PCB_GRID_HELPER::BestSnapAnchor() fix overflow due to use of int.

GRID_HELPER::GetVisibleGrid() needs double, does not work with int (overflow).
Fixes #15389
https://gitlab.com/kicad/code/kicad/-/issues/15389

common/tool/grid_helper.cpp

@@ -56,11 +56,9 @@ VECTOR2I GRID_HELPER::GetGrid() const
 }
 
 
-VECTOR2I GRID_HELPER::GetVisibleGrid() const
+VECTOR2D GRID_HELPER::GetVisibleGrid() const
 {
-    VECTOR2D size = m_toolMgr->GetView()->GetGAL()->GetVisibleGridSize();
-
-    return VECTOR2I( KiROUND( size.x ), KiROUND( size.y ) );
+    return m_toolMgr->GetView()->GetGAL()->GetVisibleGridSize();
 }
 
 

include/tool/grid_helper.h

@@ -40,7 +40,7 @@ public:
     virtual ~GRID_HELPER();
 
     VECTOR2I GetGrid() const;
-    VECTOR2I GetVisibleGrid() const;
+    VECTOR2D GetVisibleGrid() const;
     VECTOR2I GetOrigin() const;
 
     void SetAuxAxes( bool aEnable, const VECTOR2I& aOrigin = VECTOR2I( 0, 0 ) );

pcbnew/tools/pcb_grid_helper.cpp

@@ -286,8 +286,10 @@ VECTOR2I PCB_GRID_HELPER::BestSnapAnchor( const VECTOR2I& aOrigin, const LSET& a
     // see https://gitlab.com/kicad/code/kicad/-/issues/5638
     // see https://gitlab.com/kicad/code/kicad/-/issues/7125
     // see https://gitlab.com/kicad/code/kicad/-/issues/12303
-    int snapScale = KiROUND( snapSize / m_toolMgr->GetView()->GetGAL()->GetWorldScale() );
-    int snapRange = m_enableGrid ? std::min( snapScale, GetVisibleGrid().x ) : snapScale;
+    double snapScale = snapSize / m_toolMgr->GetView()->GetGAL()->GetWorldScale();
+    // warning: GetVisibleGrid().x sometimes returns a value > INT_MAX. Intermediate calculation
+    // needs double.
+    int snapRange = KiROUND( m_enableGrid ? std::min( snapScale, GetVisibleGrid().x ) : snapScale );
     int snapDist = snapRange;
 
     //Respect limits of coordinates representation