of children in the list for the specified window.
Private Extern XQueryTree(displayP As Pointer, w As Long, root_return As Pointer, parent_return As Pointer, children_return As Pointer, nchildren_return As Pointer) As Integer

' Status XGetClassHint(Display *display, Window w, XClassHint *class_hints_return)
' Returns the class hint of the specified window to the members of the supplied structure.
Private Extern XGetClassHint(displayP As Pointer, w As Long, class_hints_return As XClassHint) As Integer

' XCloseDisplay (display)
' Closes a display or disconnect from the X server.
Private Extern XCloseDisplay(displayP As Pointer)


' Window XmuClientWindow(Display *dpy, Window win)
' Finds a window at or below the specified window which has a WM_STATE property.
Private Extern XmuClientWindow(displayP As Pointer, w As Long) As Long In "libXmu:6.2.0"


' void exit(int status)
' Terminates the calling process immediately.Any Open file descriptors belonging To the process are closed And any children Of the process are inherited.
Private Extern exitus(status As Integer) In "libc:6" Exec "exit"


Public Sub Main()

 Dim i, nc As Integer
 Dim dis, figli As Pointer
 Dim dm, root, client, l As Long
 Dim st As Stream
   
  dis = XOpenDisplay(Null)
  If IsNull(dis) Then Error.Raise("Impossibile aprire lo schermo !")
   
  root = XDefaultRootWindow(dis)
  Proprieta_Clienti(dis, root)

  If Not XQueryTree(dis, root, VarPtr(dm), VarPtr(dm), VarPtr(figli), VarPtr(nc)) Then Return

  st = Memory figli For Read

  For i = 0 To nc - 1
    Read #st, l
    client = XmuClientWindow(dis, l)
    If client <> 0 Then Proprieta_Clienti(dis, client)
  Next
  st.Close
   
   
' Va in chiusura:
  XCloseDisplay(dis)
  exitus(0)
   
End


Private Procedure Proprieta_Clienti(dis As Pointer, w As Long)

 Dim mxtp, nxtp, xtp As New XTextproperty
 Dim clh As New XClassHint
 Dim cli, i As Integer
 Dim clip, p As Pointer
 Dim st As Stream
 Dim s As String
 
  If Not XGetWMClientMachine(dis, w, mxtp) Then
    mxtp.value = 0
    mxtp.encoding = 0
  Endif

  clip = Alloc(8)

  If Not XGetCommand(dis, w, VarPtr(clip), VarPtr(cli)) Then
    If IsNull(mxtp.value) = False Then XFree(mxtp.value)
    Return
  Endif

' Scrive l'informazione d'intestzione dell'applicazione:
  Print "\nFinestra &"; Hex(w); ":"
  If IsNull(mxtp.value) Then Print "nullo", Hex(w)
  Testo(dis, "  Machine:  ", mxtp)

  If XGetWMName(dis, w, nxtp) Then
    Testo(dis, "  Name:  ", nxtp)
    If IsNull(nxtp.value) = False Then XFree(nxtp.value)
  Endif

  If IsNull(mxtp.value) = False Then XFree(mxtp.value)

  If XGetWMIconName(dis, w, xtp) <> 0 Then
    Testo(dis, "  Icon Name:  ", xtp)
    If IsNull(xtp.value) = False Then XFree(xtp.value)
  Endif

' Scrive il comando dell'applicazione:
  st = Memory clip For Read

  While i < cli
    Read #st, p
    Print "  Command:  "; String@(p)
    Inc i
  Wend
  st.Close


  s = "  Instance/Class:  "
  If XGetClassHint(dis, w, clh) Then
    If IsNull(clh.res_name) = False Then
      s &= String@(clh.res_name)
      XFree(clh.res_name)
    Endif
    s &= "/"
    If IsNull(clh.res_class) = False Then
      s &= String@(clh.res_class)
      XFree(clh.res_class)
    Endif
  Endif
  Print s
    
End


Private Procedure Testo(dis As Pointer, s As String, xtp As XTextproperty)
 
  If (xtp.encoding = 0) Or (xtp.formatI = 0) Then
    Print ""
    Return
  Endif

  If (xtp.encoding = XA_STRING) And (xtp.formatI = 8) Then
    If IsNull(xtp.value) = False Then
      s &= String@(xtp.value)
      Print s
    Endif
  Else
    s &= Sconosciuto(dis, xtp.encoding, xtp.formatI)
  Endif

End


Private Function Sconosciuto(dis As Pointer, tipo As Long, formato As Integer) As String
  
 Dim s As String
 
  s = "<Tipo sconosciuto "
   
  If tipo = 0 Then
    s &= "Nessuno"
  Else If IsNull(XGetAtomName(dis, tipo)) = False Then
    s &= XGetAtomName(dis, tipo)
  Else
    Print Null
  Endif

  s &= CStr(tipo) & " o formato " & CLong(formato) & ">"
   
  Return s
 
End