Preventing a window from moving less than 140 pixels from the top of the screen

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Hey guys,

I'm working in VB.net 2010, and I'm trying to prevent a window from moving less than 140pixels from the top of the screen.

I'm trying to use Wndproc but so far I've failed.

I've tried modifiying the X,Y paramaters in the following messages:

WM_SYSCOMMAND with a wparam of SC_MOVE
WM_MOVING
WM_WINDOWPOSCHANGING
WM_GETMINMAXINFO

I've also tried using the form methods for Move, Resize, and Shown as suggested below, but they cause the form to flash between the mouse cursor location and my boundary(140px).

The project consists of multiple forms. One form is fixed at the top of the screen with a height of 140, set to always be on top (lets call it the navigation bar). I'm trying to prevent the other forms from being moved behind this "navigation bar".

What is the correct way to prevent a form from moving in a certain direction.

Thanks!

Posted 6-Jun-12 12:06pm

rcintorino

Updated 6-Jun-12 16:22pm

v2

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Sergey Alexandrovich Kryukov 6-Jun-12 18:54pm

WPF, Forms? Anything else? Tag it.
--SA

1 solution

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Sergey Alexandrovich Kryukov · Answer 1 · 2012-06-06T13:01:00

Solution 1

To do what your try to do, you apparently have to use P/Invoke. By doing this, you totally loose platform compatibility. Did you know that your application, even the Forms application (but not WPF) if written accurately, can run on many systems without recompilations, such as Linux, Mac OS X and more? You are going to loose it. No need.

All you need is using the property Top (or whatever) and fixing position/size; for example, in the event handler of the event System.Windows.Forms.Form.Shown:

VB

Me.Shown += Function(sender, eventArgs)
    If Me.Top < 140 Then
        Me.Top = 140
    End If
End Function

Something like that. Try to forget about using Windows API unless this is absolutely needed. You probably will be amazed how rarely it is the case.

[EDIT]

And I agree with AspNetDev who reminded us that it would require adding appropriate handlers to events like SizeChanged and Move. Please see our discussion in comments below.

—SA

Posted 6-Jun-12 13:01pm

Sergey Alexandrovich Kryukov

Updated 6-Jun-12 14:17pm

v5

Comments

AspDotNetDev 6-Jun-12 19:10pm

Probably also a good idea to hook up to a few more events, such as move and resize. Here is some info for the OP on the move event: http://msdn.microsoft.com/en-us/library/system.windows.forms.control.move(v=vs.100).aspx

Sergey Alexandrovich Kryukov 6-Jun-12 19:13pm

Sure, but the whole idea to keep a window away from certain area is a sign of poop UI design to me...
--SA

AspDotNetDev 6-Jun-12 19:34pm

Maybe, maybe not. Maybe they are building screen capture software and have some reason not to have the window near the edge of the screen, or maybe they are building a remote desktop utility and want to avoid having the window near the hover location that causes the toolbar to appear, or maybe they are building a puzzle game out of windows that involves the user placing windows in certain configurations without violating certain rules (e.g., not within 140px of the edge of the screen). I don't think we can make assumptions like this being poop UI design when we have no idea what is being designed.

Sergey Alexandrovich Kryukov 6-Jun-12 20:12pm

Well, I have to agree with you. I just said "a sign of", not a sure fact...
--SA

Sergey Alexandrovich Kryukov 6-Jun-12 20:16pm

I credited your useful note in my answer, after [EDIT].
--SA

VJ Reddy 6-Jun-12 19:55pm

Good answer. 5!

Sergey Alexandrovich Kryukov 6-Jun-12 20:11pm

Thank you, VJ.
--SA

rcintorino 6-Jun-12 22:16pm

Unfortunately using the form events for Move, Shown, and Resize cause the window to flash. I need a solution that will not make the window flash. Also I'm not sure what you mean by using P/Invoke. I looked up P/Invoke and it seems to be just a way to import API functions?

Sergey Alexandrovich Kryukov 6-Jun-12 23:14pm

Flash is a different issue. Correctly designed window does not flash. It depends on what it does, but you can use double buffering and correct ways of handling those events (so your window would not jerk back and force). Yes, the P/Invoke imports unmanaged methods from unmanaged DLLs. Are you using it already or not? Or you just handle messages by the Form.DefWndProc? You don't have to do it.
--SA

rcintorino 7-Jun-12 9:01am

Currently I'm not using P/Invoke, I'm not sure what I would be using it for? a Hook? what exactly would I be hooking? Currently I'm trying to do this through Form.WndProc, and nothing I've done is working so far.

What do you mean by double buffering? and what is the correct way to handle this? if you could provide some links or examples it would be greatly appreciated.

Thanks!