diff --git a/src/gui/src/grid_window.cpp b/src/gui/src/grid_window.cpp
index 8c681e5..d0a69ef 100644
--- a/src/gui/src/grid_window.cpp
+++ b/src/gui/src/grid_window.cpp
@@ -17,10 +17,10 @@
 #include <utility>
 
 
-GridWindow::LineEvent::LineEvent(picross::ObserverEvent event, const picross::Line* line, unsigned int misc, const ObserverGrid& grid)
+GridWindow::LineEvent::LineEvent(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid)
     : m_event(event)
     , m_line_id()
-    , m_misc(misc)
+    , m_data(data)
     , m_grid(grid)
 {
     if (line) { m_line_id = std::make_optional<picross::LineId>(*line); }
@@ -310,7 +310,7 @@ void GridWindow::reset_solutions()
     text_buffer->buffer.appendf("Grid %s\n", picross::str_input_grid_size(grid).c_str());
 }
 
-void GridWindow::observer_callback(picross::ObserverEvent event, const picross::Line* line, unsigned int, unsigned int misc, const ObserverGrid& l_grid)
+void GridWindow::observer_callback(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& l_grid)
 {
     // Filter out events useless to the GUI
     if (event != picross::ObserverEvent::DELTA_LINE && event != picross::ObserverEvent::SOLVED_GRID && event != picross::ObserverEvent::PROGRESS)
@@ -329,7 +329,7 @@ void GridWindow::observer_callback(picross::ObserverEvent event, const picross::
                 ||  this->abort_solver_thread();
         });
     }
-    line_events.emplace_back(event, line, misc, l_grid);
+    line_events.emplace_back(event, line, data, l_grid);
 }
 
 unsigned int GridWindow::process_line_events(std::vector<LineEvent>& events)
@@ -343,7 +343,7 @@ unsigned int GridWindow::process_line_events(std::vector<LineEvent>& events)
         if (event.m_event == picross::ObserverEvent::PROGRESS)
         {
             // Only indicative
-            solver_progress = reinterpret_cast<const float&>(static_cast<const std::uint32_t&>(event.m_misc));
+            solver_progress = event.m_data.m_misc_f;
             continue;
         }
         assert(event.m_event == picross::ObserverEvent::DELTA_LINE || event.m_event == picross::ObserverEvent::SOLVED_GRID);
diff --git a/src/gui/src/grid_window.h b/src/gui/src/grid_window.h
index 11ae5a4..3d943a8 100644
--- a/src/gui/src/grid_window.h
+++ b/src/gui/src/grid_window.h
@@ -23,11 +23,11 @@ class GridWindow : public GridObserver
 public:
     struct LineEvent
     {
-        LineEvent(picross::ObserverEvent event, const picross::Line* line, unsigned int misc, const ObserverGrid& grid);
+        LineEvent(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid);
 
         picross::ObserverEvent          m_event;
         std::optional<picross::LineId>  m_line_id;
-        unsigned int                    m_misc;
+        picross::ObserverData           m_data;
         ObserverGrid                    m_grid;
     };
 public:
@@ -42,7 +42,7 @@ class GridWindow : public GridObserver
 
 private:
     void reset_solutions();
-    void observer_callback(picross::ObserverEvent event, const picross::Line* line, unsigned int, unsigned int, const ObserverGrid& grid) override;
+    void observer_callback(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid) override;
     unsigned int process_line_events(std::vector<LineEvent>& events);
     void solve_picross_grid();
     void save_grid();
diff --git a/src/picross/include/picross/picross_observer.h b/src/picross/include/picross/picross_observer.h
index ab77590..b613a30 100644
--- a/src/picross/include/picross/picross_observer.h
+++ b/src/picross/include/picross/picross_observer.h
@@ -9,6 +9,7 @@
  ******************************************************************************/
 #pragma once
 
+#include <cstdint>
 #include <functional>
 #include <ostream>
 #include <string>
@@ -20,10 +21,10 @@ namespace picross
 //
 // The observer is a function object with the following signature:
 //
-// void observer(Event event, const Line* line, unsigned int depth, unsigned int misc);
+// void observer(Event event, const Line* line, { uint32_t depth, uint32_t misc_i, float misc_f });
 //
-//  * event = KNOWN_LINE        line = known_line           depth is set        misc = nb_alternatives (before)
-//  * event = DELTA_LINE        line = delta                depth is set        misc = nb_alternatives (after)
+//  * event = KNOWN_LINE        line = known_line           depth is set        misc_i = nb_alternatives (before)
+//  * event = DELTA_LINE        line = delta                depth is set        misc_i = nb_alternatives (after)
 //
 //      A line of the output grid has been updated, the delta between the previous value of that line
 //      and the new one is given in event DELTA_LINE.
@@ -31,8 +32,8 @@ namespace picross
 //      The number of alternatives before (resp. after) the line solver are given in the event KNOWN_LINE
 //      (resp. DELTA_LINE).
 //
-//  * event = BRANCHING         line = known_line           depth >= 0          misc = nb_alternatives    (NODE)
-//  * event = BRANCHING         line = nullptr              depth > 0           misc = 0                  (EDGE)
+//  * event = BRANCHING         line = known_line           depth >= 0          misc_i = nb_alternatives    (NODE)
+//  * event = BRANCHING         line = nullptr              depth > 0           misc_i = 0                  (EDGE)
 //
 //      This event occurs when the algorithm is branching between several alternative solutions, or
 //      when it is going back to an earlier branch. Upon starting a new branch the depth is increased
@@ -43,19 +44,18 @@ namespace picross
 //          branching line and the number of alternatives, and the EDGE event each time an alternative
 //          of the branching line is being tested.
 //
-//  * event = SOLVED_GRID       line = nullptr              depth is set        misc = 0
+//  * event = SOLVED_GRID       line = nullptr              depth is set        misc_i = 0
 //
 //      A solution grid has been found. The sum of all the delta lines up until that stage is the solved grid.
 //
-//  * event = INTERNAL_STATE    line = nullptr              depth is set        misc = state
+//  * event = INTERNAL_STATE    line = nullptr              depth is set        misc_i = internal state
 //
 //      Internal state of the solver given as an integer
 //
-//  * event = PROGRESS          line = nullptr              deptb is set        misc = reinterpret_cast<uint32_t&>(progress);
+//  * event = PROGRESS          line = nullptr              depth is set        misc_f = progress_ratio
 //
-//      Progress is a float between 0.f and 1.f, whose binary representation is copied in the 'misc' integer.
-//
-enum class ObserverEvent {
+enum class ObserverEvent
+{
     KNOWN_LINE,
     DELTA_LINE,
     BRANCHING,
@@ -63,11 +63,17 @@ enum class ObserverEvent {
     INTERNAL_STATE,
     PROGRESS
 };
+struct ObserverData
+{
+    std::uint32_t   m_depth = 0u;
+    std::uint32_t   m_misc_i = 0u;
+    float           m_misc_f = 0.f;
+};
 class Line;
-using Observer = std::function<void(ObserverEvent,const Line*,unsigned int,unsigned int)>;
+using Observer = std::function<void(ObserverEvent,const Line*,const ObserverData&)>;
 
 std::ostream& operator<<(std::ostream& out, ObserverEvent event);
 
-std::string str_solver_internal_state(unsigned int internal_state);
+std::string str_solver_internal_state(std::uint32_t internal_state);
 
 } // namespace picross
diff --git a/src/picross/src/solver.cpp b/src/picross/src/solver.cpp
index e9e8000..b6e9b29 100644
--- a/src/picross/src/solver.cpp
+++ b/src/picross/src/solver.cpp
@@ -146,7 +146,7 @@ std::ostream& operator<<(std::ostream& out, ObserverEvent event)
     return out;
 }
 
