QElectroTech — DXF import/export coding

Re: DXF import/export coding

null@example.com (rdsivd) — Sat, 24 Aug 2019 18:34:20 +0000

OK, but we have to change the sequence on how to export.

if we look to a drawing page in qet, it is build with

elements
lines between connectors
titelblock
shapes and free text

Before we can export the entities section in dxf
we need to create the dxf block section where we create a block definition for eacht

element
titelblock

this block section is fillet with the same basic functions already in the dxfexport functions.

After this is write to the dxf file we can create the entities section in dxf
this have a command insert block to write a element in the entities sections.

shapes and free text is writen directly in the entitie sections

The conected lines are also writen in the entities sections

Re: DXF import/export coding

null@example.com (scorpio810) — Fri, 23 Aug 2019 14:18:40 +0000

Here DXF export commits :
https://git.tuxfamily.org/qet/qet.git/l … &q=dxf

Re: DXF import/export coding

null@example.com (scorpio810) — Fri, 23 Aug 2019 11:26:40 +0000

Hi Ronny,

in exportdialog you can found functions to export project to DXF :

// Determine les elements a "XMLiser"
 
        foreach(QGraphicsItem *qgi, diagram -> items()) {
 
            if (Element *elmt = qgraphicsitem_cast<Element *>(qgi)) {
 
                list_elements << elmt;
 
            } else if (Conductor *f = qgraphicsitem_cast<Conductor *>(qgi)) {
 
                list_conductors << f;
 
            } else if (IndependentTextItem *iti = qgraphicsitem_cast<IndependentTextItem *>(qgi)) {
 
                list_texts << iti;
 
            } else if (DiagramImageItem *dii = qgraphicsitem_cast<DiagramImageItem *>(qgi)) {
 
                list_images << dii;
 
            } else if (QetShapeItem *dii = qgraphicsitem_cast<QetShapeItem *>(qgi)) {
 
                list_shapes << dii;
 
            } else if (DynamicElementTextItem *deti = qgraphicsitem_cast<DynamicElementTextItem *>(qgi)) {
 
                list_texts << deti;
 
            }
 
        }
 
    }

After for parsing to QTextStream

//Draw elements
    foreach(Element *elmt, list_elements)
    {
        double rotation_angle = elmt -> orientation() * 90;
 
        qreal elem_pos_x = elmt -> pos().x();
        qreal elem_pos_y = elmt -> pos().y();// - (diagram -> margin / 2);
 
        qreal hotspot_x = (elem_pos_x) * Createdxf::xScale;
        qreal hotspot_y = Createdxf::sheetHeight - (elem_pos_y) * Createdxf::yScale;
 
        ElementPictureFactory::primitives primitives = ElementPictureFactory::instance()->getPrimitives(elmt->location());
 
        for(QGraphicsSimpleTextItem *text : primitives.m_texts)
        {
            qreal fontSize = text->font().pointSizeF();
            if (fontSize < 0) 
                fontSize = text->font().pixelSize();
 
            fontSize *= Createdxf::yScale;
            qreal x = elem_pos_x + text->pos().x();
            qreal y = elem_pos_y + text->pos().y();
            x *= Createdxf::xScale;
            y = Createdxf::sheetHeight - (y * Createdxf::yScale);// - fontSize;
            QPointF transformed_point = rotation_transformed(x, y, hotspot_x, hotspot_y, rotation_angle);
            x = transformed_point.x();
            y = transformed_point.y();
            QStringList lines = text->text().split('\n');
            y += (fontSize/2) * (lines.count()-1);
            for (QString line : lines)
            {
                qreal angle = 360 - (text->rotation() + rotation_angle);
                if (line.size() > 0 && line != "_" ) {
                    Createdxf::drawText(file_path, line, x, y, fontSize, angle, 0);
                }
                angle += 1080;
                // coordinates for next line
                if (int(angle) % 360 == 0) // no rotation
                    y -= fontSize*1.06;
                else if (int(angle - 180) % 360 == 0) // 180 degrees rotation
                    y += fontSize*1.06;
                else if (int(angle - 270) % 360 == 0) // 270 degrees rotation
                    x -= fontSize*1.06;
                else // ((angle - 90) % 360 == 0) 90 degrees rotation
                    x += fontSize*1.06;
            }
        }
 
