Show supported SQL dialects for ogr layers, linked to doc pages

src/gui/qgsquerybuilder.cpp

@@ -32,6 +32,8 @@
 #include <QPushButton>
 #include <QTextStream>
 
+#include <gdal.h>
+
 
 // constructor used when the query builder must make its own
 // connection to the database
@@ -95,11 +97,45 @@ QgsQueryBuilder::QgsQueryBuilder( QgsVectorLayer *layer,
 
   lblDataUri->setText( tr( "Set provider filter on %1" ).arg( layer->name() ) );
 
+  lblProviderStorageType->setOpenExternalLinks(true);
+
+  //TODO what to put there for other providers, e.g. postgis?
+  QStringList supportedSqlDialectsText = QStringList();
+  if ( layer->dataProvider()->name() == "ogr" ) {
+
+    GDALDriverH driver = GDALGetDriverByName( layer->dataProvider()->storageType().toLocal8Bit().constData() );
+    const char* supportedSqlDialects = GDALGetMetadataItem( driver, GDAL_DMD_SUPPORTED_SQL_DIALECTS, nullptr );
+
+    QStringList supportedSqlDialectsList = QString(supportedSqlDialects).split(" ");
+    int count = supportedSqlDialectsList.count();
+    for( int i=0; i<count; i++ )
+    {
+      QString supportedSqlDialect = supportedSqlDialectsList.at(i);
+      QString link = QString();
+      QString title = supportedSqlDialect;
+      if ( supportedSqlDialect == "NATIVE" ) {
+        const QString gdalDriverHelpTopic = GDALGetMetadataItem( driver, GDAL_DMD_HELPTOPIC, nullptr );  // e.g. "drivers/vector/ili.html"
+        link = "https://gdal.org/en/latest/" + gdalDriverHelpTopic;
+        title = layer->dataProvider()->storageType();
+      } else if ( supportedSqlDialect == "OGRSQL" ) {
+        link = "https://gdal.org/user/ogr_sql_dialect.html";
+      } else if ( supportedSqlDialect == "SQLITE" ) {
+        link = "https://gdal.org/user/sql_sqlite_dialect.html";
+      }
+      const QString supportedSqlDialectText = "<a href='" + link +"'>" + title + "</a>";
+      supportedSqlDialectsText.append(supportedSqlDialectText);
+    }
+  }
+
   if ( layer->dataProvider()->name() == QStringLiteral( "virtual" ) )
     // virtual data provider has a long storage type description that isn't useful for the user
     lblProviderStorageType->setText( tr( "Provider: <b>%1</b>" ).arg( layer->dataProvider()->name() ) );
   else
     lblProviderStorageType->setText( tr( "Provider: <b>%1</b>, Storage Type: <b>%2</b>" ).arg( layer->dataProvider()->name() ).arg( layer->dataProvider()->storageType() ) );
+
+  if ( !supportedSqlDialectsText.isEmpty() )
+    lblProviderStorageType->setText ( lblProviderStorageType->text() + ", Supported SQL Dialects: " + supportedSqlDialectsText.join(", ") );
+
   lblProviderStorageType->setToolTip( tr( "The available options are depending on the layer's provider and storage type." ) );
 
   mTxtSql->setText( mOrigSubsetString );