-std::string str_solver_internal_state(unsigned int internal_state)
+std::string str_solver_internal_state(std::uint32_t internal_state)
 {
     std::stringstream ss;
     ss << static_cast<WorkGridState>(internal_state);
diff --git a/src/picross/src/work_grid.cpp b/src/picross/src/work_grid.cpp
index 3307cb9..ade44c2 100644
--- a/src/picross/src/work_grid.cpp
+++ b/src/picross/src/work_grid.cpp
@@ -66,18 +66,13 @@ void update_line_range(LineRange& range, const std::vector<bool>& source)
     assert(range.m_begin <= range.m_end);
 }
 
-template <typename RET_UINT>
-RET_UINT progress_bar(const std::pair<float, float>& progress_bar, LineAlternatives::NbAlt progress, LineAlternatives::NbAlt nb_alternatives)
+float progress_bar(const std::pair<float, float>& progress_bar, LineAlternatives::NbAlt progress, LineAlternatives::NbAlt nb_alternatives)
 {
-    static_assert(std::is_integral_v<RET_UINT> && std::is_unsigned_v<RET_UINT>);
-    static_assert(std::numeric_limits<RET_UINT>::digits >= std::numeric_limits<std::uint32_t>::digits);
     assert(progress <= nb_alternatives);
-    const float ratio_f = static_cast<float>(progress) / static_cast<float>(nb_alternatives);
-    assert(0.f <= ratio_f && ratio_f <= 1.f);
-    const auto progress_f = std::make_unique<float>(progress_bar.first + (progress_bar.second - progress_bar.first) * ratio_f);
-    // reinterpret as integer to go through the observer interface
-    const std::uint32_t ratio = *reinterpret_cast<const std::uint32_t*>(progress_f.get());
-    return static_cast<RET_UINT>(ratio);
+    const float ratio = static_cast<float>(progress) / static_cast<float>(nb_alternatives);
+    assert(0.f <= ratio && ratio <= 1.f);
+    const float progress_f = progress_bar.first + (progress_bar.second - progress_bar.first) * ratio;
+    return progress_f;
 }
 
 std::pair<float, float> nested_progress_bar(const std::pair<float, float>& progress_bar, LineAlternatives::NbAlt progress, LineAlternatives::NbAlt nb_alternatives)
@@ -323,7 +318,10 @@ Solver::Status WorkGrid<SolverPolicy>::line_solve(const Solver::SolutionFound& s
         {
             if (m_observer)
             {
-                m_observer(ObserverEvent::INTERNAL_STATE, nullptr, m_branching_depth, static_cast<unsigned int>(m_state));
+                ObserverData data;
+                data.m_depth = m_branching_depth;
+                data.m_misc_i = static_cast<std::uint32_t>(m_state);
+                m_observer(ObserverEvent::INTERNAL_STATE, nullptr, data);
             }
 
             switch (m_state)
@@ -430,7 +428,10 @@ Solver::Status WorkGrid<SolverPolicy>::solve(const Solver::SolutionFound& soluti
             assert(m_solver_policy.m_branching_allowed);
             if (m_observer)
             {
-                m_observer(ObserverEvent::INTERNAL_STATE, nullptr, m_branching_depth, static_cast<unsigned int>(m_state));
+                ObserverData data;
+                data.m_depth = m_branching_depth;
+                data.m_misc_i = static_cast<std::uint32_t>(m_state);
+                m_observer(ObserverEvent::INTERNAL_STATE, nullptr, data);
             }
 
