GRID_HELPER: Keep edited items out of snap

Distinguish between the snap-from and snap-to items.  Previously, we
used the SELECTED or DRAGGED flags but the flagging arcitecture was
inherently fragile.  This specifies items directly that should not be
used as snap targets.

Fixes: lp:1802795
* https://bugs.launchpad.net/kicad/+bug/1802795

pcbnew/tools/edit_tool.cpp

@@ -366,6 +366,16 @@ int EDIT_TOOL::Main( const TOOL_EVENT& aEvent )
     controls->SetAutoPan( true );
 
     auto curr_item = static_cast<BOARD_ITEM*>( selection.Front() );
+    std::vector<BOARD_ITEM*> sel_items;
+
+    for( auto it : selection )
+    {
+        auto item = dynamic_cast<BOARD_ITEM*>( it );
+
+        if( item )
+            sel_items.push_back( item );
+    }
+
     bool restore_state = false;
     VECTOR2I totalMovement;
     GRID_HELPER grid( editFrame );
@@ -385,7 +395,8 @@ int EDIT_TOOL::Main( const TOOL_EVENT& aEvent )
         {
             if( m_dragging && evt->Category() == TC_MOUSE )
             {
-                m_cursor = grid.BestSnapAnchor( controls->GetMousePosition(), item_layers );
+                m_cursor = grid.BestSnapAnchor( controls->GetMousePosition(),
+                        item_layers, sel_items );
                 controls->ForceCursorPosition(true, m_cursor );
                 VECTOR2I movement( m_cursor - prevPos );
                 selection.SetReferencePoint( m_cursor );
@@ -438,15 +449,6 @@ int EDIT_TOOL::Main( const TOOL_EVENT& aEvent )
                         }
                     }
 
-                    for( auto item : selection )
-                    {
-                        item->SetFlags( IS_DRAGGED ); //todo: flags structure rework
-
-                        if( auto module = dyn_cast<MODULE*>( item ) )
-                            module->RunOnChildren( [&] ( BOARD_ITEM* bitem )
-                                    { bitem->SetFlags( IS_DRAGGED ); } );
-                    }
-
                     editFrame->UndoRedoBlock( true );
                     m_cursor = controls->GetCursorPosition();
 
@@ -567,15 +569,6 @@ int EDIT_TOOL::Main( const TOOL_EVENT& aEvent )
     if( unselect || restore_state )
         m_toolMgr->RunAction( PCB_ACTIONS::selectionClear, true );
 
-    for( auto item : selection )
-    {
-        item->ClearFlags( IS_DRAGGED ); //todo: flags structure rework
-
-        if( auto module = dyn_cast<MODULE*>( item ) )
-            module->RunOnChildren( [&] ( BOARD_ITEM* bitem )
-                    { bitem->SetFlags( IS_DRAGGED ); } );
-    }
-
     if( restore_state )
         m_commit->Revert();
     else

pcbnew/tools/grid_helper.cpp

@@ -226,7 +226,8 @@ VECTOR2I GRID_HELPER::BestDragOrigin( const VECTOR2I &aMousePos, BOARD_ITEM* aIt
 }
 
 
-std::set<BOARD_ITEM*> GRID_HELPER::queryVisible( const BOX2I& aArea ) const
+std::set<BOARD_ITEM*> GRID_HELPER::queryVisible( const BOX2I& aArea,
+        const std::vector<BOARD_ITEM*> aSkip ) const
 {
     std::set<BOARD_ITEM*> items;
     std::vector<KIGFX::VIEW::LAYER_ITEM_PAIR> selectedItems;
@@ -241,14 +242,15 @@ std::set<BOARD_ITEM*> GRID_HELPER::queryVisible( const BOX2I& aArea ) const
         BOARD_ITEM* item = static_cast<BOARD_ITEM*>( it.first );
 
