Effects: allow clearing effect chains via preset selectors

src/effects/effectchain.cpp

@@ -202,7 +202,24 @@ const QString& EffectChain::presetName() const {
 
 void EffectChain::loadChainPreset(EffectChainPresetPointer pPreset) {
     slotControlClear(1);
-    VERIFY_OR_DEBUG_ASSERT(pPreset) {
+    if (!pPreset) {
+        // This may happen when a chain is cleared by selecting the empty '---'
+        // item in WEffectChainPresetSelector or in deck Quick Effect selectors
+        // in DlgPrefEq.
+        // Quick Effect chains and other chains need to be treated differently:
+        // * storing Quick Effect chain presets requires a preset name, otherwise
+        //  (empty name) will cause the default preset being loaded on next start.
+        //  Thus, we name the empty preset kNoEffectString so that the respective
+        //  item is selected in the chain preset selector and also no chain will be
+        //  loaded on next start.
+        // * storing states of regular [EffectRack1] chains doesn't require a preset
+        //  name, also they can be edited, so kNoEffectString would be incorrect
+        //  after loading an effect. Thus, if this is not a Quick Effetc chain, we
+        //  just clear the preset name which in turn clears the chain's preset
+        //  selector and chain name label.
+        m_presetName = m_isQuickEffectChain ? kNoEffectString : QString();
+        emit chainPresetChanged(m_presetName);
+        setControlLoadedPresetIndex(std::nullopt);
         return;
     }
 

src/effects/presets/effectchainpresetmanager.cpp

@@ -696,9 +696,20 @@ EffectsXmlData EffectChainPresetManager::readEffectsXml(
         QDomElement presetNameElement = quickEffectNodeList.at(i).toElement();
         if (!presetNameElement.isNull()) {
             QString deckGroup = presetNameElement.attribute(QStringLiteral("group"));
-            auto pPreset = m_effectChainPresets.value(presetNameElement.text());
-            if (pPreset != nullptr) {
-                quickEffectPresets.insert(deckGroup, pPreset);
+            QString presetName = presetNameElement.text();
+            if (presetName == kNoEffectString) {
+                // kNoEffectString is not allowed as preset name (import,
+                // export, save as new), it can only be set by selecting
+                // kNoEffectString in the Quick Effect slot preset selector
+                // (skin & EQ preferences).
+                // Thus, it's safe to use kNoEffectString to explicitly load
+                // an empty preset.
+                quickEffectPresets.insert(deckGroup, nullptr);
+            } else { // any name incl. empty string
+                auto pPreset = m_effectChainPresets.value(presetName);
+                if (pPreset != nullptr) {
+                    quickEffectPresets.insert(deckGroup, pPreset);
+                }
             }
         }
     }

src/preferences/dialog/dlgprefeq.cpp

@@ -297,23 +297,21 @@ void DlgPrefEQ::populateDeckQuickEffectBoxList(
     int deck = 0;
     for (QComboBox* box : boxList) {
         box->clear();
-        int currentIndex = -1; // Nothing selected
+
+        // Add empty item at the top: no effect
+        box->addItem(kNoEffectString);
+        // Note: now there's an index offset (items vs. actual presets).
+        // Compensate with a nullptr in slotQuickEffectChangedOnDeck().
 
         QString deckGroupName = PlayerManager::groupForDeck(deck);
         QString unitGroup = QuickEffectChain::formatEffectChainGroup(deckGroupName);
         EffectChainPointer pChain = m_pEffectsManager->getEffectChain(unitGroup);
-
-        // Add empty item at the top: no effect
-        box->addItem(kNoEffectString);
-        int i = 1;
         for (const auto& pChainPreset : presetList) {
             box->addItem(pChainPreset->name());
-            if (pChain->presetName() == pChainPreset->name()) {
-                currentIndex = i;
-            }
-            ++i;
         }
-        box->setCurrentIndex(currentIndex);
+
+        // Nothing selected (-1) if preset name was not found
+        box->setCurrentIndex(box->findText(pChain->presetName()));
         ++deck;
     }
 }
@@ -490,10 +488,15 @@ void DlgPrefEQ::slotQuickEffectChangedOnDeck(int effectIndex) {
     QString deckGroupName = PlayerManager::groupForDeck(deckNumber);
     QString unitGroup = QuickEffectChain::formatEffectChainGroup(deckGroupName);
     EffectChainPointer pChain = m_pEffectsManager->getEffectChain(unitGroup);
-    QList<EffectChainPresetPointer> presetList =
-            m_pChainPresetManager->getQuickEffectPresetsSorted();
-    if (pChain && effectIndex > 0 && effectIndex <= presetList.size()) {
-        pChain->loadChainPreset(presetList[effectIndex - 1]);
+    QList<EffectChainPresetPointer> presetList;
+    // add nullptr for empty kNoEffectString item so combobox effectIndex
+    // matches index in presetList
+    presetList.append(nullptr);
+    // add available Quick Effect chains
+    presetList.append(m_pChainPresetManager->getQuickEffectPresetsSorted());
+
+    if (pChain && effectIndex > -1 && effectIndex <= presetList.size()) {
+        pChain->loadChainPreset(presetList[effectIndex]);
     }
 }
 

src/widget/weffectchainpresetselector.cpp

@@ -63,6 +63,10 @@ void WEffectChainPresetSelector::populate() {
 
     QFontMetrics metrics(font());
 
+    // This is used to clear the effect chain
+    addItem(kNoEffectString, kNoEffectString);
+    setItemData(0, QVariant(tr("No effect chain loaded.")), Qt::ToolTipRole);
+
     QList<EffectChainPresetPointer> presetList;
     if (m_bQuickEffectChain) {
         presetList = m_pEffectsManager->getChainPresetManager()->getQuickEffectPresetsSorted();
@@ -76,14 +80,16 @@ void WEffectChainPresetSelector::populate() {
                 Qt::ElideMiddle,
                 view()->width() - 2);
         addItem(elidedDisplayName, QVariant(pChainPreset->name()));
-        setItemData(i, pChainPreset->name(), Qt::ToolTipRole);
+        setItemData(i + 1, pChainPreset->name(), Qt::ToolTipRole);
     }
 
     slotChainPresetChanged(m_pChain->presetName());
     blockSignals(false);
 }
 
 void WEffectChainPresetSelector::slotEffectChainPresetSelected(int index) {
+    // If kNoEffectString was selected the chain will be cleared.
+    // See EffectChain::loadChainPreset for details.
     m_pChain->loadChainPreset(
             m_pChainPresetManager->getPreset(currentData().toString()));
     setBaseTooltip(itemData(index, Qt::ToolTipRole).toString());
@@ -95,8 +101,12 @@ void WEffectChainPresetSelector::slotEffectChainPresetSelected(int index) {
 }
 
 void WEffectChainPresetSelector::slotChainPresetChanged(const QString& name) {
-    setCurrentIndex(findData(name));
-    setBaseTooltip(itemData(currentIndex(), Qt::ToolTipRole).toString());
+    // This is called by signal EffectChain::chainPresetChanged(name) emitted by
+    // EffectChain::loadChainPreset. See that slot for details about the preset
+    // names being emitted for different chain types.
+    int newIndex = findData(name);
+    setCurrentIndex(newIndex);
+    setBaseTooltip(itemData(newIndex, Qt::ToolTipRole).toString());
 }
 
 bool WEffectChainPresetSelector::event(QEvent* pEvent) {