1 files changed, 128 insertions, 0 deletions
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..9014f22
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,128 @@
+#include <SDL3/SDL.h>
+#include <math.h>
+#include <stdio.h>
+
+#define LOG(...)                                                               \
+  do {                                                                         \
+    fprintf(stderr, __VA_ARGS__);                                              \
+    fprintf(stderr, "\n");                                                     \
+  } while (0)
+
+#define QUADRATIC_BEZIER_CURVE_CONTROL_POINT_COUNT 4
+#define CONTROL_POINT_RECTANGLE_SIZE 20.f
+
+struct vec2 {
+  float x;
+  float y;
+};
+struct vec2 vec2_add(struct vec2 lhs, struct vec2 rhs) {
+  return (struct vec2){.x = lhs.x + rhs.x, .y = lhs.y + rhs.y};
+}
+
+struct vec2 vec2_mul_scalar(struct vec2 lhs, float rhs) {
+  return (struct vec2){.x = lhs.x * rhs, .y = lhs.y * rhs};
+}
+
+struct vec2 bezier_quadratic(
+    float t, const struct vec2
+                 control_points[QUADRATIC_BEZIER_CURVE_CONTROL_POINT_COUNT]) {
+
+  struct vec2 a = vec2_mul_scalar(control_points[0], powf(1.f - t, 3.f));
+  struct vec2 b =
+      vec2_mul_scalar(control_points[1], 3 * powf(1.f - t, 2.f) * t);
+  struct vec2 c = vec2_mul_scalar(control_points[2], 3 * (1.f - t) * t * t);
+  struct vec2 d = vec2_mul_scalar(control_points[3], t * t * t);
+  return vec2_add(a, vec2_add(b, vec2_add(c, d)));
+}
+
+struct state {
+  struct vec2 control_points[QUADRATIC_BEZIER_CURVE_CONTROL_POINT_COUNT];
+  int set_control_point_count;
+};
+void state_render(const struct state *state, SDL_Renderer *renderer) {
+  for (int set_control_point_index = 0;
+       set_control_point_index < state->set_control_point_count;
+       set_control_point_index++) {
+    const struct vec2 *set_control_point =
+        &state->control_points[set_control_point_index];
+    SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0x00, 0xFF);
+    SDL_RenderFillRect(
+        renderer,
+        &(const SDL_FRect){
+            set_control_point->x - CONTROL_POINT_RECTANGLE_SIZE / 2.f,
+            set_control_point->y - CONTROL_POINT_RECTANGLE_SIZE / 2.f,
+            CONTROL_POINT_RECTANGLE_SIZE, CONTROL_POINT_RECTANGLE_SIZE});
+  }
+
+  if (state->set_control_point_count ==
+      QUADRATIC_BEZIER_CURVE_CONTROL_POINT_COUNT) {
+    float prev_t = 0.f;
+    for (int ti = 0; ti < 100; ti += 1) {
+      float t = ti / 100.f;
+      struct vec2 first_point = bezier_quadratic(prev_t, state->control_points);
+      struct vec2 second_point = bezier_quadratic(t, state->control_points);
+      SDL_SetRenderDrawColor(renderer, 0xFF, 0x00, 0x00, 0xFF);
+      SDL_RenderLine(renderer, first_point.x, first_point.y, second_point.x,
+                     second_point.y);
+      prev_t = t;
+    }
+  }
+}
+void state_on_click(struct state *state, struct vec2 position) {
+  if (state->set_control_point_count <
+      QUADRATIC_BEZIER_CURVE_CONTROL_POINT_COUNT) {
+    state->control_points[state->set_control_point_count++] = position;
+  }
+}
+
+int main(void) {
+  bool sdl_initialized = SDL_Init(SDL_INIT_VIDEO);
+  SDL_Window *window = NULL;
+  if (sdl_initialized) {
+    window = SDL_CreateWindow("bezier", 1280, 720, 0);
+  }
+
+  SDL_Renderer *renderer = NULL;
+  if (window) {
+    renderer = SDL_CreateRenderer(window, NULL);
+  }
+
+  struct state state = {0};
+
+  if (renderer) {
+    bool running = true;
+    while (running) {
+      SDL_Event event;
+      while (SDL_PollEvent(&event)) {
+        bool quit = event.type == SDL_EVENT_QUIT;
+        bool escape_pressed =
+            event.type == SDL_EVENT_KEY_DOWN && event.key.key == SDLK_ESCAPE;
+
+        if (quit || escape_pressed) {
+          running = false;
+        } else if (event.type == SDL_EVENT_MOUSE_BUTTON_DOWN &&
+                   event.button.button == SDL_BUTTON_LEFT) {
+          state_on_click(
+              &state, (struct vec2){.x = event.button.x, .y = event.button.y});
+        }
+      }
+
+      SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xFF);
+      SDL_RenderClear(renderer);
+      state_render(&state, renderer);
+      SDL_RenderPresent(renderer);
+    }
+  }
+
+  if (renderer) {
+    SDL_DestroyRenderer(renderer);
+  }
+  if (window) {
+    SDL_DestroyWindow(window);
+  }
+  if (sdl_initialized) {
+    SDL_Quit();
+  }
+
+  return 0;
+}