             // Make a guess (branch search)
@@ -513,15 +514,21 @@ bool WorkGrid<SolverPolicy>::update_line(const LineSpan& line, unsigned int nb_a
 
     if (m_observer)
     {
+        ObserverData data;
+        data.m_depth = m_branching_depth;
+
         if (line_changed)
         {
-            m_observer(ObserverEvent::KNOWN_LINE, &observer_original_line, m_branching_depth, observer_original_nb_alt);
+            data.m_misc_i = observer_original_nb_alt;
+            m_observer(ObserverEvent::KNOWN_LINE, &observer_original_line, data);
             const Line delta = get_line(line_type, line_index) - observer_original_line;
-            m_observer(ObserverEvent::DELTA_LINE, &delta, m_branching_depth, nb_alt);
+            data.m_misc_i = nb_alt;
+            m_observer(ObserverEvent::DELTA_LINE, &delta, data);
         }
         else
         {
-            m_observer(ObserverEvent::KNOWN_LINE, &observer_original_line, m_branching_depth, nb_alt);
+            data.m_misc_i = nb_alt;
+            m_observer(ObserverEvent::KNOWN_LINE, &observer_original_line, data);
         }
     }
 
@@ -764,8 +771,10 @@ typename WorkGrid<SolverPolicy>::PassStatus WorkGrid<SolverPolicy>::full_grid_pa
         {
             if (m_observer)
             {
+                ObserverData data;
+                data.m_depth = m_branching_depth;
                 const Line contradictory_line = line_from_line_span(get_line(*it));
-                m_observer(ObserverEvent::KNOWN_LINE, &contradictory_line, m_branching_depth, 0);
+                m_observer(ObserverEvent::KNOWN_LINE, &contradictory_line, data);
             }
             break;
         }
@@ -867,7 +876,10 @@ typename WorkGrid<SolverPolicy>::ProbingResult WorkGrid<SolverPolicy>::probe(Lin
     if (m_observer)
     {
         const auto line_known_tiles = line_from_line_span(known_tiles);
-        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, m_branching_depth, nb_alt);
+        ObserverData data;
+        data.m_depth = m_branching_depth;
+        data.m_misc_i = nb_alt;
+        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, data);
     }
 
     if (m_grid_stats != nullptr)
@@ -891,7 +903,9 @@ typename WorkGrid<SolverPolicy>::ProbingResult WorkGrid<SolverPolicy>::probe(Lin
         probing_work_grid.configure(nested_solver_policy, WorkGridState::LINEAR_REDUCTION, nested_stats.get(), nested_progress.first, nested_progress.second);
         if (m_observer)
         {
-            m_observer(ObserverEvent::BRANCHING, nullptr, probing_work_grid.m_branching_depth, 0);
+            ObserverData data;
+            data.m_depth = probing_work_grid.m_branching_depth;
+            m_observer(ObserverEvent::BRANCHING, nullptr, data);
         }
 
         // Set one line in the new_grid according to the hypothesis we made. That line is then complete
@@ -940,7 +954,10 @@ typename WorkGrid<SolverPolicy>::ProbingResult WorkGrid<SolverPolicy>::probe(Lin
     if (m_observer)
     {
         const auto line_known_tiles = line_from_line_span(known_tiles);
-        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, m_branching_depth, nb_alt);
+        ObserverData data;
+        data.m_depth = m_branching_depth;
+        data.m_misc_i = nb_alt;
+        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, data);
     }
 
     if (!reduced_grid)
@@ -990,8 +1007,11 @@ Solver::Status WorkGrid<SolverPolicy>::branch(const Solver::SolutionFound& solut
 
     if (m_observer)
     {
+        ObserverData data;
+        data.m_depth = m_branching_depth;
+        data.m_misc_i = nb_alt;
         const auto line_known_tiles = line_from_line_span(known_tiles);
-        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, m_branching_depth, nb_alt);
+        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, data);
     }
 
     if (m_grid_stats != nullptr)
@@ -1019,7 +1039,9 @@ Solver::Status WorkGrid<SolverPolicy>::branch(const Solver::SolutionFound& solut
         branching_work_grid.configure(nested_solver_policy, WorkGridState::LINEAR_REDUCTION, nested_stats.get(), nested_progress.first, nested_progress.second);
         if (m_observer)
         {
-            m_observer(ObserverEvent::BRANCHING, nullptr, branching_work_grid.m_branching_depth, 0);
+            ObserverData data;
+            data.m_depth = branching_work_grid.m_branching_depth;
+            m_observer(ObserverEvent::BRANCHING, nullptr, data);
         }
 
