[tracer] Integration of tracing into GUI

Checking the new 'enable tracing' button will switch capture tools
to tracing mode. Tracing can be turned on/off even while digitizing
is in progress

Author: wonder-sk

images/images.qrc

@@ -529,6 +529,7 @@
         <file>flags/zh.png</file>
         <file>icons/qgis-icon-16x16_xmas.png</file>
         <file>icons/qgis-icon-60x60_xmas.png</file>
+        <file>themes/default/mActionTracing.png</file>
     </qresource>
     <qresource prefix="/images/tips">
         <file alias="symbol_levels.png">qgis_tips/symbol_levels.png</file>

images/themes/default/mActionTracing.png

@@ -164,6 +164,7 @@
 #include "qgslogger.h"
 #include "qgsmapcanvas.h"
 #include "qgsmapcanvassnappingutils.h"
+#include "qgsmapcanvastracer.h"
 #include "qgsmaplayer.h"
 #include "qgsmaplayerregistry.h"
 #include "qgsmaplayerstyleguiutils.h"
@@ -554,6 +555,7 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, QWidget * parent,
     , mComposerManager( nullptr )
     , mpTileScaleWidget( nullptr )
     , mpGpsWidget( nullptr )
+    , mTracer( nullptr )
     , mSnappingUtils( nullptr )
     , mProjectLastModified()
     , mWelcomePage( nullptr )
@@ -1020,6 +1022,7 @@ QgisApp::QgisApp()
     , mMacrosWarn( nullptr )
     , mUserInputDockWidget( nullptr )
     , mVectorLayerTools( nullptr )
+    , mTracer( nullptr )
     , mActionFilterLegend( nullptr )
     , mLegendExpressionFilterButton( nullptr )
     , mSnappingUtils( nullptr )
@@ -1098,6 +1101,8 @@ QgisApp::~QgisApp()
 
   delete mComposerManager;
 
+  delete mTracer;
+
   delete mVectorLayerTools;
   delete mWelcomePage;
 
@@ -1968,6 +1973,9 @@ void QgisApp::createToolBars()
 
   // Cad toolbar
   mAdvancedDigitizeToolBar->insertAction( mActionUndo, mAdvancedDigitizingDockWidget->enableAction() );
+
+  mTracer = new QgsMapCanvasTracer( mMapCanvas );
+  mAdvancedDigitizeToolBar->insertAction( mActionUndo, mTracer->actionEnableTracing() );
 }
 
 void QgisApp::createStatusBar()
@@ -9626,6 +9634,7 @@ void QgisApp::activateDeactivateLayerRelatedActions( QgsMapLayer* layer )
     mActionMergeFeatures->setEnabled( false );
     mActionMergeFeatureAttributes->setEnabled( false );
     mActionRotatePointSymbols->setEnabled( false );
+    mTracer->actionEnableTracing()->setEnabled( false );
 
     mActionPinLabels->setEnabled( false );
     mActionShowHideLabels->setEnabled( false );
@@ -9746,6 +9755,9 @@ void QgisApp::activateDeactivateLayerRelatedActions( QgsMapLayer* layer )
       mActionRotateFeature->setEnabled( isEditable && canChangeGeometry );
       mActionNodeTool->setEnabled( isEditable && canChangeGeometry );
 
+      mTracer->actionEnableTracing()->setEnabled( isEditable && canAddFeatures &&
+          ( vlayer->geometryType() == QGis::Line || vlayer->geometryType() == QGis::Polygon ) );
+
       if ( vlayer->geometryType() == QGis::Point )
       {
         mActionAddFeature->setIcon( QgsApplication::getThemeIcon( "/mActionCapturePoint.svg" ) );

images/themes/default/mActionTracing.svg

@@ -81,6 +81,7 @@ class QgsAdvancedDigitizingDockWidget;
 class QgsSnappingDialog;
 class QgsGPSInformationWidget;
 class QgsStatisticalSummaryDockWidget;
+class QgsMapCanvasTracer;
 
 class QgsDecorationItem;
 
@@ -1690,6 +1691,9 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
 
     QgsVectorLayerTools* mVectorLayerTools;
 
+    //! A class that facilitates tracing of features
+    QgsMapCanvasTracer* mTracer;
+
     QAction* mActionFilterLegend;
 
