Add placeholder steering wheel option for VR driving

runtime/tests/vr_config_tests.cpp

@@ -26,6 +26,11 @@ int main() {
     Require(Parse("[vr]\ncockpit_item_throw = false\n").vrCockpitItemThrow == false);
     Require(Parse("[vr]\ncockpit_item_throw = true\n").vrCockpitItemThrow == true);
     Require(!Parse("[vr]\n").vrCockpitItemThrow.has_value());
+    // [vr] placeholder_steering_wheel: the separate VR wheel or handlebar is opt-in.
+    Require(!RuntimeConfigFile::kVrPlaceholderSteeringWheelDefault);
+    Require(Parse("[vr]\nplaceholder_steering_wheel = true\n").vrPlaceholderSteeringWheel == true);
+    Require(Parse("[vr]\nplaceholder_steering_wheel = false\n").vrPlaceholderSteeringWheel == false);
+    Require(!Parse("[vr]\n").vrPlaceholderSteeringWheel.has_value());
     // [vr] foveation: the Quest's foveated rendering level, index-matched to
     // aurora_set_stereo_foveation.
     for (std::string_view level : RuntimeConfigFile::kVrFoveationLevels) {

runtime/tests/vr_hand_steering_tests.cpp

@@ -108,6 +108,21 @@ void TestSeatFrame() {
     CheckNear(m[11], -1.0f, "lean turns up into forward", 1e-5f);
 }
 
+void TestPlaceholderControl() {
+    // Arguments: steering_wheel, native_steering_wheel, native_mesh_prepared, placeholder.
+    Check(!driving::DrawsPlaceholderControl(true, true, false, false),
+          "no placeholder while the vehicle's own is not animated, unless asked for");
+    Check(!driving::DrawsPlaceholderControl(true, false, false, false),
+          "no placeholder with the vehicle's own wheel off, unless asked for");
+    Check(driving::DrawsPlaceholderControl(true, true, false, true),
+          "the placeholder stands in while the vehicle's own is not animated");
+    Check(driving::DrawsPlaceholderControl(true, false, true, true),
+          "the placeholder replaces the vehicle's own wheel when that is off");
+    Check(!driving::DrawsPlaceholderControl(true, true, true, true),
+          "no placeholder while the vehicle's own is the one turning");
+    Check(!driving::DrawsPlaceholderControl(false, false, false, true), "no wheel turns at all");
+}
+
 } // namespace
 
 int main() {
@@ -115,6 +130,7 @@ int main() {
     TestMaxAngle();
     TestVisual();
     TestSeatFrame();
+    TestPlaceholderControl();
     if (g_failures != 0) {
         std::cerr << g_failures << " check(s) failed\n";
         return 1;