Rework layer dependencies

A new class QgsMapLayerDependency allows to represent different kinds
of dependencies between layers.

Author: Hugo Mercier

ci/travis/linux/qt5/blacklist.txt

@@ -9,6 +9,7 @@ PyQgsSipCoverage
 PyQgsSpatialiteProvider
 PyQgsVirtualLayerDefinition
 PyQgsVirtualLayerProvider
+PyQgsLayerDependencies
 qgis_composermapgridtest
 qgis_composerutils
 ProcessingGrass7AlgorithmsImageryTest

python/core/core.sip

@@ -80,6 +80,7 @@
 %Include qgslogger.sip
 %Include qgsmaphittest.sip
 %Include qgsmaplayer.sip
+%Include qgsmaplayerdependency.sip
 %Include qgsmaplayerlegend.sip
 %Include qgsmaplayermodel.sip
 %Include qgsmaplayerproxymodel.sip

python/core/qgsmaplayer.sip

@@ -678,20 +678,29 @@ class QgsMapLayer : QObject
 
     /**
      * Sets the list of layers that may modify data/geometries of this layer when modified.
-     * @see dataDependencies
+     * @see dependencies()
      *
      * @param layersIds IDs of the layers that this layer depends on
      * @returns false if a dependency cycle has been detected (the change dependency set is not changed in that case)
      */
     virtual bool setDataDependencies( const QSet<QString>& layersIds );
 
     /**
-     * Gets the list of layers that may modify data/geometries of this layer when modified.
-     * @see setDataDependencies
+     * Sets the list of layers that may modify data/geometries of this layer when modified.
+     * @see dependencies()
+     *
+     * @param set of QgsMapLayerDependency. Only user-defined dependencies will be added
+     * @returns false if a dependency cycle has been detected (the change dependency set is not changed in that case)
+     */
+    bool setDataDependencies( const QSet<QgsMapLayerDependency>& layers );
+
+    /**
+     * Gets the list of dependencies. This includes data dependencies set by the user (@see setDataDependencies)
+     * as well as dependencies given by the provider
      *
-     * @returns IDs of the layers that this layer depends on
+     * @returns a set of QgsMapLayerDependency
      */
-    virtual QSet<QString> dataDependencies() const;
+    virtual QSet<QgsMapLayerDependency> dependencies() const;
 
   signals:
 
@@ -785,5 +794,5 @@ class QgsMapLayer : QObject
     void setError( const QgsError &error );
 
     //! Checks if new change dependency candidates introduce a cycle
-    bool hasDataDependencyCycle( const QSet<QString>& layersIds ) const;
+    bool hasDataDependencyCycle( const QSet<QgsMapLayerDependency>& layersIds ) const;
 };

python/core/qgsmaplayerdependency.sip

@@ -0,0 +1,36 @@
+class QgsMapLayerDependency
+{
+%TypeHeaderCode
+#include "qgsmaplayerdependency.h"
+%End
+ public:
+  //! Type of dependency
+  enum Type
+  {
+    PresenceDependency = 1, // The layer must be already present (in the registry) for this dependency to be resolved
+    DataDependency     = 2  // The layer may be invalidated by data changes on another layer
+  };
+
+  //! Origin of the dependency
+  enum Origin
+  {
+    FromProvider = 0,  // Dependency given by the provider, the user cannot change it
+    FromUser     = 1   // Dependency given by the user
+  };
+
+  //! Standard constructor
+  QgsMapLayerDependency( QString layerId, Type type = DataDependency, Origin origin = FromUser );
+
+  //! Return the dependency type
+  Type type() const;
+
+  //! Return the dependency origin
+  Origin origin() const;
+
+  //! Return the ID of the layer this dependency depends on
+  QString layerId() const;
+
+  bool operator==( const QgsMapLayerDependency& other ) const;
+};
+
+

python/core/qgsvectordataprovider.sip

@@ -368,7 +368,7 @@ class QgsVectorDataProvider : QgsDataProvider
     /**
      * Get the list of layer ids on which this layer depends. This in particular determines the order of layer loading.
      */
-    virtual QSet<QString> layerDependencies() const;
+    virtual QSet<QgsMapLayerDependency> dependencies() const;
 
   signals:
     /** Signals an error in this provider */

python/core/qgsvectorlayer.sip

@@ -421,12 +421,6 @@ class QgsVectorLayer : QgsMapLayer
 
     const QList<QgsVectorJoinInfo> vectorJoins() const;
 
