[FEATURE][layouts] Snapping to item bounds when creating new items

Previously snapping to item bounds would only occur when resizing
or moving items, now it also applies to item creation

Author: nyalldawson

python/gui/layout/qgslayoutviewmouseevent.sip

@@ -40,6 +40,14 @@ class QgsLayoutViewMouseEvent : QMouseEvent
  \param snap set to true to snap the point using the layout's snapping settings
 %End
 
+    void snapPoint( QGraphicsLineItem *horizontalSnapLine = 0, QGraphicsLineItem *verticalSnapLine = 0 );
+%Docstring
+ Manually triggers a snap for the mouse event position using the layout's snapper.
+
+ If the ``horizontalSnapLine`` and ``verticalSnapLine`` arguments are specified, then the snapper
+ will automatically display and position these lines to indicate snapping positions to item bounds.
+%End
+
     QPointF layoutPoint() const;
 %Docstring
  Returns the event point location in layout coordinates.

src/app/layout/qgslayoutdesignerdialog.cpp

@@ -141,6 +141,7 @@ QgsLayoutDesignerDialog::QgsLayoutDesignerDialog( QWidget *parent, Qt::WindowFla
 
   connect( mActionShowGuides, &QAction::triggered, this, &QgsLayoutDesignerDialog::showGuides );
   connect( mActionSnapGuides, &QAction::triggered, this, &QgsLayoutDesignerDialog::snapToGuides );
+  connect( mActionSmartGuides, &QAction::triggered, this, &QgsLayoutDesignerDialog::snapToItems );
 
   connect( mActionShowBoxes, &QAction::triggered, this, &QgsLayoutDesignerDialog::showBoxes );
 
@@ -344,6 +345,7 @@ void QgsLayoutDesignerDialog::setCurrentLayout( QgsLayout *layout )
   mActionSnapGrid->setChecked( mLayout->snapper().snapToGrid() );
   mActionShowGuides->setChecked( mLayout->guides().visible() );
   mActionSnapGuides->setChecked( mLayout->snapper().snapToGuides() );
+  mActionSmartGuides->setChecked( mLayout->snapper().snapToItems() );
   mActionShowBoxes->setChecked( mLayout->context().boundingBoxesVisible() );
 
   connect( mLayout->undoStack()->stack(), &QUndoStack::canUndoChanged, mActionUndo, &QAction::setEnabled );
@@ -460,6 +462,11 @@ void QgsLayoutDesignerDialog::snapToGuides( bool enabled )
   mLayout->snapper().setSnapToGuides( enabled );
 }
 
+void QgsLayoutDesignerDialog::snapToItems( bool enabled )
+{
+  mLayout->snapper().setSnapToItems( enabled );
+}
+
 void QgsLayoutDesignerDialog::closeEvent( QCloseEvent * )
 {
   emit aboutToClose();

src/app/layout/qgslayoutdesignerdialog.h

@@ -141,6 +141,11 @@ class QgsLayoutDesignerDialog: public QMainWindow, private Ui::QgsLayoutDesigner
      */
     void snapToGuides( bool enabled );
 
+    /**
+     * Toggles whether snapping to the item guides ("smart" guides) is \a enabled.
+     */
+    void snapToItems( bool enabled );
+
   signals:
 
     /**

src/gui/layout/qgslayoutmousehandles.cpp

@@ -408,9 +408,10 @@ Qt::CursorShape QgsLayoutMouseHandles::cursorForPosition( QPointF itemCoordPos )
         return Qt::SizeVerCursor;
       }
     case SelectItem:
-      // default:
       return Qt::ArrowCursor;
   }
+
+  return Qt::ArrowCursor;
 }
 
 QgsLayoutMouseHandles::MouseAction QgsLayoutMouseHandles::mouseActionForPosition( QPointF itemCoordPos )

src/gui/layout/qgslayoutview.cpp

@@ -74,6 +74,13 @@ void QgsLayoutView::setCurrentLayout( QgsLayout *layout )
   mSnapMarker->hide();
   layout->addItem( mSnapMarker.get() );
 
