1 files changed, 29 insertions, 16 deletions

diff --git a/src/sandbox.cpp b/src/sandbox.cpp
index d0d918c..efc2bd0 100644
--- a/src/sandbox.cpp
+++ b/src/sandbox.cpp
@@ -25,23 +25,25 @@ uint32_t Tile::get_color() const {
     return material_color_lut[std::to_underlying(so)];
 }
 
-Sandbox::Sandbox(int w, int h)
-    : _bitmap(w * h)
-    , _a(w * h)
-    // TODO random seed
-    , _rand()
+Sandbox::Sandbox(int w, int h, RandomState rand)
+    : bitmap(new uint32_t[w * h])
+    , tiles(new Tile[w * h])
+    , _rand(std::move(rand))
     , _wall_tile{ Tile::ROCK }
     , width{ w }
     , height{ h } //
 {
-    memset(_bitmap.data(), 0xff, _bitmap.size() * sizeof(_bitmap[0]));
+    memset(bitmap, 0xff, (w * h) * sizeof(bitmap[0]));
+}
+
+Sandbox::~Sandbox() {
+    delete[] bitmap;
+    delete[] tiles;
 }
 
 static void simulate_sand_tile(Sandbox& self, int x, int y) {
     const auto at0 = self.gs(x, y);
     if (at0.updated) {
-        // Clear update bit for next cycle
-        self.gs(x, y).updated = false;
         return;
     }
 
@@ -91,13 +93,20 @@ static void simulate_sand_tile(Sandbox& self, int x, int y) {
 }
 
 void Sandbox::simulate_step() {
-    _x = 0;
-    _y = 0;
-    for (; _y < height; ++_y) {
-        for (; _x < width; ++_x) {
+    dirty_curr = dirty_writeto;
+    dirty_writeto = {};
+    const auto [x0, y0] = dirty_curr.bl;
+    const auto [x1, y1] = dirty_curr.tr;
+    // Clear update bit for this cycle
+    for (_y = y0; _y <= y1; ++_y) {
+        for (_x = x0; _x <= x1; ++_x) {
+            gs(_x, _y).updated = false;
+        }
+    }
+    for (_y = y0; _y <= y1; ++_y) {
+        for (_x = x0; _x <= x1; ++_x) {
             simulate_sand_tile(*this, _x, _y);
         }
-        _x = 0;
     }
     ++ncycle;
 }
@@ -105,16 +114,20 @@ void Sandbox::simulate_step() {
 Tile& Sandbox::gs(int x, int y) {
     if (x < 0 || x >= width || y < 0 || y >= height)
         return _wall_tile;
-    return _a[y * width + x];
+    return tiles[y * width + x];
 }
 
 void Sandbox::set_sand(int x, int y, Tile sand) {
-    auto& target = _a[y * width + x];
+    auto& target = tiles[y * width + x];
     target = sand;
     // Set update bit if the target is after cursor
     if (y < _y || x > _x)
         target.updated = true;
-    _bitmap[y * width + x] = sand.get_color();
+    bitmap[y * width + x] = sand.get_color();
+    if (dirty_writeto == Rect())
+        dirty_writeto = Rect(x, y, x, y);
+    else
+        dirty_writeto = rect_union(dirty_writeto, Pt(x, y));
 }
 
 // std::vector<uint32_t> Sandbox::to_bitmap() const {