add to gui

gui/gui.h

@@ -28,6 +28,15 @@ struct EngineStats {
     std::vector<StatEntry> extra_stats;
 };
 
+// Which parasitic-load accessories are toggled on, via checkboxes drawn
+// in the left column by render(). Placeholders (Alternator, A/C, Power
+// Steering) until there's an actual load model behind them.
+struct AccessoryState {
+    bool alternator = false;
+    bool ac = false;
+    bool power_steering = false;
+};
+
 class Gui {
 public:
     bool init();                     // create window + ImGui context
@@ -36,6 +45,20 @@ public:
     void end_frame();                 // swap buffers
     void shutdown();
 
+    // Reflects the throttle lever as of the most recent render() call.
+    // Spring-loaded: holds whatever value the drag left it at only
+    // while the mouse is down, and snaps back to 0 the instant it's
+    // released. Read it any time after render() this frame, or before
+    // render() next frame, to feed it into the engine.
+    double throttle() const { return static_cast<double>(m_throttle_lever); }
+
+    // Reflects the checkbox state as of the most recent render() call —
+    // read it any time after render() this frame, or before render()
+    // next frame, to feed accessory load into the engine.
+    const AccessoryState& accessories() const { return m_accessories; }
+
 private:
     GLFWwindow* m_window = nullptr;
+    float m_throttle_lever = 0.0f;
+    AccessoryState m_accessories;
 };