     QgsLegendFilterButton* mLegendExpressionFilterButton;

src/app/qgisapp.cpp

@@ -212,6 +212,7 @@ SET(QGIS_GUI_SRCS
   qgsmapcanvasmap.cpp
   qgsmapcanvassnapper.cpp
   qgsmapcanvassnappingutils.cpp
+  qgsmapcanvastracer.cpp
   qgsmaplayeractionregistry.cpp
   qgsmaplayercombobox.cpp
   qgsmaplayermodel.cpp
@@ -344,6 +345,7 @@ SET(QGIS_GUI_MOC_HDRS
   qgsmanageconnectionsdialog.h
   qgsmapcanvas.h
   qgsmapcanvassnappingutils.h
+  qgsmapcanvastracer.h
   qgsmaplayeractionregistry.h
   qgsmaplayercombobox.h
   qgsmaplayermodel.h
@@ -557,6 +559,7 @@ SET(QGIS_GUI_HDRS
   qgsmapcanvasmap.h
   qgsmapcanvassnapper.h
   qgsmapcanvassnappingutils.h
+  qgsmapcanvastracer.h
   qgsmaptip.h
   qgsmapmouseevent.h
   qgsnumericsortlistviewitem.h

src/app/qgisapp.h

@@ -0,0 +1,51 @@
+#include "qgsmapcanvastracer.h"
+
+#include "qgsapplication.h"
+#include "qgsmapcanvas.h"
+#include "qgsmaplayerregistry.h"
+#include "qgsvectorlayer.h"
+
+#include <QAction>
+
+QHash<QgsMapCanvas*, QgsMapCanvasTracer*> QgsMapCanvasTracer::sTracers;
+
+
+QgsMapCanvasTracer::QgsMapCanvasTracer( QgsMapCanvas* canvas )
+    : mCanvas( canvas )
+{
+  sTracers.insert( canvas, this );
+
+  connect( canvas, SIGNAL( destinationCrsChanged() ), this, SLOT( updateSettings() ) );
+  connect( canvas, SIGNAL( layersChanged() ), this, SLOT( updateSettings() ) );
+  // TODO: watch for snapping changes
+
+  mActionEnableTracing = new QAction( QIcon( QgsApplication::getThemeIcon( "/mActionTracing.png" ) ), tr( "Enable Tracing" ), this );
+  mActionEnableTracing->setShortcut( Qt::Key_T );
+  mActionEnableTracing->setCheckable( true );
+
+  updateSettings(); // initialize
+}
+
+QgsMapCanvasTracer::~QgsMapCanvasTracer()
+{
+  sTracers.remove( mCanvas );
+}
+
+QgsMapCanvasTracer* QgsMapCanvasTracer::tracerForCanvas( QgsMapCanvas* canvas )
+{
+  return sTracers.value( canvas, 0 );
+}
+
+void QgsMapCanvasTracer::updateSettings()
+{
+  QList<QgsVectorLayer*> layers;
+  foreach ( const QString& layerId, mCanvas->mapSettings().layers() )
+  {
+    QgsVectorLayer* vl = qobject_cast<QgsVectorLayer*>( QgsMapLayerRegistry::instance()->mapLayer( layerId ) );
+    if ( vl )
+      layers << vl;
+  }
+  setLayers( layers );
+
+  setDestinationCrs( mCanvas->mapSettings().destinationCrs() );
+}

src/gui/CMakeLists.txt

@@ -0,0 +1,35 @@
+#ifndef QGSMAPCANVASTRACER_H
+#define QGSMAPCANVASTRACER_H
+
+#include "qgstracer.h"
+
+class QAction;
+class QgsMapCanvas;
+
+class GUI_EXPORT QgsMapCanvasTracer : public QgsTracer
+{
+    Q_OBJECT
+
+  public:
+    explicit QgsMapCanvasTracer( QgsMapCanvas* canvas );
+    ~QgsMapCanvasTracer();
+
+    QAction* actionEnableTracing() { return mActionEnableTracing; }
+
+    //! Retrieve instance of this class associated with given canvas (if any).
+    //! The class keeps a simple registry of tracers associated with map canvas
+    //! instances for easier access to the common tracer by various map tools
+    static QgsMapCanvasTracer* tracerForCanvas( QgsMapCanvas* canvas );
+
+  private slots:
+    void updateSettings();
+
+  private:
+    QgsMapCanvas* mCanvas;
+
+    QAction* mActionEnableTracing;
+
+    static QHash<QgsMapCanvas*, QgsMapCanvasTracer*> sTracers;
+};
+
+#endif // QGSMAPCANVASTRACER_H

src/gui/qgsmapcanvastracer.cpp

@@ -21,6 +21,7 @@
 #include "qgslinestringv2.h"
 #include "qgslogger.h"
 #include "qgsmapcanvas.h"
+#include "qgsmapcanvastracer.h"
 #include "qgsmapmouseevent.h"
 #include "qgsmaprenderer.h"
 #include "qgspolygonv2.h"
@@ -134,6 +135,63 @@ void QgsMapToolCapture::currentLayerChanged( QgsMapLayer *layer )
   }
 }
 
