Ellipses!

.vscode/settings.json

@@ -1,5 +1,13 @@
 {
     "files.associations": {
-        "stdbool.h": "c"
+        "*.h": "c",
+        "stdbool.h": "c",
+        "chrono": "c",
+        "cmath": "c",
+        "cstdlib": "c",
+        "format": "c",
+        "ratio": "c",
+        "xlocnum": "c",
+        "xutility": "c"
     }
 }

README.md

@@ -1,3 +1,17 @@
 # Croc Party!
 
-A tiny platform game in C/SDL.
+A tiny platform game in C/SDL.
+
+# Commands
+
+## Run (release)
+
+```
+$ bazel run -c opt sdl_host.exe
+```
+
+## Run 
+
+```
+$ bazel run sdl_host.exe
+```

game/game.c

@@ -4,6 +4,16 @@
 
 uint32_t game_frame;
 
+int32_t ellipse_x0 = 32;
+int32_t ellipse_y0 = 32;
+int32_t ellipse_dx0 = 1;
+int32_t ellipse_dy0 = 2;
+int32_t ellipse_x1 = 96;
+int32_t ellipse_y1 = 96;
+int32_t ellipse_dx1 = 3;
+int32_t ellipse_dy1 = 4;
+
+
 const char* game_title() {
     return "Croc Party!";
 }
@@ -35,6 +45,16 @@ void game_destroy() {
 
 void game_update() {
     game_frame += 4;
+
+    ellipse_x0 += ellipse_dx0;
+    if (ellipse_x0 < 0 || ellipse_x0 > DEVICE_W) { ellipse_dx0 *= -1; }
+    ellipse_y0 += ellipse_dy0;
+    if (ellipse_y0 < 0 || ellipse_y0 > DEVICE_W) { ellipse_dy0 *= -1; }
+
+    ellipse_x1 += ellipse_dx1;
+    if (ellipse_x1 < 0 || ellipse_x1 > DEVICE_H) { ellipse_dx1 *= -1; }
+    ellipse_y1 += ellipse_dy1;
+    if (ellipse_y1 < 0 || ellipse_y1 > DEVICE_H) { ellipse_dy1 *= -1; }
 }
 
 void game_draw() {
@@ -58,4 +78,7 @@ void game_draw() {
     for (int i = 0; i < DEVICE_BUTTON_N; i++) {
         sys_pixel_set(i, 0, device_buttons[i] ? 0x00 : 0xff);
     }
+
+    sys_oval_draw_ext(ellipse_x0, ellipse_y0, ellipse_x1, ellipse_y1, 10, true);
+    sys_oval_draw_ext(ellipse_x0, ellipse_y0, ellipse_x1, ellipse_y1, 245, false);
 }

sys/sys_graphics.c

@@ -8,6 +8,9 @@ sys_color sys_dpal[256];
 
 // primitives (forward declare)
 void sys_pixel_internal_set(sys_i32 x, sys_i32 y, sys_color c);
+void sys_scanline_internal_set(
+    sys_i32 x0, sys_i32 x1, sys_i32 y, sys_color c, bool fill
+);
 
 // == public ==
 void sys_clip_set(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1) {
@@ -75,7 +78,89 @@ void sys_camera_reset() {
     sys_camera_set(0, 0);
 }
 
