[vb6] Class to make Image Controls Support PNG, TIF, GIF Animation

[Jonney]

Give up.
IPicture.Render hardly do partial painting at vertical direction. But Horizontal can be partial. Am I right?

Public Function Render(ByVal hdc As Long, _
                             Optional ByVal destX As Single, Optional ByVal destY As Single, _
                             Optional ByVal destWidth As Single, Optional ByVal destHeight As Single, _
                             Optional ByVal srcX As Single, Optional ByVal srcY As Single, _
                             Optional ByVal srcWidth As Single, Optional ByVal srcHeight As Single) As Boolean
  '-- If using variables, surround them with parentheses, i.e., (x), (y)
  '-- You can use numbers as is, i.e., 0, 256
  '-- The destination coordinates and dimensions are in pixels (scale your destination parameters to pixels)
  '-- The source coordinates and dimensions are in himetrics (scale your source parameters to himetric)
  'Remember to use the negative height as shown in that other post of mine
   If srcWidth = 0 Then
      srcWidth = m_objPicture.Width
   Else
      srcWidth = srcWidth * 2540& * Screen.TwipsPerPixelX / 1440&
   End If
   If srcHeight = 0 Then
      srcHeight = -(m_objPicture.Height)
   Else
      srcHeight = -(srcHeight * 2540& * Screen.TwipsPerPixelY / 1440&)
   End If
   
   With m_objPicture
      '.Render (hdc), (destX), (destY), (destWidth), (destHeight), 0, (.Height - 1&), .Width, -.Height, ByVal 0&
      .Render (hdc), (destX), (destY), (destWidth), (destHeight), _
                      (srcX * 2540& * Screen.TwipsPerPixelX / 1440&), (m_objPicture.Height - 1 - (srcY * 2540& * Screen.TwipsPerPixelY / 1440&)), _
                      (srcWidth), (srcHeight), ByVal 0&
   Debug.Print srcHeight,m_objPicture.Height
   End With
End Function

For Example, If srcHeight is -4947.708 (Image Height is 5715), the whole graphic disappear.

Hard to understand why VB6 design .Render should give a negative value.