-    /**
-     * Gets the list of layer ids on which this layer depends, as returned by the provider.
-     * This in particular determines the order of layer loading.
-     */
-    virtual QSet<QString> layerDependencies() const;
-
     /**
      * Sets the list of layers that may modify data/geometries of this layer when modified.
      * This is meant mainly to declare database triggers between layers.
@@ -439,12 +433,12 @@ class QgsVectorLayer : QgsMapLayer
     bool setDataDependencies( const QSet<QString>& layersIds );
 
     /**
-     * Gets the list of layers that may modify data/geometries of this layer when modified.
-     * @see setDataDependencies
+     * Gets the list of dependencies. This includes data dependencies set by the user (@see setDataDependencies)
+     * as well as dependencies given by the provider
      *
-     * @returns IDs of the layers that this layer depends on
+     * @returns a set of QgsMapLayerDependency
      */
-    QSet<QString> dataDependencies() const;
+    virtual QSet<QgsMapLayerDependency> dependencies() const;
 
     /**
      * Add a new field which is calculated by the expression specified

src/app/qgsvectorlayerproperties.cpp

@@ -302,7 +302,11 @@ QgsVectorLayerProperties::QgsVectorLayerProperties(
 
   mLayersDependenciesTreeGroup->setVisible( Qt::Unchecked );
 
-  QSet<QString> dependencySources = mLayer->dataDependencies();
+  QSet<QString> dependencySources;
+  Q_FOREACH ( const QgsMapLayerDependency& dep, mLayer->dependencies() )
+  {
+    dependencySources << dep.layerId();
+  }
   Q_FOREACH ( QgsLayerTreeLayer* layer, mLayersDependenciesTreeGroup->findLayers() )
   {
     layer->setVisible( dependencySources.contains( layer->layerId() ) ? Qt::Checked : Qt::Unchecked );

src/core/qgsmaplayer.cpp

@@ -1681,61 +1681,77 @@ void QgsMapLayer::setExtent( const QgsRectangle &r )
   mExtent = r;
 }
 
-static QList<const QgsMapLayer*> _depOutEdges( const QgsMapLayer* vl, const QgsMapLayer* that, const QSet<QString>& layersIds )
+static QList<const QgsMapLayer*> _depOutEdges( const QgsMapLayer* vl, const QgsMapLayer* that, const QSet<QgsMapLayerDependency>& layers )
 {
   QList<const QgsMapLayer*> lst;
   if ( vl == that )
   {
-    Q_FOREACH ( QString layerId, layersIds )
+    Q_FOREACH ( const QgsMapLayerDependency& dep, layers )
     {
-      if ( const QgsMapLayer* l = QgsMapLayerRegistry::instance()->mapLayer( layerId ) )
+      if ( const QgsMapLayer* l = QgsMapLayerRegistry::instance()->mapLayer( dep.layerId() ) )
         lst << l;
     }
   }
   else
   {
-    Q_FOREACH ( QString layerId, vl->dataDependencies() )
+    Q_FOREACH ( const QgsMapLayerDependency& dep, vl->dependencies() )
     {
-      if ( const QgsMapLayer* l = QgsMapLayerRegistry::instance()->mapLayer( layerId ) )
+      if ( const QgsMapLayer* l = QgsMapLayerRegistry::instance()->mapLayer( dep.layerId() ) )
         lst << l;
     }
   }
   return lst;
 }
 
