[advanced digitizing] Implement visual construction guides

python/PyQt6/core/auto_generated/qgscadutils.sip.in

@@ -132,7 +132,6 @@ Returns the recent CAD point at the specified ``index`` (in map coordinates).
 
 .. versionadded:: 3.22
 %End
-
 %Property( name = cadPointList, get = _cadPointList, set = _setCadPointList )
         void _setCadPointList( const QList< QgsPointXY > &list );
         QList< QgsPointXY > _cadPointList() const;

python/PyQt6/gui/auto_generated/qgsadvanceddigitizingdockwidget.sip.in

@@ -277,7 +277,36 @@ Sets whether M is enabled
 
     bool constructionMode() const;
 %Docstring
-construction mode is used to draw intermediate points. These points won't be given any further (i.e. to the map tools)
+Returns whether the construction mode is activated. The construction mode is used to draw intermediate
+points that will not be part of a geometry being digitized.
+%End
+
+    QgsVectorLayer *constructionGuidesLayer() const;
+%Docstring
+Returns the vector layer within which construction guides are stored.
+
+.. versionadded:: 3.40
+%End
+
+    bool showConstructionGuides() const;
+%Docstring
+Returns whether the construction guides are visible.
+
+.. versionadded:: 3.40
+%End
+
+    bool snapToConstructionGuides() const;
+%Docstring
+Returns whether points should snap to construction guides.
+
+.. versionadded:: 3.40
+%End
+
+    bool recordConstructionGuides() const;
+%Docstring
+Returns whether construction guides are being recorded.
+
+.. versionadded:: 3.40
 %End
 
     Qgis::BetweenLineConstraint betweenLineConstraint() const;

python/core/auto_generated/qgscadutils.sip.in

@@ -132,7 +132,6 @@ Returns the recent CAD point at the specified ``index`` (in map coordinates).
 
 .. versionadded:: 3.22
 %End
-
 %Property( name = cadPointList, get = _cadPointList, set = _setCadPointList )
         void _setCadPointList( const QList< QgsPointXY > &list );
         QList< QgsPointXY > _cadPointList() const;

python/gui/auto_generated/qgsadvanceddigitizingdockwidget.sip.in

@@ -277,7 +277,36 @@ Sets whether M is enabled
 
     bool constructionMode() const;
 %Docstring
-construction mode is used to draw intermediate points. These points won't be given any further (i.e. to the map tools)
+Returns whether the construction mode is activated. The construction mode is used to draw intermediate
+points that will not be part of a geometry being digitized.
+%End
+
+    QgsVectorLayer *constructionGuidesLayer() const;
+%Docstring
+Returns the vector layer within which construction guides are stored.
+
+.. versionadded:: 3.40
+%End
+
+    bool showConstructionGuides() const;
+%Docstring
+Returns whether the construction guides are visible.
+
+.. versionadded:: 3.40
+%End
+
+    bool snapToConstructionGuides() const;
+%Docstring
+Returns whether points should snap to construction guides.
+
+.. versionadded:: 3.40
+%End
+
+    bool recordConstructionGuides() const;
+%Docstring
+Returns whether construction guides are being recorded.
+
+.. versionadded:: 3.40
 %End
 
     Qgis::BetweenLineConstraint betweenLineConstraint() const;

src/core/qgscadutils.cpp

@@ -48,8 +48,8 @@ QgsCadUtils::AlignMapPointOutput QgsCadUtils::alignMapPoint( const QgsPointXY &o
   res.softLockX = std::numeric_limits<double>::quiet_NaN();
   res.softLockY = std::numeric_limits<double>::quiet_NaN();
 
-  // try to snap to anything
-  const QgsPointLocator::Match snapMatch = ctx.snappingUtils->snapToMap( originalMapPoint, nullptr, true );
+  // try to snap to project layer(s) as well as visible construction guides
+  QgsPointLocator::Match snapMatch = ctx.snappingUtils->snapToMap( originalMapPoint, nullptr, true );
   res.snapMatch = snapMatch;
   QgsPointXY point = snapMatch.isValid() ? snapMatch.point() : originalMapPoint;
   QgsPointXY edgePt0, edgePt1;

src/core/qgscadutils.h

@@ -195,7 +195,6 @@ class CORE_EXPORT QgsCadUtils
          */
         QQueue< QgsPointLocator::Match > lockedSnapVertices() const { return mLockedSnapVertices; } SIP_SKIP;
 