-// TODO: Continue from sys_circ_draw_ext
+// Based on bresenham implementations by alois zingl
+// https://zingl.github.io/bresenham.html
+void sys_circ_draw(sys_i32 x, sys_i32 y, sys_i32 r, sys_color c) {
+    assert(sys_get_initialized());
+
+    sys_circ_draw_ext(x, y, r, c, false);
+}
+
+void sys_circ_fill(sys_i32 x, sys_i32 y, sys_i32 r, sys_color c) {
+    assert(sys_get_initialized());
+
+    sys_circ_draw_ext(x, y, r, c, true);
+}
+
+void sys_circ_draw_ext(
+    sys_i32 x, sys_i32 y, sys_i32 r, sys_color c, bool fill
+) {
+    assert(sys_get_initialized());
+
+    if (r < 0) { return; }
+
+    sys_oval_draw_ext(x - r, y - r, x + r + 1, y + r + 1, c, fill);
+}
+
+void sys_oval_draw(
+    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c
+) {
+    assert(sys_get_initialized());
+
+    sys_oval_draw_ext(x0, y0, x1, y1, c, false);
+}
+
+void sys_oval_fill(
+    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c
+) {
+    assert(sys_get_initialized());
+
+    sys_oval_draw_ext(x0, y0, x1, y1, c, true);
+}
+
+void sys_oval_draw_ext(
+    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c, bool fill
+) {
+    if (x0 == x1 || y0 == y1) { return; }
+    if (x0 > x1) { sys_i32 tmp = x0; x0 = x1; x1 = tmp; }
+    if (y0 > y1) { sys_i32 tmp = y0; y0 = y1; y1 = tmp; }
+    // alois' algorithm for this implies the bounds are inclusive 
+    x1 -= 1; y1 -= 1;
+
+    int64_t a = x1 - x0;
+    int64_t b = y1 - y0;
+    int64_t b1 = b & 1;
+
+    int64_t dx = 4 * (1 - a) * b * b;
+    int64_t dy = 4 * (b1 + 1) * a * a;
+    int64_t err = dx + dy + b1 * a * a;
+
+    y0 += (b + 1) / 2;
+    y1 = y0 - b1;
+    a *= 8 * a;
+    b1 = 8 * b * b;
+
+    do {
+        // draw the points at the edge of the line
+        sys_scanline_internal_set(x0, x1, y0, c, false);
+        sys_scanline_internal_set(x0, x1, y1, c, false);
+        int64_t e2 = 2 * err;
+        if (e2 <= dy) { 
+            if (fill) {
+                // draw the whole line
+                sys_scanline_internal_set(x0, x1, y0, c, true);
+                sys_scanline_internal_set(x0, x1, y1, c, true);
+            }
+            y0++; y1--; dy += a; err += dy; 
+        }
+        if (e2 >= dx || 2 * err > dy) { x0++; x1--; dx += b1; err += dx; }
+    } while (x0 <= x1);
+
+    while (y0 - y1 < b) {
+        sys_scanline_internal_set(x0 - 1, x1 + 1, y0, c, fill); y0++;
+        sys_scanline_internal_set(x0 - 1, x1 + 1, y1, c, fill); y1--;
+    }
+}
 
 void sys_spal_set(sys_color c0, sys_screen_color rc1) {
     assert(sys_get_initialized());
@@ -123,4 +208,17 @@ void sys_pixel_internal_set(sys_i32 x, sys_i32 y, sys_color c) {
     assert(y < DEVICE_H);
 
     device_pixels[y][x] = realc;
+}
+void sys_scanline_internal_set(
+    sys_i32 x0, sys_i32 x1, sys_i32 y, sys_color c, 
+    bool fill
+) {
+    if (fill) {
+        for (sys_i32 x = x0; x <= x1; x++) {
+            sys_pixel_internal_set(x, y, c);
+        }
+    } else {
+        sys_pixel_internal_set(x0, y, c);
+        sys_pixel_internal_set(x1, y, c);
+    }
 }

sys/sys_graphics.h

@@ -75,29 +75,25 @@ void sys_camera_reset();
 /**
  * Draw or fill a circle at `(x, y)` with radius `r`.
  * 
- * The circle consists of a "stroke" region and a "fill" region which the user
- * can decide individually on whether or not to fill.
+ * The circle is centered at the center of the pixel, not at the junction
+ * between pixels.
  * 
  * If r is negative, the circle is not drawn.
  * 
  * This is a special case of sys_circ_oval_draw_ext.
  */
-void sys_circ_draw_ext(sys_i32 x, sys_i32 y, sys_i32 r, sys_color c, bool stroke, bool fill);
 void sys_circ_draw(sys_i32 x, sys_i32 y, sys_i32 r, sys_color c);  
 void sys_circ_fill(sys_i32 x, sys_i32 y, sys_i32 r);  
+void sys_circ_draw_ext(sys_i32 x, sys_i32 y, sys_i32 r, sys_color c, bool fill);
 
 /**
  * Draw or fill an oval in the rectangle from `(x0, y0)` to `(x1, y1)`
- * 
- * The oval consists of a "stroke" region and a "fill" region which the user
- * can decide individually on whether or not to fill.
  */
-void sys_oval_draw_ext(
-    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c,
-    bool stroke, bool fill
-);
 void sys_oval_draw(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c);
 void sys_oval_fill(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c);
+void sys_oval_draw_ext(
+    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c, bool fill
+);
 
 /**
  * Draw a line from x0 to y0.
@@ -107,12 +103,11 @@ void sys_line_draw(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c);
 /**
  * Draw or fill a rectangle `(x, y, w, h)`
  */
-void sys_rect_draw_ext(
-    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c,
-    bool stroke, bool fill
-);
 void sys_rect_draw(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c);
 void sys_rect_fill(sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c);
+void sys_rect_draw_ext(
+    sys_i32 x0, sys_i32 y0, sys_i32 x1, sys_i32 y1, sys_color c, bool fill
+);
 
 /**
  * Set screen palette.