[FEATURE] New API for labeling engine (QgsLabelingEngineV2)

The idea is to make the engine more flexible compared to QgsPalLabeling implementation:
- abstract dealing with text labels / diagrams from the engine itself
- allow multiple types of labels per layer
- support custom label providers (e.g. implemented by plugins)
- make the labeling engine independent from map rendering engine
- make it easier to auto-test the labeling engine and its components

This code has been funded by Tuscany Region (Italy) - SITA (CIG: 63526840AE) and commissioned to Gis3W s.a.s.

Author: wonder-sk

src/core/CMakeLists.txt

@@ -112,6 +112,7 @@ SET(QGIS_CORE_SRCS
   qgslayerdefinition.cpp
   qgslabel.cpp
   qgslabelattributes.cpp
+  qgslabelingenginev2.cpp
   qgslabelsearchtree.cpp
   qgslegacyhelpers.cpp
   qgslegendrenderer.cpp
@@ -178,12 +179,14 @@ SET(QGIS_CORE_SRCS
   qgsvectorfilewriter.cpp
   qgsvectorlayer.cpp
   qgsvectorlayercache.cpp
+  qgsvectorlayerdiagramprovider.cpp
   qgsvectorlayereditbuffer.cpp
   qgsvectorlayereditpassthrough.cpp
   qgsvectorlayereditutils.cpp
   qgsvectorlayerfeatureiterator.cpp
   qgsvectorlayerimport.cpp
   qgsvectorlayerjoinbuffer.cpp
+  qgsvectorlayerlabelprovider.cpp
   qgsvectorlayerrenderer.cpp
   qgsvectorlayerundocommand.cpp
   qgsvectorsimplifymethod.cpp
@@ -562,6 +565,7 @@ SET(QGIS_CORE_HDRS
   qgslayerdefinition.h
   qgslabel.h
   qgslabelattributes.h
+  qgslabelingenginev2.h
   qgslabelsearchtree.h
   qgslegacyhelpers.h
   qgslegendrenderer.h
@@ -612,9 +616,11 @@ SET(QGIS_CORE_HDRS
   qgsvectordataprovider.h
   qgsvectorlayercache.h
   qgsvectorfilewriter.h
+  qgsvectorlayerdiagramprovider.h
   qgsvectorlayereditutils.h
   qgsvectorlayerfeatureiterator.h
   qgsvectorlayerimport.h
+  qgsvectorlayerlabelprovider.h
   qgsvectorlayerrenderer.h
   qgsvectorlayerundocommand.h
   qgsvectorsimplifymethod.h

src/core/pal/layer.cpp

@@ -40,6 +40,9 @@
 #include <cmath>
 #include <vector>
 
+#include "qgslabelingenginev2.h"
+#include "qgspalgeometry.h"
+
 namespace pal
 {
 
@@ -261,6 +264,22 @@ namespace pal
     return addedFeature; // true if we've added something
   }
 
+  bool Layer::registerFeature( QgsLabelFeature* label )
+  {
+    QgsPalGeometry* g = label->geometry();
+    if ( !registerFeature( g->strId(), g, label->size().width(), label->size().height() ) )
+      return false;
+
+    pal::Feature* pf = getFeature( g->strId() );
+    pf->setLabelInfo( g->info() );
+    pf->setPriority( label->priority() );
+    pf->setDistLabel( label->distLabel() );
+    pf->setFixedQuadrant( label->hasFixedQuadrant() );
+    pf->setIsObstacle( label->isObstacle() );
+    pf->setObstacleFactor( label->obstacleFactor() );
+    return true;
+  }
+
   void Layer::addFeaturePart( FeaturePart* fpart, const QString& labelText )
   {
     double bmin[2];

src/core/pal/layer.h

@@ -37,6 +37,8 @@
 #include <QHash>
 #include <fstream>
 
+class QgsLabelFeature;
+
 namespace pal
 {
 
@@ -266,6 +268,8 @@ namespace pal
                             int xQuadOffset = 0, int yQuadOffset = 0, double xOffset = 0.0, double yOffset = 0.0,
                             bool alwaysShow = false, double repeatDistance = 0 );
 
+      bool registerFeature( QgsLabelFeature* label );
+
       /** Return pointer to feature or NULL if doesn't exist */
       Feature* getFeature( const QString &geom_id );