Question

If I have multiple TextBoxes and other text insertion controls and I want to create some buttons that insert special characters into whichever TextBox is in focus, what is the best control for this and what properties should be set?

Requirements for the buttons:

1. Buttons do not steal focus when clicked.
2. Buttons can insert text (e.g. special characters) into any control that accepts keyboard input.
3. The cursor should move as if the user had entered the text on the keyboard.

If #2 is not possible, it will suffice to limit the controls to only TextBoxes.

NOTE: I do not want to make the buttons unfocusable, only such that they do not steal focus when clicked.

Answer 1

I’m not aware of any button that is not stealing focus when it is clicked, but in button click event handle you can return focus to previous owner. If I had to implement this I’d create an behavior that is attached to parent panel of all special textboxes and all buttons that are to insert some text.

  <StackPanel>
    <i:Interaction.Behaviors>
        <local:TextBoxStateTracker/>
    </i:Interaction.Behaviors>
    <TextBox />

    <Button Content="description" Tag="?" />
</StackPanel>

For sample simplicity I’ve put text that is to be inserted to textbox in Tag property.

public class TextBoxStateTracker : Behavior<Panel>
{
private TextBox _previouslySelectedElement;
private int _selectionStart;
private int _selectionLength;

protected override void OnAttached()
{
//after control and all its children are created find textboxes and buttons
    AssociatedObject.Initialized += (x, y) =>
        {
            var textBoxElements = FindChildren<TextBox>(AssociatedObject);
            foreach (var item in textBoxElements)
            {
                item.LostFocus += new RoutedEventHandler(item_LostFocus);
            }

            var buttons = FindChildren<Button>(AssociatedObject);
            foreach (var item in buttons)
            {
                item.Click += new RoutedEventHandler(item_Click);
            }
        };
}

private void item_Click(object sender, RoutedEventArgs e)
{
    if (_previouslySelectedElement == null) return;
    //simply replace selected text in previously focused textbox with whatever is in tag property
    var button = (Button)sender;
    var textToInsert = (string)button.Tag;

    _previouslySelectedElement.Text = _previouslySelectedElement.Text.Substring(0, _selectionStart)
        + textToInsert +
        _previouslySelectedElement.Text.Substring(_selectionStart + _selectionLength);
    _previouslySelectedElement.Focus();
    _previouslySelectedElement.SelectionStart = _selectionStart + textToInsert.Length;
}

private void item_LostFocus(object sender, RoutedEventArgs e)
{
    //this method is fired when textboxes loose their focus note that this
    //might not be fired by button click
    _previouslySelectedElement = (TextBox)sender;
    _selectionStart = _previouslySelectedElement.SelectionStart;
    _selectionLength = _previouslySelectedElement.SelectionLength;
}

public List<TChild> FindChildren<TChild>(DependencyObject d)
   where TChild : DependencyObject
{
    List<TChild> children = new List<TChild>();

    int childCount = VisualTreeHelper.GetChildrenCount(d);

    for (int i = 0; i < childCount; i++)
    {
        DependencyObject o = VisualTreeHelper.GetChild(d, i);

        if (o is TChild)
            children.Add(o as TChild);

        foreach (TChild c in FindChildren<TChild>(o))
            children.Add(c);
    }

    return children;
}

}

This does more or less what you described but it is far from perfect I think it is enough to get you started.