Progress Event

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.Forms.DocumentWriters

' Windows API functions needed to load/delete an EMF
<DllImport("gdi32.dll")> _
Private Shared Function GetEnhMetaFile(ByVal lpszMetaFile As String) As IntPtr
End Function
<DllImport("gdi32.dll")> _
Private Shared Function DeleteEnhMetaFile(ByVal hemf As IntPtr) As Boolean
End Function

Private Sub DocumentWriterProgressExample()
   ' Create a new instance of the LEADTOOLS Document Writer
   Dim docWriter As New DocumentWriter()

   ' Get the file names to use
   Dim pdfFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "DocumentWriter.pdf")

   Dim emfFileNames() As String = _
   { _
      Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.emf"), _
      Path.Combine(LEAD_VARS.ImagesDir, "Ocr2.emf"), _
      Path.Combine(LEAD_VARS.ImagesDir, "Ocr3.emf"), _
      Path.Combine(LEAD_VARS.ImagesDir, "Ocr4.emf") _
   }

   ' Show the progress dialog
   Using dlg As New MyProgressDialog(docWriter, emfFileNames, pdfFileName)
      If (dlg.ShowDialog() = DialogResult.OK) Then
         MessageBox.Show("Done!")
      Else
         MessageBox.Show("User has canceled the operation or an error occured.")
      End If
   End Using
End Sub

' Dialog box to show the 
Private Class MyProgressDialog
   Inherits Form
   ' The controls on the dialog
   Private _descriptionLabel As Label
   Private _progressBar As ProgressBar
   Private _cancelButton As Button
   Private _operation As String

   ' Conversion properties
   Private _docWriter As DocumentWriter
   Private _emfFileNames() As String
   Private _pdfFileName As String

   ' Has the operation been canceled?
   Private _isCanceled As Boolean
   ' Is the dialog working?
   Private _isWorking As Boolean

   Public Sub New(ByVal docWriter As DocumentWriter, ByVal emfFileNames() As String, ByVal pdfFileName As String)
      InitializeComponent()

      _docWriter = docWriter
      _emfFileNames = emfFileNames
      _pdfFileName = pdfFileName

      _isCanceled = False
      _isWorking = True
   End Sub

   Protected Overrides Sub OnLoad(ByVal e As EventArgs)
      ' To keep the UI functioning, do the conversion in a separate thread
      BeginInvoke(New MethodInvoker(AddressOf DoWork))

      MyBase.OnLoad(e)
   End Sub

   Private Sub DoWork()
      ' Subscribe to the progress event
      AddHandler _docWriter.Progress, AddressOf _docWriter_Progress

      ' Create the document
      _operation = "Creating the document..."
      _docWriter.BeginDocument(_pdfFileName, DocumentFormat.Pdf)

      ' Add the pages
      For i As Integer = 0 To _emfFileNames.Length - 1
         ' Use the Windows API to load the EMF
         Dim emfHandle As IntPtr = GetEnhMetaFile(_emfFileNames(i))

         ' Add the page, notice we will not be using image/text feature (the default)
         Dim page As DocumentPage = DocumentPage.Empty
         page.EmfHandle = emfHandle
         page.Image = Nothing

         _operation = String.Format("Adding page {0} of {1}...", i + 1, _emfFileNames.Length)
         _docWriter.AddPage(page)

         ' Use the Windows API to delete the EMF
         DeleteEnhMetaFile(emfHandle)
      Next

      ' Finally finish writing the PDF file on disk
      _operation = "Finishing the document..."
      _docWriter.EndDocument()

      RemoveHandler _docWriter.Progress, AddressOf _docWriter_Progress

      ' Set the dialog results based on whether the user has canceled the operation
      If (_isCanceled) Then
         DialogResult = DialogResult.Cancel
      Else
         DialogResult = DialogResult.OK
      End If

      ' The dialog can be closed now
      _isWorking = False

      ' We are done
      Close()
   End Sub

   Private Sub _docWriter_Progress(ByVal sender As Object, ByVal e As DocumentProgressEventArgs)
      ' Update the description label progress bar
      _descriptionLabel.Text = _operation
      _progressBar.Value = e.Percentage

      ' Check if the user clicked the Cancel button, if so, abort the operation
      If (_isCanceled) Then
         e.Cancel = True
      End If

      Application.DoEvents()
   End Sub

   Private Sub _cancelButton_Click(ByVal sender As Object, ByVal e As EventArgs)
      ' Set the isCanceled variable to true, this will break from the
      ' progress callback and closes the dialog

      _isCanceled = True
   End Sub

   Protected Overrides Sub OnFormClosing(ByVal e As FormClosingEventArgs)
      ' Dont allow the form to close while the callback is still working
      ' Instead, cancel the operation
      If (_isWorking) Then
         e.Cancel = True
      End If

      MyBase.OnFormClosing(e)
   End Sub

   Private Sub InitializeComponent()
      ' Create the controls in this form, a text label, a progress bar and a cancel button
      SuspendLayout()

      ' Text label
      _descriptionLabel = New Label()
      _descriptionLabel.Location = New Point(26, 21)
      _descriptionLabel.Name = "_descriptionLabel"
      _descriptionLabel.Size = New Size(367, 23)
      _descriptionLabel.TabIndex = 0
      _descriptionLabel.TextAlign = ContentAlignment.MiddleLeft
      _descriptionLabel.Text = "Creating final document..."

      ' Progress bar
      _progressBar = New ProgressBar()
      _progressBar.Location = New Point(27, 47)
      _progressBar.Name = "_progressBar"
      _progressBar.Size = New Size(364, 23)
      _progressBar.TabIndex = 1

      ' Cancel button
      _cancelButton = New Button()
      _cancelButton.DialogResult = DialogResult.Cancel
      _cancelButton.Location = New Point(172, 76)
      _cancelButton.Name = "_cancelButton"
      _cancelButton.Size = New Size(75, 23)
      _cancelButton.TabIndex = 2
      _cancelButton.Text = "Cancel"
      _cancelButton.UseVisualStyleBackColor = True
      AddHandler _cancelButton.Click, AddressOf _cancelButton_Click

      ' Add the controls
      Controls.Add(_descriptionLabel)
      Controls.Add(_progressBar)
      Controls.Add(_cancelButton)

      ' Initialize the dialog
      AutoScaleDimensions = New SizeF(6.0F, 13.0F)
      AutoScaleMode = AutoScaleMode.Font
      CancelButton = _cancelButton
      ClientSize = New Size(420, 118)
      FormBorderStyle = FormBorderStyle.FixedDialog
      MaximizeBox = False
      MinimizeBox = False
      Name = "MyProgressDialog"
      ShowInTaskbar = False
      StartPosition = FormStartPosition.CenterParent
      Text = "DocumentWriter Progress Example"

      ResumeLayout()
   End Sub
End Class