Function TBHandleEvent() | Xbase++

Functions and Directives Functions and Directives

Processes event codes (such as those returned by the function AppEvent()) for a TBrowse object.

TBHandleEvent( <oTBrowse>, <nEvent>, ;
               [<mp1>], [<mp2>], [<oXbp>]) --> nBrowseDirection

<oTBrowse> is a TBrowse object which is to process the event code.

<nEvent> is the numeric event returned from the function AppEvent().

<mp1>

<mp1> is the first message parameter of the function AppEvent().

<mp2>

<mp2> is the second message parameter of the function AppEvent().

<oXbp>

<oXbp> is an Xbase Part which is to process the event instead of the TBrowse object (addressee of an event). This parameter is only relevant when Xbase Parts are used in the program. This parameter is provided by the function AppEvent() (see AppEvent()).

The function TBHandleEvent() returns a numeric code which identifies the direction in which the TBrowse cursor will be moved in the next stabilization cycle. The return value orients itself at the numeric keypad (2 means "down", 6 means "to the right", 1 means "lower left," etc). When the event code is not processed, the return value is zero and the Tbrowse cursor is not moved. If the event <nEvent> is linked to a code block by the function SetAppEvent(), the code block is evaluated and the function returns -1.

The function TBHandleEvent() implements the default behavior of TBrowse objects for the processing events such as those returned by the function AppEvent(). To handle mouse events it calls the function TBtoMousePos(). TBHandleEvent() is a service function for programming with TBrowse objects and its source code is contained in the file BROWUTIL.PRG. To process events using TBHandleEvent(), the function AppEvent() must be used in the code handling the Tbrowse object.

The default behavior for keyboard navigation of TBrowse objects implemented in the function TBHandleEvent() is listed in the following table:

Key	Event constant	Action
Up Arrow	xbeK_UP	Previous row
Down Arrow	xbeK_DOWN	Next row
Left Arrow	xbeK_LEFT	One column to the left
Right Arrow	xbeK_RIGHT	One column to the right
Home	xbeK_HOME	Left column in the window
End	xbeK_END	Right column in the window
Page Up	xbeK_PGUP	Previous screen
Page Down	xbeK_PGDN	Next screen
Ctrl+Left Arrow	xbeK_CTRL_LEFT	Scrolls columns left
Ctrl+Right Arrow	xbeK_CTRL_RIGHT	Scrolls columns right
Ctrl+Home	xbeK_CTRL_HOME	First column
Ctrl+End	xbeK_CTRL_END	Last column
Ctrl+Page Up	xbeK_CTRL_PGUP	First row of table
Ctrl+Page Down	xbeK_CTRL_PGDN	Last row of table
Left mouse button	xbeM_LbClick	TBrowse cursor is moved to the mouse pointer

The return value of TBHandleEvent() gives information about the direction in which the TBrowse cursor will be moved in the next stabilization cycle. Possible return values are as follows:

Return value	Direction for TBrowse cursor
9	Right up
8	Up
7	Left up
6	Right
5	Mouse click in the TBrowse cursor, TBrowse cursor is not moved
4	Left
3	Right down
2	Down
1	Left down
0	Unknown event, TBrowse cursor is not moved
-1	TBrowse cursor is not moved, a SetAppEvent() code block is evaluated

TBHandleEvent()

// The example generates a TBrowse object and illustrates 
// how TBHandleEvent() can be used for navigating a TBrowse 
// object. 

#include "Appevent.ch" 

PROCEDURE Main 
   LOCAL oTB, nDirection, nEvent, mp1, mp2, oXbp 

   USE Address                      // open file 
   SetMouse(.T.) 

   oTB := TBrowseDB( 2, 2, 22, 78 ) // creates TBrowse 
   AEval( DbStruct(), {|a| oTB:AddColumn(             ; 
                              TBColumn():new( a[1],   ; 
                                 FieldBlock(a[1]) ) ) } ) 

   nEvent     := 0 
   CLS 
   @ 1,1 TO 23,79 DOUBLE 
   oTB:forceStable()                // display complete TBrowse 


   DO WHILE nEvent <> xbeK_ESC      // terminate on Esc key 

      DO WHILE ! oTB:stabilize()    // incremental display 
         nEvent:= AppEvent( @mp1, @mp2, @oXbp, .01 ) 
         IF nEvent  > xbe_None     .AND. ; 
            nEvent <> xbeM_Motion 
            EXIT 
         ENDIF 
      ENDDO 

      IF oTB:stable                  // TBrowse is stable 
         nEvent := xbeM_Motion       // filter out event 
         DO WHILE nEvent == xbeM_Motion  // "mouse is moved" 
            nEvent := AppEvent( @mp1, @mp2, @oXbp, 0 ) 
         ENDDO 
      ENDIF 
                                     // process event 
      nDirection := TBHandleEvent( oTB, nEvent, mp1, mp2, oXbp ) 

      @ MaxRow(),0                   // display browse direction 
      QQOut( "Browse direction:", nDirection ) 

   ENDDO 

RETURN

Function TBHandleEvent() Foundation