Fix dead level meters on device slot changes

- Remember the meter gate in DeviceRackController instead of only pushing
  it onto the devices that existed when the dialog became visible

Author: juzzlin

CHANGELOG

@@ -43,6 +43,9 @@ New features:
 
 Bug fixes:
 
+* Fix the level meters staying dead for a device added or replaced while the
+  Device Rack or Mixer is open
+
 * Fix the Piano
   - Let the top octaves speak and ring
   - Play in tune across the keyboard

src/unit_tests/device_rack_controller_test/device_rack_controller_test.cpp

@@ -419,6 +419,31 @@ void DeviceRackControllerTest::test_deviceMeterLevels_shouldReportPreInsertLevel
     QVERIFY(!device->meter().active());
 }
 
+void DeviceRackControllerTest::test_deviceMeterLevels_afterSlotChanged_shouldFollowTheActiveGate()
+{
+    // The gate is set when the rack goes on screen, but a device dropped into a slot afterwards is
+    // born with its taps off, so replacing one used to leave a permanently dead meter.
+    const auto audioEngine = std::make_shared<AudioEngine>();
+    const auto deviceService = std::make_shared<DeviceService>(audioEngine, std::make_shared<DataService>());
+    DeviceRackController controller { deviceService, {}, std::make_shared<MockEditorService>() };
+
+    controller.setMetersActive(true);
+    controller.setDevice(0, QString::fromStdString(Kick808Device::typeIdString()));
+    QVERIFY(deviceService->device(0)->meter().active());
+    QVERIFY(deviceService->device(0)->loadMeter().active());
+
+    controller.clearDevice(0);
+    controller.setDevice(0, QString::fromStdString(SynthDevice::typeIdString()));
+    QVERIFY(deviceService->device(0)->meter().active());
+    QVERIFY(deviceService->device(0)->loadMeter().active());
+
+    // Off the screen, a device added into the rack must not silently switch the taps back on.
+    controller.setMetersActive(false);
+    controller.setDevice(1, QString::fromStdString(SynthDevice::typeIdString()));
+    QVERIFY(!deviceService->device(1)->meter().active());
+    QVERIFY(!deviceService->device(1)->loadMeter().active());
+}
+
 namespace {
 //! Emits a constant level so a test can put the engine's device path either side of full scale.
 class ClippingDevice : public MockDevice

src/unit_tests/device_rack_controller_test/device_rack_controller_test.hpp

@@ -37,6 +37,7 @@ private slots:
     void test_addMethods_shouldAddDevicesToFirstEmptySlot();
     void test_availableDevices_shouldReturnCorrectList();
     void test_deviceMeterLevels_shouldReportPreInsertLevel();
+    void test_deviceMeterLevels_afterSlotChanged_shouldFollowTheActiveGate();
     void test_deviceClipped_shouldLatchUntilCleared();
     void test_deviceClipped_afterClearing_shouldStayClearWhileBelowFullScale();
     void test_deviceSettings_shouldRoundTripThroughController();

src/view/controllers/device_rack_controller.cpp

@@ -125,6 +125,8 @@ void DeviceRackController::refresh()
         m_devices = m_deviceService->internalDeviceNamesQt();
     }
     endResetModel();
+    // Slots may have gained a device since the gate was last set, and a new device's taps start off.
+    applyMetersActive();
 }
 
 void DeviceRackController::openDevice(const QString & name)
@@ -232,14 +234,23 @@ QVariantList DeviceRackController::deviceMeterLevels(int slotIndex) const
 
 void DeviceRackController::setMetersActive(bool active)
 {
+    m_metersActive = active;
+    applyMetersActive();
+}
+
+void DeviceRackController::applyMetersActive()
+{
+    if (!m_deviceService) {
+        return;
+    }
     for (int slotIndex = 0; slotIndex < deviceCount(); slotIndex++) {
         if (const auto device = m_deviceService->device(static_cast<size_t>(slotIndex))) {
-            device->meter().setActive(active);
-            device->loadMeter().setActive(active);
+            device->meter().setActive(m_metersActive);
+            device->loadMeter().setActive(m_metersActive);
         }
     }
     if (const auto engine = m_deviceService->audioEngine()) {
-        engine->loadMeter().setActive(active);
+        engine->loadMeter().setActive(m_metersActive);
     }
 }
 

src/view/controllers/device_rack_controller.hpp

@@ -163,12 +163,17 @@ class DeviceRackController : public QAbstractListModel
 private:
     QString trackNames(const QString & deviceName) const;
 
+    //! Push the current gate onto every device's taps. Needed after any slot change, because a
+    //! freshly created device starts with its meters off regardless of what is on screen.
+    void applyMetersActive();
+
     DeviceServiceS m_deviceService;
     ControllerList m_controllers;
     EditorServiceS m_editorService;
 
     QStringList m_devices;
     int m_revision { 0 };
+    bool m_metersActive { false };
 };
 
 } // namespace noteahead