Use a path resolver class instead of QgsProject::instance() in map layers

A new class QgsPathResolver is introduced for conversion between absolute
and relative paths when reading/writing XML.

Cleaned up code in layer definition file support (.qlr) to better handle
relative/absolute path conversion.

Author: wonder-sk

doc/api_break.dox

@@ -1214,6 +1214,7 @@ QgsLayerDefinition        {#qgis_api_break_3_0_QgsLayerDefinition}
 ------------------
 
 - loadLayerDefinition() now also requires QgsProject as the second argument
+- loadLayerDefinition() and exportLayerDefinition() variants that take QDomDocument as the first argument now expect QgsPathResolver as the last argument
 
 
 QgsLayerPropertiesWidget        {#qgis_api_break_3_0_QgsLayerPropertiesWidget}
@@ -1335,7 +1336,7 @@ screenUpdateRequested() were removed. These members have had no effect for a num
 - capitaliseLayerName() was renamed to capitalizeLayerName() <!--#spellok-->
 - asLayerDefinition(), fromLayerDefinition(), fromLayerDefinitionFile() were moved to QgsLayerDefinition class and renamed to exportLayerDefinitionLayers() resp. loadLayerDefinitionLayers()
 - loadNamedStyleFromDb() was renamed to loadNamedStyleFromDatabase()
-
+- readLayerXml() and writeLayerXml() expect QgsPathResolver reference as the last argument
 
 QgsMapOverviewCanvas        {#qgis_api_break_3_0_QgsMapOverviewCanvas}
 --------------------
@@ -1570,6 +1571,7 @@ QgsProject        {#qgis_api_break_3_0_QgsProject}
 - read( const QFileInfo& file ) was replaced by read( const QString& filename ).
 - write( const QFileInfo& file ) was replaced by write( const QString& filename ).
 - createEmbeddedLayer() does not take vectorLayerList as the third parameter anymore.
+- writePath() does not accept second argument (relativeBasePath) anymore. Use QgsPathResolver instead.
 
 
 QgsProjectPropertyValue        {#qgis_api_break_3_0_QgsProjectPropertyValue}

python/core/core.sip

@@ -107,6 +107,7 @@
 %Include qgspaintenginehack.sip
 %Include qgspainting.sip
 %Include qgspallabeling.sip
+%Include qgspathresolver.sip
 %Include qgspluginlayer.sip
 %Include qgspluginlayerregistry.sip
 %Include qgspoint.sip

python/core/qgslayerdefinition.sip

@@ -12,12 +12,12 @@ class QgsLayerDefinition
 %End
   public:
     static bool loadLayerDefinition( const QString & path, QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage /Out/ );
-    static bool loadLayerDefinition( QDomDocument doc, QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage /Out/ );
+    static bool loadLayerDefinition( QDomDocument doc, QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage /Out/, const QgsPathResolver& pathResolver );
     static bool exportLayerDefinition( QString path, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage /Out/ );
-    static bool exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage, const QString& relativeBasePath = QString::null );
+    static bool exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage /Out/, const QgsPathResolver& pathResolver );
 
-    static QDomDocument exportLayerDefinitionLayers( const QList<QgsMapLayer*>& layers, const QString& relativeBasePath = QString::null );
-    static QList<QgsMapLayer*> loadLayerDefinitionLayers( QDomDocument& document ) /Factory/;
+    static QDomDocument exportLayerDefinitionLayers( const QList<QgsMapLayer*>& layers, const QgsPathResolver& pathResolver );
+    static QList<QgsMapLayer*> loadLayerDefinitionLayers( QDomDocument& document, const QgsPathResolver& pathResolver ) /Factory/;
     static QList<QgsMapLayer*> loadLayerDefinitionLayers( const QString &qlrfile ) /Factory/;
 
     /**

python/core/qgsmaplayer.sip

@@ -321,39 +321,9 @@ class QgsMapLayer : QObject
      */
     virtual bool isSpatial() const;
 
