drop the now-dead payloads from the sim-backed state-change events

TickAdvanced, BuildingBlocksChanged, ExpansionCostChanged, BossWaveUpdated and
ArtifactCountChanged all duplicated state the Simulation already owns. With
every subscriber re-reading from the sim, the fields had no readers left, so
the five events become payload-free refresh signals and the emitters keep the
values only as locals for change detection.

This makes the convention uniform: a state-change event backed by the
simulation carries nothing. Events whose state lives in the view (selection,
game speed, deconstruct and debug-draw modes) keep their payloads, since there
is no sim getter behind them.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/eventsystem/event/ArtifactCountChangedEvent.h

@@ -2,10 +2,9 @@
 
 #include "Event.h"
 
+// Fired when the collected artifact count changes. Carries no payload —
+// subscribers re-read Simulation::getArtifactCount(), and the win count from
+// world.artifacts.artifactWinCount.
 class ArtifactCountChangedEvent : public Event
 {
-public:
-    ArtifactCountChangedEvent(int count, int winCount) : count(count), winCount(winCount) {}
-    const int count;
-    const int winCount;
 };

src/lib/eventsystem/event/BossWaveUpdatedEvent.h

@@ -2,16 +2,11 @@
 #define BOSS_WAVE_UPDATED_EVENT_H
 
 #include "Event.h"
-#include "Tick.h"
 
+// Fired when the boss wave counter or its countdown changes. Carries no payload —
+// subscribers re-read Simulation::getBossWaveCounter() and getBossCountdownTicks().
 class BossWaveUpdatedEvent : public Event
 {
-public:
-	BossWaveUpdatedEvent(int counter, Tick countdownTicks)
-	    : counter(counter), countdownTicks(countdownTicks) {}
-	const int  counter;
-	const Tick countdownTicks;
 };
 
 #endif   // BOSS_WAVE_UPDATED_EVENT_H
-

src/lib/eventsystem/event/BuildingBlocksChangedEvent.h

@@ -3,12 +3,10 @@
 
 #include "Event.h"
 
+// Fired when the building block stock changes. Carries no payload — subscribers
+// re-read Simulation::getBuildingBlocksStock().
 class BuildingBlocksChangedEvent : public Event
 {
-public:
-	explicit BuildingBlocksChangedEvent(int blocks) : blocks(blocks) {}
-	const int blocks;
 };
 
 #endif   // BUILDING_BLOCKS_CHANGED_EVENT_H
-

src/lib/eventsystem/event/ExpansionCostChangedEvent.h

@@ -4,14 +4,11 @@
 #include "Event.h"
 
 // Fired when the current asteroid-expansion cost changes (REQ-EXP-COST): once at
-// startup and again after each expansion is purchased. Carries the cost in
+// startup and again after each expansion is purchased. Carries no payload — the
-// building blocks so the header Expand button can update its caption/enabled
+// header Expand button re-reads Simulation::getCurrentExpansionCost() to update
-// state (REQ-UI-EXPAND-BUTTON).
+// its caption and enabled state (REQ-UI-EXPAND-BUTTON).
 class ExpansionCostChangedEvent : public Event
 {
-public:
-	explicit ExpansionCostChangedEvent(int cost) : cost(cost) {}
-	const int cost;
 };
 
 #endif   // EXPANSION_COST_CHANGED_EVENT_H

src/lib/eventsystem/event/TickAdvancedEvent.h

@@ -2,14 +2,11 @@
 #define TICK_ADVANCED_EVENT_H
 
 #include "Event.h"
-#include "Tick.h"
 
+// Fired when the simulation tick advances. Carries no payload — subscribers
+// re-read Simulation::getCurrentTick().
 class TickAdvancedEvent : public Event
 {
-public:
-	explicit TickAdvancedEvent(Tick tick) : tick(tick) {}
-	const Tick tick;
 };
 
 #endif   // TICK_ADVANCED_EVENT_H
-

src/ui/BlueprintPanel.cpp

@@ -27,7 +27,6 @@ BlueprintPanel::BlueprintPanel(Simulation* sim, const GameConfig* config, QWidge
     : QWidget(parent)
     , m_sim(sim)
     , m_config(config)
-    , m_currentBlocks(0)
 {
     QVBoxLayout* layout = new QVBoxLayout(this);
     layout->setContentsMargins(4, 4, 4, 4);
@@ -71,9 +70,8 @@ void BlueprintPanel::onSelectionChanged(const std::vector<BuildingId>& ids)
     refreshButtonStates();
 }
 
-void BlueprintPanel::handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> event)
+void BlueprintPanel::handleEvent(std::shared_ptr<const BuildingBlocksChangedEvent> /*event*/)
 {
-    m_currentBlocks = event->blocks;
     refreshButtonStates();
 }
 
@@ -247,10 +245,12 @@ void BlueprintPanel::refreshButtonStates()
     // A construction site counts the same as an operational building (REQ-UI-BLUEPRINT-CREATE).
     m_createBtn->setEnabled(selectionHasPlaceableBuilding(*m_sim, m_selectedBuildingIds));
 
