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Resize, lock at minimum size

Posted on 2004-04-12
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Last Modified: 2008-02-01
how to disable resize in order to have a minimum size for the window, just like paint.exe, without flashing ?
i'm in VB6.
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Question by:ennixo
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by:BrianGEFF719
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The only way to do this is by subclassing.


-Brian
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by:BrianGEFF719
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by:BrianGEFF719
Comment Utility
Taken from the above link:

'===============Bas module code============
Type POINTAPI
     x As Long
     y As Long
End Type

Type MINMAXINFO
     ptReserved As POINTAPI
     ptMaxSize As POINTAPI
     ptMaxPosition As POINTAPI
     ptMinTrackSize As POINTAPI
     ptMaxTrackSize As POINTAPI
End Type

Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
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 Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)

Public Const GWL_WNDPROC = (-4)
Const WM_GETMINMAXINFO = &H24

Public OldProc As Long
Public MinWidth As Long
Public MinHeight As Long
Dim MMinfo As MINMAXINFO

Public Function WndProc(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
  Select Case wMsg
    Case WM_GETMINMAXINFO
         CopyMemory MMinfo, ByVal lParam, LenB(MMinfo)
       ' Max/Min size when tracking
         MMinfo.ptMinTrackSize.x = MinWidth
         MMinfo.ptMinTrackSize.y = MinHeight
'         MMinfo.ptMaxTrackSize.x = MaxWidth
'         MMinfo.ptMaxTrackSize.y = MaxHeight
         CopyMemory ByVal lParam, MMinfo, LenB(MMinfo)
         Exit Function
    End Select
    WndProc = CallWindowProc(OldProc, hwnd, wMsg, wParam, lParam)
End Function

'===========Form code===========
Private Sub Form_Load()
   MinWidth = 128
   MinHeight = 128
   Me.AutoRedraw = True
   Me.Print "Minimum size of this form" & vbCrLf & "is limited to 128x128 pixels"
   OldProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WndProc)
End Sub

Private Sub Form_Unload(Cancel As Integer)
    Call SetWindowLong(hwnd, GWL_WNDPROC, OldProc)
End Sub
'=================================
Note: this code use subclassing, so don't stop it with IDE stop button, use form [x] button to close form.








Good Luck
-Brian
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by:ChenChen
Comment Utility
I think you can use the Resize event, have a function there to test if the height and width is greater then your minimum size, otherwise set it to the minimum values, something like this:

private sub form_resize()

if me.width<MINIMUM_WIDTH then
me.width=MINIMUM_WIDTH
end if

'same to the form height

end sub
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by:BrianGEFF719
Comment Utility
ChenChen: The flicker he is refering to in his question is because he is doing it like that.

When you resize like that you will see a flicker, subclassing allows the resize event to not be passed to the form if the dimensions are smaller than specified. So therefore, no flicker.


-Brian
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Author Comment

by:ennixo
Comment Utility
BrianGEFF719: your code works great but :

- if i add "End" on query unload it crashes and i must add it to end the app if other windows are opened.
- i removed AutoRedraw = true because i draw everything with api, so this is faster a lot ! is it good or bad ?
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by:prgmrdave
Comment Utility
ennixo,

Don't use End until you've done the SetWindowLong in the Form_Unload() event. End will work just as well if you put it in Form_Unload as in Form_QueryUnload.

David
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by:ennixo
Comment Utility
in my Form_QueryUnload sub i added End after the Call SetWindowLong(Me.hWnd, GWL_WNDPROC, OldProc) and it crashes...
if i comment the End, it doesn't crashes...

(it's not really a crash, it's just that the VB-IDE is closed... is it normal ? is it because in "debug mode" the subclass is made by VB ?)

is there another way ?
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by:BrianGEFF719
Comment Utility
ennixo: This is normal, subclassed programs FUNCTION WEIRD in the IDE.


Always make sure to close the program with the "X" and not "End"


-Brian
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Accepted Solution

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BrianGEFF719 earned 500 total points
Comment Utility
AutoRedrew is fine. Secondly, wait on adding the "END" until you are done testing in the IDE. Then add it just before you compile and test.


-Brian
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Expert Comment

by:prgmrdave
Comment Utility
If you are using End because your application has other windows open, do something like this rather than using End:

Dim frm As Form
For Each frm In Forms
    If Not frm Is Me Then Unload frm
Next frm

That way, when this form unloads, it will be the last one, and the app will exit.
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by:wd006451
Comment Utility
Hello, i have a question, what if i have 2 forms, im limiting the size, and i want the sizes of them both to be diffrent.  There child mdi forms.
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