+  mHorizontalSnapLine.reset( createSnapLine() );
+  mHorizontalSnapLine->hide();
+  layout->addItem( mHorizontalSnapLine.get() );
+  mVerticalSnapLine.reset( createSnapLine() );
+  mVerticalSnapLine->hide();
+  layout->addItem( mVerticalSnapLine.get() );
+
   if ( mHorizontalRuler )
   {
     connect( &layout->guides(), &QAbstractItemModel::dataChanged, mHorizontalRuler, [ = ] { mHorizontalRuler->update(); } );
@@ -318,7 +325,11 @@ void QgsLayoutView::mouseMoveEvent( QMouseEvent *event )
   QPointF cursorPos = mapToScene( mMouseCurrentXY );
   if ( mTool )
   {
-    std::unique_ptr<QgsLayoutViewMouseEvent> me( new QgsLayoutViewMouseEvent( this, event, mTool->flags() & QgsLayoutViewTool::FlagSnaps ) );
+    std::unique_ptr<QgsLayoutViewMouseEvent> me( new QgsLayoutViewMouseEvent( this, event, false ) );
+    if ( mTool->flags() & QgsLayoutViewTool::FlagSnaps )
+    {
+      me->snapPoint( mHorizontalSnapLine.get(), mVerticalSnapLine.get() );
+    }
     if ( mTool->flags() & QgsLayoutViewTool::FlagSnaps )
     {
       //draw snapping point indicator
@@ -494,6 +505,16 @@ void QgsLayoutView::wheelZoom( QWheelEvent *event )
   }
 }
 
+QGraphicsLineItem *QgsLayoutView::createSnapLine() const
+{
+  std::unique_ptr< QGraphicsLineItem>  item( new QGraphicsLineItem( nullptr ) );
+  QPen pen = QPen( QColor( Qt::blue ) );
+  pen.setStyle( Qt::DotLine );
+  pen.setWidthF( 0.0 );
+  item->setPen( pen );
+  item->setZValue( QgsLayout::ZSmartGuide );
+  return item.release();
+}
 
 //
 // QgsLayoutViewSnapMarker

src/gui/layout/qgslayoutview.h

@@ -300,10 +300,14 @@ class GUI_EXPORT QgsLayoutView: public QGraphicsView
 
     std::unique_ptr< QgsLayoutViewSnapMarker > mSnapMarker;
 
+    std::unique_ptr< QGraphicsLineItem > mHorizontalSnapLine;
+    std::unique_ptr< QGraphicsLineItem > mVerticalSnapLine;
+
     int mCurrentPage = 0;
 
     friend class TestQgsLayoutView;
 
+    QGraphicsLineItem *createSnapLine() const;
 };
 
 

src/gui/layout/qgslayoutviewmouseevent.cpp

@@ -33,6 +33,14 @@ QgsLayoutViewMouseEvent::QgsLayoutViewMouseEvent( QgsLayoutView *view, QMouseEve
   }
 }
 
+void QgsLayoutViewMouseEvent::snapPoint( QGraphicsLineItem *horizontalSnapLine, QGraphicsLineItem *verticalSnapLine )
+{
+  if ( mView->currentLayout() )
+  {
+    mSnappedPoint = mView->currentLayout()->snapper().snapPoint( mLayoutPoint, mView->transform().m11(), mSnapped, horizontalSnapLine, verticalSnapLine );
+  }
+}
+
 QPointF QgsLayoutViewMouseEvent::layoutPoint() const
 {
   return mLayoutPoint;

src/gui/layout/qgslayoutviewmouseevent.h

@@ -21,6 +21,7 @@
 #include "qgis_gui.h"
 
 class QgsLayoutView;
+class QGraphicsLineItem;
 
 /**
  * \ingroup gui
@@ -52,6 +53,14 @@ class GUI_EXPORT QgsLayoutViewMouseEvent : public QMouseEvent
      */
     QgsLayoutViewMouseEvent( QgsLayoutView *view, QMouseEvent *event, bool snap = false );
 
+    /**
+     * Manually triggers a snap for the mouse event position using the layout's snapper.
+     *
+     * If the \a horizontalSnapLine and \a verticalSnapLine arguments are specified, then the snapper
+     * will automatically display and position these lines to indicate snapping positions to item bounds.
+     */
+    void snapPoint( QGraphicsLineItem *horizontalSnapLine = nullptr, QGraphicsLineItem *verticalSnapLine = nullptr );
+
     /**
      * Returns the event point location in layout coordinates.
      * \see pos()

src/ui/layout/qgslayoutdesignerbase.ui

@@ -127,6 +127,7 @@
     <addaction name="separator"/>
     <addaction name="mActionShowGuides"/>
     <addaction name="mActionSnapGuides"/>
+    <addaction name="mActionSmartGuides"/>
     <addaction name="mActionManageGuides"/>
     <addaction name="mActionClearGuides"/>
     <addaction name="separator"/>
@@ -451,6 +452,20 @@
     <string>Ctrl+Shift+B</string>
    </property>
   </action>
+  <action name="mActionSmartGuides">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="text">
+    <string>S&amp;mart Guides</string>
+   </property>
+   <property name="toolTip">
+    <string>Smart guides</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+Alt+;</string>
+   </property>
+  </action>
  </widget>
  <resources>
   <include location="../../../images/images.qrc"/>