fix issue where beams were also disappearing while the game was paused

src/balancing/ArenaView.cpp

@@ -40,7 +40,6 @@ ArenaView::ArenaView(ArenaSimulation* sim, const VisualsConfig* visuals,
     : QOpenGLWidget(parent)
     , m_sim(sim)
     , m_visuals(visuals)
-    , m_wallMs(0)
     , m_gameSpeedMultiplier(1.0)
     , m_prevNonZeroSpeed(1.0)
     , m_rng(std::random_device{}())
@@ -99,7 +98,6 @@ void ArenaView::togglePause()
 void ArenaView::onFrame()
 {
     const qint64 elapsed = m_frameTimer.restart();
-    m_wallMs += elapsed;
 
     {
         const int ticks = m_tickDriver.advance(
@@ -120,12 +118,14 @@ void ArenaView::onFrame()
         }
     }
 
-    // Expire old beams
+    // Expire old beams. Lifetime is measured in game ticks so beams stay
+    // visible while the simulation is paused or slowed (REQ-SHP-FIRING-BEAM).
     {
+        const Tick now = m_sim->currentTick();
         std::vector<ActiveBeam> live;
         for (const ActiveBeam& b : m_activeBeams)
         {
-            if (m_wallMs - b.emittedWallMs < kBeamLifetimeMs)
+            if (now - b.event.emittedAt < kBeamLifetimeTicks)
             {
                 live.push_back(b);
             }
@@ -165,7 +165,6 @@ void ArenaView::handleEvent(std::shared_ptr<const BeamFiredEvent> event)
 
     ActiveBeam beam;
     beam.event         = *event;
-    beam.emittedWallMs = m_wallMs;
     beam.targetOffset  = QVector2D(radius * std::cos(angle),
                                    radius * std::sin(angle));
     m_activeBeams.push_back(beam);