-    /** Sets state from Dom document
-       @param layerElement The Dom element corresponding to ``maplayer'' tag
-       @note
+    bool readLayerXml( const QDomElement& layerElement, const QgsPathResolver& pathResolver );
 
-       The Dom node corresponds to a Dom document project file XML element read
-       by QgsProject.
-
-       This, in turn, calls readXml(), which is over-rideable by sub-classes so
-       that they can read their own specific state from the given Dom node.
-
-       Invoked by QgsProject::read().
-
-       @returns true if successful
-     */
-    bool readLayerXml( const QDomElement& layerElement );
-
-    /** Stores state in Dom node
-     * @param layerElement is a Dom element corresponding to ``maplayer'' tag
-     * @param document is a the dom document being written
-     * @param relativeBasePath base path for relative paths
-     * @note
-     *
-     * The Dom node corresponds to a Dom document project file XML element to be
-     * written by QgsProject.
-     *
-     * This, in turn, calls writeXml(), which is over-rideable by sub-classes so
-     * that they can write their own specific state to the given Dom node.
-     *
-     * Invoked by QgsProject::write().
-     *
-     * @returns true if successful
-     */
-    bool writeLayerXml( QDomElement& layerElement, QDomDocument& document, const QString& relativeBasePath = QString::null ) const;
+    bool writeLayerXml( QDomElement& layerElement, QDomDocument& document, const QgsPathResolver& pathResolver ) const;
 
     /** Set a custom property for layer. Properties are stored in a map and saved in project file.
      * @see customProperty()

python/core/qgspathresolver.sip

@@ -0,0 +1,15 @@
+
+class QgsPathResolver
+{
+%TypeHeaderCode
+#include <qgspathresolver.h>
+%End
+
+  public:
+    explicit QgsPathResolver( const QString& baseFileName = QString() );
+
+    QString writePath( const QString& filename ) const;
+
+    QString readPath( const QString& filename ) const;
+
+};

python/core/qgsproject.sip

@@ -233,12 +233,14 @@ class QgsProject : QObject, QgsExpressionContextGenerator
      */
     void dumpProperties() const;
 
+    QgsPathResolver pathResolver() const;
+
     /**
      * Prepare a filename to save it to the project file.
      * Creates an absolute or relative path according to the project settings.
      * Paths written to the project file should be prepared with this method.
     */
-    QString writePath( const QString& filename, const QString& relativeBasePath = QString::null ) const;
+    QString writePath( const QString& filename ) const;
 
     /** Turn filename read from the project file to an absolute path */
     QString readPath( QString filename ) const;

src/core/CMakeLists.txt

@@ -187,6 +187,7 @@ SET(QGIS_CORE_SRCS
   qgspaintenginehack.cpp
   qgspainting.cpp
   qgspallabeling.cpp
+  qgspathresolver.cpp
   qgspluginlayer.cpp
   qgspluginlayerregistry.cpp
   qgspoint.cpp
@@ -727,6 +728,7 @@ SET(QGIS_CORE_HDRS
   qgspaintenginehack.h
   qgspainting.h
   qgspallabeling.h
+  qgspathresolver.h
   qgspluginlayerregistry.h
   qgspointlocator.h
   qgsprojectbadlayerhandler.h

src/core/qgslayerdefinition.cpp

@@ -22,6 +22,7 @@
 #include "qgslayertree.h"
 #include "qgslogger.h"
 #include "qgsmaplayer.h"
+#include "qgspathresolver.h"
 #include "qgspluginlayer.h"
 #include "qgspluginlayerregistry.h"
 #include "qgsproject.h"
@@ -48,10 +49,10 @@ bool QgsLayerDefinition::loadLayerDefinition( const QString &path, QgsProject* p
   QFileInfo fileinfo( file );
   QDir::setCurrent( fileinfo.absoluteDir().path() );
 
