2.4 Managing the Output Buffer
     
     
    
      Most CLX functions cause output requests to be generated to an X server.
      Output requests are not transmitted immediately but instead are stored
      in an output buffer for the appropriate display. Requests in the
      output buffer are typically sent only when the buffer is filled.
      Alternatively, buffered requests can be sent prior to processing an
      event in the input event queue (see
      paragrpah
      12.3, Processing Events). In either case,
      CLX sends the output buffer automatically without explicit instructions
      from the client application. 
    
      However, in some cases, explicit control over the output buffer is
      needed, typically to ensure that the X server is in a consistent state
      before proceeding further. The
      display-force-output
      and
      display-finish-output
      functions allow a client program to synchronize with buffered output
      requests. 
    
      
      
      
      
        
          
          
          
        
          | display-after-function | display | Function | 
      
      
        
          |  | 
              
                display 
              
                A
                display object.
             
              Returns and (with setf) sets the after-function
              for the given display. If after-function is
              non-nil, it is a function that is called after every
              protocol request is generated, even those inside an explicit
              with-display,
              but never called from inside the after-function. The
              function is called inside the effective
              with-display
              for the associated request. The default value is nil.
              This can be set, for example, to
              #'display-force-output
              or #' display-finish-output. 
             
              
                after-function 
              
                Type function or null. 
             | 
      
     
     
    
      
      
      
      
        
          
          
          
        
          | display-force-output | display | Function | 
      
      
        
          |  | 
              
                display 
              
                A
                display object.
             
              Forces any buffered output to be sent to the X server. 
           | 
      
     
     
    
      
      
      
      
        
          
          
          
        
          | display-finish-output | display | Function | 
      
      
        
          |  | 
              
                display 
              
                A
                display object.
             
              Forces any buffered output to be sent to the X server and then
              waits until all requests have been received and processed. Any
              errors generated are read and handled by the display error
              handler. Any events generated by output requests are read and
              stored in the event queue. 
           |