Using Win32 functions in Visual FoxPro Image Gallery
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Form Magnifier
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Form Magnifier

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Before you begin:

After you activate the magnifier the form`s part under the mouse cursor will be constantly redrawn on the main FoxPro window.

See also:
  • Scrolling text on the form horizontally (a newsreel)
  • Scrolling text on the form vertically (a movie cast)
  • Shaking VFP form controls
  • Playing AVI on _screen
  • Displaying animated images

  • LOCAL oForm
    oForm = CREATEOBJECT("Tform")
    * end of main
    DEFINE CLASS Tform As Form
        ADD OBJECT chMagnify As CheckBox WITH Value=.F.,;
        Left=20, Top=20, Autosize=.T., Caption="Activate Magnifier"
        ADD OBJECT chInvert As CheckBox WITH Value=.F.,;
        Left=20, Top=56, Autosize=.T., Caption="Invert colors"
        ADD OBJECT lbl1 As Label WITH;
        Left=190, Top=20, Autosize=.T., Caption="Scale:"
        ADD OBJECT cmbScale As ComboBox WITH Style=2,;
        Left=240, Top=20, Width=70, Height=21
        ADD OBJECT cmdClose As CommandButton WITH Cancel=.T.,;
        Left=140, Top=112, Width=70, Height=27, Caption="Close"
    PROCEDURE Activate
        IF THIS.hForm = 0
            THIS.hForm = GetFocus()
            THIS.hDC = GetDC(THIS.hForm)
    PROCEDURE Destroy
        IF THIS.hDC <> 0
            = ReleaseDC(THIS.hForm, THIS.hDC)
    PROCEDURE cmdClose.Click
    PROCEDURE cmbScale.Init
        WITH THIS
            .AddItem("x 2")
            .AddItem("x 3")
            .AddItem("x 4")
    PROCEDURE MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE chMagnify.MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE chInvert.MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE lbl1.MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE cmbScale.MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE cmdClose.MouseMove
    LPARAMETERS nButton, nShift, nXCoord, nYCoord
    PROCEDURE Magnify
    #DEFINE NOTSRCCOPY 0x00330008
    #DEFINE cnDstWidth 600
    #DEFINE cnDstHeight 140
        IF THIS.chMagnify.Value
            LOCAL cBuffer, nX, nY, hDstWin, hDstDC,;
                nMode, nSrcWidth, nSrcHeight, nScale
            hDstWin = GetActiveWindow()
            hDstDC = GetWindowDC(hDstWin)
            cBuffer = REPLICATE(Chr(0), 8)
            = GetCursorPos(@cBuffer)
            = ScreenToClient(THIS.hForm, @cBuffer)
            nX = buf2dword(SUBSTR(cBuffer, 1,4))
            nY = buf2dword(SUBSTR(cBuffer, 5,4))
            nScale = THIS.cmbScale.ListIndex
            nSrcWidth = INT(cnDstWidth/nScale)
            nSrcHeight = INT(cnDstHeight/nScale)
            nMode = IIF(THIS.chInvert.Value,;
                NOTSRCCOPY, SRCCOPY)
            = StretchBlt(hDstDC, 10, 100,;
                cnDstWidth, cnDstHeight, THIS.hDC,;
                nX-nSrcWidth/2, nY-nSrcHeight/2,;
                nSrcWidth, nSrcHeight, nMode)
            = ReleaseDC(hDstWin, hDstDC)
    PROCEDURE declare
        DECLARE INTEGER GetActiveWindow IN user32
        DECLARE INTEGER GetCursorPos IN user32 STRING @lpPoint
        DECLARE INTEGER GetWindowDC IN user32 INTEGER hwnd
        DECLARE INTEGER GetDC IN user32 INTEGER hwnd
        DECLARE INTEGER GetFocus IN user32
        DECLARE INTEGER ReleaseDC IN user32;
            INTEGER hWindow, INTEGER hdc
        DECLARE INTEGER ScreenToClient IN user32;
            INTEGER hWindow, STRING @lpPoint
        DECLARE INTEGER StretchBlt IN gdi32;
            INTEGER hdcDest, INTEGER nXOriginDest,;
            INTEGER nYOriginDest, INTEGER nWidthDest,;
            INTEGER nHeightDest, INTEGER hdcSrc,;
            INTEGER nXOriginSrc, INTEGER nYOriginSrc,;
            INTEGER nWidthSrc, INTEGER nHeightSrc,;
            INTEGER dwRop
    FUNCTION buf2dword(lcBuffer)
    RETURN Asc(SUBSTR(lcBuffer, 1,1)) + ;
        BitLShift(Asc(SUBSTR(lcBuffer, 2,1)), 8) +;
        BitLShift(Asc(SUBSTR(lcBuffer, 3,1)), 16) +;
        BitLShift(Asc(SUBSTR(lcBuffer, 4,1)), 24)

    User rating: 7/10 (2 votes)
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    3530 bytes  
    Created: 2003-07-14 21:11:08  
    Modified: 2007-03-15 11:33:17  
    Visits in 7 days: 86  
    Listed functions:
    Printer friendly API declarations
    My comment:
    StretchBlt function copies a rectangle area of the form to the main FoxPro window.
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