-  return loadLayerDefinition( doc, project, rootGroup, errorMessage );
+  return loadLayerDefinition( doc, project, rootGroup, errorMessage, QgsPathResolver( path ) );
 }
 
-bool QgsLayerDefinition::loadLayerDefinition( QDomDocument doc, QgsProject* project, QgsLayerTreeGroup *rootGroup, QString &errorMessage )
+bool QgsLayerDefinition::loadLayerDefinition( QDomDocument doc, QgsProject* project, QgsLayerTreeGroup *rootGroup, QString &errorMessage, const QgsPathResolver& pathResolver )
 {
   Q_UNUSED( errorMessage );
 
@@ -140,7 +141,7 @@ bool QgsLayerDefinition::loadLayerDefinition( QDomDocument doc, QgsProject* proj
     loadInLegend = false;
   }
 
-  QList<QgsMapLayer*> layers = QgsLayerDefinition::loadLayerDefinitionLayers( doc );
+  QList<QgsMapLayer*> layers = QgsLayerDefinition::loadLayerDefinitionLayers( doc, pathResolver );
 
   project->addMapLayers( layers, loadInLegend );
 
@@ -179,18 +180,16 @@ bool QgsLayerDefinition::exportLayerDefinition( QString path, const QList<QgsLay
     return false;
   }
 
-  QFileInfo fileinfo( file );
-
   QDomDocument doc( QStringLiteral( "qgis-layer-definition" ) );
-  if ( !exportLayerDefinition( doc, selectedTreeNodes, errorMessage, fileinfo.canonicalFilePath() ) )
+  if ( !exportLayerDefinition( doc, selectedTreeNodes, errorMessage, QgsPathResolver( path ) ) )
     return false;
 
   QTextStream qlayerstream( &file );
   doc.save( qlayerstream, 2 );
   return true;
 }
 
-bool QgsLayerDefinition::exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage, const QString& relativeBasePath )
+bool QgsLayerDefinition::exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage, const QgsPathResolver& pathResolver )
 {
   Q_UNUSED( errorMessage );
   QDomElement qgiselm = doc.createElement( QStringLiteral( "qlr" ) );
@@ -209,14 +208,14 @@ bool QgsLayerDefinition::exportLayerDefinition( QDomDocument doc, const QList<Qg
   Q_FOREACH ( QgsLayerTreeLayer* layer, layers )
   {
     QDomElement layerelm = doc.createElement( QStringLiteral( "maplayer" ) );
-    layer->layer()->writeLayerXml( layerelm, doc, relativeBasePath );
+    layer->layer()->writeLayerXml( layerelm, doc, pathResolver );
     layerselm.appendChild( layerelm );
   }
   qgiselm.appendChild( layerselm );
   return true;
 }
 
-QDomDocument QgsLayerDefinition::exportLayerDefinitionLayers( const QList<QgsMapLayer *>& layers, const QString& relativeBasePath )
+QDomDocument QgsLayerDefinition::exportLayerDefinitionLayers( const QList<QgsMapLayer *>& layers, const QgsPathResolver& pathResolver )
 {
   QDomDocument doc( QStringLiteral( "qgis-layer-definition" ) );
   QDomElement qgiselm = doc.createElement( QStringLiteral( "qlr" ) );
@@ -225,14 +224,14 @@ QDomDocument QgsLayerDefinition::exportLayerDefinitionLayers( const QList<QgsMap
   Q_FOREACH ( QgsMapLayer* layer, layers )
   {
     QDomElement layerelm = doc.createElement( QStringLiteral( "maplayer" ) );
-    layer->writeLayerXml( layerelm, doc, relativeBasePath );
+    layer->writeLayerXml( layerelm, doc, pathResolver );
     layerselm.appendChild( layerelm );
   }
   qgiselm.appendChild( layerselm );
   return doc;
 }
 
