Topmost window over everything, except child processes

Question

My program is full screen and topmost, and I would like all the child processes of that window to be above my program's main window. The processes are unknown, and external.

I can launch the process using System.Diagnostics.Process.Start(exeName,procArgs).WaitForExit(), but from there I am stuck.

Answer 1

Basically you use the SetParent() API to make the external app a child of yours. Here I'm also using the GetWindowRect() and SetWindowPos() APIs to keep the window in the same launch position after its parent is changed. Finally, you need to keep track of the processes and close them manually so they do not become orphaned when the form is closed:

Imports System.ComponentModel
Imports System.IO
Imports System.Runtime.InteropServices
Imports System.Text.RegularExpressions

Public Class Form1

    Private Const SWP_NOSIZE As Integer = &H0001

    <StructLayout(LayoutKind.Sequential)>
    Public Structure RECT
        Public Left As Integer, Top As Integer, Right As Integer, Bottom As Integer
    End Structure

    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)>
    Public Shared Function SetParent(ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As IntPtr
    End Function

    <DllImport("user32.dll")>
    Private Shared Function GetWindowRect(ByVal hWnd As IntPtr, ByRef lpRect As RECT) As Boolean
    End Function

    <DllImport("user32.dll", SetLastError:=True)>
    Private Shared Function SetWindowPos(ByVal hWnd As IntPtr, ByVal hWndInsertAfter As IntPtr, ByVal X As Integer, ByVal Y As Integer, ByVal cx As Integer, ByVal cy As Integer, ByVal uFlags As Integer) As Boolean
    End Function

    Private Ps As New List(Of Process)

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim exeName As String = "Notepad"
        Dim procArgs As String = ""
        LaunchExe(exeName, procArgs)
    End Sub

    Private Sub LaunchExe(ByVal exeName As String, ByVal procArgs As String)
        Try
            Dim p As Process = System.Diagnostics.Process.Start(exeName, procArgs)
            If Not IsNothing(p) Then
                p.WaitForInputIdle()
                Dim rc As RECT
                GetWindowRect(p.MainWindowHandle, rc)
                Dim pt As New Point(rc.Left, rc.Top)
                pt = Me.PointToClient(pt)
                SetParent(p.MainWindowHandle, Me.Handle)
                SetWindowPos(p.MainWindowHandle, 0, pt.X, pt.Y, 0, 0, SWP_NOSIZE)
                Ps.Add(p)
            End If
        Catch ex As Exception
            MessageBox.Show(exeName & vbCrLf & procArgs, "Error Starting Application")
        End Try
    End Sub

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Me.Close()
    End Sub

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
        For Each P As Process In Ps
            If Not P.HasExited Then
                P.CloseMainWindow()
            End If
        Next
    End Sub

End Class