Poner un Formulario MDI en Fullscreen

Este es un módulo que nos permitirá poner un formulario MDI en modo FullScreen cuando está maximizado, la ventaja de esto es ganarle un poco más de espacio al monitor, y sobre todo cuando el software tiene un papel protagónico en el PC que lo ejecuta.

Código del módulo bas «MdiFullScreen»

Option Explicit
 
Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function SetWindowPos Lib "user32.dll" (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function RegisterHotKey Lib "user32" (ByVal hwnd As Long, ByVal ID As Long, ByVal fsModifiers As Long, ByVal vk As Long) As Long
Private Declare Function UnregisterHotKey Lib "user32" (ByVal hwnd As Long, ByVal ID As Long) As Long
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long
 
Private Const HWND_TOPMOST          As Long = -1
Private Const HWND_NOTOPMOST        As Long = -2
 
Private Const SWP_NOACTIVATE        As Long = &H10
Private Const SWP_NOSIZE            As Long = &H1
Private Const SWP_NOMOVE            As Long = &H2
Private Const SWP_SHOWWINDOW        As Long = &H40
 
Private Const WS_MAXIMIZEBOX        As Long = &H10000
Private Const WS_MINIMIZEBOX        As Long = &H20000
Private Const WS_THICKFRAME         As Long = &H40000
Private Const WS_SYSMENU            As Long = &H80000
Private Const WS_CAPTION            As Long = &HC00000
 
Private Const SC_RESTORE            As Long = &HF120&
 
Private Const WM_ACTIVATEAPP        As Long = &H1C
Private Const WM_HOTKEY             As Long = &H312
Private Const WM_SYSCOMMAND         As Long = &H112
 
Private Const GWL_STYLE             As Long = (-16)
Private Const GWL_WNDPROC           As Long = (-4)
 
Const MyHotKey                      As Long = &H1000
 
Dim WndStyle As Long
Dim bFullScreen As Boolean
Dim PrevProc As Long
 
 
Public Sub ShowFullScreen(hwnd As Long) 
    If Not bFullScreen Then 
        bFullScreen = True 
        Call RegisterHotKey(hwnd, MyHotKey, 0, vbKeyEscape) 
        WndStyle = GetWindowLong(hwnd, GWL_STYLE) 
        SetWindowLong hwnd, GWL_STYLE, WndStyle And Not WS_MAXIMIZEBOX And Not WS_MINIMIZEBOX And Not WS_THICKFRAME And Not WS_CAPTION
        SetWindowPos hwnd, HWND_TOPMOST, 0, 0, Screen.Width / 15, Screen.Height / 15, SWP_NOACTIVATE 
        PrevProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc) 
    End If 
End Sub
 
Public Sub EndFullScreen(hwnd)
    If bFullScreen Then
        bFullScreen = False
 
        SetWindowLong hwnd, GWL_STYLE, WndStyle 
        SendMessage hwnd, WM_SYSCOMMAND, SC_RESTORE, ByVal 0& 
        SetWindowLong hwnd, GWL_WNDPROC, PrevProc
 
        Call UnregisterHotKey(hwnd, MyHotKey)
 
    End If
End Sub
 
Public Function WindowProc(ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    WindowProc = CallWindowProc(PrevProc, hwnd, uMsg, wParam, lParam)
 
    If uMsg = WM_ACTIVATEAPP Then
        EndFullScreen hwnd
    End If
 
    If uMsg = WM_HOTKEY Then
        If wParam = MyHotKey Then
            EndFullScreen hwnd
        End If
    End If
 
End Function

Código en el Formulario MDI»

Option Explicit
 
Private Sub MDIForm_Load()
Form1.Show
End Sub
 
Private Sub MDIForm_Resize()
    If Me.WindowState = vbMaximized Then
        ShowFullScreen Me.hwnd
    Else
        EndFullScreen Me.hwnd
    End If