        for (QLineF line : primitives.m_lines)
        {
            qreal x1 = (elem_pos_x + line.p1().x()) * Createdxf::xScale;
            qreal y1 = Createdxf::sheetHeight - (elem_pos_y + line.p1().y()) * Createdxf::yScale;
            QPointF transformed_point = rotation_transformed(x1, y1, hotspot_x, hotspot_y, rotation_angle);
            x1 = transformed_point.x();
            y1 = transformed_point.y();
            qreal x2 = (elem_pos_x + line.p2().x()) * Createdxf::xScale;
            qreal y2 = Createdxf::sheetHeight - (elem_pos_y + line.p2().y()) * Createdxf::yScale;
            transformed_point = rotation_transformed(x2, y2, hotspot_x, hotspot_y, rotation_angle);
            x2 = transformed_point.x();
            y2 = transformed_point.y();
            Createdxf::drawLine(file_path, x1, y1, x2, y2, 0);
        }
 
        for (QRectF rect : primitives.m_rectangles)
        {
            qreal x1 = (elem_pos_x + rect.bottomLeft().x()) * Createdxf::xScale;
            qreal y1 = Createdxf::sheetHeight - (elem_pos_y + rect.bottomLeft().y()) * Createdxf::yScale;
            qreal w = rect.width() * Createdxf::xScale;
            qreal h = rect.height() * Createdxf::yScale;
            // opposite corner
            qreal x2 = x1 + w;
            qreal y2 = y1 + h;
            QPointF transformed_point = rotation_transformed(x1, y1, hotspot_x, hotspot_y, rotation_angle);
            x1 = transformed_point.x();
            y1 = transformed_point.y();
            transformed_point = rotation_transformed(x2, y2, hotspot_x, hotspot_y, rotation_angle);
            x2 = transformed_point.x();
            y2 = transformed_point.y();
            qreal bottom_left_x = (x1 < x2) ? x1 : x2;
            qreal bottom_left_y = (y1 < y2) ? y1 : y2;
            w = (x1 < x2) ? x2-x1 : x1-x2;
            h = (y1 < y2) ? y2-y1 : y1-y2;
            Createdxf::drawRectangle(file_path, bottom_left_x, bottom_left_y, w, h, 0);
        }
 
        for (QRectF circle_rect : primitives.m_circles)
        {
            qreal x1 = (elem_pos_x + circle_rect.center().x()) * Createdxf::xScale;
            qreal y1 = Createdxf::sheetHeight - (elem_pos_y + circle_rect.center().y()) * Createdxf::yScale;
            qreal r = circle_rect.width() * Createdxf::xScale / 2;
            QPointF transformed_point = rotation_transformed(x1, y1, hotspot_x, hotspot_y, rotation_angle);
            x1 = transformed_point.x();
            y1 = transformed_point.y();
            Createdxf::drawCircle(file_path, r, x1, y1, 0);
        }
 
        for (QVector<QPointF> polygon : primitives.m_polygons)
        {
            if (polygon.size() == 0)
                continue;
            qreal x1 = (elem_pos_x + polygon.at(0).x()) * Createdxf::xScale;
            qreal y1 = Createdxf::sheetHeight - (elem_pos_y + polygon.at(0).y()) * Createdxf::yScale;
            QPointF transformed_point = rotation_transformed(x1, y1, hotspot_x, hotspot_y, rotation_angle);
            x1 = transformed_point.x();
            y1 = transformed_point.y();
            for (int i = 1; i < polygon.size(); ++i ) {
                qreal x2 = (elem_pos_x + polygon.at(i).x()) * Createdxf::xScale;
                qreal y2 = Createdxf::sheetHeight - (elem_pos_y + polygon.at(i).y()) * Createdxf::yScale;
                QPointF transformed_point = rotation_transformed(x2, y2, hotspot_x, hotspot_y, rotation_angle);
                x2 = transformed_point.x();
                y2 = transformed_point.y();
                Createdxf::drawLine(file_path, x1, y1, x2, y2, 0);
                x1 = x2;
                y1 = y2;
            }
        }
 
