3 files changed, 28 insertions(+), 6 deletions(-)

M include/mandelbrot.h
M src/main.c
M src/math.c

@@ 21,11 21,11 @@ typedef struct position_s {
 // math.c
 int mandelbrot_iterations(double cr, double ci, int max_iter);
 void calculate_points(position_t* pos);
+void mandelbrot_at_point(double cr, double ci, int* iter_out, double* zr_out, double* zi_out);
 
 // draw.c
 // TODO: color struct or something
 void get_color(int iter, int max_iter, int* r, int* g, int* b);
 void draw_points(SDL_Surface* surface);
 
-
 #endif

@@ 101,11 101,15 @@ int main(void) {
                 }
                 float mx, my;
                 SDL_GetMouseState(&mx, &my);
-                int ix = (int)floor(mx);
-                int iy = (int)floor(my);
-                int iter = points[iy * WINDOW_WIDTH + ix];
-                snprintf(debug_text, sizeof(debug_text), "x: %d  y: %d  iterations: %d", ix, iy,
-                         iter);
+                double cr =
+                    position.x_min + (position.x_max - position.x_min) * mx / (WINDOW_WIDTH - 1);
+                double ci =
+                    position.y_min + (position.y_max - position.y_min) * my / (WINDOW_HEIGHT - 1);
+                int iter;
+                double zr, zi;
+                mandelbrot_at_point(cr, ci, &iter, &zr, &zi);
+                snprintf(debug_text, sizeof(debug_text),
+                         "c = %.6f %+.6fi | z = %.6f %+.6fi | iteration %d", cr, ci, zr, zi, iter);
             }
 
             if (e.type == SDL_EVENT_MOUSE_MOTION) {

@@ 35,6 35,24 @@ int mandelbrot_iterations(double cr, double ci, int max_iter) {
 
 extern int points[WINDOW_WIDTH * WINDOW_HEIGHT];
 
+void mandelbrot_at_point(double cr, double ci, int* iter_out, double* zr_out, double* zi_out) {
+    double zr = 0.0, zi = 0.0;
+    int iter = 0;
+    while (iter < 100) {
+        double zr2 = zr * zr;
+        double zi2 = zi * zi;
+        if (zr2 + zi2 > 4.0) {
+            break;
+        }
+        zi = 2.0 * zr * zi + ci;
+        zr = zr2 - zi2 + cr;
+        iter++;
+    }
+    *iter_out = iter;
+    *zr_out = zr;
+    *zi_out = zi;
+}
+
 void calculate_points(position_t* pos) {
     int max_iter = 100;
     for (int py = 0; py < WINDOW_HEIGHT; py++) {