MDI & SDI switching

[JanH]

i've got a question:
how can i change from MDI to SDI(and back), runtime or with restarting?
i know it is possible, because Visual Basic itselvses also uses this. (in Options)

i don't mind if i have to restart the application.

[mlewis]

I don't think even APIs can change that around. Besides, MDIForms are different classes than Forms, its not just a style flag or something, so you'd have trouble there anyway.

[ExcalibursZone]

True enough indeed. But if there is a setting which chooses whether you use an SDI version of a form or an MDI version of a form though you have to keep 2 copies of each form, you can choose to have either at run time (you have to reload the project ...) The only forms you mess with are the MDI Children. Here is some sample code that I slopped together to show you what I mean.
Start a New Project.

Add Another Form (Form2)
Add An MDIForm (MdiForm1)
Set Form1's MDIChild to True.

Set the project to run with the MDIForm1.
Add a Menu to MDIForm1, Name it Test, Set it's caption to Test.
Add a Picturebox to MDIForm1 (Picture1)

Place the following code in the MDIForm1:

Dim Choice As Boolean

Private Sub MDIForm_Load()
    Dim Temp As String
    Temp = InputBox("SDI or MDI?", , "MDI")
    If Temp = "SDI" Then
        Choice = True
        Me.Height = 0 + (Picture1.Height * 2) - 90
        Else
        Choice = False
    End If
End Sub

Private Sub MDIForm_Resize()
    If Choice = True Then
        If Me.WindowState > 1 Then
            Me.WindowState = 0
            Me.Top = 0
            Me.Left = 0
            Me.Width = Screen.Width
            Exit Sub
        End If
        If Me.Height <> 0 + (Picture1.Height * 2) - 90 And _
        Me.WindowState < 1 Then
            Me.Height = 0 + (Picture1.Height * 2) - 90
        End If
    End If
End Sub

Private Sub test_Click()
    If Choice = True Then
        Dim FormSDI As New Form2
        Set FormSDI = New Form2
        FormSDI.Show
        Else
        Dim FormMDI As New Form1
        Set FormMDI = New Form1
        FormMDI.Show
    End If
End Sub

Place this Code in the form load event of Form1 & Form2:

Private Sub Form_Load()
    MsgBox "I have been loaded"
End Sub

When you start up the project, you are asked to choose either MDI or SDI. If you use the default of MDI, everytime you hit the test button, you reieve the message "I have been loaded" and when you click ok, the form displays in the MDI parent area.

If you choose SDI (by typing it in), you will recieve a 'minimized' mdi form, which is just the height of the titlebar, picturebox, and menu. If you try to resize the window, it snaps back to that height. If you hit maximize, it moves to the top of the screen and changes it's width to match the screen width, you are still unable to resize it. If you hit minimize, it will minimize to the tray. If you click on test, Form2 displays as an SDI window. You can set this to vbModal if you wish ...

As you can see, the idea is possible, you just need to change the inputbox to a setting (from the registry, ini file, or whatnot, possibly even a menu item). You keep MDIForm as the main form, you just swap to a new Form style.

Hope this clears that up.

-Excalibur

[Edited by ExcalibursZone on 09-29-2000 at 01:37 PM]

[ExcalibursZone]

I did a little tinkering with the code and found that with a few case statements a new menu item and a new subroutine, you can change modes during runtime. What I mean by changing mode is the pseudo swap between MDI & SDI It's ugly, yes, but it works ...

You could also set up another form called SDIMain, add a module and start the project off of sub main(). Based on the users saved setting, the program could launch either the sdimain form or the mdiform1 and give you the same functionality as the VB IDE. Though doing it this way means that you can't swap between the two form styles at runtime either ...

There might be some minor intricate details I have missed (I'm at work and have little time to code this properly atm) but this should get the general effect down.

-Excalibur

[JanH]

ok. thanks for the quick replies. i'll see if i can manage this SDI/MDI switching

[mlewis]

wait! I don't know if this will work, but it may be worth trying. If you use CreateWindow/CreateWindowEx and a bunch of other calls, you can get a basic MDI window to exist. I know this works; the shaky part is here: I think if you can find a style flag on the windows or an API that will make your forms MDIChildren without using the VB property, then you can set them as children of the MDI window on the fly, as well as destroy the MDI window and leave the little guys standing.

Again, I don't know if its feasible, but give it a shot.