        // Draw arcs and ellipses
        for (QVector<qreal> arc : primitives.m_arcs)
        {
            if (arc.size() == 0)
                continue;
            qreal x = (elem_pos_x + arc.at(0)) * Createdxf::xScale;
            qreal y = Createdxf::sheetHeight - (elem_pos_y + arc.at(1)) * Createdxf::yScale;
            qreal w = arc.at(2) * Createdxf::xScale;
            qreal h = arc.at(3) * Createdxf::yScale;
            qreal startAngle = arc.at(4);
            qreal spanAngle = arc .at(5);
            Createdxf::drawArcEllipse(file_path, x, y, w, h, startAngle, spanAngle, hotspot_x, hotspot_y, rotation_angle, 0);
        }
    }
 
    //Draw conductors
    foreach(Conductor *cond, list_conductors) {
        foreach(ConductorSegment *segment, cond -> segmentsList()) {
            qreal x1 = (segment -> firstPoint().x()) * Createdxf::xScale;
            qreal y1 = Createdxf::sheetHeight - (segment -> firstPoint().y() * Createdxf::yScale);
            qreal x2 = (segment -> secondPoint().x()) * Createdxf::xScale;
            qreal y2 = Createdxf::sheetHeight - (segment -> secondPoint().y() * Createdxf::yScale);
            Createdxf::drawLine(file_path, x1, y1, x2, y2, 0);
        }
        //Draw conductor text item
        ConductorTextItem *textItem = cond -> textItem();
        if (textItem) {
            qreal fontSize = textItem -> font().pointSizeF();
            if (fontSize < 0)
                fontSize = textItem -> font().pixelSize();
            fontSize *= Createdxf::yScale;
            qreal x = (textItem -> pos().x()) * Createdxf::xScale;
            qreal y = Createdxf::sheetHeight - (textItem -> pos().y() * Createdxf::yScale) - fontSize;
            QStringList lines = textItem->toPlainText().split('\n');
            foreach (QString line, lines) {
                qreal angle = 360 - (textItem -> rotation());
                if (line.size() > 0 && line != "_" )
                    Createdxf::drawText(file_path, line, x, y, fontSize, angle, 0 );
 
                angle += 1080;
                // coordinates for next line
                if (int(angle) % 360 == 0) // no rotation
                    y -= fontSize*1.06;
                else if (int(angle - 180) % 360 == 0) // 180 degrees rotation
                    y += fontSize*1.06;
                else if (int(angle - 270) % 360 == 0) // 270 degrees rotation
                    x -= fontSize*1.06;
                else // ((angle - 90) % 360 == 0) 90 degrees rotation
                    x += fontSize*1.06;
            }
 
        }
    }
 
    //Draw text items
    foreach(DiagramTextItem *dti, list_texts) {
        qreal fontSize = dti -> font().pointSizeF();
        if (fontSize < 0)
            fontSize = dti -> font().pixelSize();
        fontSize *= Createdxf::yScale;
        qreal x = (dti->scenePos().x()) * Createdxf::xScale;
        qreal y = Createdxf::sheetHeight - (dti->scenePos().y() * Createdxf::yScale) - fontSize*1.05;
        QStringList lines = dti -> toPlainText().split('\n');
        foreach (QString line, lines) {
            qreal angle = 360 - (dti -> rotation());
            if (line.size() > 0 && line != "_" )
                Createdxf::drawText(file_path, line, x, y, fontSize, angle, 0);
 
            angle += 1080;
            // coordinates for next line
            if (int(angle) % 360 == 0) // no rotation
                y -= fontSize*1.06;
            else if (int(angle - 180) % 360 == 0) // 180 degrees rotation
                y += fontSize*1.06;
            else if (int(angle - 270) % 360 == 0) // 270 degrees rotation
                x -= fontSize*1.06;
            else // ((angle - 90) % 360 == 0) 90 degrees rotation
                x += fontSize*1.06;
        }
    }
    Createdxf::dxfEnd(file_path);
 
 saveReloadDiagramParameters(diagram, false);
}
 
void ExportDialog::fillRow(const QString& file_path, const QRectF &row_rect, QString author, const QString& title,
                             QString folio, QString date)
{
    qreal x = row_rect.bottomLeft().x();
    qreal y = row_rect.bottomLeft().y();
 
    x *= Createdxf::xScale;
    y = Createdxf::sheetHeight - y * Createdxf::yScale;
    qreal height = row_rect.height() * Createdxf::yScale *0.7;
    y += height*0.2;
 
    Createdxf::drawTextAligned(file_path, std::move(folio),
                             x + 0.02*DiagramFolioList::colWidths[0]*row_rect.width()*Createdxf::xScale, y, height, 0, 0, 5, 0,
                             x + 0.95*DiagramFolioList::colWidths[0]*row_rect.width()*Createdxf::xScale, 0);
 
    x += DiagramFolioList::colWidths[0]*row_rect.width()*Createdxf::xScale;
    QString heading = tr("Titre");
    if (title == heading)
        Createdxf::drawTextAligned(file_path, title,
                                 x + 0.02*DiagramFolioList::colWidths[1]*row_rect.width()*Createdxf::xScale, y, height, 0, 0, 5, 0,
                                 x + 0.02*DiagramFolioList::colWidths[1]*row_rect.width()*Createdxf::xScale, 0);
    else
        Createdxf::drawTextAligned(file_path, title,
                                 x + 0.02*DiagramFolioList::colWidths[1]*row_rect.width()*Createdxf::xScale, y, height, 0, 0, 5, 0,
                                 x + 0.02*DiagramFolioList::colWidths[1]*row_rect.width()*Createdxf::xScale, 0, true);
 
    x += DiagramFolioList::colWidths[1]*row_rect.width()*Createdxf::xScale;
    Createdxf::drawTextAligned(file_path, std::move(author),
                             x + 0.02*DiagramFolioList::colWidths[2]*row_rect.width()*Createdxf::xScale, y, height, 0, 0, 5, 0,
                             x + 3.02*DiagramFolioList::colWidths[2]*row_rect.width()*Createdxf::xScale, 0);
 
    x += DiagramFolioList::colWidths[2]*row_rect.width()*Createdxf::xScale;
    Createdxf::drawTextAligned(file_path, std::move(date),
                             x + 0.02*DiagramFolioList::colWidths[3]*row_rect.width()*Createdxf::xScale, y, height, 0, 0, 5, 0,
                             x + 5.02*DiagramFolioList::colWidths[3]*row_rect.width()*Createdxf::xScale, 0);
}
 
QPointF ExportDialog::rotation_transformed(qreal px, qreal py , qreal origin_x, qreal origin_y, qreal angle) {
 
    angle *= -3.14159265 / 180;
 
    float s = sin(angle);
    float c = cos(angle);
 
    // Vector to rotate:
    qreal Vx = px - origin_x;
    qreal Vy = py - origin_y;
 
    // rotate vector
    float xnew = Vx * c - Vy * s;
    float ynew = Vx * s + Vy * c;
 
    return QPointF(xnew + origin_x, ynew + origin_y);
}

Re: DXF import/export coding

null@example.com (rdsivd) — Thu, 22 Aug 2019 19:18:52 +0000

Compare qet format agains dxf :

= dwg blocks = symbols

dxf/dwg layers : are used to make it posible (in acad) to switch on and off, if u have a drawing with a lot of information, the you can show less or more information with turning layers on and off in acad, also usefull when defining printouts and you dont wont to show some information

These layer are definet in a Layer table

Line types

The line types are also define into a table, so in the convertion to dxf we have to create a line type table with the acad names in it and use these names when creathing the nesecary

Re: DXF import/export coding

null@example.com (rdsivd) — Thu, 22 Aug 2019 19:10:13 +0000

Hi Lauret,

Try to explain wath we need to ceat dxf export (or import)

So i try to explain tha dxf parts with a example from the code of the exporter now.

