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Thread: Magnifying glass for your desktop

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  1. Oct 29th, 2005, 06:17 PM #1
    moeur
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    Magnifying glass for your desktop

    In response to another thread I developed this little app that makes your form into a magnifying glass for your desktop. Try it out it's pretty cool.

    When the form loads, I create a memory device context to store the current contents of the desktop.
    VB Code:
    1. [FONT=Courier New][COLOR=#0000FF]Private[/COLOR] [COLOR=#0000FF]Sub[/COLOR] Form_Load()

    2.  
    3.     Me.AutoRedraw = True

    4.     ScaleFactor = 2

    5.     

    6. [COLOR=#007A00]' Create a normal DC and a memory DC for the entire screen. The

    7. ' normal DC provides a "snapshot" of the screen contents. The

    8. ' memory DC keeps a copy of this "snapshot" in the associated

    9. ' bitmap.

    10. [/COLOR] 

    11. hdcScreen = CreateDC("[COLOR=#7A0000]DISPLAY[/COLOR]", vbNullString, vbNullString, 0&)

    12. [COLOR=#0000FF]If[/COLOR] hdcScreen = 0 [COLOR=#0000FF]Then

    13. [/COLOR]    MsgBox "[COLOR=#7A0000]CreateDC failed[/COLOR]"

    14.     [COLOR=#0000FF]Exit[/COLOR] [COLOR=#0000FF]Sub

    15. End[/COLOR] [COLOR=#0000FF]If

    16. [/COLOR]

    17.  
    18. hdcCompatible = CreateCompatibleDC(hdcScreen)

    19. [COLOR=#0000FF]If[/COLOR] hdcCompatible = 0 [COLOR=#0000FF]Then

    20. [/COLOR]    MsgBox "[COLOR=#7A0000]hdcCompatible failed[/COLOR]"

    21.     [COLOR=#0000FF]Exit[/COLOR] [COLOR=#0000FF]Sub

    22. End[/COLOR] [COLOR=#0000FF]If

    23. [/COLOR] 

    24. ScreenWidth = GetDeviceCaps(hdcScreen, HORZRES)

    25. screenHeight = GetDeviceCaps(hdcScreen, VERTRES)

    26.  
    27. [COLOR=#007A00]' Create a compatible bitmap for hdcScreen.

    28. [/COLOR]hbmScreen = CreateCompatibleBitmap(hdcScreen, _

    29.                      ScreenWidth, _

    30.                      screenHeight)

    31.  

    32. [COLOR=#0000FF]If[/COLOR] (hbmScreen = 0) [COLOR=#0000FF]Then

    33. [/COLOR]    MsgBox "[COLOR=#7A0000]hbmScreen failed[/COLOR]"

    34.     [COLOR=#0000FF]Exit[/COLOR] [COLOR=#0000FF]Sub

    35. End[/COLOR] [COLOR=#0000FF]If

    36. [/COLOR] 

    37. [COLOR=#007A00]' Select the bitmaps into the compatible DC.

    38. [/COLOR][COLOR=#0000FF]If[/COLOR] SelectObject(hdcCompatible, hbmScreen) = 0 [COLOR=#0000FF]Then

    39. [/COLOR]    MsgBox "[COLOR=#7A0000]Compatible Bitmap Selection Failed![/COLOR]"

    40.     [COLOR=#0000FF]Exit[/COLOR] [COLOR=#0000FF]Sub

    41. End[/COLOR] [COLOR=#0000FF]If

    42. [/COLOR] 

    43.     UpDateImage

    44.     ZoomIn ScaleFactor

    45.     

    46. [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]Sub[/COLOR][/FONT]
    Now, when the user holds down the left mouse button I make the form invisible and read-in the contents of the current desktop to the memory DC.
    VB Code:
    1. [FONT=Courier New][COLOR=#0000FF]Private[/COLOR] [COLOR=#0000FF]Sub[/COLOR] Form_MouseDown(Button [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Integer[/COLOR], Shift [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Integer[/COLOR], X [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Single[/COLOR], Y [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Single[/COLOR])

    2.     [COLOR=#0000FF]Select[/COLOR] [COLOR=#0000FF]Case[/COLOR] Button

    3.     [COLOR=#0000FF]Case[/COLOR] vbLeftButton

    4.         XX = X

    5.         YY = Y

    6.         UpDateImage

    7.     [COLOR=#0000FF]Case[/COLOR] vbRightButton

    8.         PopupMenu mnPopup

    9.     [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]Select

    10. End[/COLOR] [COLOR=#0000FF]Sub

    11. [/COLOR]

    12. [COLOR=#0000FF]Sub[/COLOR] UpDateImage()

    13.     Me.Visible = False

    14.     DoEvents

    15.          [COLOR=#007A00]'Copy color data for the entire display into a

    16. [/COLOR]         [COLOR=#007A00]'bitmap that is selected into a compatible DC.