         // Set one line in the new_grid according to the hypothesis we made. That line is then complete
@@ -1050,7 +1072,10 @@ Solver::Status WorkGrid<SolverPolicy>::branch(const Solver::SolutionFound& solut
         progress++;
         if (m_observer)
         {
-            m_observer(ObserverEvent::PROGRESS, nullptr, branching_work_grid.m_branching_depth, progress_bar<unsigned int>(m_progress_bar, progress, nb_alt));
+            ObserverData data;
+            data.m_depth = branching_work_grid.m_branching_depth;
+            data.m_misc_f = progress_bar(m_progress_bar, progress, nb_alt);
+            m_observer(ObserverEvent::PROGRESS, nullptr, data);
         }
 
         if (status == Solver::Status::ABORTED)
@@ -1063,8 +1088,11 @@ Solver::Status WorkGrid<SolverPolicy>::branch(const Solver::SolutionFound& solut
     // Repeat start branching message
     if (m_observer)
     {
+        ObserverData data;
+        data.m_depth = m_branching_depth;
+        data.m_misc_i = nb_alt;
         const auto line_known_tiles = line_from_line_span(known_tiles);
-        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, m_branching_depth, nb_alt);
+        m_observer(ObserverEvent::BRANCHING, &line_known_tiles, data);
     }
 
     return flag_solution_found ? Solver::Status::OK : Solver::Status::CONTRADICTORY_GRID;
@@ -1088,7 +1116,12 @@ bool WorkGrid<SolverPolicy>::found_solution(const Solver::SolutionFound& solutio
     assert(is_valid_solution());
     const auto adjusted_branching_depth = m_branching_depth + m_probing_depth_incr;
     if (m_grid_stats != nullptr) { m_grid_stats->nb_solutions++; }
-    if (m_observer) { m_observer(ObserverEvent::SOLVED_GRID, nullptr, adjusted_branching_depth, 0); }
+    if (m_observer)
+    {
+        ObserverData data;
+        data.m_depth = adjusted_branching_depth;
+        m_observer(ObserverEvent::SOLVED_GRID, nullptr, data);
+    }
 
     // Shallow copy of only the grid data
     return solution_found(Solver::Solution{ OutputGrid(*this), adjusted_branching_depth, FULL_SOLUTION });
diff --git a/src/utils/include/utils/console_observer.h b/src/utils/include/utils/console_observer.h
index ae6be71..e8e3e62 100644
--- a/src/utils/include/utils/console_observer.h
+++ b/src/utils/include/utils/console_observer.h
@@ -19,7 +19,7 @@ class ConsoleObserver final : public GridObserver
     void verify_against_goal(const picross::OutputGrid& goal);
 
 private:
-    void observer_callback(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc, const ObserverGrid& grid) override;
+    void observer_callback(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid) override;
 
 private:
     std::ostream&                      m_ostream;
diff --git a/src/utils/include/utils/console_progress_observer.h b/src/utils/include/utils/console_progress_observer.h
index 88a4ab9..41bae6a 100644
--- a/src/utils/include/utils/console_progress_observer.h
+++ b/src/utils/include/utils/console_progress_observer.h
@@ -13,7 +13,7 @@ class ConsoleProgressObserver final
 public:
     explicit ConsoleProgressObserver(std::ostream& ostream);
 
-    void operator()(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc);
+    void operator()(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data);
 
 private:
     std::ostream&   m_ostream;
diff --git a/src/utils/include/utils/grid_observer.h b/src/utils/include/utils/grid_observer.h
index a9d926c..adfd66f 100644
--- a/src/utils/include/utils/grid_observer.h
+++ b/src/utils/include/utils/grid_observer.h
@@ -35,13 +35,13 @@ class GridObserver
     explicit GridObserver(const picross::InputGrid& grid);
     virtual ~GridObserver() = default;
 