These basic function are all working i think, if not we have to check whats be wrong on them.

How the current exporter is reading the qet file is for me not clear, i have to spent to match time to figure out how qet is prosesing the qet file.

We need to change the current sequence on how the dxf file is created and add some extra function to get it to work correctly.

Re: DXF import/export coding

null@example.com (scorpio810) — Tue, 20 Aug 2019 17:13:32 +0000

Thanks Ronny.

but convertion not read the XML but the mapscene.
I hope Joshua can explain it better than me. ;-)

Re: DXF import/export coding

null@example.com (rdsivd) — Mon, 19 Aug 2019 19:37:04 +0000

Tables function

Function_table () /* 2 things to write to dxf file */
{

to_dxf << "0"
to_dxf << "SECTION"
to_dxf << "2"
to_dxf << "TABLES"
to_dxf << "0"
to_dxf << "TABLE" /* line type tables starts here */
to_dxf << "2"
to_dxf << "LTYPE" /* table entry */
to_dxf << "5"
to_dxf << "5"
to_dxf << "330"
to_dxf << "0"
to_dxf << "70"
to_dxf << "1"
to_dxf << "0"
to_dxf << "LTYPE"
to_dxf << "5"
to_dxf << "14"
to_dxf << "330"
to_dxf << "5"
to_dxf << "2"
to_dxf << "ByBlock"
to_dxf << "70"
to_dxf << "0"
to_dxf << "3"
to_dxf << " "
to_dxf << "72"
to_dxf << "65"
to_dxf << "73"
to_dxf << "0"
to_dxf << "40"
to_dxf << "0.0"
to_dxf << "0"
to_dxf << "LTYPE"
to_dxf << "5"
to_dxf << "15"
to_dxf << "330"
to_dxf << "5"
to_dxf << "2"
to_dxf << "ByLayer"
to_dxf << "70"
to_dxf << "0"
to_dxf << "3"
to_dxf << " "
to_dxf << "72"
to_dxf << "65"
to_dxf << "73"
to_dxf << "0"
to_dxf << "40"
to_dxf << "0.0"
to_dxf << "0"
to_dxf << "LTYPE"
to_dxf << "5"
to_dxf << "16"
to_dxf << "330"
to_dxf << "5"
to_dxf << "2"
to_dxf << "Continuous"
to_dxf << "70"
to_dxf << "0"
to_dxf << "3"
to_dxf << "Solid line"
to_dxf << "72"
to_dxf << "65"
to_dxf << "73"
to_dxf << "0"
to_dxf << "40"
to_dxf << "0.0"
to_dxf << "0"
to_dxf << "ENDTAB"

to_dxf << "0"
to_dxf << "TABLE" /* second layer tables */
to_dxf << "2"
to_dxf << "LAYER"
to_dxf << "5"
to_dxf << "2"





}

Re: DXF import/export coding

null@example.com (rdsivd) — Mon, 19 Aug 2019 19:25:36 +0000

Header function

Header_function () /* step 1 things to write to dxf file */
{

to_dxf << "O"
to_dxf << "SECTION"
to_dxf << "2"
to_dxf << "HEADER"
to_dxf << "9"
to_dxf << "$ACADVER"
to_dxf << "1"
to_dxf << "AC1015"
to_dxf << "9"
to_dxf << "$DWGCODEPAGE"
to_dxf << "3"
to_dxf << "ANSI_1252"
to_dxf << "9"
to_dxf << "$INSBASE"
to_dxf << "10"
to_dxf << "0.0"
to_dxf << "20"
to_dxf << "0.0"
to_dxf << "30"
to_dxf << "0.0"


to_dxf << "0"
to_dxf << "ENDSEC"


}

DXF import/export coding

null@example.com (rdsivd) — Sun, 18 Aug 2019 14:25:13 +0000

I try to explain how a dxf file is constructed and what have to be changed on exportdxf.cpp to get it working again.

if we take a look at the exportdxf.cpp file, a lot of the basic drawing types are there and maybe need some fine tunning on function of the changes that have to be made for the dxf export.

