How to move a Form to the foreground when clicking a Window of another app parented to a Panel-CodePudding

I use the code down below to start an application and move it into a Panel on my Form. In this example I use Notepad, only as an example. Later I will use a different application.

When another application is moved in front of my Form, I can only move my Form to the foreground by clicking the title bar. If I click on the MDI child area (so the Panel where Notepad is moved into), nothing happens.
Is there a way to enable that?

Imports System.Runtime.InteropServices
Public Class Form1
    Declare Auto Function SetParent Lib "user32.dll" (ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As Integer
    Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim proc As Process
        proc = Process.Start("notepad.exe")
        proc.WaitForInputIdle()
        SetParent(proc.MainWindowHandle, Me.Panel1.Handle)
        SendMessage(proc.MainWindowHandle, 274, 61488, 0)
    End Sub
End Class

CodePudding user response：

The problem is that a hosted (re-parented) Window, when activated, doesn't cause the hosing Form to also activate, so it's brought to the foreground.
The hosted Window is not exactly a child Window and the hosting Form doesn't receive any message from it.

A possible method to bring to the foreground the Form that hosts a foreign Window, when this Window receives the focus (you click or otherwise activate it)
It uses SetWinEventHook to install a Hook that monitors changes in state of the placement of a Window (EVENT_SYSTEM_FOREGROUND).
You specify the handle of the Window of interests, (your proc.MainWindowHandle here), plus its ProcessId and ThreadId. Note that these are not the same as your app's, a call to GetWindowThreadProcessId() is required to get this information.

When you activate the foreign Window, the Hooks calls the specified callback delegate (here, ForegrundChangedEventDelegate), which in turn executes the method that it points to (ForegroundStateChangedCallback)
When this method is called, it checks whether the object that caused the notification is OBJID_WINDOW and that the event is actually EVENT_SYSTEM_FOREGROUND. If that's the case, it calls SetWindowPos to bring the hosting Form to the foreground, but without activating it, so the hosted Window doesn't lose focus

Notes:

The SetWinEvetHook delegate is created in the Constructor (Sub New()) of the parent Form, along with a GC SafeHandle that is used to prevent the delegate from being garbage-collected at the wrong time.
It's released in the OnHandleDestroyed() override, where also the hook proc is un-hooked

see the imports statement in the Form:

  Imports [Your App Namespace].NativeMethods

this means that you have to specify the namespace of your app for the import to work as intended. In VB.Net, usually the name of the app and its main NameSpace match; if your app is named, WinFormsApp1, then its Imports WinFormsApp1.NativeMethods

To activate the Hook, as soon as you have changed the Parent of that Window, use its handle to call the SetForegroundStateChangedHook() method. That's all.
When the Form closes, the hook is released

I suggest using the code in Unhook Window into its original State to set the Parent (and, possibly, set it back to the original value before closing the hosting form). You can send WM_CLOSE to the Window if needed.

Imports [Your App Namespace].NativeMethods

Public Class SomeForm

    Private hForegrundChangedEventHook As IntPtr
    Private ReadOnly ForegrundChangedEventDelegate As WinEventDelegate
    Private Shared GCForegroundStateSafetyHandle As GCHandle

    Public Sub New()
        InitializeComponent()
        ForegrundChangedEventDelegate = New WinEventDelegate(AddressOf ForegroundStateChangedCallback)
        GCForegroundStateSafetyHandle = GCHandle.Alloc(ForegrundChangedEventDelegate)
    End Sub

    Protected Overrides Sub OnHandleDestroyed(e As EventArgs)
        GCForegroundStateSafetyHandle.Free()
        UnhookWinEvent(hForegrundChangedEventHook)
        MyBase.OnHandleDestroyed(e)
    End Sub

    Private Sub SetForegroundStateChangedHook(hWnd As IntPtr)
        Dim processId As UInteger
        Dim targetThreadId = GetWindowThread(hWnd, processId)
        hForegrundChangedEventHook = WinEventHookOne(SWEH_Events.EVENT_SYSTEM_FOREGROUND, ForegrundChangedEventDelegate, processId, targetThreadId)
    End Sub

    Friend Sub ForegroundStateChangedCallback(hWinEventHook As IntPtr, eventType As SWEH_Events, hWnd As IntPtr, idObject As SWEH_ObjectId, idChild As Long, dwEventThread As UInteger, dwmsEventTime As UInteger)
        If idObject = SWEH_ObjectId.OBJID_WINDOW AndAlso eventType = SWEH_Events.EVENT_SYSTEM_FOREGROUND Then
            Dim flags = SWP_Flags.SWP_ASYNCWINDOWPOS Or SWP_Flags.SWP_NOACTIVATE Or SWP_Flags.SWP_NOSIZE Or SWP_Flags.SWP_NOMOVE
            SetWindowPos(Handle, IntPtr.Zero, 0, 0, 0, 0, flags)
        End If
    End Sub
End Class

NativeMethods class

Add this class to the Project and import in your Form as described

Imports System.Runtime.InteropServices

Public Class NativeMethods

    <DllImport("user32.dll", SetLastError:=True)>
    Friend Shared Function GetWindowThreadProcessId(hWnd As IntPtr, ByRef lpdwProcessId As UInteger) As UInteger
    End Function

    <DllImport("user32.dll", SetLastError:=True)>
    Friend Shared Function SetWindowPos(hWnd As IntPtr, hWndInsertAfter As IntPtr, x As Integer, y As Integer, cx As Integer, cy As Integer, uFlags As SWP_Flags) As Boolean
    End Function

    Friend Delegate Sub WinEventDelegate(
        hWinEventHook As IntPtr,
        eventType As SWEH_Events,
        hwnd As IntPtr, idObject As SWEH_ObjectId,
        idChild As Long,
        dwEventThread As UInteger,
        dwmsEventTime As UInteger)

    <DllImport("user32.dll", SetLastError:=False)>
    Friend Shared Function SetWinEventHook(
        eventMin As SWEH_Events,
        eventMax As SWEH_Events,
        hmodWinEventProc As IntPtr,
        lpfnWinEventProc As WinEventDelegate,
        idProcess As UInteger,
        idThread As UInteger,
        dwFlags As SWEH_dwFlags) As IntPtr
    End Function

    <DllImport("user32.dll", SetLastError:=False)>
    Friend Shared Function UnhookWinEvent(hWinEventHook As IntPtr) As Boolean
    End Function

    Friend Shared WinEventHookInternalFlags As SWEH_dwFlags =
        SWEH_dwFlags.WINEVENT_OUTOFCONTEXT Or SWEH_dwFlags.WINEVENT_SKIPOWNPROCESS


    Friend Shared Function WinEventHookOne(evt As SWEH_Events, weDelegate As WinEventDelegate, idProcess As UInteger, idThread As UInteger) As IntPtr
        Return SetWinEventHook(evt, evt, IntPtr.Zero, weDelegate, idProcess, idThread, WinEventHookInternalFlags)
    End Function


    Friend Shared Function GetWindowThread(hWnd As IntPtr, ByRef processID As UInteger) As UInteger
    #If NETFX Then
        new UIPermission(UIPermissionWindow.AllWindows).Demand();
    #End If
        processID = 0
        Return GetWindowThreadProcessId(hWnd, processID)
    End Function


    ' SetWinEventHook Events
    Friend Enum SWEH_Events As UInteger
        EVENT_MIN = &H1
        EVENT_MAX = &H7FFFFFFF
        EVENT_SYSTEM_SOUND = &H1
        EVENT_SYSTEM_ALERT = &H2
        EVENT_SYSTEM_FOREGROUND = &H3
        EVENT_SYSTEM_MENUSTART = &H4
        EVENT_SYSTEM_MENUEND = &H5
        EVENT_SYSTEM_MENUPOPUPSTART = &H6
        EVENT_SYSTEM_MENUPOPUPEND = &H7
        EVENT_SYSTEM_CAPTURESTART = &H8
        EVENT_SYSTEM_CAPTUREEND = &H9
        EVENT_SYSTEM_MOVESIZESTART = &HA
        EVENT_SYSTEM_MOVESIZEEND = &HB
        EVENT_SYSTEM_CONTEXTHELPSTART = &HC
        EVENT_SYSTEM_CONTEXTHELPEND = &HD
        EVENT_SYSTEM_DRAGDROPSTART = &HE
        EVENT_SYSTEM_DRAGDROPEND = &HF
        EVENT_SYSTEM_DIALOGSTART = &H10
        EVENT_SYSTEM_DIALOGEND = &H11
        EVENT_SYSTEM_SCROLLINGSTART = &H12
        EVENT_SYSTEM_SCROLLINGEND = &H13
        EVENT_SYSTEM_SWITCHSTART = &H14
        EVENT_SYSTEM_SWITCHEND = &H15
        EVENT_SYSTEM_MINIMIZESTART = &H16
        EVENT_SYSTEM_MINIMIZEEND = &H17
        EVENT_SYSTEM_DESKTOPSWITCH = &H20
        EVENT_SYSTEM_END = &HFF
        EVENT_OEM_DEFINED_START = &H101
        EVENT_OEM_DEFINED_END = &H1FF
        EVENT_UIA_EVENTID_START = &H4E00
        EVENT_UIA_EVENTID_END = &H4EFF
        EVENT_UIA_PROPID_START = &H7500
        EVENT_UIA_PROPID_END = &H75FF
        EVENT_CONSOLE_CARET = &H4001
        EVENT_CONSOLE_UPDATE_REGION = &H4002
        EVENT_CONSOLE_UPDATE_SIMPLE = &H4003
        EVENT_CONSOLE_UPDATE_SCROLL = &H4004
        EVENT_CONSOLE_LAYOUT = &H4005
        EVENT_CONSOLE_START_APPLICATION = &H4006
        EVENT_CONSOLE_END_APPLICATION = &H4007
        EVENT_CONSOLE_END = &H40FF
        EVENT_OBJECT_CREATE = &H8000
        EVENT_OBJECT_DESTROY = &H8001
        EVENT_OBJECT_SHOW = &H8002
        EVENT_OBJECT_HIDE = &H8003
        EVENT_OBJECT_REORDER = &H8004
        EVENT_OBJECT_FOCUS = &H8005
        EVENT_OBJECT_SELECTION = &H8006
        EVENT_OBJECT_SELECTIONADD = &H8007
        EVENT_OBJECT_SELECTIONREMOVE = &H8008
        EVENT_OBJECT_SELECTIONWITHIN = &H8009
        EVENT_OBJECT_STATECHANGE = &H800A
        EVENT_OBJECT_LOCATIONCHANGE = &H800B
        EVENT_OBJECT_NAMECHANGE = &H800C
        EVENT_OBJECT_DESCRIPTIONCHANGE = &H800D
        EVENT_OBJECT_VALUECHANGE = &H800E
        EVENT_OBJECT_PARENTCHANGE = &H800F
        EVENT_OBJECT_HELPCHANGE = &H8010
        EVENT_OBJECT_DEFACTIONCHANGE = &H8011
        EVENT_OBJECT_ACCELERATORCHANGE = &H8012
        EVENT_OBJECT_INVOKED = &H8013
        EVENT_OBJECT_TEXTSELECTIONCHANGED = &H8014
        EVENT_OBJECT_CONTENTSCROLLED = &H8015
        EVENT_SYSTEM_ARRANGMENTPREVIEW = &H8016
        EVENT_OBJECT_END = &H80FF
        EVENT_AIA_START = &HA000
        EVENT_AIA_END = &HAFFF
    End Enum

    ' SetWinEventHook Window Objects
    Friend Enum SWEH_ObjectId As Long
        OBJID_WINDOW = &H0
        OBJID_SYSMENU = &HFFFFFFFFUI
        OBJID_TITLEBAR = &HFFFFFFFEUI
        OBJID_MENU = &HFFFFFFFDUI
        OBJID_CLIENT = &HFFFFFFFCUI
        OBJID_VSCROLL = &HFFFFFFFBUI
        OBJID_HSCROLL = &HFFFFFFFAUI
        OBJID_SIZEGRIP = &HFFFFFFF9UI
        OBJID_CARET = &HFFFFFFF8UI
        OBJID_CURSOR = &HFFFFFFF7UI
        OBJID_ALERT = &HFFFFFFF6UI
        OBJID_SOUND = &HFFFFFFF5UI
        OBJID_QUERYCLASSNAMEIDX = &HFFFFFFF4UI
        OBJID_NATIVEOM = &HFFFFFFF0UI
    End Enum

