Code Comparison: Visual FoxPro Grid & Clipper/DOS Tbrowse

ID: Q130439

3.00 WINDOWS

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

CA-Clipper version 5.x has five predefined classes built into its language. One of these is the Tbrowse class, which is similar to Visual FoxPro's Grid class. This article compares the two.

NOTE: This article only describes how to create a Grid control in a program. Grids can also be created visually through drag-drop and the Visual Class Designer.

MORE INFORMATION

Clipper actually provides two Tbrowse classes - TbrowseDB() and TbrowseNew(). TbrowseDB() browses tables, and TbrowseNew() browses other data sources, such as text files and arrays.

Below are comparisons of how to browse a table that contains three columns. In each comparison, the Clipper code is shown followed by the equivalent program in Visual FoxPro.

NOTE: Run the following program first to create the TEST table used in the comparisons.

   *** Code to create the TEST table ***
   &&   In Clipper, execute these 5 lines:
   &&   aDbf := {}
   &&   AADD(aDbf, { "Fld1", "N", 3, 0 })
   &&   AADD(aDbf, { "Fld2", "C", 4, 0 })
   &&   AADD(aDbf, { "Fld3", "C", 20, 0 })
   &&   DBCREATE("Test",aDbf)

   &&   In FoxPro, execute the next line:
   &&   CREATE TABLE Test (fld1 n(3),fld2 c(4),fld3 c(20))

   USE Test
   FOR i=1 TO 50
     APPEND BLANK
     REPLACE Fld1 WITH i
     REPLACE Fld2 WITH ALLTRIM(STR(i))
     REPLACE Fld3 WITH REPLICATE(CHR(64+i),20)
   NEXT
   CLOSE ALL
   *** End of code to create TEST table ***

Clipper

   #include "inkey.ch"
   #include "setcurs.ch"

   #define  MYCOLORS   "BG/B,RB+/W,W/N,N,GR+/W,G+/B,R+/B,GR+/B"
   #define  HEADSEP    CHR(205) + CHR(209) + CHR(205)
   #define  COLSEP     CHR(32)  + CHR(179) + CHR(32)

   FUNCTION Main()
      LOCAL b, column, nKey
      SET SCOREBOARD OFF
      SET DATE       BRITISH
      SET CONFIRM    ON

      USE test

      SETCURSOR(SC_NONE)
      SETCOLOR("N/W")
      SCROLL()
      SETCOLOR("BG/B,RB+/W,,,BG/N")
      SCROLL( 2, 6, 22, 72 )
      @  2, 6 TO 22,72 DOUBLE

      b := TBrowseDB( 3, 7, 21, 71 )
      b:colorSpec := MYCOLORS
      b:colSep  := COLSEP
      b:headSep := HEADSEP

      // Custom Skipper
      b:skipBlock     := {|nRecs| Skipper( nRecs )}

      // TBColumn objects
      column := TBColumnNew( "Field 1", {|| test->fld1} )
      b:addColumn( column )
      column := TBColumnNew( "Field 2", {|| test->fld2} )
      b:addColumn( column )
      column := TBColumnNew( "Field 3", {|| test->fld3} )
      b:addColumn( column )

      WHILE .T.
         WHILE ( !b:stabilize() )
            nKey := INKEY()
            IF ( nKey != 0 )
               EXIT
            ENDIF
         END

         IF ( b:stable )
            nKey := INKEY(0)
         ENDIF

         // Process key
         IF ( nKey == K_DOWN )
            b:down()
         ELSEIF ( nKey == K_UP )
            b:up()
         ELSEIF ( nKey == K_PGDN )
            b:pageDown()
         ELSEIF ( nKey == K_PGUP )
            b:pageUp()
         ELSEIF ( nKey == K_CTRL_PGUP )
            b:goTop()
         ELSEIF ( nKey == K_CTRL_PGDN )
         b:goBottom()
         ELSEIF ( nKey == K_RIGHT )
            b:right()
         ELSEIF ( nKey == K_LEFT )
            b:left()
         ELSEIF ( nKey == K_HOME )
            b:home()
         ELSEIF ( nKey == K_END )
            b:end()
         ELSEIF ( nKey == K_CTRL_LEFT )
            b:panLeft()
         ELSEIF ( nKey == K_CTRL_RIGHT )
            b:panRight()
         ELSEIF ( nKey == K_CTRL_HOME )
            b:panHome()
         ELSEIF ( nKey == K_CTRL_END )
         b:panEnd()
         ELSEIF ( nKey == K_ESC )
            SCROLL()
            EXIT
         ENDIF
      END
   RETURN NIL

