Fix update loop direction

Going up to down causes the sand to collide in mid-air

1 files changed, 20 insertions, 9 deletions

diff --git a/src/sandbox.cpp b/src/sandbox.cpp
index ccfde52..6daa807 100644
--- a/src/sandbox.cpp
+++ b/src/sandbox.cpp
@@ -7,15 +7,22 @@
 // Copied from IM_COL32
 #define COL_U32(r, g, b, a) (((uint32_t)(A) << IM_COL32_A_SHIFT) | ((uint32_t)(B) << IM_COL32_B_SHIFT) | ((uint32_t)(G) << IM_COL32_G_SHIFT) | ((uint32_t)(R) << IM_COL32_R_SHIFT))
 
-static constexpr uint32_t MAT_COLOR_LUT[] = {
-    0xffffff'ff, // AIR
-    0xababab'ff, // SOLID
-    0xfffca8'ff, // SAND
-    0x435bf7'ff, // WATER
+// Correct byte order for this platform
+constexpr uint32_t bo(uint32_t n) {
+    if (std::endian::native == std::endian::little)
+        return std::byteswap(n);
+    return n;
+}
+
+static constexpr uint32_t material_color_lut[] = {
+    bo(0xffffff'ff), // AIR
+    bo(0xababab'ff), // SOLID
+    bo(0xe3dd24'ff), // SAND
+    bo(0x435bf7'ff), // WATER
 };
 
 uint32_t Tile::get_color() const {
-    return MAT_COLOR_LUT[std::to_underlying(so)];
+    return material_color_lut[std::to_underlying(so)];
 }
 
 Sandbox::Sandbox(int w, int h)
@@ -28,7 +35,11 @@ Sandbox::Sandbox(int w, int h)
     , height{ h } //
 {
     memset(_bitmap.data(), 0xff, _bitmap.size() * sizeof(_bitmap[0]));
-    set_sand(10, 80, Tile{ .so = Tile::SAND });
+    for (int y = 80; y <= 90; ++y) {
+        for (int x = 10; x <= 13; ++x) {
+            set_sand(x, y, Tile{ .so = Tile::SAND });
+        }
+    }
 }
 
 static void simulate_sand_tile(Sandbox& self, int x, int y) {
@@ -86,8 +97,8 @@ static void simulate_sand_tile(Sandbox& self, int x, int y) {
 
 void Sandbox::simulate_step() {
     _x = 0;
-    _y = height ;
-    for (; _y >= 0; --_y) {
+    _y = 0;
+    for (; _y < height; ++_y) {
         for (; _x < width; ++_x) {
             simulate_sand_tile(*this, _x, _y);
         }