-    void operator()(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc);
+    void operator()(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data);
 
 protected:
     void observer_clear();
 
 private:
-    virtual void observer_callback(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc, const ObserverGrid& grid) = 0;
+    virtual void observer_callback(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid) = 0;
 
 private:
     std::vector<ObserverGrid> m_grids;
diff --git a/src/utils/src/console_observer.cpp b/src/utils/src/console_observer.cpp
index 7b879a8..eebe965 100644
--- a/src/utils/src/console_observer.cpp
+++ b/src/utils/src/console_observer.cpp
@@ -19,7 +19,7 @@ void ConsoleObserver::verify_against_goal(const picross::OutputGrid& goal)
     m_goal = goal;
 }
 
-void ConsoleObserver::observer_callback(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc, const ObserverGrid& grid)
+void ConsoleObserver::observer_callback(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data, const ObserverGrid& grid)
 {
     m_ostream << event;
     switch (event)
@@ -29,28 +29,28 @@ void ConsoleObserver::observer_callback(picross::ObserverEvent event, const picr
         {
             m_ostream << " NODE";
             m_ostream << " known: " << picross::str_line_full(*line);
-            m_ostream << " depth: " << depth;
-            m_ostream << " nb_alt: " << misc;
+            m_ostream << " depth: " << data.m_depth;
+            m_ostream << " nb_alt: " << data.m_misc_i;
         }
         else
         {
             m_ostream << " EDGE";
-            m_ostream << " depth: " << depth;
+            m_ostream << " depth: " << data.m_depth;
         }
         break;
 
     case picross::ObserverEvent::KNOWN_LINE:
         assert(line);
         m_ostream << " known: " << picross::str_line_full(*line)
-                  << " depth: " << depth
-                  << " nb_alt: " << misc;
+                  << " depth: " << data.m_depth
+                  << " nb_alt: " << data.m_misc_i;
         break;
 
     case picross::ObserverEvent::DELTA_LINE:
         assert(line);
         m_ostream << " delta: " << picross::str_line_full(*line)
-                  << " depth: " << depth
-                  << " nb_alt: " << misc;
+                  << " depth: " << data.m_depth
+                  << " nb_alt: " << data.m_misc_i;
         break;
 
     case picross::ObserverEvent::SOLVED_GRID:
@@ -59,16 +59,15 @@ void ConsoleObserver::observer_callback(picross::ObserverEvent event, const picr
         break;
 
     case picross::ObserverEvent::INTERNAL_STATE:
-        m_ostream << " state: " << picross::str_solver_internal_state(misc)
-                  << " depth: " << depth;
+        m_ostream << " state: " << picross::str_solver_internal_state(data.m_misc_i)
+                  << " depth: " << data.m_depth;
         break;
 
     case picross::ObserverEvent::PROGRESS:
     {
-        const auto progress_i = std::make_unique<std::uint32_t>(static_cast<std::uint32_t>(misc));
-        const float progress_f = *reinterpret_cast<const float*>(progress_i.get());
-        m_ostream << " progress: " << progress_f
-                  << " depth: " << depth;
+        const float& progress = data.m_misc_f;
+        m_ostream << " progress: " << progress
+                  << " depth: " << data.m_depth;
         break;
     }
 
@@ -78,7 +77,7 @@ void ConsoleObserver::observer_callback(picross::ObserverEvent event, const picr
     m_ostream << std::endl;
 
     // Detect discrepancy with set goal
-    if (m_goal.has_value() && depth == 0 && event == picross::ObserverEvent::DELTA_LINE)
+    if (m_goal.has_value() && data.m_depth == 0 && event == picross::ObserverEvent::DELTA_LINE)
     {
         assert(line);
         picross::LineId line_id(*line);
diff --git a/src/utils/src/console_progress_observer.cpp b/src/utils/src/console_progress_observer.cpp
index 138b9dc..e3371f3 100644
--- a/src/utils/src/console_progress_observer.cpp
+++ b/src/utils/src/console_progress_observer.cpp
@@ -11,7 +11,7 @@ ConsoleProgressObserver::ConsoleProgressObserver(std::ostream& ostream)
 {
 }
 
