Rendering of SVG for layer symbols using QGIS?

Question

I have a little problem with the rendering of SVG for layer symbol. I want to creeate a categorized symbol to show different style of buoy I have for that two icons the first is an half circle filled, and the second is a triangle filled, both are yellow, no rotate, same size. So I define the property of the symbol as descibe in the qgis cookbook page 149 here is my Code in C++ to do that

QgsStringMap MyBoyStyle,MyBoyStyle2;
QString lBoyIcoType1 = "../data/Icones/iconeS52/" + pNameCouche+QString("_")+"RVER1"+ EXT_ICONE;//attention au path icone "../data/Icones/iconeS52/" au lieu de PATH_ICONE
QString lBoyIcoType2 = "../data/Icones/iconeS52/" + pNameCouche+QString("_")+"RVER2"+ EXT_ICONE;//attention au path icone "../data/Icones/iconeS52/" au lieu de PATH_ICONE

// list of property for the boystyle
QStringList MyBoyPropertyName;
MyBoyPropertyName << "fill" << "name" << "outline" << "outline-width" << "size";
// list of corresponding value 1
QStringList MyBoyPropertyValue;
MyBoyPropertyValue << "#f3e54d" << lBoyIcoType1 << "#000000" << "6.8" << "6";
QStringList MyBoyPropertyValue2;
MyBoyPropertyValue2 << "#f3e54d" << lBoyIcoType2 << "#000000" << "6.8" << "6";

// create the map 1 et 2
for (int i =0; i < MyBoyPropertyName.size(); i++){
    //1ere bouee
    MyBoyStyle.insert(MyBoyPropertyName.at(i),MyBoyPropertyValue.at(i));
    //2eme bouee
    MyBoyStyle2.insert(MyBoyPropertyName.at(i),MyBoyPropertyValue2.at(i));
}
// creation du svg marker layer
QgsSymbolLayerV2* MySymbolLayer1;
MySymbolLayer1 = QgsSvgMarkerSymbolLayerV2::create(MyBoyStyle);
QgsSymbolLayerV2* MySymbolLayer2;
MySymbolLayer2 = QgsSvgMarkerSymbolLayerV2::create(MyBoyStyle2);

QList <QgsSymbolLayerV2*> MyLayerList;
MyLayerList << MySymbolLayer1 << MySymbolLayer2;

then I create the categories :

QList<QgsRendererCategoryV2> Categories;
QStringList lListValue; lListValue << "1" << "2";
QStringList lListIcone; lListIcone << pNameCouche+QString("_")+"RVER1" << pNameCouche+QString("_")+"RVER2";

for(int i = 0 ; i < lListValue.size() ; i++){
    QgsSymbolV2* newsymbol = QgsSymbolV2::defaultSymbol(pLayer->geometryType() );
    newsymbol->appendSymbolLayer(MyLayerList[i]);
    //newsymbol->setColor(QColor("#f3e54d"));
    QgsRendererCategoryV2 MyCategorie = QgsRendererCategoryV2(QVariant( lListValue.at(i) ),newsymbol,PATH_ICONE+lListIcone.at(i)+EXT_ICONE);
    Categories.append(MyCategorie);
}
// for the rendering
lrenderer = new QgsCategorizedSymbolRendererV2("RVER",Categories);
pLayer->setRendererV2(lrenderer);

when I launch the application, the file s57 was loaded and the buoy are display good but for the second icon or symbol I have a superposition of shape i have the default symbollayer which is a circle in background of my symbollayer which is a triangle filled in yellow.

Any Idea ?

Answer 1

Here is the solution,I finally understand why In fact a defaultSymbol is been created when I instanciate newsymbol , so instead of do an appendSymbolLayer I had to delete the default symbolLayer first and insert the new one to replace it The code is now :

for(int i = 0 ; i < lListValue.size() ; i++) {
    QgsSymbolV2* newsymbol =    QgsSymbolV2::defaultSymbol(pLayer->geometryType() );
    //newsymbol->appendSymbolLayer(MyLayerList[i]); // old method
    newsymbol->deleteSymbolLayer(0);
    newsymbol->insertSymbolLayer(0,MyLayerList[i]);
    QgsRendererCategoryV2 MyCategorie = QgsRendererCategoryV2(QVariant( lListValue.at(i) ),newsymbol,PATH_ICONE+lListIcone.at(i)+EXT_ICONE);
    Categories.append(MyCategorie);
}

the rendering is compliant with what I expected.