Initial commit

main.c

@@ -0,0 +1,68 @@
+#include "math.h"
+
+#define HEIGHT 600
+#define WIDTH 800
+#define SQ_SIZE 100
+
+typedef struct { double x, y; } Vec2d;
+typedef struct { unsigned char r, g, b, a; } Color;
+
+Color gradient[SQ_SIZE*SQ_SIZE] = {0};
+Color buffer[WIDTH*HEIGHT] = {0};
+Vec2d pos = {0};
+double time = 0;
+
+Color* get_buffer_ptr() {
+    return buffer;
+}
+
+int get_buffer_len() {
+    return WIDTH*HEIGHT;
+}
+
+void compute_gradient(Color* output_buffer, int width, int height) {
+    for (int y = 0; y < height; y++) {
+        for (int x = 0; x < width; x++) {
+            output_buffer[y*width+x] = (Color){
+                .r = (x * 255) / (width - 1),
+                .g = (y * 255) / (height - 1),
+                .b = 0,
+                .a = 255
+            };
+        }
+    }
+}
+
+void init() {
+    compute_gradient(gradient, SQ_SIZE, SQ_SIZE);
+}
+
+void render_frame(double dt) {
+    time += dt;
+    double x = 0.5 + __builtin_cos(2.0 * PI / 10.0 * time) * 0.5;
+    double y = 0.5 + __builtin_sin(2.0 * PI / 10.0 * time) * 0.5;
+    pos.x = x * (WIDTH - SQ_SIZE);
+    pos.y = y * (HEIGHT - SQ_SIZE);
+
+    // Clear the framebuffer before drawing the next frame.
+    __builtin_memset(buffer, 0, sizeof(buffer));
+
+    // Clamp coordinates before indexing the framebuffer to avoid a bad
+    // coordinate from turning into an out-of-bounds write.
+    int pos_x = (int)pos.x;
+    int pos_y = (int)pos.y;
+    if (pos_x < 0) pos_x = 0;
+    if (pos_y < 0) pos_y = 0;
+    if (pos_x > WIDTH - SQ_SIZE) pos_x = WIDTH - SQ_SIZE;
+    if (pos_y > HEIGHT - SQ_SIZE) pos_y = HEIGHT - SQ_SIZE;
+
+    for (int y = pos_y; y < pos_y + SQ_SIZE; ++y) {
+        for (int x = pos_x; x < pos_x + SQ_SIZE; ++x) {
+            // Sample point from gradient
+            int local_x = x - pos_x;
+            int local_y = y - pos_y;
+            Color c = gradient[local_y * SQ_SIZE + local_x];
+            buffer[y * WIDTH + x] = c;
+        }
+    }
+}