pcbnew: Remove snapping to hidden items

Items and layers that are hidden in the view should not be used as snap
points.  This happens in multiple locations:
1) Grid Helper for normal tools
2) TOOL_BASE::snapToItem for router

Resolves KiPro Issue #116

Fixes: lp:1833128
* https://bugs.launchpad.net/kicad/+bug/1833128

pcbnew/router/pns_kicad_iface.cpp

@@ -1069,6 +1069,23 @@ bool PNS_KICAD_IFACE::IsAnyLayerVisible( const LAYER_RANGE& aLayer )
 }
 
 
+bool PNS_KICAD_IFACE::IsItemVisible( const PNS::ITEM* aItem )
+{
+    if( !m_view )
+        return false;
+
+    auto item = aItem->Parent();
+    auto activeLayers = m_view->GetPainter()->GetSettings()->GetActiveLayers();
+    bool isHighContrast = m_view->GetPainter()->GetSettings()->GetHighContrast();
+
+    if( m_view->IsVisible( item ) && ( !isHighContrast || activeLayers.count( item->GetLayer() ) )
+            && item->ViewGetLOD( item->GetLayer(), m_view ) < m_view->GetScale() )
+        return true;
+
+    return false;
+}
+
+
 void PNS_KICAD_IFACE::SyncWorld( PNS::NODE *aWorld )
 {
     int worstPadClearance = 0;

pcbnew/router/pns_kicad_iface.h

@@ -53,6 +53,7 @@ public:
     void SyncWorld( PNS::NODE* aWorld ) override;
     void EraseView() override;
     bool IsAnyLayerVisible( const LAYER_RANGE& aLayer ) override;
+    bool IsItemVisible( const PNS::ITEM* aItem ) override;
     void HideItem( PNS::ITEM* aItem ) override;
     void DisplayItem( const PNS::ITEM* aItem, int aColor = 0, int aClearance = 0, bool aEdit = false ) override;
     void AddItem( PNS::ITEM* aItem ) override;

pcbnew/router/pns_router.h

@@ -95,6 +95,7 @@ enum DRAG_MODE
         virtual void AddItem( ITEM* aItem ) = 0;
         virtual void RemoveItem( ITEM* aItem ) = 0;
         virtual bool IsAnyLayerVisible( const LAYER_RANGE& aLayer ) = 0;
+        virtual bool IsItemVisible( const PNS::ITEM* aItem ) = 0;
         virtual void DisplayItem( const ITEM* aItem, int aColor = -1, int aClearance = -1, bool aEdit = false ) = 0;
         virtual void HideItem( ITEM* aItem ) = 0;
         virtual void Commit() = 0;

pcbnew/router/pns_tool_base.cpp

@@ -382,7 +382,7 @@ const VECTOR2I TOOL_BASE::snapToItem( bool aEnabled, ITEM* aItem, VECTOR2I aP)
 {
     VECTOR2I anchor;
 
-    if( !aItem || !aEnabled )
+    if( !aItem || !aEnabled || !m_iface->IsItemVisible( aItem ) )
     {
         return m_gridHelper->Align( aP );
     }

pcbnew/tools/grid_helper.cpp

@@ -35,12 +35,12 @@ using namespace std::placeholders;
 #include <class_module.h>
 #include <class_zone.h>
 
+#include <gal/graphics_abstraction_layer.h>
+#include <geometry/shape_line_chain.h>
+#include <math/vector2d.h>
 #include <painter.h>
 #include <view/view.h>
 #include <view/view_controls.h>
-#include <gal/graphics_abstraction_layer.h>
-
-#include <geometry/shape_line_chain.h>
 
 #include "grid_helper.h"
 
@@ -51,6 +51,7 @@ GRID_HELPER::GRID_HELPER( PCB_BASE_FRAME* aFrame ) :
     m_enableSnap = true;
     m_enableGrid = true;
     m_snapSize = 100;
+    m_snapItem = nullptr;
     KIGFX::VIEW* view = m_frame->GetCanvas()->GetView();
 
     m_viewAxis.SetSize( 20000 );
@@ -228,7 +229,8 @@ std::set<BOARD_ITEM*> GRID_HELPER::queryVisible( const BOX2I& aArea,
         BOARD_ITEM* item = static_cast<BOARD_ITEM*>( it.first );
 
         // The item must be visible and on an active layer
-        if( view->IsVisible( item ) && ( !isHighContrast || activeLayers.count( it.second ) ) )
+        if( view->IsVisible( item ) && ( !isHighContrast || activeLayers.count( it.second ) )
+                && item->ViewGetLOD( it.second, view ) < view->GetScale() )
             items.insert ( item );
     }
 
@@ -310,6 +312,9 @@ BOARD_ITEM* GRID_HELPER::GetSnapped( void ) const
 void GRID_HELPER::computeAnchors( BOARD_ITEM* aItem, const VECTOR2I& aRefPos, bool aFrom )
 {
     VECTOR2I origin;
+    auto     view = m_frame->GetCanvas()->GetView();
+    auto     activeLayers = view->GetPainter()->GetSettings()->GetActiveLayers();
+    bool     isHighContrast = view->GetPainter()->GetSettings()->GetHighContrast();
 
     switch( aItem->Type() )
     {
@@ -319,8 +324,12 @@ void GRID_HELPER::computeAnchors( BOARD_ITEM* aItem, const VECTOR2I& aRefPos, bo
 
             for( auto pad : mod->Pads() )
             {
+                // Getting pads from the module requires re-checking that the pad is shown
                 if( ( aFrom || m_frame->Settings().m_MagneticPads == CAPTURE_ALWAYS )
-                    && pad->GetBoundingBox().Contains( wxPoint( aRefPos.x, aRefPos.y ) ) )
+                        && pad->GetBoundingBox().Contains( wxPoint( aRefPos.x, aRefPos.y ) )
+                        && view->IsVisible( pad )
+                        && ( !isHighContrast || activeLayers.count( pad->GetLayer() ) )
+                        && pad->ViewGetLOD( pad->GetLayer(), view ) < view->GetScale() )
                 {
                     addAnchor( pad->GetPosition(), CORNER | SNAPPABLE, pad );
                     break;