Push m_forceMarkObstaclesMode down into the DRAGGER.

The existing flag was never read anyway, and it's only the DRAGGER
that knows that the starting state is already colliding and that we
need to force mark-obstacles mode.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/8641

pcbnew/router/pns_dragger.cpp

@@ -41,6 +41,7 @@ DRAGGER::DRAGGER( ROUTER* aRouter ) :
     m_dragStatus = false;
     m_currentMode = RM_MarkObstacles;
     m_freeAngleMode = false;
+    m_forceMarkObstaclesMode = false;
 }
 
 
@@ -112,11 +113,16 @@ bool DRAGGER::startDragSegment( const VECTOR2D& aP, SEGMENT* aSeg )
     m_draggedLine      = m_world->AssembleLine( aSeg, &m_draggedSegmentIndex );
     m_lastDragSolution = m_draggedLine;
 
-    if( m_shove )
+    if ( m_world->CheckColliding( &m_draggedLine ) )
     {
-        m_shove->SetInitialLine( m_draggedLine );
+        // If we're already in a state that violates DRC then there's not much we can do but
+        // switch to mark obstacles mode (and ignore other DRC violation).
+        m_forceMarkObstaclesMode = true;
     }
 
+    if( m_shove )
+        m_shove->SetInitialLine( m_draggedLine );
+
     auto distA = ( aP - aSeg->Seg().A ).EuclideanNorm();
     auto distB = ( aP - aSeg->Seg().B ).EuclideanNorm();
 
@@ -153,6 +159,13 @@ bool DRAGGER::startDragArc( const VECTOR2D& aP, ARC* aArc )
     m_shove->SetInitialLine( m_draggedLine );
     m_mode = DM_ARC;
 
+    if ( m_world->CheckColliding( &m_draggedLine ) )
+    {
+        // If we're already in a state that violates DRC then there's not much we can do but
+        // switch to mark obstacles mode (and ignore other DRC violation).
+        m_forceMarkObstaclesMode = true;
+    }
+
     return true;
 }
 
@@ -164,6 +177,13 @@ bool DRAGGER::startDragVia( VIA* aVia )
 
     m_mode = DM_VIA;
 
+    if ( m_world->CheckColliding( aVia ) )
+    {
+        // If we're already in a state that violates DRC then there's not much we can do but
+        // switch to mark obstacles mode (and ignore other DRC violation).
+        m_forceMarkObstaclesMode = true;
+    }
+
     return true;
 }
 
@@ -209,6 +229,7 @@ bool DRAGGER::Start( const VECTOR2I& aP, ITEM_SET& aPrimitives )
     m_draggedItems.Clear();
     m_currentMode = Settings().Mode();
     m_freeAngleMode = (m_mode & DM_FREE_ANGLE);
+    m_forceMarkObstaclesMode = false;
     m_lastValidPoint = aP;
 
     m_mouseTrailTracer.Clear();
@@ -320,7 +341,7 @@ bool DRAGGER::dragMarkObstacles( const VECTOR2I& aP )
     }
     }
 
-    if( Settings().AllowDRCViolations() )
+    if( m_forceMarkObstaclesMode || Settings().AllowDRCViolations() )
         m_dragStatus = true;
     else
         m_dragStatus = !m_lastNode->CheckColliding( m_draggedItems );
@@ -718,7 +739,7 @@ bool DRAGGER::FixRoute()
                 return false;
         }
 
-        if( !m_dragStatus && !Settings().AllowDRCViolations() )
+        if( !m_dragStatus && !Settings().AllowDRCViolations() && !m_forceMarkObstaclesMode )
             return false;
 
         Router()->CommitRouting( node );
@@ -735,7 +756,7 @@ bool DRAGGER::Drag( const VECTOR2I& aP )
 
     bool ret = false;
 
-    if( m_freeAngleMode )
+    if( m_freeAngleMode || m_forceMarkObstaclesMode )
     {
         ret = dragMarkObstacles( aP );
     }

pcbnew/router/pns_dragger.h

@@ -157,6 +157,7 @@ private:
 
     ///< If true, moves the connection lines without maintaining 45 degrees corners
     bool                   m_freeAngleMode;
+    bool                   m_forceMarkObstaclesMode;
     MOUSE_TRAIL_TRACER     m_mouseTrailTracer;
 };
 

pcbnew/router/pns_router.cpp

@@ -189,16 +189,10 @@ bool ROUTER::StartDragging( const VECTOR2I& aP, ITEM_SET aStartItems, int aDragM
     if( aStartItems.Count( ITEM::SOLID_T ) == aStartItems.Size() )
     {
         m_dragger = std::make_unique<COMPONENT_DRAGGER>( this );
-        m_forceMarkObstaclesMode = true;
         m_state = DRAG_COMPONENT;
     }
     else
     {
-        if( aDragMode & DM_FREE_ANGLE )
-            m_forceMarkObstaclesMode = true;
-        else
-            m_forceMarkObstaclesMode = false;
-
         m_dragger = std::make_unique<DRAGGER>( this );
         m_state = DRAG_SEGMENT;
     }
@@ -420,8 +414,6 @@ bool ROUTER::StartRouting( const VECTOR2I& aP, ITEM* aStartItem, int aLayer )
     if( !isStartingPointRoutable( aP, aStartItem, aLayer ) )
         return false;
 
-    m_forceMarkObstaclesMode = false;
-
     switch( m_mode )
     {
     case PNS_MODE_ROUTE_SINGLE:

pcbnew/router/pns_router.h

@@ -248,7 +248,6 @@ private:
     ROUTER_IFACE*     m_iface;
 
     int               m_iterLimit;
-    bool              m_forceMarkObstaclesMode = false;
 
     ROUTING_SETTINGS* m_settings;
     SIZES_SETTINGS    m_sizes;