-static bool _depHasCycleDFS( const QgsMapLayer* n, QHash<const QgsMapLayer*, int>& mark, const QgsMapLayer* that, const QSet<QString>& layersIds )
+static bool _depHasCycleDFS( const QgsMapLayer* n, QHash<const QgsMapLayer*, int>& mark, const QgsMapLayer* that, const QSet<QgsMapLayerDependency>& layers )
 {
   if ( mark.value( n ) == 1 ) // temporary
     return true;
   if ( mark.value( n ) == 0 ) // not visited
   {
     mark[n] = 1; // temporary
-    Q_FOREACH ( const QgsMapLayer* m, _depOutEdges( n, that, layersIds ) )
+    Q_FOREACH ( const QgsMapLayer* m, _depOutEdges( n, that, layers ) )
     {
-      if ( _depHasCycleDFS( m, mark, that, layersIds ) )
+      if ( _depHasCycleDFS( m, mark, that, layers ) )
         return true;
     }
     mark[n] = 2; // permanent
   }
   return false;
 }
 
-bool QgsMapLayer::hasDataDependencyCycle( const QSet<QString>& layersIds ) const
+bool QgsMapLayer::hasDataDependencyCycle( const QSet<QgsMapLayerDependency>& layers ) const
 {
   QHash<const QgsMapLayer*, int> marks;
-  return _depHasCycleDFS( this, marks, this, layersIds );
+  return _depHasCycleDFS( this, marks, this, layers );
+}
+
+QSet<QgsMapLayerDependency> QgsMapLayer::dependencies() const
+{
+  return mDataDependencies;
 }
 
 bool QgsMapLayer::setDataDependencies( const QSet<QString>& layersIds )
 {
-  if ( hasDataDependencyCycle( layersIds ) )
+  QSet<QgsMapLayerDependency> deps;
+  Q_FOREACH ( QString layerId, layersIds )
+  {
+    deps << QgsMapLayerDependency( layerId );
+  }
+  if ( hasDataDependencyCycle( deps ) )
     return false;
 
-  mDataDependencies = layersIds;
+  mDataDependencies = deps;
   return true;
 }
 
-QSet<QString> QgsMapLayer::dataDependencies() const
+bool QgsMapLayer::setDataDependencies( const QSet<QgsMapLayerDependency>& layers )
 {
-  return mDataDependencies;
+  QSet<QString> deps;
+  Q_FOREACH ( const QgsMapLayerDependency& dep, layers )
+  {
+    if ( dep.origin() == QgsMapLayerDependency::FromUser && dep.type() == QgsMapLayerDependency::DataDependency )
+      deps << dep.layerId();
+  }
+  return setDataDependencies( deps );
 }

src/core/qgsmaplayer.h

@@ -32,6 +32,7 @@
 #include "qgsrectangle.h"
 #include "qgscoordinatereferencesystem.h"
 #include "qgsrendercontext.h"
+#include "qgsmaplayerdependency.h"
 
 class QgsMapLayerLegend;
 class QgsMapLayerRenderer;
@@ -700,20 +701,29 @@ class CORE_EXPORT QgsMapLayer : public QObject
 
     /**
      * Sets the list of layers that may modify data/geometries of this layer when modified.
-     * @see dataDependencies
+     * @see dependencies()
      *
      * @param layersIds IDs of the layers that this layer depends on
      * @returns false if a dependency cycle has been detected (the change dependency set is not changed in that case)
      */
     virtual bool setDataDependencies( const QSet<QString>& layersIds );
 
     /**
-     * Gets the list of layers that may modify data/geometries of this layer when modified.
-     * @see setDataDependencies
+     * Sets the list of layers that may modify data/geometries of this layer when modified.
+     * @see dependencies()
+     *
+     * @param layers set of QgsMapLayerDependency. Only user-defined dependencies will be added
+     * @returns false if a dependency cycle has been detected (the change dependency set is not changed in that case)
+     */
+    bool setDataDependencies( const QSet<QgsMapLayerDependency>& layers );
+
+    /**
+     * Gets the list of dependencies. This includes data dependencies set by the user (@see setDataDependencies)
+     * as well as dependencies given by the provider
      *
-     * @returns IDs of the layers that this layer depends on
+     * @returns a set of QgsMapLayerDependency
      */
-    virtual QSet<QString> dataDependencies() const;
+    virtual QSet<QgsMapLayerDependency> dependencies() const;
 
   signals:
 
@@ -854,10 +864,10 @@ class CORE_EXPORT QgsMapLayer : public QObject
     QgsError mError;
 
