level solid; basic collision/gravity

1 files changed, 56 insertions, 0 deletions

diff --git a/include/components/solid.hpp b/include/components/solid.hpp
new file mode 100644
index 0000000..d02d229
--- /dev/null
+++ b/include/components/solid.hpp
@@ -0,0 +1,56 @@
+#ifndef COMPONENTS_SOLID_HPP
+#define COMPONENTS_SOLID_HPP
+
+#include "components/point.hpp"
+#include "window.hpp"
+
+#include <algorithm>
+#include <cstdint>
+
+class Solid {
+public:
+    Solid(const char *path) {
+        bitmap = sdl2LoadSolid(path);
+    }
+
+    ~Solid() {
+        if (bitmap != nullptr)
+            SDL_FreeSurface(bitmap);
+    }
+
+    float collision(Vec2 p) const noexcept {
+        float dy = 0.f;
+
+        if (at(p)) {
+            auto up = p;
+            while (up.y > 0 && at(up))
+                up.y--;
+
+            auto down = p;
+            while (down.y < bitmap->h && at(down))
+                down.y++;
+
+            if (down.y - p.y > p.y - up.y)
+                dy = -(p.y - up.y);
+            else
+                dy = down.y - p.y;
+        }
+
+        return dy;
+    }
+
+private:
+    SDL_Surface *bitmap;
+
+    bool at(Vec2 p) const noexcept {
+        const auto bm = reinterpret_cast<std::uint8_t *>(bitmap->pixels);
+        const int x = std::clamp(static_cast<int>(p.x), 0, bitmap->w);
+        const int y = std::clamp(static_cast<int>(p.y), 0, bitmap->h);
+        const int i = y * bitmap->w + x;
+        const auto val = bm[i * bitmap->format->BytesPerPixel];
+        return val > 0;
+    }
+};
+
+#endif // COMPONENTS_SOLID_HPP
+