Windows.Forms.Panel 32767 size limit

Question

I have an application that uses Windows.Forms.Panel to display a list of pictures. When the height of the panel exceeds 32767 pixels the rest of the content is

Answer 1

Solution without a paint method

I had this exact problem. I didn't want to have to re-write functionality that was already coded into my child controls. This routine manages the child controls via a scrollbar, and keeps the out-of-play ones hidden and just offscreen.

Public Class ManuallyScrollingPanel
  Inherits Panel

  Public WithEvents sbar As New System.Windows.Forms.VScrollBar

  Sub New()
    MyBase.New()
    Controls.Add(sbar)
    sbar.Visible = True
    Me.AutoScroll = False
  End Sub

  Sub SetScrollParams()
    If PanelPositions.Any Then
      Dim NewMax = CInt((From item In PanelPositions.Values Select item.Bottom).Max + 500) - Height
      If sbar.Maximum <> NewMax Then
        sbar.Maximum = NewMax
      End If
    End If
  End Sub

  Public Sub RegisterChildSize(pnl As Panel, DesiredBounds As Drawing.Rectangle)
    PanelPositions(pnl) = DesiredBounds
    SetScrollParams()
  End Sub

  Dim PanelPositions As New Dictionary(Of Panel, Drawing.Rectangle)

  Private Sub ManuallyScrollingPanel_SizeChanged(sender As Object, e As EventArgs) Handles Me.SizeChanged
    sbar.Top = 0
    sbar.Left = Width - sbar.Width
    sbar.Height = Me.Height
    SetScrollParams()
    sbar.LargeChange = CInt(Height * 0.9)
    sbar.SmallChange = CInt(Height * 0.2)
  End Sub

  Private Sub sb_Scroll(sender As Object, e As ScrollEventArgs) Handles sbar.Scroll
    ScrollTo(e.NewValue)
  End Sub

  Private Sub sb_ValueChanged(sender As Object, e As EventArgs) Handles sbar.ValueChanged
    ScrollTo(sbar.Value)
  End Sub

  Sub ScrollTo(pos As Integer)
    Me.AutoScroll = False
    For Each kvp In PanelPositions
      Dim VirtBounds = New Drawing.Rectangle(CInt(kvp.Value.Left), CInt(kvp.Value.Top - pos), CInt(kvp.Value.Width), CInt(kvp.Value.Height))
      If VirtBounds.Bottom < 0 Or VirtBounds.Top > Height Then
        ' it's not visible - hide it and position offscreen
        kvp.Key.Visible = False
        kvp.Key.Top = VirtBounds.Top
      Else
        ' Visible, position it
        kvp.Key.Top = VirtBounds.Top
        kvp.Key.Visible = True
      End If
    Next
  End Sub

End Class

Then, for each child control (mine were dynamically added, sounds like the OP was doing the same thing) make this call:

CType(Parent, ManuallyScrollingPanel).RegisterChildSize(Me, PanelObject.Bounds)

Note I pass in the child's bounds separately as I build the controls from DTOs to allow the same app+views to render as a web app and a windows app. Same with limiting it to panels. Refactor out as needed.