snap to grid MDI child forms vb.net - vb.net

Question

I'm developping a modular dashboard in Visual Basic that starts as an empty container than i can add modules to populate it.
The parent form is an MDI container and every module is a child MDI form that have fixed size.
I'd like to snap all of that child form to a grid both when the user creates a new one and when moves one of it inside the container (like they are magnetized to that grid).
How can i do that? Thanks

Answer 1

If I well understand you need something like this:
Private Class ImaginaryGrid
' You can change Columns and Rows as you want
Shared Rows As Integer = 3
Shared Cols As Integer = 3
Private Shared Function SnapToGrid(target As Form) As Point
Dim AllW As Integer = Screen.PrimaryScreen.WorkingArea.Width
Dim AllH As Integer = Screen.PrimaryScreen.WorkingArea.Height
Dim parent = target.MdiParent
If parent IsNot Nothing Then
AllW = target.MdiParent.ClientSize.Width
AllH = target.MdiParent.ClientSize.Height
End If
Dim currentPoint As Point = target.Location
Dim stepW As Integer = CInt(AllW / Cols)
Dim stepH As Integer = CInt(AllH / Rows)
Dim targetCol As Integer = CInt(currentPoint.X \ stepW)
Dim targetRow As Integer = CInt(currentPoint.Y \ stepH)
Dim newX As Integer = targetCol * stepW
Dim newY As Integer = targetRow * stepH
target.Location = New Point(newX, newY)
target.Width = stepW
target.Height = stepH
End Function
Shared Sub AttachFormToStayInGrid(frm As Form)
AddHandler frm.ResizeEnd, Sub()
SnapToGrid(frm)
End Sub
SnapToGrid(frm)
End Sub
End Class
Usage:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
ImaginaryGrid.AttachFormToStayInGrid(Me)
End Sub
Take changes (if needed) as comments below shows:

Answer 2

Here's a beefed up version based on the same idea as G3nt_M3caj's suggestion:
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ImaginaryGrid.Client = Me.Controls.OfType(Of MdiClient).FirstOrDefault
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim frm As New Form
ImaginaryGrid.AttachFormToStayInGrid(frm)
End Sub
Private Class ImaginaryGrid
Public Shared WithEvents Client As MdiClient
Public Shared FixedChildSize As New Size(250, 150)
Private Shared Function SnapToGrid(target As Form) As Rectangle
Dim colX As Integer = target.Location.X / FixedChildSize.Width
Dim colY As Integer = target.Location.Y / FixedChildSize.Height
Dim newX As Integer = colX * FixedChildSize.Width
Dim newY As Integer = colY * FixedChildSize.Height
Return New Rectangle(New Point(newX, newY), FixedChildSize)
End Function
Shared Sub AttachFormToStayInGrid(frm As Form)
frm.Size = FixedChildSize
frm.FormBorderStyle = FormBorderStyle.FixedSingle
frm.MdiParent = Client.Parent
frm.Show()
SnapChild(frm)
AddHandler frm.ResizeEnd, Sub()
SnapChild(frm)
End Sub
AddHandler frm.LocationChanged, Sub()
If frm.WindowState = FormWindowState.Normal Then
snapRectangle = SnapToGrid(frm)
Client.Refresh()
End If
End Sub
End Sub
Private Shared Sub SnapChild(ByVal frm As Form)
If frm.WindowState = FormWindowState.Normal Then
Dim rc As Rectangle = SnapToGrid(frm)
frm.Bounds = rc
snapRectangle = Nothing
Client.Refresh()
End If
End Sub
Private Shared snapRectangle? As Rectangle
Private Shared Sub Client_Paint(sender As Object, e As PaintEventArgs) Handles Client.Paint
If snapRectangle.HasValue Then
e.Graphics.DrawRectangle(Pens.Black, snapRectangle)
End If
End Sub
End Class
End Class