''' <summary>
''' Adds and builds a button form field.
''' </summary>
''' <param name="annotationTool">The PDF annotation tool, which will build a field.</param>
Public Shared Sub AddAndBuildButtonField(annotationTool As Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationTool)
    Dim focusedPage As Vintasoft.Imaging.Pdf.Tree.PdfPage = annotationTool.FocusedPage
    If focusedPage Is Nothing Then
        Throw New System.InvalidOperationException()
    End If

    ' create a Button form field
    Dim field As New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormPushButtonField(focusedPage.Document, GetFieldName(focusedPage.Document, Nothing, "Button{0}"), New System.Drawing.RectangleF(0, 0, 150, 22))

    ' set the field appearance generator
    Dim appearanceGenerator As New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.AppearanceGenerators.PdfButton3DBorderFieldAppearanceGenerator()
    field.Annotation.AppearanceGenerator = appearanceGenerator
    appearanceGenerator.NormalCaption = "JavaScript 'Hello!'"
    appearanceGenerator.FontSize = 14

    ' if tool mode does not allow to build annotation
    If annotationTool.InteractionMode <> Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationInteractionMode.Edit Then
        ' change the tool mode
        annotationTool.InteractionMode = Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationInteractionMode.Edit
    End If

    ' set JavaScript action to Activate trigger event
    field.Annotation.ActivateAction = New Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction(focusedPage.Document, "app.alert('Hello!', 3);")

    ' add and build annotation
    annotationTool.AddAndBuildFormField(field)
End Sub

''' <summary>
''' Returns the name of new field.
''' </summary>
''' <param name="document">PDF document.</param>
''' <param name="parentField">The parent interactive form field.</param>
''' <param name="fieldNameFormat">The format of field name.</param>
''' <returns>The name of new field.</returns>
Private Shared Function GetFieldName(document As Vintasoft.Imaging.Pdf.PdfDocument, parentField As Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField, fieldNameFormat As String) As String
    Dim format As String = fieldNameFormat
    If parentField IsNot Nothing Then
        format = String.Format("{0}.{1}", parentField.FullyQualifiedName, fieldNameFormat)
    End If
    If document.InteractiveForm Is Nothing Then
        Return String.Format(fieldNameFormat, 1)
    End If
    Dim i As Integer = 1
    While document.InteractiveForm.FindField(String.Format(format, i)) IsNot Nothing
        i += 1
    End While
    Return String.Format(fieldNameFormat, i)
End Function

/// <summary>
/// Adds and builds a button form field.
/// </summary>
/// <param name="annotationTool">The PDF annotation tool, which will build a field.</param>
public static void AddAndBuildButtonField(Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationTool annotationTool)
{
    Vintasoft.Imaging.Pdf.Tree.PdfPage focusedPage = annotationTool.FocusedPage;
    if (focusedPage == null)
        throw new System.InvalidOperationException();

    // create a Button form field
    Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormPushButtonField field = 
        new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormPushButtonField(
            focusedPage.Document,
            GetFieldName(focusedPage.Document, null, "Button{0}"),
            new System.Drawing.RectangleF(0, 0, 150, 22));

    // set the field appearance generator
    Vintasoft.Imaging.Pdf.Tree.InteractiveForms.AppearanceGenerators.PdfButton3DBorderFieldAppearanceGenerator appearanceGenerator =
        new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.AppearanceGenerators.PdfButton3DBorderFieldAppearanceGenerator();
    field.Annotation.AppearanceGenerator = appearanceGenerator;
    appearanceGenerator.NormalCaption = "JavaScript 'Hello!'";
    appearanceGenerator.FontSize = 14;

    // if tool mode does not allow to build annotation
    if (annotationTool.InteractionMode != Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationInteractionMode.Edit)
        // change the tool mode
        annotationTool.InteractionMode = Vintasoft.Imaging.Pdf.UI.Annotations.PdfAnnotationInteractionMode.Edit;

    // set JavaScript action to Activate trigger event
    field.Annotation.ActivateAction =
        new Vintasoft.Imaging.Pdf.Tree.PdfJavaScriptAction(focusedPage.Document, "app.alert('Hello!', 3);");

    // add and build annotation
    annotationTool.AddAndBuildFormField(field);
}

/// <summary>
/// Returns the name of new field.
/// </summary>
/// <param name="document">PDF document.</param>
/// <param name="parentField">The parent interactive form field.</param>
/// <param name="fieldNameFormat">The format of field name.</param>
/// <returns>The name of new field.</returns>
private static string GetFieldName(
    Vintasoft.Imaging.Pdf.PdfDocument document,
    Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField parentField,
    string fieldNameFormat)
{
    string format = fieldNameFormat;
    if (parentField != null)
        format = string.Format("{0}.{1}", parentField.FullyQualifiedName, fieldNameFormat);
    if (document.InteractiveForm == null)
        return string.Format(fieldNameFormat, 1);
    int i = 1;
    while (document.InteractiveForm.FindField(string.Format(format, i)) != null)
        i++;
    return string.Format(fieldNameFormat, i);
}