Since built in functionality for positioning forms in VB.NET are not always suitable to use I try to make my sub to do that.
But I missed something...
Public Sub form_center(ByVal frm As Form, Optional ByVal parent As Form = Nothing)
Dim x As Integer
Dim y As Integer
Dim r As Rectangle
If Not parent Is Nothing Then
r = parent.ClientRectangle
x = r.Width - frm.Width + parent.Left
y = r.Height - frm.Height + parent.Top
r = Screen.PrimaryScreen.WorkingArea
x = r.Width - frm.Width
y = r.Height - frm.Height
x = CInt(x / 2)
y = CInt(y / 2)
frm.StartPosition = FormStartPosition.Manual
frm.Location = New Point(x, y)
The code is just wrong. It is also essential that this code runs late enough, the constructor is too early. Be sure to call it from the Load event, at that time the form is properly auto-scaled and adjusted for the user's preferences, the StartPosition property no longer matters then. Fix:
Public Shared Sub CenterForm(ByVal frm As Form, Optional ByVal parent As Form = Nothing) '' Note: call this from frm's Load event! Dim r As Rectangle If parent IsNot Nothing Then r = parent.RectangleToScreen(parent.ClientRectangle) Else r = Screen.FromPoint(frm.Location).WorkingArea End If Dim x = r.Left + (r.Width - frm.Width) \ 2 Dim y = r.Top + (r.Height - frm.Height) \ 2 frm.Location = New Point(x, y) End Sub
Incidentally, one of the very few reasons to actually implement the Load event handler.