Function TBApplyKey() Foundation

Processes a key code (Inkey() value) for a TBrowse object.

TBApplyKey( <oTbrowse>, <nKey> ) --> nBrowseDirection
<oTBrowse> is a TBrowse object which is to process the keypress.
<nKey> is the numeric Inkey() key code of the key which is to be processed by <oTBrowse>.

The function TBApplyKey() returns a numeric code which identifies the direction in which the TBrowse cursor is to be moved in the next stabilization cycle. The return value orients itself to the numeric keypad (2 means "down", 6 means "to the right" etc). When the Inkey code is not processed, the return value is zero and the Tbrowse cursor is not moved. If the key with the Inkey code <nKey> is linked to a code block via the function SetKey(), the code block is evaluated and the function returns -1.


The TBrowse function TBApplyKey() implements the default behavior of TBrowse objects for processing key codes such as those returned by the function Inkey(). It is a service function for programming with TBrowse objects and its source code is contained in the file BROWUTIL.PRG.

The default behavior for keyboard navigation of TBrowse objects implemented by the function TBApplyKey() is shown in the following table:

Keyboard navigation of Tbrowse objects
Key Inkey constant Action
Up Arrow K_UP Previous row
Down Arrow K_DOWN Next row up
Left Arrow K_LEFT One column to the left
Right Arrow K_RIGHT One column to the right
Home K_HOME Left column in the window
End K_END Right column in the window
Page Up K_PGUP One screen up
Page Down K_PGDN One screen down
Ctrl+Left Arrow K_CTRL_LEFT Scrolls columns to the left
Ctrl+Right Arrow K_CTRL_RIGHT Scrolls columns to the right
Ctrl+Home K_CTRL_HOME First column
Ctrl+End K_CTRL_END Last column
Ctrl+Page Up K_CTRL_PGUP First row of the table
Ctrl+Page Down K_CTRL_PGDN Last row of the table

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

Return values of TBApplyKey()
Return value Direction for TBrowse cursor
8 Up
6 To the right
4 To the left
2 Down
0 TBrowse cursor is not moved
-1 TBrowse cursor is not moved, because a SetKey() code block was evaluated

// The example generates a TBrowse object and illustrates how 
// TBApplyKey() can be used for the navigating a TBrowse 
// object with the keyboard. 

#include "" 

   LOCAL oTB, nDirection, nKey 

   USE Address                      // open file 

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

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

   DO WHILE nKey <> K_ESC           // terminate on Esc 

      DO WHILE ! oTB:stabilize()    // incremental display 
         IF (nKey := Inkey()) <> 0 

      IF oTB:stable                  // TBrowse is stable 
         nKey := Inkey(0)            // wait for keystroke 
                                     // process key 
      nDirection := TBApplyKey( oTB, nKey ) 

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



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