Overhaul IsJunctionNeeded logic to support all the different cases.

Several clients were using this with different needs.  The API is
now more explicit (and there are more options under the hood).

Fixes https://gitlab.com/kicad/code/kicad/issues/9518

eeschema/bus-wire-junction.cpp

@@ -170,7 +170,7 @@ bool SCH_EDIT_FRAME::SchematicCleanUp( SCH_SCREEN* aScreen )
 
     for( SCH_ITEM* item : aScreen->Items().OfType( SCH_JUNCTION_T ) )
     {
-        if( !aScreen->IsJunctionNeeded( item->GetPosition() ) )
+        if( !aScreen->IsExplicitJunction( item->GetPosition() ) )
             remove_item( item );
         else
             junctions.push_back( static_cast<SCH_JUNCTION*>( item ) );

eeschema/sch_edit_frame.cpp

@@ -1214,7 +1214,7 @@ void SCH_EDIT_FRAME::AddItemToScreenAndUndoList( SCH_SCREEN* aScreen, SCH_ITEM*
             for( auto j = i + 1; j != pts.end(); j++ )
                 TrimWire( *i, *j );
 
-            if( aScreen->IsJunctionNeeded( *i, true ) )
+            if( aScreen->IsExplicitJunctionNeeded( *i ) )
                 AddJunction( aScreen, *i, true, false );
         }
 

eeschema/sch_line.cpp

@@ -564,7 +564,7 @@ SCH_LINE* SCH_LINE::MergeOverlap( SCH_SCREEN* aScreen, SCH_LINE* aLine, bool aCh
 
     bool touching = leftmost_end == rightmost_start;
 
-    if( touching && aCheckJunctions && aScreen->IsJunctionNeeded( leftmost_end ) )
+    if( touching && aCheckJunctions && aScreen->IsJunction( leftmost_end ) )
         return nullptr;
 
     // Make a new segment that merges the 2 segments

eeschema/sch_screen.cpp

@@ -400,10 +400,55 @@ std::set<SCH_ITEM*> SCH_SCREEN::MarkConnections( SCH_LINE* aSegment )
 }
 
 
-bool SCH_SCREEN::IsJunctionNeeded( const wxPoint& aPosition, bool aNew ) const
+bool SCH_SCREEN::IsJunction( const wxPoint& aPosition ) const
+{
+    bool hasExplicitJunction;
+    bool hasBusEntry;
+    bool isJunction = doIsJunction( aPosition, false, &hasExplicitJunction, &hasBusEntry );
+
+    return isJunction;
+}
+
+
+bool SCH_SCREEN::IsExplicitJunction( const wxPoint& aPosition ) const
+{
+    bool hasExplicitJunction;
+    bool hasBusEntry;
+    bool isJunction = doIsJunction( aPosition, false, &hasExplicitJunction, &hasBusEntry );
+
+    return isJunction && !hasBusEntry;
+}
+
+
+bool SCH_SCREEN::IsExplicitJunctionNeeded( const wxPoint& aPosition ) const
+{
+    bool hasExplicitJunction;
+    bool hasBusEntry;
+    bool isJunction = doIsJunction( aPosition, false, &hasExplicitJunction, &hasBusEntry );
+
+    return isJunction && !hasBusEntry && !hasExplicitJunction;
+}
+
+
+bool SCH_SCREEN::IsExplicitJunctionAllowed( const wxPoint& aPosition ) const
+{
+    bool hasExplicitJunction;
+    bool hasBusEntry;
+    bool isJunction = doIsJunction( aPosition, true, &hasExplicitJunction, &hasBusEntry );
+
+    return isJunction && !hasBusEntry;
+}
+
+
+
+bool SCH_SCREEN::doIsJunction( const wxPoint& aPosition, bool aBreakCrossings,
+                             bool* aHasExplicitJunctionDot, bool* aHasBusEntry ) const
 {
     enum layers { WIRES = 0, BUSES };
 
+    *aHasExplicitJunctionDot = false;
+    *aHasBusEntry = false;
+
     bool                          breakLines[ 2 ] = { false };
     std::unordered_set<int>       exitAngles[ 2 ];
     std::vector<const SCH_LINE*>  midPointLines[ 2 ];
@@ -419,8 +464,8 @@ bool SCH_SCREEN::IsJunctionNeeded( const wxPoint& aPosition, bool aNew ) const
         switch( item->Type() )
         {
         case SCH_JUNCTION_T:
-            if( aNew && item->HitTest( aPosition, -1 ) )
+            if( item->HitTest( aPosition, -1 ) )
-                return false;
+                *aHasExplicitJunctionDot = true;
 
             break;
 
@@ -445,7 +490,7 @@ bool SCH_SCREEN::IsJunctionNeeded( const wxPoint& aPosition, bool aNew ) const
             }
             else if( line->HitTest( aPosition, -1 ) )
             {
-                if( aNew )
+                if( aBreakCrossings )
                     breakLines[ layer ] = true;
 
                 // Defer any line midpoints until we know whether or not we're breaking them
@@ -461,6 +506,7 @@ bool SCH_SCREEN::IsJunctionNeeded( const wxPoint& aPosition, bool aNew ) const
                 exitAngles[ BUSES ].insert( uniqueAngle++ );
                 breakLines[ WIRES ] = true;
                 exitAngles[ WIRES ].insert( uniqueAngle++ );
+                *aHasBusEntry = true;
             }
 
             break;

eeschema/sch_screen.h

@@ -310,19 +310,38 @@ public:
     size_t CountConnectedItems( const wxPoint& aPos, bool aTestJunctions ) const;
 