+    const int blocks = m_sim->getBuildingBlocksStock();
+
     for (int i = 0; i < static_cast<int>(m_blueprintButtons.size()); ++i)
     {
         const int  cost      = computeBlueprintCost(m_blueprints[static_cast<std::size_t>(i)]);
-        const bool canAfford = m_currentBlocks >= cost;
+        const bool canAfford = blocks >= cost;
         m_blueprintButtons[static_cast<std::size_t>(i)]->setEnabled(
             canAfford || m_activeIndex == i);
     }

src/ui/BlueprintPanel.h

@@ -53,10 +53,11 @@ private:
     void      loadFromDisk();
     void      saveToDisk() const;
 
+    // The simulation is the single source of truth for the block stock; the
+    // change event is only a refresh signal.
     Simulation*               m_sim;
     const GameConfig*         m_config;
     std::vector<BuildingId>     m_selectedBuildingIds;
-    int                       m_currentBlocks;
     std::optional<int>        m_activeIndex;  // nullopt = no blueprint selected
     std::vector<Blueprint>    m_blueprints;
     std::vector<QPushButton*> m_blueprintButtons;

src/ui/GameWorldView.cpp

@@ -403,26 +403,26 @@ void GameWorldView::onFrame()
         {
             m_lastTick = newTick;
             EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<TickAdvancedEvent>(newTick));
+                std::make_shared<TickAdvancedEvent>());
         }
         if (newBlocks != m_lastBlocks)
         {
             m_lastBlocks = newBlocks;
             EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BuildingBlocksChangedEvent>(newBlocks));
+                std::make_shared<BuildingBlocksChangedEvent>());
         }
         if (newExpCost != m_lastExpansionCost)
         {
             m_lastExpansionCost = newExpCost;
             EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<ExpansionCostChangedEvent>(newExpCost));
+                std::make_shared<ExpansionCostChangedEvent>());
         }
         if (newBoss != m_lastBossCounter || newCountdown != m_lastBossCountdown)
         {
             m_lastBossCounter   = newBoss;
             m_lastBossCountdown = newCountdown;
             EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BossWaveUpdatedEvent>(newBoss, newCountdown));
+                std::make_shared<BossWaveUpdatedEvent>());
         }
 
         // Unlocked building set changes only after a drop is applied or on Restart
@@ -485,8 +485,7 @@ void GameWorldView::onFrame()
     {
         m_lastArtifactCount = currentArtifactCount;
         EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ArtifactCountChangedEvent>(
+            std::make_shared<ArtifactCountChangedEvent>());
-                currentArtifactCount, m_sim->getConfig().world.artifacts.artifactWinCount));
     }
 
     update();

src/ui/HeaderBar.cpp

@@ -107,9 +107,9 @@ HeaderBar::~HeaderBar()
     unregisterForEvents();
 }
 
-void HeaderBar::handleEvent(std::shared_ptr<const TickAdvancedEvent> event)
+void HeaderBar::handleEvent(std::shared_ptr<const TickAdvancedEvent> /*event*/)
 {
-    const int totalSeconds = static_cast<int>(ticksToSeconds(event->tick));
+    const int totalSeconds = static_cast<int>(ticksToSeconds(m_sim->getCurrentTick()));
     m_timeLabel->setText(
         QString("%1:%2")
             .arg(totalSeconds / 60, 2, 10, QChar('0'))
@@ -195,22 +195,26 @@ void HeaderBar::handleEvent(std::shared_ptr<const GameSpeedChangedEvent> event)
     }
 }
 
-void HeaderBar::handleEvent(std::shared_ptr<const BossWaveUpdatedEvent> event)
+void HeaderBar::handleEvent(std::shared_ptr<const BossWaveUpdatedEvent> /*event*/)
 {
+    const Tick countdownTicks = m_sim->getBossCountdownTicks();
     const int  bossSeconds    = static_cast<int>(
-        ticksToSeconds(event->countdownTicks > 0 ? event->countdownTicks : 0));
+        ticksToSeconds(countdownTicks > 0 ? countdownTicks : 0));
 	m_bossWaveLabel->setText(
 		tr("Boss Wave #%1")
-		.arg(event->counter));
+		.arg(m_sim->getBossWaveCounter()));
 	m_nextBossLabel->setText(
 		tr("Next boss: %1:%2")
 		.arg(bossSeconds / 60)
 		.arg(bossSeconds % 60, 2, 10, QChar('0')));
 }
 
-void HeaderBar::handleEvent(std::shared_ptr<const ArtifactCountChangedEvent> event)
+void HeaderBar::handleEvent(std::shared_ptr<const ArtifactCountChangedEvent> /*event*/)
 {
-    m_artifactsLabel->setText(tr("Artifacts: %1/%2").arg(event->count).arg(event->winCount));
+    m_artifactsLabel->setText(
+        tr("Artifacts: %1/%2")
+            .arg(m_sim->getArtifactCount())
+            .arg(m_sim->getConfig().world.artifacts.artifactWinCount));
 }
 
 void HeaderBar::onSpeedButton(int index)

src/ui/HeaderBar.h

@@ -75,8 +75,8 @@ private:
 
     ItemIconCache*           m_itemIcons;  // Not owned; lives in MainWindow.
 
-    // The simulation is the single source of truth for the block stock and the
+    // The simulation is the single source of truth for everything the header
-    // expansion cost; the change events are only refresh signals.
+    // displays; the change events are only refresh signals.
     const Simulation*        m_sim;
 
     static const double kSpeeds[];