Legend refactoring: first steps towards legend customization

- map layers have associated QgsMapLayerLegend instance
- QgsMapLayerLegend is interface for generation of legend with some default implementations
- QgsLayerTreeModelLegendNode is interface for representation of legend item in layer tree model with some default implementations

Author: wonder-sk

python/core/core.sip

@@ -47,6 +47,7 @@
 %Include qgslabelsearchtree.sip
 %Include qgslogger.sip
 %Include qgsmaplayer.sip
+%Include qgsmaplayerlegend.sip
 %Include qgsmaplayerregistry.sip
 %Include qgsmaplayerrenderer.sip
 %Include qgsmaprenderer.sip

python/core/qgsmaplayer.sip

@@ -366,6 +366,17 @@ class QgsMapLayer : QObject
     /** @deprecated since 2.4 - does nothing */
     virtual void onCacheImageDelete() /Deprecated/;
 
+    /**
+     * Assign a legend controller to the map layer. The object will be responsible for providing legend items.
+     * @param legend Takes ownership of the object. Can be null pointer
+     * @note added in 2.6
+     */
+    void setLegend( QgsMapLayerLegend* legend /Transfer/ );
+    /**
+     * @note added in 2.6
+     */
+    QgsMapLayerLegend* legend() const;
+
   public slots:
 
     /** Event handler for when a coordinate transform fails due to bad vertex error */
@@ -430,6 +441,12 @@ class QgsMapLayer : QObject
     /** Signal emitted when renderer is changed */
     void rendererChanged();
 
+    /**
+     * Signal emitted when legend of the layer has changed
+     * @note added in 2.6
+     */
+    void legendChanged();
+
   protected:
     /** Set the extent */
     virtual void setExtent( const QgsRectangle &rect );

python/core/qgsmaplayerlegend.sip

@@ -0,0 +1,163 @@
+
+/**
+ * The QgsLegendRendererItem class is abstract interface for legend items
+ * returned from QgsMapLayerLegend implementation.
+ *
+ * The objects are used in QgsLayerTreeModel. Custom implementations may offer additional interactivity
+ * and customized look.
+ *
+ * @note added in 2.6
+ */
+class QgsLayerTreeModelLegendNode : QObject
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+    
+  public:
+
+    /** Return pointer to the parent layer node */
+    QgsLayerTreeLayer* parent() const;
+
+    /** Return item flags associated with the item. Default implementation returns Qt::ItemIsEnabled. */
+    virtual Qt::ItemFlags flags() const;
+
+    /** Return data associated with the item. Must be implemented in derived class. */
+    virtual QVariant data( int role ) const = 0;
+
+    /** Set some data associated with the item. Default implementation does nothing and returns false. */
+    virtual bool setData( const QVariant& value, int role );
+
+  protected:
+    /** Construct the node with pointer to its parent layer node */
+    explicit QgsLayerTreeModelLegendNode( QgsLayerTreeLayer* nodeL );
+};
+
+
+/**
+ * Implementation of legend node interface for displaying preview of vector symbols and their labels
+ * and allowing interaction with the symbol / renderer.
+ *
+ * @note added in 2.6
+ */
+class QgsSymbolV2LegendNode : QgsLayerTreeModelLegendNode
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+  public:
+    QgsSymbolV2LegendNode( QgsLayerTreeLayer* nodeLayer, QgsSymbolV2* symbol, const QString& label, int rendererRef = -1 );
+
+    virtual Qt::ItemFlags flags() const;
+    virtual QVariant data( int role ) const;
+    virtual bool setData( const QVariant& value, int role );
+};
+
+
+/**
+ * Implementation of legend node interface for displaying arbitrary label with icon.
+ *
+ * @note added in 2.6
+ */
+class QgsSimpleLegendNode : QgsLayerTreeModelLegendNode
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+  public:
+    QgsSimpleLegendNode( QgsLayerTreeLayer* nodeLayer, const QString& label, const QIcon& icon = QIcon() );
+
+    virtual QVariant data( int role ) const;
+};
+
+
+/**
+ * The QgsMapLayerLegend class is abstract interface for implementations
+ * of legends for one map layer.
+ *
+ * @note added in 2.6
+ */
+class QgsMapLayerLegend : QObject
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+    
+  public:
+    explicit QgsMapLayerLegend( QObject *parent /TransferThis/ = 0 );
+
+    // TODO: type, load/save settings
+
+    /**
+     * Return list of legend nodes to be used for a particular layer tree layer node.
+     * Ownership is transferred to the caller.
+     */
+    virtual QList<QgsLayerTreeModelLegendNode*> createLayerTreeModelLegendNodes( QgsLayerTreeLayer* nodeLayer ) = 0 /Factory/;
+
+    // TODO: support for layer tree view delegates
+
+    // TODO: support for legend renderer
+
+
+    //! Create new legend implementation for vector layer
+    static QgsMapLayerLegend* defaultVectorLegend( QgsVectorLayer* vl ) /Factory/;
+
+    //! Create new legend implementation for raster layer
+    static QgsMapLayerLegend* defaultRasterLegend( QgsRasterLayer* rl ) /Factory/;
+
+    //! Create new legend implementation for raster layer
+    static QgsMapLayerLegend* defaultPluginLegend( QgsPluginLayer* pl ) /Factory/;
+
+  signals:
+    //! Emitted when existing items/nodes got invalid and should be replaced by new ones
+    void itemsChanged();
+};
+
+
+/** Default legend implementation for vector layers
+ * @note added in 2.6
+ */
+class QgsDefaultVectorLayerLegend : QgsMapLayerLegend
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+  public:
+    explicit QgsDefaultVectorLayerLegend( QgsVectorLayer* vl );
+
+    virtual QList<QgsLayerTreeModelLegendNode*> createLayerTreeModelLegendNodes( QgsLayerTreeLayer* nodeLayer ) /Factory/;
+
+};
+
+
+/** Default legend implementation for raster layers
+ * @note added in 2.6
+ */
+class QgsDefaultRasterLayerLegend : QgsMapLayerLegend
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+  public:
+    explicit QgsDefaultRasterLayerLegend( QgsRasterLayer* rl );
+
+    virtual QList<QgsLayerTreeModelLegendNode*> createLayerTreeModelLegendNodes( QgsLayerTreeLayer* nodeLayer ) /Factory/;
+
+};
+
+
+/** Default legend implementation for plugin layers
+ * @note added in 2.6
+ */
+class QgsDefaultPluginLayerLegend : QgsMapLayerLegend
+{
+%TypeHeaderCode
+#include <qgsmaplayerlegend.h>
+%End
+  public:
+    explicit QgsDefaultPluginLayerLegend( QgsPluginLayer* pl );
+
+    virtual QList<QgsLayerTreeModelLegendNode*> createLayerTreeModelLegendNodes( QgsLayerTreeLayer* nodeLayer ) /Factory/;
+
+};
+