         // The item must be visible and on an active layer
-        // It cannot be moving as a moving item is being snapped _from_
-        // rather than considered a potential target
         if( view->IsVisible( item )
-                && ( !isHighContrast || activeLayers.count( it.second ) )
+                && ( !isHighContrast || activeLayers.count( it.second ) ) )
-                && !item->IsDragging() )
             items.insert ( item );
     }
 
+
+    for( auto ii : aSkip )
+        items.erase( ii );
+
     return items;
 }
 
@@ -256,17 +258,22 @@ std::set<BOARD_ITEM*> GRID_HELPER::queryVisible( const BOX2I& aArea ) const
 VECTOR2I GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, BOARD_ITEM* aDraggedItem )
 {
     LSET layers;
+    std::vector<BOARD_ITEM*> item;
 
     if( aDraggedItem )
+    {
         layers = aDraggedItem->GetLayerSet();
+        item.push_back( aDraggedItem );
+    }
     else
         layers = LSET::AllLayersMask();
 
-    return BestSnapAnchor( aOrigin, layers );
+    return BestSnapAnchor( aOrigin, layers, item );
 }
 
 
-VECTOR2I GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLayers )
+VECTOR2I GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLayers,
+        const std::vector<BOARD_ITEM*> aSkip )
 {
     double worldScale = m_frame->GetGalCanvas()->GetGAL()->GetWorldScale();
     int snapRange = (int) ( m_snapSize / worldScale );
@@ -275,7 +282,7 @@ VECTOR2I GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLaye
 
     clearAnchors();
 
-    for( BOARD_ITEM* item : queryVisible( bb ) )
+    for( BOARD_ITEM* item : queryVisible( bb, aSkip ) )
     {
         computeAnchors( item, aOrigin );
     }

pcbnew/tools/grid_helper.h

@@ -57,7 +57,8 @@ public:
 
     VECTOR2I BestDragOrigin( const VECTOR2I& aMousePos, BOARD_ITEM* aItem );
     VECTOR2I BestSnapAnchor( const VECTOR2I& aOrigin, BOARD_ITEM* aDraggedItem );
-    VECTOR2I BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLayers );
+    VECTOR2I BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& aLayers,
+            const std::vector<BOARD_ITEM*> aSkip = {} );
 
     void SetSnap( bool aSnap )
     {
@@ -94,7 +95,8 @@ private:
 
     std::vector<ANCHOR> m_anchors;
 
-    std::set<BOARD_ITEM*> queryVisible( const BOX2I& aArea ) const;
+    std::set<BOARD_ITEM*> queryVisible( const BOX2I& aArea,
+            const std::vector<BOARD_ITEM*> aSkip ) const;
 
     void addAnchor( const VECTOR2I& aPos, int aFlags = CORNER | SNAPPABLE, BOARD_ITEM* aItem = NULL )
     {

pcbnew/tools/point_editor.cpp

@@ -364,7 +364,8 @@ int POINT_EDITOR::OnSelectionChange( const TOOL_EVENT& aEvent )
             }
 
             //TODO: unify the constraints to solve simultaneously instead of sequentially
-            m_editedPoint->SetPosition( grid.BestSnapAnchor( evt->Position(), snapLayers ) );
+            m_editedPoint->SetPosition( grid.BestSnapAnchor( evt->Position(),
+                    snapLayers, { item } ) );
             bool enableAltConstraint = !!evt->Modifier( MD_CTRL );
 
             if( enableAltConstraint != (bool) m_altConstraint )  // alternative constraint
@@ -375,7 +376,8 @@ int POINT_EDITOR::OnSelectionChange( const TOOL_EVENT& aEvent )
             else
                 m_editedPoint->ApplyConstraint();
 
-            m_editedPoint->SetPosition( grid.BestSnapAnchor( m_editedPoint->GetPosition(), snapLayers ) );
+            m_editedPoint->SetPosition( grid.BestSnapAnchor( m_editedPoint->GetPosition(),
+                    snapLayers, { item } ) );
 
             updateItem();
             updatePoints();