/// <summary>
/// Intercept Windows messages to the TextBox in order to sanitize input.
/// </summary>
/// <param name="m">Windows message</param>
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
if (_dontProcessMessages)
{
return;
}
// Pre-store initial text and selection on key down/idle
const int WM_KEYDOWN = 0x100;
const int WM_ENTERIDLE = 0x121;
const int VK_DELETE = 0x2e;
bool delete = m.Msg == WM_KEYDOWN && (int)m.WParam == VK_DELETE;
if ((m.Msg == WM_KEYDOWN && !delete) || m.Msg == WM_ENTERIDLE)
{
DontProcessMessage(() => {
_validText = Text;
_selectionStart = SelectionStart;
_selectionEnd = SelectionLength;
});
}
// Store new character or pasted/edited text from key down
const int WM_CHAR = 0x102;
const int WM_PASTE = 0x302;
if (m.Msg == WM_CHAR || m.Msg == WM_PASTE || delete)
{
string newText = null;
DontProcessMessage(() => {
newText = Text;
});
// Raise text validation event with the new text
var e = new TextValidatingEventArgs(newText);
OnTextValidating(this, e);
// Restore pre-stored text if validation fails
if (e.Cancel)
{
DontProcessMessage(() => {
Text = _validText;
SelectionStart = _selectionStart;
SelectionLength = _selectionEnd;
});
}
}
}
// Handle text validation of the GoTo line number.
private void TxtGotoLine_TextValidating(object sender, TextValidatingEventArgs e)
{
// Cancel the text entry if the text is non-empty and cannot be parsed as an int
e.Cancel = (!(string.IsNullOrEmpty(e.NewText)) && !int.TryParse(e.NewText, out int i));
}
/// <summary>
/// Raise event to parent so registered delegates receive it.
/// </summary>
/// <param name="sender">The TextBox that needs to validate text.</param>
/// <param name="e">The new text to be validated.</param>
protected virtual void OnTextValidating(object sender, TextValidatingEventArgs e)
{
TextValidating?.Invoke(sender, e);
}