I'm trying to implement a .net form control with functionality similar to a combo box, but I don't know the proper method to intercept mouse events anywhere on the form to un-expand the list of items.
How do I prevent other controls from responding to mouse events while the list is being shown?
How do I efficiently and safely catch a mouse click event to anywhere on the form, to hide the expanded list?
Just use a ToolStripControlHost along with the ToolStripDropDown, and it will work just like the ComboBox dropdown. You won't have to worry about handling the mouse events.
I've used this before:
Private Sub ShowControl(ByVal fromControl As Control, ByVal whichControl As Control)
'\\ whichControl needs MinimumSize set:'
whichControl.MinimumSize = whichControl.Size
Dim toolDrop As New ToolStripDropDown()
Dim toolHost As New ToolStripControlHost(whichControl)
toolHost.Margin = New Padding(0)
toolDrop.Padding = New Padding(0)
toolDrop.Items.Add(toolHost)
toolDrop.Show(Me, New Point(fromControl.Left, fromControl.Bottom))
End Sub
Quick Demo with a Button control on a form:
Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
ShowControl(Button1, New MonthCalendar)
End Sub
To answer the question in your title, I think the pinvoke calls of SetCapture and Release Capture are used to handle that type of functionality.
As explained in the documentation, you now "Own" the mouse (until someone else captures it - though that's bad form). You receive all mouse messages and can handle a "Down" not on your control to dismiss.