allow to (multi) select scrap

src/lib/sim/EntityHitTest.cpp

@@ -1,9 +1,11 @@
 #include "EntityHitTest.h"
 
+#include <algorithm>
 #include <cmath>
 
 #include "EntityAdmin.h"
 #include "PositionComponent.h"
+#include "ScrapDataComponent.h"
 #include "StationBodyComponent.h"
 #include "HealthComponent.h"
 
@@ -54,3 +56,48 @@ entt::entity entityAtWorldPos(EntityAdmin& admin, QVector2D worldPos)
 
     return bestShip;
 }
+
+entt::entity scrapAtWorldPos(EntityAdmin& admin, QVector2D worldPos)
+{
+    // Slightly larger than the scrap's rendered radius (0.2 tiles) so small piles
+    // remain easy to click; tunable.
+    constexpr float kScrapHitRadiusSquared = 0.35f * 0.35f;
+    entt::entity bestScrap = entt::null;
+    float bestDistSquared = kScrapHitRadiusSquared;
+
+    admin.forEach<ScrapDataComponent, PositionComponent>(
+        [&](entt::entity entity, const ScrapDataComponent& /*sd*/, const PositionComponent& pos)
+        {
+            const float dx = pos.value.x() - worldPos.x();
+            const float dy = pos.value.y() - worldPos.y();
+            const float distSquared = dx * dx + dy * dy;
+            if (distSquared < bestDistSquared)
+            {
+                bestDistSquared = distSquared;
+                bestScrap = entity;
+            }
+        });
+
+    return bestScrap;
+}
+
+std::vector<entt::entity> scrapInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB)
+{
+    const int minX = std::min(tileA.x(), tileB.x());
+    const int maxX = std::max(tileA.x(), tileB.x());
+    const int minY = std::min(tileA.y(), tileB.y());
+    const int maxY = std::max(tileA.y(), tileB.y());
+
+    std::vector<entt::entity> result;
+    admin.forEach<ScrapDataComponent, PositionComponent>(
+        [&](entt::entity entity, const ScrapDataComponent& /*sd*/, const PositionComponent& pos)
+        {
+            const int tileX = static_cast<int>(std::floor(pos.value.x()));
+            const int tileY = static_cast<int>(std::floor(pos.value.y()));
+            if (tileX >= minX && tileX <= maxX && tileY >= minY && tileY <= maxY)
+            {
+                result.push_back(entity);
+            }
+        });
+    return result;
+}

src/lib/sim/EntityHitTest.h

@@ -1,5 +1,8 @@
 #pragma once
 
+#include <vector>
+
+#include <QPoint>
 #include <QVector2D>
 
 #include "entt/entity/entity.hpp"
@@ -7,3 +10,12 @@
 class EntityAdmin;
 
 entt::entity entityAtWorldPos(EntityAdmin& admin, QVector2D worldPos);
+
+// Returns the nearest scrap pile whose center is within the scrap pick radius of
+// worldPos, or entt::null if none (REQ-UI-SCRAP-CLICK-SELECT). Scrap is picked only
+// after actors: entityAtWorldPos never returns scrap (scrap has no HealthComponent).
+entt::entity scrapAtWorldPos(EntityAdmin& admin, QVector2D worldPos);
+
+// Returns every scrap pile whose position falls within the inclusive tile rectangle
+// spanned by tileA and tileB, in any corner order (REQ-UI-SCRAP-MULTI-SELECT).
+std::vector<entt::entity> scrapInBox(EntityAdmin& admin, QPoint tileA, QPoint tileB);