How is a dxf file constructed :

The file is devide into sections, each section is starting with a 0, SECTION, 2 HEADER

0
SECTION
  2
HEADER
  9
$ACADVER
  1
AC1012

The key code in a dxf file = 0
followed by the command = SECTION
The code 2 give section name.

if we take a look to createdxf.cpp : void Createdxf::dxfBegin (const QString& fileName)

 QTextStream To_Dxf(&file);
            To_Dxf << 999           << "\r\n";
            To_Dxf << "QET"         << "\r\n";
            To_Dxf << 0             << "\r\n";
            To_Dxf << "SECTION"     << "\r\n";
            To_Dxf << 2             << "\r\n";
            To_Dxf << "HEADER"      << "\r\n";
            To_Dxf << 9             << "\r\n";
            To_Dxf << "$ACADVER"    << "\r\n";
            To_Dxf << 1             << "\r\n";
            To_Dxf << "AC1006"      << "\r\n";

The linse 58-59 have to be removed, the are not neaded and telling autocad that it is not a acad created dxf file.

A good starting point for dxf codes :[url=https://knowledge.autodesk.com/search-result/caas/CloudHelp/cloudhelp/2017/ENU/AutoCAD-DXF/files/GUID-235B22E0-A567-4CF6-92D3-38A2306D73F3-htm.html] acad dxf codes
[/url]
see also numerical list o dxf codes
A dxf file have 7 sections, so we need to created for each section a function to file it.We don't need to use them all, just the one we need.

The following functions have to be created :

I we look to the existhing code, everthing is put into the dxf file like it is.

The major change that have to be made is that the titelblocks and elements used i a qet page has to be writen to the block section and be used in the entities section, it is the same way you are using them in qelectrotech.

If we take a look to a simple qeletrotech project file :


    
        2019-08-18
        C:/Users/ronny.desmedt/OneDrive/dxf/basic file.qet
        17:53
        basic file
    
    
        
        
            
                
                
            
        
        
        
        
            
            
            
        
        
        
        
    
    
        
            
            
        
        
        
            
                
                    
                    
                    
                    
                
                
                
                    
                
                
                    
                        
                        label
                    
                
                
            
        
        
            
                
                
            
            
                
                
            
        
    
    
        
            
                Elementy importowane
                Imported elements
                Importerede elementer
                Εισηγμένα στοιχεία
                Éléments importés
                Elementen geïmporteerd
                İthal öğeler
                Elementos importados
                Импортированные элементы
                Uvezeni elementi
                Importierte elemente
                Uvoženi elementi
                Elements importats
                Zavedené prvky
                elementos importados
                Elementi importati
                Elemente importate
            
            
                
                    Elektrotechnika
                    Electric
                    Elektrisk
                    Ηλεκτρικά
                    Elektrotechniek
                    Electrique
                    Электротехника
                    Eléctrica
                    Elektrik
                    Elettrica
                    Elektrotechnika
                
                
                    
                        Schematy wieloliniowe
                        All-pole
                        Flere ledere
                        Πολυγραμμικό
                        Multifilaire
                        Veel polig
                        Многополюсные
                        Multifilar
                        Allpolig
                        Vícežilový
                        Multifilare
                    
                    
                        
                            Łączniki i zabezpieczenia
                            Fuses and protective gears
                            Sikringer og beskyttelsesudstyr
                            Ασφάλειες και εξαρτήματα προστασίας
                            Fusibles et protections
                            Zekeringen en beveiligingen
                            Предохранители и элементы защиты
                            Fusibles y protecciones
                            Sicherungen und Schutzeinrichtungen
                            Fusibili e protezioni
                            Tavné pojistky a ochrany
                        
                        
                            
