Effects: allow clearing effect chains via '---' item in preset selectors

src/effects/effectchain.cpp

@@ -216,7 +216,18 @@ void EffectChain::loadChainPreset(EffectChainPresetPointer pPreset) {
     setMixMode(pPreset->mixMode());
     m_pControlChainSuperParameter->setDefaultValue(pPreset->superKnob());
 
-    m_presetName = pPreset->name();
+    // If this is a regular, editable effect chain (i.e. not a QuickEffectChain)
+    // and the empty '---' preset was selected, set an empty name in order to
+    // * clear WEffectChainPresetSelector (index will be -1)
+    // * not store '---' in the effects config file (e.g. because the respective
+    //  empty '---' preset is not going to be stored either)
+    // For details check EffectsManager::saveEffectsXml()
+    if (pPreset->name() == kNoEffectString &&
+            !m_pEffectsManager->chainIsQuickEffectChain(this)) {
+        m_presetName = QString();
+    } else {
+        m_presetName = pPreset->name();
+    }
     emit chainPresetChanged(m_presetName);
 
     setControlLoadedPresetIndex(presetIndex());
@@ -350,8 +361,8 @@ void EffectChain::slotControlLoadedChainPresetRequest(double value) {
 }
 
 void EffectChain::setControlLoadedPresetIndex(uint index) {
-    // add 1 to make the ControlObject 1-indexed like other ControlObjects
-    m_pControlLoadedChainPreset->setAndConfirm(index + 1);
+    // 0 means no preset loaded, e.g. when empty '---' preset was loaded
+    m_pControlLoadedChainPreset->setAndConfirm(index);
 }
 
 void EffectChain::slotControlNextChainPreset(double value) {

src/effects/presets/effectchainpresetmanager.cpp

@@ -557,6 +557,11 @@ void EffectChainPresetManager::resetToDefaults() {
 }
 
 bool EffectChainPresetManager::savePresetXml(EffectChainPresetPointer pPreset) {
+    // Don't store the empty '---' preset
+    // Should'n be possible anyway via GUI because the 'Update Preset' button
+    // is not shown in WEffectChainPresetButton if this preset is loaded.
+    DEBUG_ASSERT(pPreset->name() != kNoEffectString);
+
     QString path(m_pConfig->getSettingsPath() + kEffectChainPresetDirectory);
     QDir effectsChainsDir(path);
     if (!effectsChainsDir.exists()) {
@@ -683,6 +688,22 @@ EffectsXmlData EffectChainPresetManager::readEffectsXml(
 
     prependRemainingPresetsToLists();
 
+    // Create the empty '---' chain preset on each start.
+    // Its sole purpose is to eject the current effect chain presets via GUI.
+    // It will not be saved to effects/chains and nor written to effects.xml.
+    // It will not be visible in the effects preferencs.
+    EffectManifestPointer pEmptyChainManifest(new EffectManifest());
+    pEmptyChainManifest->setName(kNoEffectString);
+    pEmptyChainManifest->setShortName(kNoEffectString);
+
+    auto pEmptyChainPreset =
+            EffectChainPresetPointer(new EffectChainPreset(pEmptyChainManifest));
+    pEmptyChainPreset->setName(pEmptyChainManifest->name());
+
+    m_effectChainPresets.insert(pEmptyChainPreset->name(), pEmptyChainPreset);
+    m_effectChainPresetsSorted.prepend(pEmptyChainPreset);
+    m_quickEffectChainPresetsSorted.prepend(pEmptyChainPreset);
+
     emit effectChainPresetListUpdated();
     emit quickEffectChainPresetListUpdated();
 
@@ -723,6 +744,10 @@ void EffectChainPresetManager::saveEffectsXml(QDomDocument* pDoc, const EffectsX
     QDomElement chainPresetListElement =
             pDoc->createElement(EffectXml::kChainPresetList);
     for (const auto& pPreset : std::as_const(m_effectChainPresetsSorted)) {
+        // Don't store the empty '---' preset
+        if (pPreset->name() == kNoEffectString) {
+            continue;
+        }
         XmlParse::addElement(*pDoc,
                 chainPresetListElement,
                 EffectXml::kChainPresetName,
@@ -734,6 +759,10 @@ void EffectChainPresetManager::saveEffectsXml(QDomDocument* pDoc, const EffectsX
     QDomElement quickEffectChainPresetListElement =
             pDoc->createElement(EffectXml::kQuickEffectList);
     for (const auto& pPreset : std::as_const(m_quickEffectChainPresetsSorted)) {
+        // Don't store the empty '---' preset
+        if (pPreset->name() == kNoEffectString) {
+            continue;
+        }
         XmlParse::addElement(*pDoc,
                 quickEffectChainPresetListElement,
                 EffectXml::kChainPresetName,

src/preferences/dialog/dlgprefeffects.cpp

@@ -163,13 +163,21 @@ void DlgPrefEffects::clearChainInfoDisableButtons() {
 void DlgPrefEffects::loadChainPresetLists() {
     QStringList chainPresetNames;
     for (const auto& pChainPreset : m_pChainPresetManager->getPresetsSorted()) {
+        // Don't show the empty '---' preset
+        if (pChainPreset->name() == kNoEffectString) {
+            continue;
+        }
         chainPresetNames << pChainPreset->name();
     }
     auto pModel = dynamic_cast<EffectChainPresetListModel*>(chainListView->model());
     pModel->setStringList(chainPresetNames);
 
     QStringList quickEffectChainPresetNames;
     for (const auto& pChainPreset : m_pChainPresetManager->getQuickEffectPresetsSorted()) {
+        // Don't show the empty '---' preset
+        if (pChainPreset->name() == kNoEffectString) {
+            continue;
+        }
         quickEffectChainPresetNames << pChainPreset->name();
     }
     pModel = dynamic_cast<EffectChainPresetListModel*>(quickEffectListView->model());

src/widget/weffectchainpresetbutton.cpp

@@ -48,6 +48,10 @@ void WEffectChainPresetButton::populateMenu() {
     // Chain preset items
     bool chainIsPreset = false;
     for (const auto& pChainPreset : m_pChainPresetManager->getPresetsSorted()) {
+        // Don't show the empty '---' preset
+        if (pChainPreset->name() == kNoEffectString) {
+            continue;
+        }
         QString title = pChainPreset->name();
         if (title == m_pChain->presetName()) {
             title = QChar(0x2713) + // CHECK MARK

src/widget/weffectchainpresetselector.cpp

@@ -84,8 +84,12 @@ void WEffectChainPresetSelector::populate() {
 }
 
 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()));
+    // TODO(ronso0) Clean up. This is set again in slotChainPresetChanged
+    // after the new preset was actually loaded.
     setBaseTooltip(itemData(index, Qt::ToolTipRole).toString());
     // After selecting an effect move focus to the tracks table in order
     // to immediately allow keyboard shortcuts again.
@@ -95,8 +99,15 @@ 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);
+    QString toolTip = newIndex > -1
+            ? itemData(newIndex, Qt::ToolTipRole).toString()
+            : tr("No preset loaded");
+    setBaseTooltip(toolTip);
 }
 
 bool WEffectChainPresetSelector::event(QEvent* pEvent) {