delete instead of compressing unmodified chunks

libswan/include/swan/Chunk.h

@@ -17,6 +17,13 @@ class Chunk {
 public:
 	using RelPos = TilePos;
 
+	// What does this chunk want the world gen to do after a tick?
+	enum class TickAction {
+		DEACTIVATE,
+		DELETE,
+		NOTHING,
+	};
+
 	Chunk(ChunkPos pos): pos_(pos) {
 		data_.reset(new uint8_t[CHUNK_WIDTH * CHUNK_HEIGHT * sizeof(Tile::ID)]);
 	}
@@ -30,10 +37,11 @@ public:
 	void compress();
 	void decompress();
 	void draw(const Context &ctx, Win &win);
-	void tick(float dt);
+	TickAction tick(float dt);
 
-	bool keepActive(); // Returns true if chunk was inactive
 	bool isActive() { return deactivate_timer_ > 0; }
+	bool keepActive(); // Returns true if chunk was inactive
+	void markModified() { is_modified_ = true; }
 
 	ChunkPos pos_;
 
@@ -51,6 +59,7 @@ private:
 	ssize_t compressed_size_ = -1; // -1 if not compressed, a positive number if compressed
 	bool need_render_ = false;
 	float deactivate_timer_ = DEACTIVATE_INTERVAL;
+	bool is_modified_ = false;
 
 	CPtr<SDL_Texture, SDL_DestroyTexture> texture_;
 };

libswan/src/Chunk.cc

@@ -2,6 +2,7 @@
 
 #include <zlib.h>
 #include <stdint.h>
+#include <assert.h>
 
 #include "log.h"
 #include "Clock.h"
@@ -57,11 +58,11 @@ void Chunk::compress() {
 		info
 			<< "Compressed chunk " << pos_ << " from "
 			<< CHUNK_WIDTH * CHUNK_HEIGHT * sizeof(Tile::ID) << " bytes "
-			<< "to " << destlen << " bytes.";
+			<< "to " << destlen << " bytes";
 	} else if (ret == Z_BUF_ERROR) {
 		info
 			<< "Didn't compress chunk " << pos_ << " "
-			<< "because compressing it would've made it bigger.";
+			<< "because compressing it would've made it bigger";
 	} else {
 		warn << "Chunk compression error: " << ret << " (Out of memory?)";
 	}
@@ -153,14 +154,18 @@ void Chunk::draw(const Context &ctx, Win &win) {
 		texture_.get(), &rect);
 }
 
-void Chunk::tick(float dt) {
-	if (deactivate_timer_ <= 0)
-		return;
+Chunk::TickAction Chunk::tick(float dt) {
+	assert(isActive());
 
 	deactivate_timer_ -= dt;
 	if (deactivate_timer_ <= 0) {
-		compress();
+		if (is_modified_)
+			return TickAction::DEACTIVATE;
+		else
+			return TickAction::DELETE;
 	}
+
+	return TickAction::NOTHING;
 }
 
 bool Chunk::keepActive() {

libswan/src/WorldPlane.cc

@@ -28,7 +28,12 @@ static Chunk::RelPos relPos(TilePos pos) {
 }
 
 Context WorldPlane::getContext() {
-	return { .game = *world_->game_, .world = *world_, .plane = *this, .resources = world_->resources_ };
+	return {
+		.game = *world_->game_,
+		.world = *world_,
+		.plane = *this,
+		.resources = world_->resources_
+	};
 }
 
 Entity *WorldPlane::spawnEntity(const std::string &name, const SRF &params) {
@@ -81,7 +86,11 @@ void WorldPlane::setTileID(TilePos pos, Tile::ID id) {
 	Chunk &chunk = getChunk(chunkPos(pos));
 	Chunk::RelPos rp = relPos(pos);
 
-	chunk.setTileID(rp, id, world_->getTileByID(id).image_.texture_.get());
+	Tile::ID old = chunk.getTileID(rp);
+	if (id != old) {
+		chunk.setTileID(rp, id, world_->getTileByID(id).image_.texture_.get());
+		chunk.markModified();
+	}
 
 	if (active_chunks_.find(&chunk) == active_chunks_.end()) {
 		active_chunks_.insert(&chunk);
@@ -210,10 +219,28 @@ void WorldPlane::tick(float dt) {
 	for (auto &ent: entities_)
 		ent->tick(getContext(), dt);
 
-	for (auto &chunk: active_chunks_)
-		chunk->tick(dt);
-
-	std::erase_if(active_chunks_, [](Chunk *chunk) { return !chunk->isActive(); });
+	auto iter = active_chunks_.begin();
+	auto last = active_chunks_.end();
+	while (iter != last) {
+		auto &chunk = *iter;
+		auto action = chunk->tick(dt);
+
+		switch (action) {
+		case Chunk::TickAction::DEACTIVATE:
+			info << "Compressing inactive modified chunk " << chunk->pos_;
+			chunk->compress();
+			iter = active_chunks_.erase(iter);
+			break;
+		case Chunk::TickAction::DELETE:
+			info << "Deleting inactive unmodified chunk " << chunk->pos_;
+			chunks_.erase(chunk->pos_);
+			iter = active_chunks_.erase(iter);
+			break;
+		case Chunk::TickAction::NOTHING:
+			++iter;
+			break;
+		}
+	}
 }
 
 void WorldPlane::debugBox(TilePos pos) {