                                Wyłączniki
                                Circuit-breakers
                                قواطع
                                Afbryder
                                Αυτόματοι διακόπτες
                                Disjoncteurs
                                Lastscheiders
                                Выключатели
                                Disyuntores
                                Leitungsschutzschalter und Lastschalter
                                Jističe
                                Disjuntores
                                Relè termici
                            
                            
                                
                                    
                                    
                                        قطب ثنائي القطبية قطبين محميين
                                        Leitungsschutzschalter 2P
                                        Circuit-breaker
                                        Disyuntor termico magnetico en 2P
                                        Int. Aut. Magneto-termico 2P
                                        Disjoncteur bipolaire 2 poles proteges
                                        Wyłącznik
                                        Lastscheider 2
                                        Dvojpólový jistič 2 póly chránící
                                    
                                    
                                        protection
                                    
                                    Author: The QElectroTech team
License: see http://qelectrotech.org/wiki/doc/elements_license

: some parts belong to header section of a dxf file
: if this the basic titelblock definition then i belong to the block section an will be used in the entitie section with a "INSERT" dxf type
: use in the entitie section with a "INSERT" dxf type
: these will be directly used in the entitie section
: these will alle be placed into the block section and used in the entitie section with the "INSERT" dxf type

DXF coding exist of to lines i a dxf file, a code line and a value line:

code 10 (11-18) : x coordinate
code 20 (21-28) : y coordinate
code 30 (31-38) : z coordinate

For example a line :

10 : value : x start point
20 : value : y start point
11 : value : x end point
21 : value : y end point

Header section

 0
SECTION
  2
HEADER
  9
$ACADVER
  1
AC1015
  9
$ACADMAINTVER
 70
    20
  9
$DWGCODEPAGE
  3
ANSI_1252
  9
$INSBASE
 10
0.0
 20
0.0
 30
0.0
  9
$EXTMIN
 10
-0.0000065245499172
 20
-92.07012943410845
 30
0.0
  9
$EXTMAX
 10
245.7932157966029
 20
92.03646890741342
 30
0.0

Every section starts with :

0
SECTION
2
HEADER
....

and ends with

0
ENDSEC

every header items starts with code 9 (only used in the header section)

9 : start code
$ACADVER : acad settings variable name
1 : Primary text value for an entity
AC1015 : value for code 1
9 : next start code for a acad settings variable

base point of a acad.dxf/dwg drawing (this must be in the export file)

9
$INSBASE
10 [color=#ff3333]: x reference[/color]
0.0 [color=#3333ff]: value of x[/color]
20 : [color=#ff3333]y reference[/color]
0.0 : [color=#3333ff]value of y[/color]
30 : [color=#ff3333]z reference[/color]
0.0 : [color=#3333ff]value of z[/color]

In DXF TABLES SECTION we need to create following tables :

BLOCK_RECORD (posible needed, have to checkout this table)
LAYER
LTYPE

Layer table

We created layers to separate qet sections:

Titelblock
Elements
Text
Shapes
....

Everithing of a titelblock wil be drawn on the layer "Titelblock" and so on for the other types.

LTYPE table

This table is used to converd the QET line types to acad line types

exportdxf.CPP

connectors will be transformet to points in DXF

0
SECTION
2
ENTITIES
0
POINT
8
0
10
111.9573116635928
20
4.929017205688296
30
0
6
Continuous

these points positions will be neded to convert the connector lines to dxf.

A symbol with connectors is insert at coordinates x,Y and the connector is relatief to these insert points (this is for both systems the same) so for drawing a line between to connectors we have to calculate the exact positions of the two connectors and the draw a polyline with 3 x,y points

0
LWPOLYLINE
5
31C1
330
1F
100
AcDbEntity
  8
0
  6
Continuous
100
AcDbPolyline
 90
        5
 70
     0
 43
0.364575
 10
111.9573116635928
 20
4.929017205688296
 10
116.9052366635928
 20
4.929017205688296
 10
116.9052366635928
 20
-14.7584827943117
 10
111.9573116635928
 20
-14.7584827943117
 10
111.9573116635928
 20
4.929017205688296

Like you can see we need tree times code 10 and 20 to define a polyline