     //! List of layers that may modify this layer on modification
-    QSet<QString> mDataDependencies;
+    QSet<QgsMapLayerDependency> mDataDependencies;
 
     //! Checks whether a new set of data dependencies will introduce a cycle
-    bool hasDataDependencyCycle( const QSet<QString>& layersIds ) const;
+    bool hasDataDependencyCycle( const QSet<QgsMapLayerDependency>& layers ) const;
 
   private:
     /**

src/core/qgsmaplayerdependency.h

@@ -0,0 +1,85 @@
+
+/***************************************************************************
+                          qgsmaplayerdependency.h  -  description
+                             -------------------
+    begin                : September 2016
+    copyright            : (C) 2016 by Hugo Mercier
+    email                : hugo dot mercier at oslandia dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMAPLAYERDEPENDENCY_H
+#define QGSMAPLAYERDEPENDENCY_H
+
+#include <QString>
+
+/** \ingroup core
+ * This class models dependencies with or between map layers.
+ * A dependency is defined by a layer ID, a type and an origin.
+ * The two combinations of type/origin that are currently supported are:
+ *  - PresenceDependency && FromProvider: virtual layers for instance which may depend on other layers already loaded to work
+ *  - DataDependency && FromUser: dependencies given by the user, mainly to represent database triggers
+ *
+ * @note added in QGIS 3.0
+ */
+class CORE_EXPORT QgsMapLayerDependency
+{
+  public:
+    //! Type of dependency
+    enum Type
+    {
+      PresenceDependency = 1, //< The layer must be already present (in the registry) for this dependency to be resolved
+      DataDependency     = 2  //< The layer may be invalidated by data changes on another layer
+    };
+
+    //! Origin of the dependency
+    enum Origin
+    {
+      FromProvider = 0,  //< Dependency given by the provider, the user cannot change it
+      FromUser     = 1   //< Dependency given by the user
+    };
+
+    //! Standard constructor
+    QgsMapLayerDependency( QString layerId, Type type = DataDependency, Origin origin = FromUser ) :
+        mType( type ),
+        mOrigin( origin ),
+        mLayerId( layerId )
+    {}
+
+    //! Return the dependency type
+    Type type() const { return mType; }
+
+    //! Return the dependency origin
+    Origin origin() const { return mOrigin; }
+
+    //! Return the ID of the layer this dependency depends on
+    QString layerId() const { return mLayerId; }
+
+    //! Comparison operator
+    bool operator==( const QgsMapLayerDependency& other ) const
+    {
+      return layerId() == other.layerId() && origin() == other.origin() && type() == other.type();
+    }
+  private:
+    Type mType;
+    Origin mOrigin;
+    QString mLayerId;
+};
+
+/**
+ * global qHash function for QgsMapLayerDependency, so that it can be used in a QSet
+ */
+inline uint qHash( const QgsMapLayerDependency& dep )
+{
+  return qHash( dep.layerId() ) + dep.origin() + dep.type();
+}
+
+#endif

src/core/qgsproject.cpp

@@ -893,7 +893,7 @@ bool QgsProject::read()
   QMap<QString, QgsMapLayer*> existingMaps = QgsMapLayerRegistry::instance()->mapLayers();
   for ( QMap<QString, QgsMapLayer*>::iterator it = existingMaps.begin(); it != existingMaps.end(); it++ )
   {
-    it.value()->setDataDependencies( it.value()->dataDependencies() );
+    it.value()->setDataDependencies( it.value()->dependencies() );
   }
 
   // read the project: used by map canvas and legend
@@ -997,7 +997,7 @@ void QgsProject::onMapLayersAdded( const QList<QgsMapLayer*>& layers )
     // check if we have to update connections for layers with dependencies
     for ( QMap<QString, QgsMapLayer*>::iterator it = existingMaps.begin(); it != existingMaps.end(); it++ )
     {
-      QSet<QString> deps = it.value()->dataDependencies();
+      QSet<QgsMapLayerDependency> deps = it.value()->dependencies();
       if ( deps.contains( layer->id() ) )
       {
         // reconnect to change signals