     /**
-     * Test if a junction is required for the items at \a aPosition on the screen.
+     * Test if a junction is required for the items at \a aPosition on the screen.  Note that
+     * this coule be either an implied junction (bus entry) or an explicit junction (dot).
      *
      * A junction is required at \a aPosition if one of the following criteria is satisfied:
      *  - One wire midpoint and one or more wire endpoints.
      *  - Three or more wire endpoints.
      *  - One wire midpoint and a symbol pin.
      *  - Two or more wire endpoints and a symbol pin.
+     *  - One bus midpoint or endpoint and a bus entry.
      *
      * @param[in] aPosition The position to test.
-     * @param aNew Checks if a _new_ junction is needed, i.e. there isn't one already
      * @return True if a junction is required at \a aPosition.
      */
-    bool IsJunctionNeeded( const wxPoint& aPosition, bool aNew = false ) const;
+    bool IsJunction( const wxPoint& aPosition ) const;
+
+    /**
+     * Indicates that a junction dot is necessary at the given location.  See IsJunctionNeeded
+     * for more info.
+     */
+    bool IsExplicitJunction( const wxPoint& aPosition ) const;
+
+    /**
+     * Indicates that a junction dot is necessary at the given location, and does not yet exist.
+     * See IsJunctionNeeded for more info.
+     */
+    bool IsExplicitJunctionNeeded( const wxPoint& aPosition ) const;
+
+    /**
+     * Indicates that a juction dot may be placed at the given location.  See IsJunctionNeeded
+     * for more info.
+     */
+    bool IsExplicitJunctionAllowed( const wxPoint& aPosition ) const;
 
     /**
      * Test if \a aPosition is a connection point on \a aLayer.
@@ -486,6 +505,10 @@ public:
      */
     double m_LastZoomLevel;
 
+private:
+    bool doIsJunction( const wxPoint& aPosition, bool aBreakCrossings,
+                       bool* aHasExplicitJunctionDot, bool* aHasBusEntry ) const;
+
 private:
     friend SCH_EDIT_FRAME;     // Only to populate m_symbolInstances.
     friend SCH_SEXPR_PARSER;   // Only to load instance information from schematic file.

eeschema/tools/sch_drawing_tools.cpp

@@ -725,7 +725,7 @@ int SCH_DRAWING_TOOLS::SingleClickPlace( const TOOL_EVENT& aEvent )
             {
                 if( type == SCH_JUNCTION_T )
                 {
-                    if( !m_frame->GetScreen()->IsJunctionNeeded( cursorPos, true ) )
+                    if( !m_frame->GetScreen()->IsExplicitJunctionAllowed( cursorPos ) )
                     {
                         m_frame->ShowInfoBarError( _( "Junction location contains no joinable "
                                                       "wires and/or pins." ) );

eeschema/tools/sch_edit_tool.cpp

@@ -1018,14 +1018,14 @@ int SCH_EDIT_TOOL::DoDelete( const TOOL_EVENT& aEvent )
         }
     }
 
-    for( auto point : pts )
+    for( const wxPoint& point : pts )
     {
         SCH_ITEM* junction = screen->GetItem( point, 0, SCH_JUNCTION_T );
 
         if( !junction )
             continue;
 
-        if( junction->HasFlag( STRUCT_DELETED ) || !screen->IsJunctionNeeded( point ) )
+        if( junction->HasFlag( STRUCT_DELETED ) || !screen->IsExplicitJunction( point ) )
             m_frame->DeleteJunction( junction, appendToUndo );
     }
 
@@ -1682,7 +1682,7 @@ int SCH_EDIT_TOOL::BreakWire( const TOOL_EVENT& aEvent )
 
     if( !lines.empty() )
     {
-        if( m_frame->GetScreen()->IsJunctionNeeded( cursorPos, true ) )
+        if( m_frame->GetScreen()->IsExplicitJunctionNeeded( cursorPos ) )
             m_frame->AddJunction( m_frame->GetScreen(), cursorPos, true, false );
 
         m_frame->TestDanglingEnds();

eeschema/tools/sch_line_wire_bus_tool.cpp

@@ -959,7 +959,7 @@ void SCH_LINE_WIRE_BUS_TOOL::finishSegments()
 
     for( const wxPoint& pt : new_ends )
     {
-        if( m_frame->GetScreen()->IsJunctionNeeded( pt, true ) )
+        if( m_frame->GetScreen()->IsExplicitJunctionNeeded( pt ) )
             m_frame->AddJunction( m_frame->GetScreen(), pt, true, false );
     }
 
@@ -1024,7 +1024,7 @@ int SCH_LINE_WIRE_BUS_TOOL::AddJunctionsIfNeeded( const TOOL_EVENT& aEvent )
 
     for( const wxPoint& point : pts )
     {
-        if( m_frame->GetScreen()->IsJunctionNeeded( point, true ) )
+        if( m_frame->GetScreen()->IsExplicitJunctionNeeded( point ) )
             m_frame->AddJunction( m_frame->GetScreen(), point, true, false );
     }
 

eeschema/tools/sch_move_tool.cpp

@@ -497,7 +497,7 @@ int SCH_MOVE_TOOL::Main( const TOOL_EVENT& aEvent )
         // to denote the state.
         for( const DANGLING_END_ITEM& it : internalPoints )
         {
-            if( m_frame->GetScreen()->IsJunctionNeeded( it.GetPosition(), true ) )
+            if( m_frame->GetScreen()->IsExplicitJunctionNeeded( it.GetPosition()) )
                 m_frame->AddJunction( m_frame->GetScreen(), it.GetPosition(), true, false );
         }