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How to determine when the mouse leaves the form?

I have a form with a lot of controls. How can I detect when a mouse leaves a form? I tried to hook up a MouseLeave event for each control and form, but this does not work, because these events fire all the time when the mouse passes controls. Is there a way that really works.?

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You must listen to:

  • MouseLeave events of all form controls
  • MouseLeave Event Forms

Just connect the listeners to a function that checks if the cursor is in the forms client.

Try the following:

protected override void OnControlAdded(ControlEventArgs e) { SubscribeEvents(e.Control); base.OnControlAdded(e); } protected override void OnControlRemoved(ControlEventArgs e) { UnsubscribeEvents(e.Control); base.OnControlRemoved(e); } private void SubscribeEvents(Control control) { control.MouseLeave += new EventHandler(control_MouseLeave); control.ControlAdded += new ControlEventHandler(control_ControlAdded); control.ControlRemoved += new ControlEventHandler(control_ControlRemoved); foreach (Control innerControl in control.Controls) { SubscribeEvents(innerControl); } } private void UnsubscribeEvents(Control control) { control.MouseLeave -= new EventHandler(control_MouseLeave); control.ControlAdded -= new ControlEventHandler(control_ControlAdded); control.ControlRemoved -= new ControlEventHandler(control_ControlRemoved); foreach (Control innerControl in control.Controls) { UnsubscribeEvents(innerControl); } } private void control_ControlAdded(object sender, ControlEventArgs e) { SubscribeEvents(e.Control); } private void control_ControlRemoved(object sender, ControlEventArgs e) { UnsubscribeEvents(e.Control); } protected override void OnMouseLeave(EventArgs e) { CheckMouseLeave(); base.OnMouseLeave(e); } private void control_MouseLeave(object sender, EventArgs e) { CheckMouseLeave(); } private void CheckMouseLeave() { Point pt = PointToClient(Cursor.Position); if (ClientRectangle.Contains(pt) == false) { OnMouseLeftFrom(); } } private void OnMouseLeftFrom() { Console.WriteLine("Mouse left the form"); }
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The only reliable way I know is with a timer. Here is an example of code that changes opacity when flipping:

  public partial class Form1 : Form { Timer timer1 = new Timer(); public Form1() { InitializeComponent(); this.Opacity = 0.10; timer1.Tick += new EventHandler(timer1_Tick); timer1.Interval = 200; timer1.Enabled = true; } void timer1_Tick(object sender, EventArgs e) { Point pos = Control.MousePosition; bool inForm = pos.X >= Left && pos.Y >= Top && pos.X < Right && pos.Y < Bottom; this.Opacity = inForm ? 0.99 : 0.10; } }
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From looking at aygunes.myopenid.com answer, I made this version on Vb.Net that recursively add MouseLeaveHandlers to all the controls in the form, and then use nice Clientrectangle.Contains (pt) to check if the mousecursor is enabled or not. I work like a charm. Cred goes to aygunes.myopenid.com.

 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load AddMouseLeaveHandlers() End Sub Sub AddMouseLeaveHandlers() For Each c As Control In Me.Controls HookItUp(c) Next AddHandler Me.MouseLeave, AddressOf CheckMouseLeave End Sub Sub HookItUp(ByVal c As Control) AddHandler c.MouseLeave, AddressOf CheckMouseLeave If c.HasChildren Then For Each f As Control In c.Controls HookItUp(f) Next End If End Sub Private Sub CheckMouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Dim pt As Point = PointToClient(Cursor.Position) If ClientRectangle.Contains(pt) = False Then MsgBox("Mouse left form") End If End Sub
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Put this in a timer:

 If PointToClient(MousePosition).X < Me.Size.Width AndAlso PointToClient(MousePosition).X > -1 AndAlso PointToClient(MousePosition).Y < Me.Size.Height AndAlso PointToClient(MousePosition).Y > -1 Then 'Mouse is inside the form Else 'Mouse is outside of form End If
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