Capture keystrokes (e.g., function keys) while a messagebox is up
- by FastAl
We have a large WinForms app, and there is a built-in bug reporting system that can be activated during testing via the F5 Key. I am capturing the F5 key with .Net's PreFilterMessage system. This works fine on the main forms, modal dialog boxes, etc.
Unfortunately, the program also displays windows messageboxes when it needs to. When there is a bug with that, e.g., wrong text in the messagebox or it shouldn't be there, the messagefilter isn't executed at all when the messagebox is up!
I realize I could fix it by either rewriting my own messagebox routine, or kicking off a separate thread that polls GetAsyncKeyState and calls the error reporter from there. However I was hoping for a method that was less of a hack. Here's code that manifests the problem:
Public Class Form1
Implements IMessageFilter
Private Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Click
MsgBox("now, a messagebox is up!")
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Application.AddMessageFilter(Me)
End Sub
Public Function PreFilterMessage(ByRef m As System.Windows.Forms.Message) _
As Boolean Implements IMessageFilter.PreFilterMessage
Const VK_F5 As Int32 = &H74
Const WM_KEYDOWN As Integer = &H100
If m.Msg = WM_KEYDOWN And m.WParam.ToInt32 = VK_F5 Then
' In reality code here takes a screenshot, saves the program state, and shows a bug report interface '
IO.File.AppendAllText("c:\bugs.txt", InputBox("Describe the bug:"))
End If
End Function
End Class
Many thanks.
