update particles garbage collection scheme

src/graphics/render/ParticlesRenderer.cpp

@@ -15,24 +15,24 @@ ParticlesRenderer::ParticlesRenderer(const Assets& assets)
 
     auto region = util::get_texture_region(assets, "blocks:grass_side", "");
     Emitter emitter(glm::vec3(0, 100, 0), Particle {
-        glm::vec3(), glm::vec3(), 5.0f, region.region
-    },region.texture, 0.001f, -1);
-    emitters.push_back(std::move(emitter));
+        nullptr, glm::vec3(), glm::vec3(), 5.0f, region.region
+    },region.texture, 0.001f, 1000);
+    emitters.push_back(std::make_unique<Emitter>(emitter));
 }
 
 ParticlesRenderer::~ParticlesRenderer() = default;
 
-void ParticlesRenderer::render(
-    const Assets& assets, const Camera& camera, float delta
-) {
+void ParticlesRenderer::renderParticles(const Camera& camera, float delta) {
     const auto& right = camera.right;
     const auto& up = camera.up;
 
-    batch->begin();
-    
-    aliveEmitters = emitters.size();
-    visibleParticles = 0;
+    std::vector<const Texture*> unusedTextures;
+
     for (auto& [texture, vec] : particles) {
+        if (vec.empty()) {
+            unusedTextures.push_back(texture);
+            continue;
+        }
         batch->setTexture(texture);
 
         visibleParticles += vec.size();
@@ -62,24 +62,36 @@ void ParticlesRenderer::render(
         }
     }
     batch->flush();
+    for (const auto& texture : unusedTextures) {
+        particles.erase(texture);
+    }
+}
+
+void ParticlesRenderer::render(const Camera& camera, float delta) {
+    batch->begin();
     
+    aliveEmitters = emitters.size();
+    visibleParticles = 0;
+
+    renderParticles(camera, delta);
+
     auto iter = emitters.begin();
     while (iter != emitters.end()) {
-        auto& emitter = *iter;
+        auto& emitter = **iter;
         auto texture = emitter.getTexture();
         const auto& found = particles.find(texture);
         std::vector<Particle>* vec;
         if (found == particles.end()) {
+            if (emitter.isDead()) {
+                // destruct Emitter only when there is no particles spawned by it
+                iter = emitters.erase(iter);
+                continue;
+            }
             vec = &particles[texture];
         } else {
             vec = &found->second;
         }
         emitter.update(delta, *vec);
-
-        if (emitter.isDead()) {
-            iter = emitters.erase(iter);
-        } else {
-            iter++;
-        }
+        iter++;
     }
 }