Add an advanced config value for the minimum sliver

The hard coded value was too small for certain calculations.  Better to
have a configurable value that is initially set to our error level to
allow for deviations that don't meet the visibility test for spikes.
These have become more apparent with Clipper2

common/advanced_config.cpp

@@ -79,6 +79,7 @@ static const wxChar DRCEpsilon[] = wxT( "DRCEpsilon" );
  * Angle and width tolerances for copper and solder mask sliver detection.
  */
 static const wxChar DRCSliverWidthTolerance[] = wxT( "DRCSliverWidthTolerance" );
+static const wxChar DRCSliverMinimumLength[] = wxT( "DRCSliverMinimumLength" );
 static const wxChar DRCSliverAngleTolerance[] = wxT( "DRCSliverAngleTolerance" );
 
 /**
@@ -298,6 +299,7 @@ ADVANCED_CFG::ADVANCED_CFG()
     m_DRCEpsilon                = 0.0005;   // 0.5um is small enough not to materially violate
                                             // any constraints.
     m_SliverWidthTolerance      = 0.08;
+    m_SliverMinimumLength       = 0.0005;
     m_SliverAngleTolerance      = 20.0;
 
     m_HoleWallThickness         = 0.020;    // IPC-6012 says 15-18um; Cadence says at least
@@ -380,6 +382,9 @@ void ADVANCED_CFG::loadSettings( wxConfigBase& aCfg )
     configParams.push_back( new PARAM_CFG_DOUBLE( true, AC_KEYS::DRCSliverWidthTolerance,
                                                   &m_SliverWidthTolerance, m_SliverWidthTolerance, 0.01, 0.25 ) );
 
+    configParams.push_back( new PARAM_CFG_DOUBLE( true, AC_KEYS::DRCSliverMinimumLength,
+                                                  &m_SliverMinimumLength, m_SliverMinimumLength, 1e-9, 10 ) );
+
     configParams.push_back( new PARAM_CFG_DOUBLE( true, AC_KEYS::DRCSliverAngleTolerance,
                                                   &m_SliverAngleTolerance, m_SliverAngleTolerance, 1.0, 90.0 ) );
 

include/advanced_config.h

@@ -105,6 +105,7 @@ public:
      * Sliver tolerances for DRC.  Units are mm and deg.
      */
     double m_SliverWidthTolerance;
+    double m_SliverMinimumLength;
     double m_SliverAngleTolerance;
 
     /**

pcbnew/drc/drc_test_provider_sliver_checker.cpp

@@ -197,7 +197,7 @@ bool DRC_TEST_PROVIDER_SLIVER_CHECKER::Run()
         // We skip very small vertices: one cannot really compute a valid orientation of
         // such a vertex
         // So skip points near than min_len (in internal units).
-        const int min_len = 3;
+        const int min_len = pcbIUScale.mmToIU( ADVANCED_CFG::GetCfg().m_SliverMinimumLength );
 
         for( int jj = 0; jj < poly.OutlineCount(); ++jj )
         {