TsgDXFImage.GetExtents - Error

[Yura]

I load from base DXF:

Code: Select all

<b>var</b> Img: TsgDXFImage;

<b>procedure</b> TMainForm.DrawCAD(ID: String; PRX, PRY:Real);
<b>var</b> vInsert: TsgDXFInsert;
    vCAD: TsgDXFImage;
    Stream:TStream;
    vPoint:TFPoint;
<b>begin</b>
  vCAD:=TsgDXFImage.Create;
  <b>try</b>
    vCAD.IsWithoutBorder:=True;
    with pFIBDataSet1 do Stream:=CreateBlobStream(FieldByName('PIC'), bmRead);

    <b>try</b>
      vCAD.LoadFromStream(Stream);
    <b>finally</b>
      FreeAndNil(Stream);
    <b>end</b>;

    <b>with</b> vCAD <b>do</b> CurrentLayout:=Converter.Layouts[Converter.DefaultLayoutIndex];

    vInsert:=TsgDXFInsert.Create;
    vInsert.AssignEntity(vCAD.Converter.Sections[csEntities].Entities[0]);
    vInsert.Block.Name:=ID;
    Img.Converter.Sections[csEntities].AddEntity(vInsert);
    vPoint.X:=PRX;
    vPoint.Y:=PRY;
    vInsert.Point:=vPoint;
    Img.Converter.Loads(vInsert);
  <b>finally</b>
    FreeAndNil(vCAD);
  <b>end</b>;

  Img.GetExtents; // Error Access Violation
<b>end</b>;

If comment a line: FreeAndNil(vCAD); // all works
Why there is an error if I release object vCAD?

[support]

Hello Yura,

1. It is necessary to use <b>Img.Converter.OnCreate(vInsert);</b> after <b>vInsert.AssignEntity(vCAD.Converter.Sections[csEntities].Entities[0]);</b>. It makes it visible.

2. Entity <b>Insert</b> which you copy to <b>vInsert</b> contains such fields as <b>Layer</b>, <b>Block</b> etc. When you call <b>FreeAndNil(vCAD);</b> you destroy <b>TsgDXFImage</b> class object which contains these objects (Layer, Block etc). So <b>vInsert</b> refers to unexisting objects. That is why <b>Error Access Violation</b> arises.
It is necessary to set these fields for <b>vInsert</b> before calling <b>Img.Converter.Loads(vInsert);</b>.

Sergey.


please post questions to the forum or write to support@cadsofttools.com

[Yura]

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
It is necessary to set these fields for <b>vInsert</b> before calling <b>Img.Converter.Loads(vInsert);</b>
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
If it is possible an example of a code please.

[support]

The following code works:

Code: Select all

<b>type</b>
  TForm1 = <b>class</b>(TForm)
    sgImage1: TsgImage;
...

<b>procedure</b> TForm1.Button2Click(Sender: TObject);
<b>type</b>
  TsgClassOfEntity = <b>class of</b> TsgDXFEntity;
<b>var</b>
  I: Integer;
  vInsert: TsgDXFInsert;
  vLayer: TsgDXFLayer;
  vBlock: TsgDXFBlock;
  vCAD: TsgDXFImage;
  vEntity: TsgDXFEntity;
  Converter: TsgDXFConverter;
<b>begin</b>
  sgImage1.Picture.Graphic := <b>nil</b>;
  Img := TsgDXFImage.Create;
  Converter := Img.Converter;
  vLayer := <b>nil</b>;
  vCAD := TsgDXFImage.Create;
  <b>try</b>
    vCAD.LoadFromFile('C:\Test.dxf'); //simple DXF file with two entities: line and inserted line
    vCAD.IsWithoutBorder := True;
    I := 0;
    <b>while</b> (I < vCAD.Converter.Counts[csEntities]) <b>and not</b> (vCAD.Converter.Entities[I] <b>is</b> TsgDXFInsert) <b>do</b>
      Inc(I);
    <b>if</b> I >= vCAD.Converter.Counts[csEntities] <b>then</b> Exit;
    vInsert := TsgDXFInsert(vCAD.Converter.Entities[I]);

    vBlock := TsgDXFBlock.Create;
    Converter.Sections[csBlocks].AddEntity(vBlock);
    vBlock.Name := vInsert.Block.EntName;
    vBlock.Offset := vInsert.Block.Offset;
    vBlock.Color := vInsert.Block.Color;
    vBlock.Layer := vLayer;
    <b>for</b> I := 0 <b>to</b> vInsert.Block.Count - 1 <b>do
    begin</b>
      vEntity := TsgClassOfEntity(vInsert.Block.Entities[I].ClassType).Create;
      vBlock.AddEntity(vEntity);
      vEntity.AssignEntity(vInsert.Block.Entities[I]);
      vEntity.Layer := vLayer;
      vEntity.SetLType(<b>nil</b>);
      Converter.Loads(vEntity);
      Converter.OnCreate(vEntity);
    <b>end</b>;
    Img.Converter.Loads(vBlock);
    vInsert := TsgDXFInsert.Create;
    Converter.Sections[csEntities].AddEntity(vInsert);
    vInsert.AssignEntity(vCAD.Converter.Entities[I]);
    vInsert.Point := MakeFPoint(100, 100, 0);
    vInsert.Block := vBlock;
    vInsert.Layer := vLayer;
    Converter.Loads(vInsert);
    Converter.OnCreate(vInsert);
  <b>finally</b>
    FreeAndNil(vCAD);
  <b>end</b>;
  Img.GetExtents;
  sgImage1.Picture.Graphic := Img;
<b>end</b>;

Sergey.

please post questions to the forum or write to support@cadsofttools.com

[Yura]

Many thanks for the detailed answer!