don't redraw the entire chunk when a tile changes

libswan/include/swan/Chunk.h

@@ -20,7 +20,6 @@ public:
 	Chunk(ChunkPos pos): pos_(pos) {
 		data_.reset(new uint8_t[CHUNK_WIDTH * CHUNK_HEIGHT * sizeof(Tile::ID)]);
 		visuals_.reset(new Visuals());
-		visuals_->dirty_ = false;
 	}
 
 	Tile::ID *getTileData();
@@ -53,7 +52,6 @@ private:
 
 	struct Visuals {
 		RaiiPtr<SDL_Texture> texture_ = makeRaiiPtr<SDL_Texture>(nullptr, SDL_DestroyTexture);
-		bool dirty_ = true;
 	};
 	std::unique_ptr<Visuals> visuals_;
 };

libswan/src/Chunk.cc

@@ -30,8 +30,12 @@ void Chunk::setTileID(RelPos pos, Tile::ID id) {
 void Chunk::drawBlock(RelPos pos, const Tile &t) {
 	keepActive();
 
-	//visuals_->tex_.update(*t.image_, pos.x * TILE_SIZE, pos.y * TILE_SIZE);
-	visuals_->dirty_ = true;
+	SDL_Rect lockrect{ pos.x * TILE_SIZE, pos.y * TILE_SIZE, TILE_SIZE, TILE_SIZE };
+	TexLock lock(visuals_->texture_.get(), &lockrect);
+
+	SDL_Rect srcrect{ 0, 0, t.image_.surface_->w, t.image_.surface_->h };
+	SDL_Rect destrect{ 0, 0, TILE_SIZE, TILE_SIZE };
+	lock.blit(&destrect, t.image_.surface_.get(), &srcrect);
 }
 
 void Chunk::compress() {
@@ -86,7 +90,6 @@ void Chunk::decompress() {
 	data_ = std::move(dest);
 
 	visuals_.reset(new Visuals());
-	visuals_->dirty_ = true;
 	need_render_ = true;
 
 	info
@@ -141,11 +144,6 @@ void Chunk::draw(const Context &ctx, Win &win) {
 		need_render_ = false;
 	}
 
-	if (visuals_->dirty_) {
-		need_render_ = true;
-		visuals_->dirty_ = false;
-	}
-
 	SDL_Rect rect{ 0, 0, CHUNK_WIDTH * TILE_SIZE, CHUNK_HEIGHT * TILE_SIZE };
 	win.showTexture(
 		pos_ * Vec2i(CHUNK_WIDTH, CHUNK_HEIGHT),