src/core/CMakeLists.txt

@@ -96,6 +96,7 @@ SET(QGIS_CORE_SRCS
   qgslegendsettings.cpp
   qgslogger.cpp
   qgsmaplayer.cpp
+  qgsmaplayerlegend.cpp
   qgsmaplayerregistry.cpp
   qgsmaprenderer.cpp
   qgsmaprenderercache.cpp
@@ -336,6 +337,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsgmlschema.h
   qgshttptransaction.h
   qgsmaplayer.h
+  qgsmaplayerlegend.h
   qgsmaplayerregistry.h
   qgsmaprenderer.h
   qgsmaprenderercache.h
@@ -469,6 +471,7 @@ SET(QGIS_CORE_HDRS
   qgslegendsettings.h
   qgslogger.h
   qgsmaplayer.h
+  qgsmaplayerlegend.h
   qgsmaplayerregistry.h
   qgsmaprenderer.h
   qgsmaprenderercache.h

src/core/qgsmaplayer.cpp

@@ -35,6 +35,7 @@
 #include "qgsmaplayer.h"
 #include "qgscoordinatereferencesystem.h"
 #include "qgsapplication.h"
+#include "qgsmaplayerlegend.h"
 #include "qgsproject.h"
 #include "qgspluginlayerregistry.h"
 #include "qgsprojectfiletransform.h"
@@ -53,6 +54,7 @@ QgsMapLayer::QgsMapLayer( QgsMapLayer::LayerType type,
     mID( "" ),
     mLayerType( type ),
     mBlendMode( QPainter::CompositionMode_SourceOver ) // Default to normal blending
+    , mLegend( 0 )
 {
   mCRS = new QgsCoordinateReferenceSystem();
 
@@ -81,6 +83,7 @@ QgsMapLayer::QgsMapLayer( QgsMapLayer::LayerType type,
 QgsMapLayer::~QgsMapLayer()
 {
   delete mCRS;
+  delete mLegend;
 }
 
 QgsMapLayer::LayerType QgsMapLayer::type() const
@@ -1376,6 +1379,25 @@ void QgsMapLayer::setCacheImage( QImage * )
   emit repaintRequested();
 }
 
+void QgsMapLayer::setLegend( QgsMapLayerLegend* legend )
+{
+  if ( legend == mLegend )
+    return;
+
+  delete mLegend;
+  mLegend = legend;
+
+  if ( mLegend )
+    connect( mLegend, SIGNAL( itemsChanged() ), this, SIGNAL( legendChanged() ) );
+
+  emit legendChanged();
+}
+
+QgsMapLayerLegend*QgsMapLayer::legend() const
+{
+  return mLegend;
+}
+
 void QgsMapLayer::clearCacheImage()
 {
   emit repaintRequested();

src/core/qgsmaplayer.h

@@ -34,6 +34,7 @@
 
 class QgsRenderContext;
 class QgsCoordinateReferenceSystem;
+class QgsMapLayerLegend;
 class QgsMapLayerRenderer;
 
 class QDomDocument;
@@ -382,6 +383,17 @@ class CORE_EXPORT QgsMapLayer : public QObject
     /** @deprecated since 2.4 - does nothing */
     Q_DECL_DEPRECATED virtual void onCacheImageDelete() {}
 
+    /**
+     * Assign a legend controller to the map layer. The object will be responsible for providing legend items.
+     * @param legend Takes ownership of the object. Can be null pointer
+     * @note added in 2.6
+     */
+    void setLegend( QgsMapLayerLegend* legend );
+    /**
+     * @note added in 2.6
+     */
+    QgsMapLayerLegend* legend() const;
+
   public slots:
 
     /** Event handler for when a coordinate transform fails due to bad vertex error */
@@ -446,6 +458,12 @@ class CORE_EXPORT QgsMapLayer : public QObject
     /** Signal emitted when renderer is changed */
     void rendererChanged();
 
+    /**
+     * Signal emitted when legend of the layer has changed
+     * @note added in 2.6
+     */
+    void legendChanged();
+
   protected:
     /** Set the extent */
     virtual void setExtent( const QgsRectangle &rect );
@@ -559,6 +577,9 @@ class CORE_EXPORT QgsMapLayer : public QObject
 
     //! Layer's persistent storage of additional properties (may be used by plugins)
     QgsObjectCustomProperties mCustomProperties;
+
+    //! Controller of legend items of this layer
+    QgsMapLayerLegend* mLegend;
 };
 
 #endif