[RESOLVED] Magnifying form

[moeur]

I finally got a chance to play around with this a bit. The problem with magnifying on the same form you're moving around is that you have to keep hiding the form so that you can see what is behind it. Maybe there is someway to tap into the buffer used to repaint the background and get your data from there. Anyway here is what I have that works pretty well.

Option Explicit
 
Private srcDc As Long
 
Private Declare Function StretchBlt Lib "gdi32" ( _
    ByVal hdc As Long, _
    ByVal x As Long, _
    ByVal y As Long, _
    ByVal nWidth As Long, _
    ByVal nHeight As Long, _
    ByVal hSrcDC As Long, _
    ByVal xSrc As Long, _
    ByVal ySrc As Long, _
    ByVal nSrcWidth As Long, _
    ByVal nSrcHeight As Long, _
    ByVal dwRop As Long _
) As Long
 
Private Declare Function GetDC Lib "user32" ( _
    ByVal hwnd As Long _
) As Long
 
Private Declare Function GetWindowRect Lib "user32" ( _
    ByVal hwnd As Long, _
    lpRect As RECT _
) As Long
 
Private Declare Function GetClientRect Lib "user32" ( _
    ByVal hwnd As Long, _
    lpRect As RECT _
) As Long
 
Private Type RECT
        Left As Long
        Top As Long
        Right As Long
        Bottom As Long
End Type
 
Private Sub Form_Load()
    Me.ScaleMode = vbPixels
    srcDc = GetDC(0&)
    Set FormSubClass = New clsSubClass
    FormSubClass.Enable Me.hwnd
End Sub
 
Sub ZoomIn(ZoomFactor As Long)
 Dim xWidth As Long, yHeight As Long
 Dim xLeft As Long, ytop As Long
 Dim nSrcWidth As Long, nSrcHeight As Long
 
 Dim xBorder As Long
 Dim yBorder As Long
 Dim wndRect As RECT
 Dim clientRect As RECT
 
 GetWindowRect Me.hwnd, wndRect
 GetClientRect Me.hwnd, clientRect
 
 'need to hide form so we can see what is behind it
  Me.Visible = False
  DoEvents
 
'get size and location of form
 xBorder = Int((wndRect.Right - wndRect.Left - clientRect.Right) / 2)
 yBorder = wndRect.Bottom - wndRect.Top - clientRect.Bottom - xBorder
 
 xWidth = clientRect.Right
 yHeight = clientRect.Bottom
 nSrcWidth = Int(xWidth / ZoomFactor)
 nSrcHeight = Int(yHeight / ZoomFactor)
 xLeft = wndRect.Left + xBorder
 ytop = wndRect.Top + yBorder
 
'make the magnified picture
 StretchBlt Me.hdc, 0, 0, xWidth, yHeight, srcDc, xLeft, ytop, nSrcWidth, nSrcHeight, vbSrcCopy
 Me.Visible = True
 
End Sub

Now, when do you call the ZoomIn routine? You can subclass the form and call it whenever the form is moved

Private Sub FormSubClass_WMArrival(hwnd As Long, uMsg As Long, _
    wParam As Long, lParam As Long, lRetVal As Long)
    Select Case uMsg
    Case WM_MOVE
        ZoomIn 2
    End Select
End Sub

This causes a lot of flashing, so maybe you just want to call it once the form has completed moving