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Text File  |  1994-09-20  |  4.0 KB  |  133 lines
  1.  
  2.  
  3.  
  4. Tk_CreateEventHandler(3T)k Library Procedures
  5.  
  6.  
  7.  
  8. _________________________________________________________________
  9.  
  10. NAME
  11.      Tk_CreateEventHandler,  Tk_DeleteEventHandler  -   associate
  12.      procedure callback with an X event
  13.  
  14. SYNOPSIS
  15.      #include <tk.h>
  16.  
  17.      Tk_CreateEventHandler(_t_k_w_i_n, _m_a_s_k, _p_r_o_c, _c_l_i_e_n_t_D_a_t_a)
  18.  
  19.      Tk_DeleteEventHandler(_t_k_w_i_n, _m_a_s_k, _p_r_o_c, _c_l_i_e_n_t_D_a_t_a)
  20.  
  21. ARGUMENTS
  22.      Tk_Window       _t_k_w_i_n        (in)      Token for  window  in
  23.                                             which    events   may
  24.                                             occur.
  25.  
  26.      unsigned long   _m_a_s_k         (in)      Bit-mask  of   events
  27.                                             (such     as     But-
  28.                                             tonPressMask)     for
  29.                                             which  _p_r_o_c should be
  30.                                             called.
  31.  
  32.      Tk_EventProc    *_p_r_o_c        (in)      Procedure  to  invoke
  33.                                             whenever  an event in
  34.                                             _m_a_s_k  occurs  in  the
  35.                                             window    given    by
  36.                                             _t_k_w_i_n.
  37.  
  38.      ClientData      _c_l_i_e_n_t_D_a_t_a   (in)      Arbitrary    one-word
  39.                                             value   to   pass  to
  40.                                             _p_r_o_c.
  41. _________________________________________________________________
  42.  
  43.  
  44. DESCRIPTION
  45.      Tk_CreateEventHandler arranges for _p_r_o_c to be invoked in the
  46.      future  whenever  one  of  the event types specified by _m_a_s_k
  47.      occurs in the window specified by _t_k_w_i_n.   The  callback  to
  48.      _p_r_o_c  will  be  made  by Tk_HandleEvent; this mechanism only
  49.      works   in   programs   that   dispatch    events    through
  50.      Tk_HandleEvent  (or  through  other  Tk procedures that call
  51.      Tk_HandleEvent, such as Tk_DoOneEvent or Tk_MainLoop).
  52.  
  53.      _P_r_o_c should have arguments and result that  match  the  type
  54.      Tk_EventProc:
  55.           typedef void Tk_EventProc(
  56.                ClientData _c_l_i_e_n_t_D_a_t_a,
  57.                XEvent *_e_v_e_n_t_P_t_r);
  58.      The _c_l_i_e_n_t_D_a_t_a parameter to _p_r_o_c is a copy of the _c_l_i_e_n_t_D_a_t_a
  59.      argument  given  to  Tk_CreateEventHandler when the callback
  60.  
  61.  
  62.  
  63. Tk                                                              1
  64.  
  65.  
  66.  
  67.  
  68.  
  69.  
  70. Tk_CreateEventHandler(3T)k Library Procedures
  71.  
  72.  
  73.  
  74.      was created.  Typically, _c_l_i_e_n_t_D_a_t_a points to a data  struc-
  75.      ture  containing  application-specific information about the
  76.      window in which the event occurred.  _E_v_e_n_t_P_t_r is  a  pointer
  77.      to  the  X event, which will be one of the ones specified in
  78.      the _m_a_s_k argument to Tk_CreateEventHandler.
  79.  
  80.      Tk_DeleteEventHandler may be called to delete a  previously-
  81.      created  event  handler:   it  deletes  the first handler it
  82.      finds that is associated with _t_k_w_i_n and  matches  the  _m_a_s_k,
  83.      _p_r_o_c,  and _c_l_i_e_n_t_D_a_t_a arguments.  If no such handler exists,
  84.      then  Tk_EventHandler  returns   without   doing   anything.
  85.      Although  Tk  supports  it, it's probably a bad idea to have
  86.      more than one callback with the same _m_a_s_k, _p_r_o_c, and _c_l_i_e_n_t_-
  87.      _D_a_t_a  arguments.   When  a  window  is  deleted  all  of its
  88.      handlers will be deleted automatically;  in this case  there
  89.      is no need to call Tk_DeleteEventHandler.
  90.  
  91.      If mutliple handlers are declared for the  same  type  of  X
  92.      event  on the same window, then the handlers will be invoked
  93.      in the order they were created.
  94.  
  95.  
  96. KEYWORDS
  97.      bind, callback, event, handler
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  129. Tk                                                              2
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