keep existing BlockPath objects alive when updating

this enables adding state to the BlockPath objects

server/src/board/map/blockpath.cpp

@@ -47,6 +47,12 @@ static bool contains(const std::vector<std::pair<std::weak_ptr<T1>, T2>>& values
   return it != values.end();
 }
 
+template <typename T>
+static inline bool operator ==(const std::weak_ptr<T>& a, const std::weak_ptr<T>& b)
+{
+    return !a.owner_before(b) && !b.owner_before(a);
+}
+
 std::vector<std::shared_ptr<BlockPath>> BlockPath::find(BlockRailTile& startBlock)
 {
   const auto& node = startBlock.node()->get();
@@ -293,6 +299,23 @@ BlockPath::BlockPath(BlockRailTile& block, BlockSide side)
 {
 }
 
+bool BlockPath::operator ==(const BlockPath& other) const noexcept
+{
+  return
+    (&m_fromBlock == &other.m_fromBlock) &&
+    (m_fromSide == other.m_fromSide) &&
+    (m_toBlock == other.m_toBlock) &&
+    (m_toSide == other.m_toSide) &&
+    (m_tiles == other.m_tiles) &&
+    (m_turnouts == other.m_turnouts) &&
+    (m_directionControls == other.m_directionControls) &&
+    (m_crossings == other.m_crossings) &&
+    (m_bridges == other.m_bridges) &&
+    (m_signals == other.m_signals) &&
+    (m_nxButtonFrom == other.m_nxButtonFrom) &&
+    (m_nxButtonTo == other.m_nxButtonTo);
+}
+
 std::shared_ptr<NXButtonRailTile> BlockPath::nxButtonFrom() const
 {
   return m_nxButtonFrom.lock();

server/src/board/map/blockpath.hpp

@@ -69,6 +69,8 @@ class BlockPath : public Path, public std::enable_shared_from_this<BlockPath>
 
     BlockPath(BlockRailTile& block, BlockSide side);
 
+    bool operator ==(const BlockPath& other) const noexcept;
+
     bool hasNXButtons() const
     {
       return !m_nxButtonFrom.expired() && !m_nxButtonTo.expired();

server/src/board/tile/rail/blockrailtile.cpp

@@ -450,7 +450,35 @@ void BlockRailTile::setRotate(TileRotate value)
 
 void BlockRailTile::boardModified()
 {
-  m_paths = BlockPath::find(*this);
+  updatePaths(); //! \todo improvement: only update if a connected tile is changed
+}
+
+void BlockRailTile::updatePaths()
+{
+  auto current = std::move(m_paths);
+  m_paths.clear(); // make sure it is empty, it problably is after the move
+  auto found = BlockPath::find(*this);
+
+  while(!current.empty())
+  {
+    auto it = std::find_if(found.begin(), found.end(),
+      [&currentPath=*current.front()](const auto& foundPath)
+      {
+        return currentPath == *foundPath;
+      });
+
+    if(it != found.end())
+    {
+      found.erase(it);
+      m_paths.emplace_back(std::move(current.front()));
+    }
+    current.erase(current.begin());
+  }
+
+  for(auto& path : found)
+  {
+    m_paths.emplace_back(std::move(path));
+  }
 }
 
 void BlockRailTile::updateHeightWidthMax()

server/src/board/tile/rail/blockrailtile.hpp

@@ -50,6 +50,7 @@ class BlockRailTile : public RailTile
     std::vector<std::shared_ptr<BlockPath>> m_paths;
     std::array<std::weak_ptr<BlockPath>, 2> m_reservedPaths; // index is BlockSide
 
+    void updatePaths();
     void updateHeightWidthMax();
 
   protected: