Use [Channel1_Stem1] pattern for Stem COs. Improve speed a bit.

res/qml/EqColumn.qml

@@ -19,7 +19,7 @@ Column {
     }
 
     function stemGroup(group, index) {
-        return `${group.substr(0, group.length-1)}Stem${index + 1}]`
+        return `${group.substr(0, group.length-1)}_Stem${index + 1}]`
     }
 
     Row {

res/skins/LateNight/stem_channel.xml

@@ -1,5 +1,5 @@
 <Template>
-  <SetVariable name="StemGroup">[Channel<Variable name="ChanNum"/>Stem<Variable name="StemNum"/>]</SetVariable>
+  <SetVariable name="StemGroup">[Channel<Variable name="ChanNum"/>_Stem<Variable name="StemNum"/>]</SetVariable>
 
 	<WidgetGroup>
 		<ObjectName>StemChannel_ControlContainer</ObjectName>

src/engine/channels/enginedeck.cpp

@@ -17,9 +17,9 @@
 namespace {
 QString getGroupForStem(const QString& deckGroup, int stemIdx) {
     DEBUG_ASSERT(deckGroup.endsWith("]"));
-    return QStringLiteral("%1Stem%2]")
-            .arg(deckGroup.left(deckGroup.size() - 1),
-                    QString::number(stemIdx));
+    QString groupForStem = deckGroup;
+    groupForStem[deckGroup.size() - 1] = QChar('_');
+    return groupForStem + QStringLiteral("Stem") + QString::number(stemIdx + 1) + QChar(']');
 }
 } // anonymous namespace
 #endif
@@ -77,14 +77,14 @@ EngineDeck::EngineDeck(
     m_stemMute.reserve(mixxx::kMaxSupportedStems);
     for (int stemIdx = 0; stemIdx < mixxx::kMaxSupportedStems; stemIdx++) {
         m_stemGain.emplace_back(std::make_unique<ControlPotmeter>(
-                ConfigKey(getGroupForStem(getGroup(), stemIdx + 1), QStringLiteral("volume"))));
+                ConfigKey(getGroupForStem(getGroup(), stemIdx), QStringLiteral("volume"))));
         // The default value is ignored and override with the medium value by
         // ControlPotmeter. This is likely a bug but fixing might have a
         // disruptive impact, so setting the default explicitly
         m_stemGain.back()->set(1.0);
         m_stemGain.back()->setDefaultValue(1.0);
         auto pMuteButton = std::make_unique<ControlPushButton>(
-                ConfigKey(getGroupForStem(getGroup(), stemIdx + 1), QStringLiteral("mute")));
+                ConfigKey(getGroupForStem(getGroup(), stemIdx), QStringLiteral("mute")));
         pMuteButton->setButtonMode(mixxx::control::ButtonMode::PowerWindow);
         m_stemMute.push_back(std::move(pMuteButton));
     }

src/mixer/playermanager.h

@@ -145,28 +145,28 @@ class PlayerManager : public QObject, public PlayerManagerInterface {
     // Returns the group for the ith sampler where i is zero indexed
     static QString groupForSampler(int i) {
         DEBUG_ASSERT(i >= 0);
-        return QStringLiteral("[Sampler") + QString::number(i + 1) + ']';
+        return QStringLiteral("[Sampler") + QString::number(i + 1) + QChar(']');
     }
 
     // Returns the group for the ith deck where i is zero indexed
     static QString groupForDeck(int i) {
         DEBUG_ASSERT(i >= 0);
-        return QStringLiteral("[Channel") + QString::number(i + 1) + ']';
+        return QStringLiteral("[Channel") + QString::number(i + 1) + QChar(']');
     }
 
 #ifdef __STEM__
     // Returns the group for the ith deck and jth stem where i and j is zero indexed
     static QString groupForDeckStem(int i, int j) {
         DEBUG_ASSERT(i >= 0);
         return QStringLiteral("[Channel") + QString::number(i + 1) +
-                QStringLiteral("Stem") + QString::number(j + 1) + ']';
+                QStringLiteral("_Stem") + QString::number(j + 1) + QChar(']');
     }
 #endif
 
     // Returns the group for the ith PreviewDeck where i is zero indexed
     static QString groupForPreviewDeck(int i) {
         DEBUG_ASSERT(i >= 0);
-        return QStringLiteral("[PreviewDeck") + QString::number(i + 1) + ']';
+        return QStringLiteral("[PreviewDeck") + QString::number(i + 1) + QChar(']');
     }
 
     // Returns the group for the ith Microphone where i is zero indexed
@@ -176,7 +176,7 @@ class PlayerManager : public QObject, public PlayerManagerInterface {
         // the group [Microphone]. For backwards compatibility we keep it that
         // way.
         if (i > 0) {
-            return QStringLiteral("[Microphone") + QString::number(i + 1) + ']';
+            return QStringLiteral("[Microphone") + QString::number(i + 1) + QChar(']');
         } else {
             return QStringLiteral("[Microphone]");
         }
@@ -185,7 +185,7 @@ class PlayerManager : public QObject, public PlayerManagerInterface {
     // Returns the group for the ith Auxiliary where i is zero indexed
     static QString groupForAuxiliary(int i) {
         DEBUG_ASSERT(i >= 0);
-        return QStringLiteral("[Auxiliary") + QString::number(i + 1) + ']';
+        return QStringLiteral("[Auxiliary") + QString::number(i + 1) + QChar(']');
     }
 
     static QAtomicPointer<ControlProxy> m_pCOPNumDecks;

src/test/stemcontrolobjecttest.cpp

@@ -12,9 +12,9 @@ class StemControlTest : public BaseSignalPathTest {
   protected:
     QString getGroupForStem(const QString& deckGroup, int stemIdx) {
         DEBUG_ASSERT(deckGroup.endsWith("]"));
-        return QStringLiteral("%1Stem%2]")
-                .arg(deckGroup.left(deckGroup.size() - 1),
-                        QString::number(stemIdx));
+        QString groupForStem = deckGroup;
+        groupForStem[deckGroup.size() - 1] = QChar('_');
+        return groupForStem + QStringLiteral("Stem") + QString::number(stemIdx) + QChar(']');
     }
     QString getFxGroupForStem(const QString& deckGroup, int stemIdx) {
         return QStringLiteral("[QuickEffectRack1_%1]")

src/waveform/renderers/allshader/waveformrendererstem.cpp

@@ -28,16 +28,16 @@ void WaveformRendererStem::initializeGL() {
     m_shader.init();
     m_textureShader.init();
     auto group = m_pEQEnabled->getKey().group;
+    DEBUG_ASSERT(group.endsWith("]"));
+    group[group.size() - 1] = QChar('_');
     for (int stemIdx = 1; stemIdx <= mixxx::kMaxSupportedStems; stemIdx++) {
-        DEBUG_ASSERT(group.endsWith("]"));
-        QString stemGroup = QStringLiteral("%1Stem%2]")
-                                    .arg(group.left(group.size() - 1),
-                                            QString::number(stemIdx));
+        QString stemGroup = group + QStringLiteral("Stem") + QString::number(stemIdx) + QChar(']');
         m_pStemGain.emplace_back(
                 std::make_unique<ControlProxy>(stemGroup,
                         QStringLiteral("volume")));
-        m_pStemMute.emplace_back(std::make_unique<ControlProxy>(
-                stemGroup, QStringLiteral("mute")));
+        m_pStemMute.emplace_back(
+                std::make_unique<ControlProxy>(stemGroup,
+                        QStringLiteral("mute")));
     }
 }