    ' WinEventDelegate flags
    Friend Enum SWEH_dwFlags As UInteger
        WINEVENT_OUTOFCONTEXT = &H0     ' Events are ASYNC - No dll needed
        WINEVENT_SKIPOWNTHREAD = &H1    ' Don't call back for events on installer's thread
        WINEVENT_SKIPOWNPROCESS = &H2   ' Don't call back for events on installer's process
        WINEVENT_INCONTEXT = &H4        ' Events are SYNC, this causes your dll to be injected into every process
    End Enum

    ' SetWindowPos flags
    <Flags>
    Public Enum SWP_Flags As UInteger
        SWP_NOSIZE = &H1
        SWP_NOMOVE = &H2
        SWP_NOZORDER = &H4
        SWP_NOREDRAW = &H8
        SWP_NOACTIVATE = &H10
        SWP_DRAWFRAME = &H20
        SWP_FRAMECHANGED = &H20
        SWP_SHOWWINDOW = &H40
        SWP_HIDEWINDOW = &H80
        SWP_NOCOPYBITS = &H100
        SWP_NOOWNERZORDER = &H200
        SWP_NOREPOSITION = &H200
        SWP_NOSENDCHANGING = &H400
        SWP_NOCLIENTSIZE = &H800
        SWP_NOCLIENTMOVE = &H1000
        SWP_DEFERERASE = &H2000
        SWP_ASYNCWINDOWPOS = &H4000
    End Enum
End Class

CodePudding user response：

Thanks to the great help of Jimi, I was able to get it work:

Add the NativeMethods class to the project, use the code from Jimi's answer above

Use the following code in the form:

Private hForegrundChangedEventHook As IntPtr
Private ReadOnly ForegrundChangedEventDelegate As WinEventDelegate
Private Shared GCForegroundStateSafetyHandle As GCHandle
Declare Auto Function SetParent Lib "user32.dll" (ByVal hWndChild As IntPtr, ByVal hWndNewParent As IntPtr) As Integer
Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
Declare Auto Function GetWindowThreadProcessId Lib "user32.dll" (ByVal hwnd As IntPtr, ByRef lpdwProcessId As Integer) As Integer
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim proc As Process
    Dim ProcId As Integer = 0
    proc = Process.Start("notepad.exe")
    proc.WaitForInputIdle()
    SetParent(proc.MainWindowHandle, Me.Panel1.Handle)
    SendMessage(proc.MainWindowHandle, 274, 61488, 0)
    GetWindowThreadProcessId(proc.MainWindowHandle, ProcId)
    SetForegroundStateChangedHook(proc.MainWindowHandle)
End Sub
Public Sub New()
    InitializeComponent()
    ForegrundChangedEventDelegate = New WinEventDelegate(AddressOf ForegroundStateChangedCallback)
    GCForegroundStateSafetyHandle = GCHandle.Alloc(ForegrundChangedEventDelegate)
End Sub
Protected Overrides Sub OnHandleDestroyed(e As EventArgs)
    GCForegroundStateSafetyHandle.Free()
    UnhookWinEvent(hForegrundChangedEventHook)
    MyBase.OnHandleDestroyed(e)
End Sub
Private Sub SetForegroundStateChangedHook(hWnd As IntPtr)
    Dim processId As UInteger
    Dim targetThreadId = GetWindowThread(hWnd, processId)
    hForegrundChangedEventHook = WinEventHookOne(SWEH_Events.EVENT_SYSTEM_FOREGROUND, ForegrundChangedEventDelegate, processId, targetThreadId)
End Sub
Friend Sub ForegroundStateChangedCallback(hWinEventHook As IntPtr, eventType As SWEH_Events, hWnd As IntPtr, idObject As SWEH_ObjectId, idChild As Long, dwEventThread As UInteger, dwmsEventTime As UInteger)
    If idObject = SWEH_ObjectId.OBJID_WINDOW AndAlso eventType = SWEH_Events.EVENT_SYSTEM_FOREGROUND Then
        Dim flags = SWP_Flags.SWP_ASYNCWINDOWPOS Or SWP_Flags.SWP_NOACTIVATE Or SWP_Flags.SWP_NOSIZE Or SWP_Flags.SWP_NOMOVE
        SetWindowPos(Handle, IntPtr.Zero, 0, 0, 0, 0, flags)
    End If
End Sub
End Class