   STATIC FUNCTION Skipper( nRequest )
      LOCAL nActually := 0

      IF (nRequest == 0)
         SKIP 0
      ELSEIF (nRequest > 0) .AND. (!EOF())
         WHILE (nActually < nRequest)
            SKIP
            IF EOF()
               SKIP -1
               EXIT
            ENDIF
            nActually++
         END
      ELSEIF (nRequest < 0)
         WHILE (nActually > nRequest)
            SKIP -1
            IF BOF()
            EXIT
            ENDIF
            nActually--
         END
      ENDIF
      RETURN nActually

Visual FoxPro

   USE test
   oFormwgrid = CREATEOBJECT("MyForm")
   oFormwgrid.show
   READ EVENTS

   DEFINE CLASS MyForm AS Form
     Width=400
     Height=250
     ADD OBJECT b AS MyGrid
   ENDDEFINE

   DEFINE CLASS MyGrid AS Grid
     Left=7
     Top=1
     Width=340
     Height=240
     ColumnCount=3

     Column1.ControlSource='fld1'
     Column2.ControlSource='fld2'
     Column3.ControlSource='fld3'
     Column1.Width=50
     Column3.Width=200

     PROCEDURE init
       This.Column1.Header1.Caption='Field 1'
       This.Column2.Header1.Caption='Field 2'
       This.Column3.Header1.Caption='Field 3'
     ENDPROC
   ENDDEFINE

Clipper is an MS-DOS-based product, so you don't need to create a window for the browse. However, because Visual FoxPro is a Windows-based product, you need to create a window for it.

The DEFINE CLASS section creates a subclass of the Form class, and the oFormwgrid=CREATEOBJECT("MyForm") line creates an instance of that object.

Visual FoxPro

   oFormwgrid=CREATEOBJECT("MyForm")
   oFormwgrid.show

   ..

   DEFINE CLASS MyForm AS Form

   ..

   ENDDEFINE

Once you have created a window, you can add the Grid to it. Again, you will sub-class the Grid class and create an instance of it with the ADD OBJECT b AS MyGrid line.

Clipper

   b := TBrowseDB( 3, 7, 21, 71 )

Visual FoxPro

   ...

   ADD OBJECT b AS MyGrid

   ...

   DEFINE CLASS MyGrid AS Grid
     Left=7
     Top=1
     Width=340
     Height=240
     ColumnCount=3

   ...

   ENDDEFINE

Now you can add columns to the Grid. Clipper creates a new column in the Tbrowse by creating an instance of the TBColumnNew class and then passing its handle to the addcolumn method of the Tbrowse.

In Visual FoxPro, you already set the property 'ColumnCount' to 3 in the sub-class, so you can just assign Column X's ControlSource property to the desired value. While the Grid is being initialized, you can set the titles of the column headers in the PROCEDURE init.

Clipper

   column := TBColumnNew( "Field 1", {|| test->fld1 })
   b:addColumn( column )
   column := TBColumnNew( "Field 2", {|| test->fld2 })
   b:addColumn( column )
   column := TBColumnNew( "Field 3", {|| test->fld3 })
   b:addColumn( column )

Visual FoxPro

   Column1.ControlSource='Test.fld1'
   Column2.ControlSource='Test.fld2'
   Column3.ControlSource='Test.fld3'

   PROCEDURE init
     This.Column1.Header1.Caption='Field 1'
     This.Column2.Header1.Caption='Field 2'
     This.Column3.Header1.Caption='Field 3'
   ENDPROC

The objects properties and methods are set in both products so you can now give it life. Clipper does this through the stabilize method, DO .. WHILE loops and INKEY(). Visual FoxPro ties in with the Windows event model so you can just issue the READ EVENTS command.

Clipper

   WHILE ( !b:stabilize() )
     nKey := INKEY()
     IF ( nKey != 0 )
       EXIT
     ENDIF
   END

   IF ( b:stable )
     nKey := INKEY(0)
   ENDIF

Visual FoxPro

   READ EVENTS

Clipper/DOS is manufactured by Computer Associates, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Additional reference words: 3.00 VFoxWin ca clipper for dos 5.01 KBCategory: KBSubcategory: FxinteropDatabase

Keywords          : kb3rdparty kbcode FxinteropDatabase 
Version           : 3.00
Platform          : WINDOWS