add arc and alt

src/hal/hal_linux.cpp

@@ -25,6 +25,7 @@
 #include <iostream>
 #include <nlohmann/json.hpp>
 #include <nlohmann/json_fwd.hpp>
+#include <numbers>
 #include <tuple>
 
 struct sdl_session {
@@ -221,6 +222,48 @@ void line(const uint16_t x1, const uint16_t y1, const uint16_t x2,
                          0xff);
   SDL_RenderLine(main_sdl_session.renderer, x1, y1, x2, y2);
 }
+
+#ifdef CONFIG_VECTOR_FOLLOW_TRACK_RATE
+void arc(uint16_t start_x, uint16_t start_y, float start_angle_rad, float speed /*in pps*/,float angular_speed_rads, uint16_t duration, color_t color) {
+  SDL_SetRenderDrawColor(main_sdl_session.renderer, color.r, color.g, color.b,
+                         0xff);
+  constexpr float DEG2RAD = std::numbers::pi / 180.0f;
+
+
+    // Handle straight line case
+    if (std::fabs(angular_speed_rads) < 1e-6f) {
+        uint16_t steps = static_cast<int>(speed * duration);
+        for (uint16_t i = 0; i <= steps; ++i) {
+            float t = i / speed;
+            float x = start_x + std::cos(start_angle_rad) * speed * t;
+            float y = start_y + std::sin(start_angle_rad) * speed * t;
+            SDL_RenderPoint(main_sdl_session.renderer,static_cast<int>(std::round(x)), static_cast<int>(std::round(y)));
+        }
+        return;
+    }
+
+    float r = speed / angular_speed_rads;
+
+    // Center of circle: perpendicular to heading
+    float center_x = start_x - r * std::sin(start_angle_rad);
+    float center_y = start_y + r * std::cos(start_angle_rad);
+
+    // Angle from center to start point
+    float radius_angle = std::atan2(start_y - center_y, start_x - center_x);
+
+    // Step size in time — approx 1 pixel arc-length per step
+    float dt = 1.0f / std::max(std::fabs(speed), 1.0f);
+    uint16_t steps = static_cast<int>(duration / dt);
+
+    for (uint16_t i = 0; i <= steps; ++i) {
+        float t = i * dt;
+        float a = radius_angle + angular_speed_rads * t;
+        float x = center_x + std::fabs(r) * std::cos(a);
+        float y = center_y + std::fabs(r) * std::sin(a);
+        SDL_RenderPoint(main_sdl_session.renderer,static_cast<int>(std::round(x)), static_cast<int>(std::round(y)));
+    }
+}
+#endif
 } // namespace draw
 
 namespace net {