    17. [/COLOR] 

    18.         [COLOR=#0000FF]If[/COLOR] BitBlt(hdcCompatible, _

    19.                0, 0, _

    20.                ScreenWidth, screenHeight, _

    21.                hdcScreen, _

    22.                0, 0, _

    23.                vbSrcCopy) = 0 [COLOR=#0000FF]Then

    24. [/COLOR] 

    25.                 MsgBox "[COLOR=#7A0000]Screen to Compat Blt Failed[/COLOR]"

    26.             [COLOR=#0000FF]Exit[/COLOR] [COLOR=#0000FF]Sub

    27. [/COLOR]        [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]If

    28. [/COLOR]    Me.Visible = True

    29.     DoEvents

    30. [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]Sub[/COLOR][/FONT]
    When the mouse is moved with the left button down, the form is dragged across the desktop and a magnified image of the desktop below the form is copied to the from from the memory DC.
    VB Code:
    1. [FONT=Courier New][COLOR=#0000FF]Private[/COLOR] [COLOR=#0000FF]Sub[/COLOR] Form_MouseMove(Button [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Integer[/COLOR], Shift [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Integer[/COLOR], X [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Single[/COLOR], Y [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Single[/COLOR])

    2. [COLOR=#0000FF]If[/COLOR] Button = vbLeftButton [COLOR=#0000FF]Then

    3. [/COLOR]        Me.Left = Me.Left - XX + X

    4.         Me.Top = Me.Top - YY + Y

    5.         ZoomIn ScaleFactor

    6.   [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]If

    7. End[/COLOR] [COLOR=#0000FF]Sub

    8. [/COLOR]

    9. [COLOR=#0000FF]Sub[/COLOR] ZoomIn(ZoomFactor [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long[/COLOR])

    10.  [COLOR=#0000FF]Dim[/COLOR] xLeft [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long[/COLOR], ytop [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long

    11. [/COLOR] [COLOR=#0000FF]Dim[/COLOR] nSrcWidth [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long[/COLOR], nSrcHeight [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long

    12. [/COLOR] [COLOR=#0000FF]Dim[/COLOR] ScaleFactor [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Single

    13. [/COLOR] [COLOR=#0000FF]Dim[/COLOR] xBorder [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long

    14. [/COLOR] [COLOR=#0000FF]Dim[/COLOR] yBorder [COLOR=#0000FF]As[/COLOR] [COLOR=#0000FF]Long

    15. [/COLOR] [COLOR=#0000FF]Dim[/COLOR] wndRect [COLOR=#0000FF]As[/COLOR] RECT

    16.  [COLOR=#0000FF]Dim[/COLOR] clientRect [COLOR=#0000FF]As[/COLOR] RECT

    17.  

    18.  GetWindowRect Me.hwnd, wndRect

    19.  GetClientRect Me.hwnd, clientRect

    20.  

    21. [COLOR=#007A00]'get size and location of form

    22. [/COLOR] xBorder = Round((wndRect.Right - wndRect.Left - clientRect.Right) / 2, 0)

    23.  yBorder = wndRect.Bottom - wndRect.Top - clientRect.Bottom - xBorder

    24.  

    25.  nSrcWidth = Round(clientRect.Right / ZoomFactor, 0)

    26.  nSrcHeight = Round(clientRect.Bottom / ZoomFactor, 0)

    27.  

    28.  [COLOR=#007A00]'align the center of windows

    29. [/COLOR] ScaleFactor = (ZoomFactor - 1) / (2 * ZoomFactor)

    30.  xLeft = wndRect.Left + xBorder + Round(clientRect.Right * ScaleFactor, 0)

    31.  ytop = wndRect.Top + yBorder + Round(clientRect.Bottom * ScaleFactor, 0)

    32.  

    33. [COLOR=#007A00]'make the magnified picture

    34. [/COLOR] StretchBlt Me.hdc, 0, 0, clientRect.Right, clientRect.Bottom, hdcCompatible, xLeft, ytop, nSrcWidth, nSrcHeight, vbSrcCopy

    35.  Me.Refresh

    36. [COLOR=#0000FF]End[/COLOR] [COLOR=#0000FF]Sub[/COLOR][/FONT]
    Attached is a project that demos this idea.
    Attached Files Attached Files
    Last edited by moeur; Nov 4th, 2005 at 12:22 PM.
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