DRC: allow testing against particular diff pair membership

pcbnew/dialogs/panel_setup_rules_help.md

@@ -94,6 +94,14 @@ True if any part of `A` lies within the given zone's outline.
     A.isPlated()
 True if `A` has a hole which is plated.
 
+    A.isDiffPair()
+True if `A` has a net that is part of a differential pair.
+
+    A.inDiffPair('<net_name>')
+True if `A` has net that is part of the specified differential pair.
+`<net_name>` is the base name of the differential pair.  For example, `inDiffPair('CLK')`
+matches items in the `CLK_P` and `CLK_N` nets.
+
     A.memberOf('<group_name>')
 True if `A` is a member of the given group. Includes nested membership.
 
@@ -161,7 +169,7 @@ For the latter use a `(layer "layer_name")` clause in the rule.
     # Specify a larger clearance around a particular diff-pair
     (rule "dp clearance"
         (constraint clearance (min "1.5mm"))
-        (condition "A.NetClass == 'diffPairClass' && B.NetClass != 'diffPairClass'"))
+        (condition "A.inDiffPair('CLK')"))
 
     # Specify a larger clearance around any diff-pair
     (rule "dp clearance"

pcbnew/drc/drc_engine.cpp

@@ -1155,8 +1155,8 @@ bool DRC_ENGINE::QueryWorstConstraint( DRC_CONSTRAINT_T aConstraintId, DRC_CONST
 
 
 // fixme: move two functions below to pcbcommon?
-static int matchDpSuffix( const wxString& aNetName, wxString& aComplementNet,
-                          wxString& aBaseDpName )
+int DRC_ENGINE::MatchDpSuffix( const wxString& aNetName, wxString& aComplementNet,
+                               wxString& aBaseDpName )
 {
     int rv = 0;
 
@@ -1219,7 +1219,7 @@ bool DRC_ENGINE::IsNetADiffPair( BOARD* aBoard, NETINFO_ITEM* aNet, int& aNetP,
     wxString refName = aNet->GetNetname();
     wxString dummy, coupledNetName;
 
-    if( int polarity = matchDpSuffix( refName, coupledNetName, dummy ) )
+    if( int polarity = MatchDpSuffix( refName, coupledNetName, dummy ) )
     {
         NETINFO_ITEM* net = aBoard->FindNet( coupledNetName );
 

pcbnew/drc/drc_engine.h

@@ -167,6 +167,16 @@ public:
 
     static bool IsNetADiffPair( BOARD* aBoard, NETINFO_ITEM* aNet, int& aNetP, int& aNetN );
 
+    /**
+     * Checks if the given net is a diff pair, returning its polarity and complement if so
+     * @param aNetName is the input net name, like DIFF_P
+     * @param aComplementNet will be filled with the complement, like DIFF_N
+     * @param aBaseDpName will be filled with the base name, like DIFF
+     * @return 1 if aNetName is the positive half of a pair, -1 if negative, 0 if not a diff pair
+     */
+    static int MatchDpSuffix( const wxString& aNetName, wxString& aComplementNet,
+                              wxString& aBaseDpName );
+
     static bool IsNetTie( BOARD_ITEM* aItem );
 
     static std::shared_ptr<SHAPE> GetShape( BOARD_ITEM* aItem, PCB_LAYER_ID aLayer );

pcbnew/pcb_expr_evaluator.cpp

@@ -566,6 +566,41 @@ static void isDiffPair( LIBEVAL::CONTEXT* aCtx, void* self )
 }
 
 
+static void inDiffPair( LIBEVAL::CONTEXT* aCtx, void* self )
+{
+    LIBEVAL::VALUE*   arg    = aCtx->Pop();
+    PCB_EXPR_VAR_REF* vref   = static_cast<PCB_EXPR_VAR_REF*>( self );
+    BOARD_ITEM*       item   = vref ? vref->GetObject( aCtx ) : nullptr;
+    LIBEVAL::VALUE*   result = aCtx->AllocValue();
+
+    result->Set( 0.0 );
+    aCtx->Push( result );
+
+    if( !arg )
+    {
+        aCtx->ReportError( wxString::Format( _( "Missing argument to '%s'" ),
+                                             wxT( "inDiffPair()" ) ) );
+        return;
+    }
+
+    if( item && item->IsConnected() )
+    {
+        NETINFO_ITEM* netinfo = static_cast<BOARD_CONNECTED_ITEM*>( item )->GetNet();
+
+        wxString refName = netinfo->GetNetname();
+        wxString baseName, coupledNet;
+
+        int polarity = DRC_ENGINE::MatchDpSuffix( refName, coupledNet, baseName );
+
+        if( polarity == 0 )
+            return;
+
+        if( baseName.Matches( arg->AsString() ) )
+            result->Set( 1.0 );
+    }
+}
+
+
 PCB_EXPR_BUILTIN_FUNCTIONS::PCB_EXPR_BUILTIN_FUNCTIONS()
 {
     RegisterAllFunctions();
@@ -584,6 +619,7 @@ void PCB_EXPR_BUILTIN_FUNCTIONS::RegisterAllFunctions()
     RegisterFunc( "memberOf('x')", memberOf );
     RegisterFunc( "fromTo('x','y')", exprFromTo );
     RegisterFunc( "isDiffPair()", isDiffPair );
+    RegisterFunc( "inDiffPair('x')", inDiffPair );
 }