Make multiple names of the net on a track

Rather than moving the netname around, we want to keep the correct
number of netnames on a track such that there is always at least one
displayed on long tracks even when panning.

This reduces calculation time while keeping the netnames visible

Fixes https://gitlab.com/kicad/code/kicad/issues/12436

pcbnew/pcb_edit_frame.cpp

@@ -525,8 +525,9 @@ void PCB_EDIT_FRAME::redrawNetnames( wxTimerEvent& aEvent )
     for( PCB_TRACK* track : GetBoard()->Tracks() )
     {
         double lod = track->ViewGetLOD( GetNetnameLayer( track->GetLayer() ), view );
+        double scale = view->GetScale();
 
-        if( lod != track->GetCachedLOD() )
+        if( lod != track->GetCachedLOD() || scale != track->GetCachedScale() )
         {
             if( lod < view->GetScale() )
             {
@@ -535,6 +536,7 @@ void PCB_EDIT_FRAME::redrawNetnames( wxTimerEvent& aEvent )
             }
 
             track->SetCachedLOD( lod );
+            track->SetCachedScale( scale );
         }
     }
 

pcbnew/pcb_painter.cpp

@@ -636,42 +636,40 @@ void PCB_PAINTER::draw( const PCB_TRACK* aTrack, int aLayer )
 
         ClipLine( &clipBox, visibleSeg.A.x, visibleSeg.A.y, visibleSeg.B.x, visibleSeg.B.y );
 
+        wxString netName = UnescapeString( aTrack->GetShortNetname() );
+        size_t  num_char = netName.size();
+
         // Check if the track is long enough to have a netname displayed
-        int seg_minlength = track_width * 6;
+        int seg_minlength = track_width * num_char;
 
         if( visibleSeg.Length() < seg_minlength )
             return;
 
-        const     wxString& netName = UnescapeString( aTrack->GetShortNetname() );
         double    textSize = track_width;
         double    penWidth = textSize / 12.0;
-        VECTOR2D  textPosition = ( visibleSeg.A + visibleSeg.B ) / 2.0;  // center of the track
         EDA_ANGLE textOrientation;
-
-        // If the last position is still on the track, and it's some reasonable distance inside
-        // the viewport then don't move the netname; just use the last position.
-        if( visibleSeg.Distance( aTrack->m_LastNetnamePosition ) < penWidth
-                && clipBox.Inflate( -seg_minlength / 2 ).Contains( aTrack->m_LastNetnamePosition ) )
-        {
-            textPosition = aTrack->m_LastNetnamePosition;
-        }
-        else
-        {
-            aTrack->m_LastNetnamePosition = textPosition;
-        }
+        int num_names = 1;
 
         if( end.y == start.y ) // horizontal
         {
             textOrientation = ANGLE_HORIZONTAL;
+            num_names = std::max( num_names,
+                    static_cast<int>( aTrack->GetLength() / viewport.GetWidth() ) );
         }
         else if( end.x == start.x ) // vertical
         {
             textOrientation = ANGLE_VERTICAL;
+            num_names = std::max( num_names,
+                    static_cast<int>( aTrack->GetLength() / viewport.GetHeight() ) );
         }
         else
         {
             textOrientation = EDA_ANGLE( visibleSeg.B - visibleSeg.A ) + ANGLE_90;
             textOrientation.Normalize90();
+
+            double min_size = std::min( viewport.GetWidth(), viewport.GetHeight() );
+            num_names = std::max( num_names,
+                    static_cast<int>( aTrack->GetLength() / ( M_SQRT2 * min_size ) ) );
         }
 
         m_gal->SetIsStroke( true );
@@ -685,7 +683,14 @@ void PCB_PAINTER::draw( const PCB_TRACK* aTrack, int aLayer )
         m_gal->SetGlyphSize( VECTOR2D( textSize * 0.55, textSize * 0.55 ) );
         m_gal->SetHorizontalJustify( GR_TEXT_H_ALIGN_CENTER );
         m_gal->SetVerticalJustify( GR_TEXT_V_ALIGN_CENTER );
-        m_gal->BitmapText( netName, textPosition, textOrientation );
+
+        for( int ii = 0; ii < num_names; ++ii )
+        {
+            VECTOR2I textPosition =
+                      VECTOR2D( start ) * static_cast<double>( num_names - ii ) / ( num_names + 1 )
+                    + VECTOR2D( end ) * static_cast<double>( ii + 1 ) / ( num_names + 1 );
+            m_gal->BitmapText( netName, textPosition, textOrientation );
+        }
 
         return;
     }

pcbnew/pcb_track.cpp

@@ -53,6 +53,7 @@ PCB_TRACK::PCB_TRACK( BOARD_ITEM* aParent, KICAD_T idtype ) :
     BOARD_CONNECTED_ITEM( aParent, idtype )
 {
     m_Width = pcbIUScale.mmToIU( 0.2 );     // Gives a reasonable default width
+    m_CachedScale = -1.0;                   // Set invalid to force update
     m_CachedLOD = 0.0;                      // Set to always display
 }
 
@@ -667,6 +668,13 @@ double PCB_TRACK::ViewGetLOD( int aLayer, KIGFX::VIEW* aView ) const
                 return HIDE;
         }
 
+        // Pick the approximate size of the netname (square chars)
+        wxString netName = UnescapeString( GetShortNetname() );
+        size_t  num_chars = netName.size();
+
+        if( GetLength() < num_chars * GetWidth() )
+            return HIDE;
+
         // When drawing netnames, clip the track to the viewport
         VECTOR2I start( GetStart() );
         VECTOR2I end( GetEnd() );
@@ -676,10 +684,8 @@ double PCB_TRACK::ViewGetLOD( int aLayer, KIGFX::VIEW* aView ) const
         ClipLine( &clipBox, start.x, start.y, end.x, end.y );
 
         VECTOR2I line = ( end - start );
-        double length = line.EuclideanNorm();
 
-        // Check if the track is long enough to have a netname displayed
-        if( length < 6 * GetWidth() )
+        if( line.EuclideanNorm() == 0 )
             return HIDE;
 
         // Netnames will be shown only if zoom is appropriate

pcbnew/pcb_track.h

@@ -238,6 +238,24 @@ public:
         m_CachedLOD = aLOD;
     }
 
+    /**
+     * Get last used zoom scale for the track net name
+     * @return scale from GetScale()
+     */
+    double GetCachedScale()
+    {
+        return m_CachedScale;
+    }
+
+    /**
+     * Set the cached scale
+     * @param aScale value from GetScale()
+     */
+    void SetCachedScale( double aScale )
+    {
+        m_CachedScale = aScale;
+    }
+
     struct cmp_tracks
     {
         bool operator()( const PCB_TRACK* aFirst, const PCB_TRACK* aSecond ) const;
@@ -250,15 +268,13 @@ public:
 protected:
     void GetMsgPanelInfoBase_Common( EDA_DRAW_FRAME* aFrame, std::vector<MSG_PANEL_ITEM>& aList ) const;
 
-public:
-    mutable VECTOR2I m_LastNetnamePosition;
-
 protected:
     int      m_Width; ///< Thickness of track, or via diameter
     VECTOR2I m_Start; ///< Line start point
     VECTOR2I m_End;   ///< Line end point
 
     double   m_CachedLOD; ///< Last LOD used to draw this track's net
+    double   m_CachedScale; ///< Last zoom scale used to draw this track's net (we want to redraw when changing zoom)
 };