-
 #ifdef SIP_RUN
         SIP_PROPERTY( name = cadPointList, get = _cadPointList, set = _setCadPointList )
 #endif

src/gui/qgsadvanceddigitizingcanvasitem.cpp

@@ -28,6 +28,7 @@ QgsAdvancedDigitizingCanvasItem::QgsAdvancedDigitizingCanvasItem( QgsMapCanvas *
   , mSnapPen( QPen( QColor( 127, 0, 0, 150 ), 1 ) )
   , mSnapLinePen( QPen( QColor( 127, 0, 0, 150 ), 1, Qt::DashLine ) )
   , mCursorPen( QPen( QColor( 127, 127, 127, 255 ), 1 ) )
+  , mConstructionGuidesPen( QPen( QColor( 20, 210, 150 ), 1, Qt::DashLine ) )
   , mAdvancedDigitizingDockWidget( cadDockWidget )
 {
 }
@@ -37,6 +38,27 @@ void QgsAdvancedDigitizingCanvasItem::paint( QPainter *painter )
   if ( !mAdvancedDigitizingDockWidget->cadEnabled() )
     return;
 
+  painter->setRenderHint( QPainter::Antialiasing );
+  painter->setCompositionMode( QPainter::CompositionMode_Difference );
+
+  // Draw construction guides
+  if ( mAdvancedDigitizingDockWidget->showConstructionGuides() )
+  {
+    if ( QgsVectorLayer *constructionGuidesLayer = mAdvancedDigitizingDockWidget->constructionGuidesLayer() )
+    {
+      QgsFeatureIterator it = constructionGuidesLayer->getFeatures( QgsFeatureRequest().setNoAttributes().setFilterRect( mMapCanvas->mapSettings().visibleExtent() ) );
+      QgsFeature feature;
+      painter->setPen( mConstructionGuidesPen );
+      while ( it.nextFeature( feature ) )
+      {
+        QgsGeometry geom = feature.geometry();
+        geom.mapToPixel( *mMapCanvas->getCoordinateTransform() );
+        const QPolygonF polygon = geom.asQPolygonF();
+        painter->drawPolyline( polygon );
+      }
+    }
+  }
+
   // Use visible polygon rather than extent to properly handle rotated maps
   QPolygonF mapPoly = mMapCanvas->mapSettings().visiblePolygon();
   const double canvasWidth = QLineF( mapPoly[0], mapPoly[1] ).length();
@@ -83,9 +105,6 @@ void QgsAdvancedDigitizingCanvasItem::paint( QPainter *painter )
     snapSegmentPix2 = toCanvasCoordinates( snappedSegment[1] );
   }
 
-  painter->setRenderHint( QPainter::Antialiasing );
-  painter->setCompositionMode( QPainter::CompositionMode_Difference );
-
   // Draw point snap
   if ( curPointExist && snappedToVertex )
   {
@@ -226,7 +245,7 @@ void QgsAdvancedDigitizingCanvasItem::paint( QPainter *painter )
     }
   }
 
-  // Draw constr
+  // Draw constraints
   if ( mAdvancedDigitizingDockWidget->betweenLineConstraint() == Qgis::BetweenLineConstraint::NoConstraint )
   {
     if ( curPointExist && previousPointExist )

src/gui/qgsadvanceddigitizingcanvasitem.h

@@ -60,6 +60,7 @@ class GUI_EXPORT QgsAdvancedDigitizingCanvasItem : public QgsMapCanvasItem
     QPen mSnapPen;
     QPen mSnapLinePen;
     QPen mCursorPen;
+    QPen mConstructionGuidesPen;
     QgsAdvancedDigitizingDockWidget *mAdvancedDigitizingDockWidget = nullptr;
 };