Displaying a preview

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The Eplan.EplApi.HEServices namespace provides the class DrawingService, which contains functionality for outputting objects (WindowMacros, SymbolVariants, Placements, or Pages) on a window or control.

Displaying the preview takes two steps:

First step is creating a so-called display list using the CreateDisplayList function. This actually processes the data into a list of graphical primitives, which can be drawn. Depending on what kind of data you want to show, this function will take some time. For example, when you want to create a preview of a macro, CreateDisplayList loads the macro file, analyzes it and creates the items to display. You need to call this function just once for a given preview.

The second step actually shows the preview (the created display list) on a window. It takes an System.Windows.Forms.PaintEventArgs object as parameter, which is provided by any control in the Paint callback.

The DrawingService class also provides the possibility to influence the look of the preview in many ways, like zooming and changing the background color.

In the following example a preview of a macro is created. The first code snippet shows creating the display list:

Eplan.EplApi.HEServices.DrawingService oDs = new DrawingService();
//...
if(oDs == null)
{
    oDs = new Eplan.EplApi.HEServices.DrawingService();
}
if (!(gProject == null))
{
    try
    {
   oDs.DrawConnections = true;
   oDs.MacroPreview = true;
   oDs.CreateDisplayList(strObj, "", 0, gProject);
    }
    catch (System.Exception ex)
    {
        new Decider().Decide(EnumDecisionType.eOkDecision, "Can't create display list: \r\n" + ex.Message, "", EnumDecisionReturn.eOK, EnumDecisionReturn.eOK);
    }
    //raise the Paint event
    oForm.Picture1.Invalidate();
}

If oDs Is Nothing Then
   oDs = New Eplan.EplApi.HEServices.DrawingService
End If
If Not gProject Is Nothing Then
   Try
      oDs.DrawConnections = True
      oDs.MacroPreview = True
      oDs.CreateDisplayList(strObj, "", 0, gProject)
   Catch ex As System.Exception
      Dim dec As Decider = New Decider
      dec.Decide(EnumDecisionType.eOkDecision, "Can't create display list:" & vbCrLf & ex.Message, "", EnumDecisionReturn.eOK, EnumDecisionReturn.eOK)
   End Try
   'raise the Paint event
   oForm.Picture1.Invalidate()
End If

The next piece of source code shows drawing the display list in the Paint method of a picture box:

private void Picture1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
 if (!(m_DS == null)) {
   try {
     m_DS.DrawDisplayList(e);
   } catch (System.Exception ex) {
     new Decider().Decide(EnumDecisionType.eOkDecision, "Can't draw display list:" + "\r\n" + ex.Message, "", EnumDecisionReturn.eOK, EnumDecisionReturn.eOK);
   }
 }
}

Private Sub Picture1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Picture1.Paint
    If Not m_DS Is Nothing Then
        Try
            m_DS.DrawDisplayList(e)
        Catch ex As System.Exception
            Dim dec As Decider = New Decider
            dec.Decide(EnumDecisionType.eOkDecision, "Can't draw display list:" & vbCrLf & ex.Message, "", EnumDecisionReturn.eOK, EnumDecisionReturn.eOK)
        End Try
    End If
End Sub

Setting image size and the viewport

For drawing more complex images it can be necessary to set resolution and a viewport of the drawn image.

Viewport is a polygon which represents part of a page that will be rendered :

This can be done by means of SetViewport method. Coordinates should be passed in graphical coordinate system.

If the passed dimensions are not proportional to the dawning area, they are adjusted automatically in a way that aspect ratio is kept:

In case of 3D drawings, it is also necessary to set image size, otherwise its quality can be worse than in Eplan GED:

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