add: Circle

frame/src/render/RenderTarget.cpp

@@ -55,8 +55,7 @@ namespace frame::render
                 {
                     pos.x += rX;
                     pos.y += rY;
-                }
-                else
+                } else
                 {
                     pos.y += rX;
                     pos.x += rY;
@@ -65,11 +64,42 @@ namespace frame::render
                 E += 2 * deltaY - 2 * deltaX;
             }
 
-            if(pos.x < 0 || pos.y < 0 || pos.x >= image.getWidth() || pos.y >= image.getHeight())
+            if(pos.x < 0 || pos.y < 0 || pos.x >= image.getWidth()
+               || pos.y >= image.getHeight())
                 break;
 
             DrawPixel(pos, color);
         }
     }
 
+    void RenderTarget::DrawCircle(Vector const& center,
+                                  int32_t radius,
+                                  Color color)
+    {
+        int32_t const r_2 = radius * radius;
+        Vector pos{0, -radius};
+
+        pos.x += 1;
+        float E =
+            pos.x * pos.x + ((float)pos.y - 0.5f) * ((float)pos.y - 0.5f) - r_2;
+
+        while(pos.x <= radius / std::sqrt(2.f))
+        {
+            if(E < 0)
+            {
+                pos.x += 1;
+
+                E += 3;
+            } else
+            {
+                pos.x += 1;
+                pos.y -= 1;
+
+                E -= 2 * (-radius) + 5;
+            }
+
+            DrawPixel(center + pos, color);
+        }
+    }
+
 } // namespace frame::render