Fix: becs.h had a few bugs that I didn't catch around deleting entities

Add: Particle sim test example1
Add: build script for example1
Add: raylib gitmodule for example1

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "examples/example1/external/raylib"]
+	path = examples/example1/external/raylib
+	url = https://github.com/raysan5/raylib

becs.h

@@ -202,6 +202,11 @@ static void BECS_ComponentPoolRemove(BECS_ComponentPool *pool, BECS_Entity entit
 
         pool->denseEntityMapping[index] = last_entity;
         pool->sparseArray[last_entity] = index;
+        pool->count--;
+    }
+    else
+    {
+        pool->count--;
     }
 
     pool->sparseArray[entity] = UINT32_MAX;
@@ -321,6 +326,7 @@ BECS_Entity BECS_EntityCreate(BECS_ECS *ecs)
         entity = ecs->freeEntities[--ecs->freeEntityCount];
         ecs->entitySignatures[entity] = 0;
         ecs->aliveEntities[entity] = true;
+        ecs->entityCount++;
         return entity;
     }
 

examples/example1/build.bat

@@ -0,0 +1,16 @@
+@echo off
+
+REM Build Script for Example 1
+
+mkdir build
+
+git submodule update --init
+
+REM pushd ".\external\raylib\"
+REM cmake -S . -B build
+REM cmake --build build --config Release
+REM popd
+
+pushd ".\build"
+cl /Zi raylib.lib user32.lib opengl32.lib gdi32.lib winmm.lib msvcrt.lib shell32.lib "..\example1.c" -Ic:"\external\raylib\build\raylib\include" /link /libpath:c:"..\external\raylib\build\raylib\Release" /NODEFAULTLIB:libcmt /NODEFAULTLIB:msvcrt /NODEFAULTLIB:libcmtd
+popd

examples/example1/example1.c

@@ -0,0 +1,123 @@
+#define BECS_MAX_ENTITIES 20
+#define BECS_MAX_COMPONENTS 4
+#define BECS_IMPLEMENTATION
+#include "../../becs.h"
+#include <stdlib.h>
+#include "external/raylib/src/raylib.h"
+
+// Component structs
+typedef struct {
+    float x, y;
+} Position;
+
+typedef struct {
+    float vx, vy;
+} Velocity;
+
+typedef struct {
+    float ax, ay;
+} Acceleration;
+
+typedef struct {
+    float radius;
+    float lifetime;
+} ParticleData;
+
+// Function to spawn a particle
+void SpawnParticle(BECS_ECS *ecs, BECS_ComponentID posID, BECS_ComponentID velID, BECS_ComponentID accID, BECS_ComponentID dataID, float x, float y) {
+    BECS_Entity entity = BECS_EntityCreate(ecs);
+    if (entity == BECS_NULL_ENTITY) return;
+
+    Position *pos = (Position *)BECS_ComponentAdd(ecs, entity, posID);
+    pos->x = x;
+    pos->y = y;
+
+    Velocity *vel = (Velocity *)BECS_ComponentAdd(ecs, entity, velID);
+    vel->vx = GetRandomValue(-100, 100);
+    vel->vy = GetRandomValue(-200, -50);
+
+    Acceleration *acc = (Acceleration *)BECS_ComponentAdd(ecs, entity, accID);
+    acc->ax = 0.0f;
+    acc->ay = 100.0f; // Gravity
+
+    ParticleData *data = (ParticleData *)BECS_ComponentAdd(ecs, entity, dataID);
+    data->radius = 5.0f;
+    data->lifetime = 2.0f;
+}
+
+int main(void) {
+    // Initialize ECS
+    size_t componentSizes[4] = {sizeof(Position), sizeof(Velocity), sizeof(Acceleration), sizeof(ParticleData)};
+    size_t memSize = BECS_GetMinMemoryArenaSize(componentSizes, 4);
+    char *memory = (char *)malloc(memSize);
+    BECS_ECS ecs = BECS_InitECS(memory, memSize);
+
+    // Register components
+    BECS_ComponentID posID = BECS_ComponentRegister(&ecs, sizeof(Position), BECS_MAX_ENTITIES);
+    BECS_ComponentID velID = BECS_ComponentRegister(&ecs, sizeof(Velocity), BECS_MAX_ENTITIES);
+    BECS_ComponentID accID = BECS_ComponentRegister(&ecs, sizeof(Acceleration), BECS_MAX_ENTITIES);
+    BECS_ComponentID dataID = BECS_ComponentRegister(&ecs, sizeof(ParticleData), BECS_MAX_ENTITIES);
+
+    InitWindow(800, 400, "2D Particle System with BECS");
+
+    while (!WindowShouldClose()) {
+        float dt = GetFrameTime();
+
+        // Update lifetimes and despawn
+        for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
+            if (!BECS_IsEntityAlive(&ecs, entity)) continue;
+            if (BECS_ComponentHas(&ecs, entity, dataID)) {
+                ParticleData *data = (ParticleData *)BECS_ComponentGet(&ecs, entity, dataID);
+                data->lifetime -= dt;
+                if (data->lifetime <= 0.0f) {
+                    BECS_EntityDestroy(&ecs, entity);
+                }
+            }
+        }
+
+        // Spawn particle on mouse click
+        if (IsMouseButtonPressed(MOUSE_LEFT_BUTTON)) {
+            Vector2 mousePos = GetMousePosition();
+            SpawnParticle(&ecs, posID, velID, accID, dataID, mousePos.x, mousePos.y);
+        }
+
+        // Physics system: update position and velocity
+        for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
+            if (!BECS_IsEntityAlive(&ecs, entity)) continue;
+            if (BECS_ComponentHas(&ecs, entity, posID) &&
+                BECS_ComponentHas(&ecs, entity, velID) &&
+                BECS_ComponentHas(&ecs, entity, accID)) {
+                Position *pos = (Position *)BECS_ComponentGet(&ecs, entity, posID);
+                Velocity *vel = (Velocity *)BECS_ComponentGet(&ecs, entity, velID);
+                Acceleration *acc = (Acceleration *)BECS_ComponentGet(&ecs, entity, accID);
+
+                vel->vx += acc->ax * dt;
+                vel->vy += acc->ay * dt;
+                pos->x += vel->vx * dt;
+                pos->y += vel->vy * dt;
+            }
+        }
+
+        BeginDrawing();
+            ClearBackground(BLACK);
+
+            // Render system: draw particles
+            for (BECS_Entity entity = 0; entity < BECS_MAX_ENTITIES; entity++) {
+                if (!BECS_IsEntityAlive(&ecs, entity)) continue;
+                if (BECS_ComponentHas(&ecs, entity, posID) && BECS_ComponentHas(&ecs, entity, dataID)) {
+                    Position *pos = (Position *)BECS_ComponentGet(&ecs, entity, posID);
+                    ParticleData *data = (ParticleData *)BECS_ComponentGet(&ecs, entity, dataID);
+                    float alpha = data->lifetime / 2.0f;
+                    Color color = {255, 255, 255, (unsigned char)(alpha * 255)};
+                    DrawCircle((int)pos->x, (int)pos->y, data->radius, color);
+                }
+            }
+
+            DrawText(TextFormat("Particles: %u", ecs.entityCount), 10, 10, 20, WHITE);
+        EndDrawing();
+    }
+
+    CloseWindow();
+    free(memory);
+    return 0;
+}

examples/example1/external/raylib

@@ -0,0 +1 @@
+Subproject commit c610d228a244f930ad53492604640f39584c66da