-void ConsoleProgressObserver::operator()(picross::ObserverEvent event, const picross::Line*, unsigned int depth, unsigned int misc)
+void ConsoleProgressObserver::operator()(picross::ObserverEvent event, const picross::Line*, const picross::ObserverData& data)
 {
     switch (event)
     {
@@ -25,14 +25,13 @@ void ConsoleProgressObserver::operator()(picross::ObserverEvent event, const pic
 
     case picross::ObserverEvent::PROGRESS:
     {
-        const auto progress_i = std::make_unique<std::uint32_t>(static_cast<std::uint32_t>(misc));
-        const float progress_f = *reinterpret_cast<const float*>(progress_i.get());
-        if ((progress_f - m_previous_progress) > 0.001f)
+        const float& progress = data.m_misc_f;
+        if ((progress - m_previous_progress) > 0.001f)
         {
-            m_ostream << "Progress: " << progress_f
-                      << " (depth: " << depth << ")"
+            m_ostream << "Progress: " << progress
+                      << " (depth: " << data.m_depth << ")"
                       << std::endl;
-            m_previous_progress = progress_f;
+            m_previous_progress = progress;
         }
         break;
     }
diff --git a/src/utils/src/grid_observer.cpp b/src/utils/src/grid_observer.cpp
index 35e245d..9abb1dc 100644
--- a/src/utils/src/grid_observer.cpp
+++ b/src/utils/src/grid_observer.cpp
@@ -53,7 +53,7 @@ GridObserver::GridObserver(const picross::InputGrid& grid)
 {
 }
 
-void GridObserver::operator()(picross::ObserverEvent event, const picross::Line* line, unsigned int depth, unsigned int misc)
+void GridObserver::operator()(picross::ObserverEvent event, const picross::Line* line, const picross::ObserverData& data)
 {
     const auto width = m_grids[0].width();
     const auto height = m_grids[0].height();
@@ -64,20 +64,20 @@ void GridObserver::operator()(picross::ObserverEvent event, const picross::Line*
         if (!line)
         {
             // BRANCHING EDGE event
-            assert(depth > 0u);
-            if (depth > m_current_depth)
+            assert(data.m_depth > 0u);
+            if (data.m_depth > m_current_depth)
             {
-                assert(depth == m_current_depth + 1u);
+                assert(data.m_depth == m_current_depth + 1u);
                 const unsigned int start_fill_depth = static_cast<unsigned int>(m_grids.size());
-                for (unsigned int d = start_fill_depth; d <= depth; d++)
+                for (unsigned int d = start_fill_depth; d <= data.m_depth; d++)
                 {
                     m_grids.emplace_back(width, height, d);
                 }
             }
-            assert(depth < m_grids.size());
-            m_grids[depth] = m_grids[depth - 1];
+            assert(data.m_depth < m_grids.size());
+            m_grids[data.m_depth] = m_grids[data.m_depth - 1];
         }
-        m_current_depth = depth;
+        m_current_depth = data.m_depth;
         break;
 
     case picross::ObserverEvent::KNOWN_LINE:
@@ -85,7 +85,7 @@ void GridObserver::operator()(picross::ObserverEvent event, const picross::Line*
 
     case picross::ObserverEvent::DELTA_LINE:
     {
-        assert(depth == m_current_depth);
+        assert(data.m_depth == m_current_depth);
         const size_t index = line->index();
         ObserverGrid& grid = m_grids.at(m_current_depth);
         if (line->type() == picross::Line::ROW)
@@ -122,7 +122,7 @@ void GridObserver::operator()(picross::ObserverEvent event, const picross::Line*
     }
 
     assert(m_current_depth < m_grids.size());
-    observer_callback(event, line, depth, misc, m_grids.at(m_current_depth));
+    observer_callback(event, line, data, m_grids.at(m_current_depth));
 }
 
 void GridObserver::observer_clear()