src: fix the move speed formula a abit

2 files changed, 89 insertions, 5 deletions

diff --git a/compat/math.hpp b/compat/math.hpp
new file mode 100644
index 00000000..d5b628c4
--- /dev/null
+++ b/compat/math.hpp
@@ -0,0 +1,79 @@
+#pragma once
+
+#include <bit>
+#include <cmath>
+
+namespace floormat::math::detail {
+
+constexpr double sqrt_newton_raphson(double x, double curr, double prev)
+{
+    return curr == prev
+           ? curr
+           : sqrt_newton_raphson(x, 0.5 * (curr + x / curr), curr);
+}
+
+template<typename T> requires std::is_floating_point_v<T> struct float_constants;
+
+template<>
+struct float_constants<double>
+{
+    static constexpr auto quiet_nan = std::bit_cast<double>(uint64_t(0x7FF8000000000000ULL));
+    static constexpr auto positive_infinity = std::bit_cast<double>(uint64_t(0x7FF0000000000000ULL));
+    static constexpr auto negative_infinity = std::bit_cast<double>(uint64_t(0xFFF0000000000000ULL));
+};
+
+template<>
+struct float_constants<float>
+{
+    static constexpr auto quiet_nan = std::bit_cast<float>(uint32_t(0x7FC00000U));
+    static constexpr auto positive_infinity = std::bit_cast<float>(uint32_t(0x7F800000U));
+    static constexpr auto negative_infinity = std::bit_cast<float>(uint32_t(0xFF800000U));
+};
+
+} // namespace floormat::math::detail
+
+namespace floormat::math {
+
+template<typename T>
+constexpr inline T sqrt(T x)
+requires std::is_floating_point_v<T>
+{
+    if (std::is_constant_evaluated())
+    {
+        using K = detail::float_constants<T>;
+        return x >= 0 && x < K::positive_infinity
+               ? T(detail::sqrt_newton_raphson(double(x), double(x), 0))
+               : K::quiet_nan;
+    }
+    else
+        return std::sqrt(x);
+}
+
+template<typename T>
+requires std::is_integral_v<T>
+constexpr inline double sqrt(T x)
+{
+    return sqrt(double(x));
+}
+
+template<typename T>
+requires std::is_floating_point_v<T>
+constexpr inline T ceil(T x)
+{
+    if (std::is_constant_evaluated())
+    {
+#ifdef __GNUG__
+        return __builtin_ceil(x);
+#else
+        const auto x0 = uint64_t(x);
+        if (x > x0)
+            return T(x0 + uint64_t(1));
+        else
+            return x0;
+#endif
+    }
+    else
+        return std::ceil(x);
+}
+
+} // namespace floormat::math
diff --git a/src/critter.cpp b/src/critter.cpp
index 9111aaf6..0e8ac643 100644
--- a/src/critter.cpp
+++ b/src/critter.cpp
@@ -4,8 +4,8 @@
 #include "src/world.hpp"
 #include "src/object.hpp"
 #include "shaders/shader.hpp"
-#include "src/RTree-search.hpp"
 #include "compat/exception.hpp"
+#include "compat/math.hpp"
 #include <cmath>
 #include <memory>
 #include <utility>
@@ -17,9 +17,13 @@ namespace {
 
 template <typename T> constexpr T sgn(T val) { return T(T(0) < val) - T(val < T(0)); }
 
-constexpr int tile_size_1 = iTILE_SIZE2.sum()/2,
-              framerate = 96 * 3, move_speed = tile_size_1 * 2 * 3;
-constexpr float frame_time = 1.f/framerate;
+constexpr auto vector_length(Vector2 vec)
+{
+    return math::sqrt(Math::dot(vec, vec));
+};
+
+constexpr float framerate = 96 * 3, move_speed = vector_length(TILE_SIZE2) * 4.25f;
+constexpr float frame_time = 1/framerate;
 
 constexpr auto arrows_to_dir(bool left, bool right, bool up, bool down)
 {
@@ -30,6 +34,7 @@ constexpr auto arrows_to_dir(bool left, bool right, bool up, bool down)
 
     const auto bits = unsigned(left << 3 | right << 2 | up << 1 | down << 0);
     constexpr unsigned L = 1 << 3, R = 1 << 2, U = 1 << 1, D = 1 << 0;
+    CORRADE_ASSUME(bits <= 0xff);
 
     switch (bits)
     {
@@ -109,7 +114,7 @@ bool critter_proto::operator==(const object_proto& e0) const
 
 int critter::allocate_frame_time(float dt)
 {
-    int d = int(delta) + int(65535u * dt);
+    int d = int(delta) + int(65535 * dt);
     constexpr int framerate_ = 65535/framerate;
     static_assert(framerate_ > 0);
     auto ret = d / framerate_;