+
+bool QgsMapToolCapture::tracingEnabled()
+{
+  QgsMapCanvasTracer* tracer = QgsMapCanvasTracer::tracerForCanvas( mCanvas );
+  return tracer && tracer->actionEnableTracing()->isChecked();
+}
+
+
+void QgsMapToolCapture::tracingMouseMove( QgsMapMouseEvent* e )
+{
+  if ( !e->isSnapped() )
+    return;
+
+  QgsPointV2 v;
+  QgsVertexId::VertexType vt;
+  mCaptureCurve.pointAt( mCaptureCurve.numPoints() - 1, v, vt );
+
+  QgsMapCanvasTracer* tracer = QgsMapCanvasTracer::tracerForCanvas( mCanvas );
+  if ( !tracer )
+    return;  // this should not happen!
+
+  QVector<QgsPoint> points = tracer->findShortestPath( QgsPoint( v.x(), v.y() ), e->mapPoint() );
+  if ( points.isEmpty() )
+    return;
+
+  //  update rubberband
+  mTempRubberBand->reset( mCaptureMode == CapturePolygon ? QGis::Polygon : QGis::Line );
+  for ( int i = 0; i < points.count(); ++i )
+    mTempRubberBand->addPoint( points.at( i ), i == points.count() - 1 );
+}
+
+
+void QgsMapToolCapture::tracingAddVertex( const QgsPoint& point )
+{
+  QgsMapCanvasTracer* tracer = QgsMapCanvasTracer::tracerForCanvas( mCanvas );
+  if ( !tracer )
+    return;  // this should not happen!
+
+  QgsPointV2 v;
+  QgsVertexId::VertexType vt;
+  mCaptureCurve.pointAt( mCaptureCurve.numPoints() - 1, v, vt );
+
+  QVector<QgsPoint> points = tracer->findShortestPath( QgsPoint( v.x(), v.y() ), point );
+  if ( points.isEmpty() )
+    return; // ignore the vertex - can't find path to the end point!
+
+  QgsPoint lp; // in layer coords
+  for ( int i = 1; i < points.count(); ++i )
+  {
+    if ( nextPoint( points[i], lp ) != 0 )
+      continue; // TODO: should completely abort
+    mRubberBand->addPoint( points[i], i == points.count() - 1 );
+    mCaptureCurve.addVertex( QgsPointV2( lp.x(), lp.y() ) );
+  }
+}
+
+
 void QgsMapToolCapture::cadCanvasMoveEvent( QgsMapMouseEvent * e )
 {
   QgsMapToolAdvancedDigitizing::cadCanvasMoveEvent( e );
@@ -165,9 +223,17 @@ void QgsMapToolCapture::cadCanvasMoveEvent( QgsMapMouseEvent * e )
     mTempRubberBand->addPoint( point );
   }
 
+
   if ( mCaptureMode != CapturePoint && mTempRubberBand && mCapturing )
   {
-    mTempRubberBand->movePoint( point );
+    if ( tracingEnabled() && mCaptureCurve.numPoints() != 0 )
+    {
+      tracingMouseMove( e );
+    }
+    else
+    {
+      mTempRubberBand->movePoint( point );
+    }
   }
 } // mouseMoveEvent
 
@@ -220,8 +286,19 @@ int QgsMapToolCapture::addVertex( const QgsPoint& point )
   {
     mRubberBand = createRubberBand( mCaptureMode == CapturePolygon ? QGis::Polygon : QGis::Line );
   }
-  mRubberBand->addPoint( point );
-  mCaptureCurve.addVertex( QgsPointV2( layerPoint.x(), layerPoint.y() ) );
+
+  if ( tracingEnabled() && mCaptureCurve.numPoints() != 0 )
+  {
+    tracingAddVertex( point );
+  }
+  else
+  {
+    // ordinary digitizing
+    mRubberBand->addPoint( point );
+    mCaptureCurve.addVertex( QgsPointV2( layerPoint.x(), layerPoint.y() ) );
+  }
+
+  // re-initialize temporary rubber band for further digitizing
 
   if ( !mTempRubberBand )
   {
@@ -231,6 +308,7 @@ int QgsMapToolCapture::addVertex( const QgsPoint& point )
   {
     mTempRubberBand->reset( mCaptureMode == CapturePolygon ? QGis::Polygon : QGis::Line );
   }
+
   if ( mCaptureMode == CaptureLine )
   {
     mTempRubberBand->addPoint( point );

src/gui/qgsmapcanvastracer.h

@@ -140,6 +140,14 @@ class GUI_EXPORT QgsMapToolCapture : public QgsMapToolAdvancedDigitizing
      */
     void closePolygon();
 
+  private:
+    //! whether tracing has been requested by the user
+    bool tracingEnabled();
+    //! handle of mouse movement when tracing enabled and capturing has started
+    void tracingMouseMove( QgsMapMouseEvent* e );
+    //! handle of addition of clicked point (with the rest of the trace) when tracing enabled
+    void tracingAddVertex( const QgsPoint& point );
+
   private:
     /** Flag to indicate a map canvas capture operation is taking place */
     bool mCapturing;