-QList<QgsMapLayer*> QgsLayerDefinition::loadLayerDefinitionLayers( QDomDocument& document )
+QList<QgsMapLayer*> QgsLayerDefinition::loadLayerDefinitionLayers( QDomDocument& document, const QgsPathResolver& pathResolver )
 {
   QList<QgsMapLayer*> layers;
   QDomNodeList layernodes = document.elementsByTagName( QStringLiteral( "maplayer" ) );
@@ -262,7 +261,7 @@ QList<QgsMapLayer*> QgsLayerDefinition::loadLayerDefinitionLayers( QDomDocument&
     if ( !layer )
       continue;
 
-    if ( layer->readLayerXml( layerElem ) )
+    if ( layer->readLayerXml( layerElem, pathResolver ) )
     {
       layers << layer;
     }
@@ -286,9 +285,7 @@ QList<QgsMapLayer *> QgsLayerDefinition::loadLayerDefinitionLayers( const QStrin
     return QList<QgsMapLayer*>();
   }
 
-  QFileInfo fileinfo( file );
-  QDir::setCurrent( fileinfo.absoluteDir().path() );
-  return QgsLayerDefinition::loadLayerDefinitionLayers( doc );
+  return QgsLayerDefinition::loadLayerDefinitionLayers( doc, QgsPathResolver( qlrfile ) );
 }
 
 

src/core/qgslayerdefinition.h

@@ -27,6 +27,7 @@ class QDomDocument;
 class QgsLayerTreeGroup;
 class QgsLayerTreeNode;
 class QgsMapLayer;
+class QgsPathResolver;
 class QgsProject;
 
 /** \ingroup core
@@ -42,11 +43,11 @@ class CORE_EXPORT QgsLayerDefinition
     //! Loads the QLR at path into QGIS.  New layers are added to given project into layer tree specified by rootGroup
     static bool loadLayerDefinition( const QString & path, QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage );
     //! Loads the QLR from the XML document.  New layers are added to given project into layer tree specified by rootGroup
-    static bool loadLayerDefinition( QDomDocument doc, QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage );
+    static bool loadLayerDefinition( QDomDocument doc,  QgsProject* project, QgsLayerTreeGroup* rootGroup, QString &errorMessage, const QgsPathResolver& pathResolver );
     //! Export the selected layer tree nodes to a QLR file
     static bool exportLayerDefinition( QString path, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage );
     //! Export the selected layer tree nodes to a QLR-XML document
-    static bool exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage, const QString& relativeBasePath = QString::null );
+    static bool exportLayerDefinition( QDomDocument doc, const QList<QgsLayerTreeNode*>& selectedTreeNodes, QString &errorMessage, const QgsPathResolver& pathResolver );
 
     /** Returns the given layer as a layer definition document
      *  Layer definitions store the data source as well as styling and custom properties.
@@ -56,12 +57,12 @@ class CORE_EXPORT QgsLayerDefinition
      *  This is a low-level routine that does not write layer tree.
      *  @see exportLayerDefinition()
      */
-    static QDomDocument exportLayerDefinitionLayers( const QList<QgsMapLayer*>& layers, const QString& relativeBasePath = QString::null );
+    static QDomDocument exportLayerDefinitionLayers( const QList<QgsMapLayer*>& layers, const QgsPathResolver& pathResolver );
 
     //! Creates new layers from a layer definition document.
     //! This is a low-level routine that does not resolve layer ID conflicts, dependencies and joins
     //! @see loadLayerDefinition()
-    static QList<QgsMapLayer*> loadLayerDefinitionLayers( QDomDocument& document );
+    static QList<QgsMapLayer*> loadLayerDefinitionLayers( QDomDocument& document, const QgsPathResolver& pathResolver );
     //! Creates new layers from a layer definition file (.QLR)
     //! This is a low-level routine that does not resolve layer ID conflicts, dependencies and joins
     //! @see loadLayerDefinition()