Initial bass-manage Qt Quick / Kirigami control panel.

PipeWire LFE/center mix UI with live pw-cli controls and conf save/reload.

.gitignore

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+# Build
+/build/
+/cmake-build-*/
+*.o
+*.a
+moc_*.cpp
+*_autogen/
+
+# Editor / OS
+*~
+*.swp
+.DS_Store
+.idea/
+.vscode/
+*.user
+*.autosave

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(bass-manage VERSION 1.0 LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_AUTOMOC ON)
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Qml Quick QuickControls2)
+
+qt_add_executable(bass-manage-gui
+    src/main.cpp
+    src/backend.cpp
+    src/backend.h
+)
+
+target_compile_definitions(bass-manage-gui PRIVATE
+    BASS_MANAGE_SOURCE_DIR="${CMAKE_SOURCE_DIR}"
+)
+
+target_link_libraries(bass-manage-gui PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Qml
+    Qt6::Quick
+    Qt6::QuickControls2
+)
+
+include(GNUInstallDirs)
+install(TARGETS bass-manage-gui RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
+install(DIRECTORY qml icons DESTINATION ${CMAKE_INSTALL_DATADIR}/bass-manage)
+install(FILES bass-manage-gui.desktop DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)

bass-manage-gui.desktop

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+[Desktop Entry]
+Type=Application
+Name=Bass Manage 7.1
+Comment=Live controls for PipeWire bass management
+Exec=bass-manage-gui
+Icon=bass-manage-gui
+Terminal=false
+Categories=AudioVideo;Audio;Qt;
+StartupNotify=true

icons/align-center-horizontal.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M2 12h20" />
+  <path d="M10 16v4a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2v-4" />
+  <path d="M10 8V4a2 2 0 0 0-2-2H6a2 2 0 0 0-2 2v4" />
+  <path d="M20 16v1a2 2 0 0 1-2 2h-2a2 2 0 0 1-2-2v-1" />
+  <path d="M14 8V7c0-1.1.9-2 2-2h2a2 2 0 0 1 2 2v1" />
+</svg>

icons/audio-lines.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M2 10v3" />
+  <path d="M6 6v11" />
+  <path d="M10 3v18" />
+  <path d="M14 8v7" />
+  <path d="M18 5v13" />
+  <path d="M22 10v3" />
+</svg>

icons/refresh-cw.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M3 12a9 9 0 0 1 9-9 9.75 9.75 0 0 1 6.74 2.74L21 8" />
+  <path d="M21 3v5h-5" />
+  <path d="M21 12a9 9 0 0 1-9 9 9.75 9.75 0 0 1-6.74-2.74L3 16" />
+  <path d="M8 16H3v5" />
+</svg>

icons/save.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M15.2 3a2 2 0 0 1 1.4.6l3.8 3.8a2 2 0 0 1 .6 1.4V19a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2z" />
+  <path d="M17 21v-7a1 1 0 0 0-1-1H8a1 1 0 0 0-1 1v7" />
+  <path d="M7 3v4a1 1 0 0 0 1 1h7" />
+</svg>

icons/sliders-horizontal.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M10 5H3" />
+  <path d="M12 19H3" />
+  <path d="M14 3v4" />
+  <path d="M16 17v4" />
+  <path d="M21 12h-9" />
+  <path d="M21 19h-5" />
+  <path d="M21 5h-7" />
+  <path d="M8 10v4" />
+  <path d="M8 12H3" />
+</svg>

icons/speaker.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <rect width="16" height="20" x="4" y="2" rx="2" />
+  <path d="M12 6h.01" />
+  <circle cx="12" cy="14" r="4" />
+  <path d="M12 14h.01" />
+</svg>

icons/timer.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <line x1="10" x2="14" y1="2" y2="2" />
+  <line x1="12" x2="15" y1="14" y2="11" />
+  <circle cx="12" cy="14" r="8" />
+</svg>

icons/volume-2.svg

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+<svg
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#000000"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <path d="M11 4.702a.705.705 0 0 0-1.203-.498L6.413 7.587A1.4 1.4 0 0 1 5.416 8H3a1 1 0 0 0-1 1v6a1 1 0 0 0 1 1h2.416a1.4 1.4 0 0 1 .997.413l3.383 3.384A.705.705 0 0 0 11 19.298z" />
+  <path d="M16 9a5 5 0 0 1 0 6" />
+  <path d="M19.364 18.364a9 9 0 0 0 0-12.728" />
+</svg>

qml/Main.qml

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+import QtQuick
+import QtQuick.Controls as Controls
+import QtQuick.Layouts
+import org.kde.kirigami as Kirigami
+
+Kirigami.ApplicationWindow {
+    id: root
+    title: "Bass Manage 7.1"
+    width: 580
+    height: 520
+    minimumWidth: 480
+    minimumHeight: 420
+    pageStack.globalToolBar.style: Kirigami.ApplicationHeaderStyle.ToolBar
+
+    // Aggregated UI values (conf uses full map; UI links FL/FR & mains)
+    property real fcFold: 0.707
+    property real dry: 1.0
+    property real lfeMains: 0.99
+    property real lfeDisc: 0.99
+    property real lfeDelay: 0.010
+    property bool suppressApply: false
+
+    function valuesMap() {
+        return {
+            "fl_dry": dry,
+            "fr_dry": dry,
+            "fc_to_fl": fcFold,
+            "fc_to_fr": fcFold,
+            "lfe_fl": lfeMains,
+            "lfe_fr": lfeMains,
+            "lfe_fc": lfeMains,
+            "lfe_lfe": lfeDisc,
+            "lfe_rl": lfeMains,
+            "lfe_rr": lfeMains,
+            "lfe_sl": lfeMains,
+            "lfe_sr": lfeMains,
+            "lfe_delay": lfeDelay
+        }
+    }
+
+    function applyFromMap(m) {
+        suppressApply = true
+        fcFold = (Number(m["fc_to_fl"]) + Number(m["fc_to_fr"])) / 2
+        dry = (Number(m["fl_dry"]) + Number(m["fr_dry"])) / 2
+        lfeMains = (Number(m["lfe_fl"]) + Number(m["lfe_fr"]) + Number(m["lfe_fc"])
+                    + Number(m["lfe_rl"]) + Number(m["lfe_rr"]) + Number(m["lfe_sl"])
+                    + Number(m["lfe_sr"])) / 7
+        lfeDisc = Number(m["lfe_lfe"])
+        lfeDelay = Number(m["lfe_delay"])
+        suppressApply = false
+    }
+
+    function scheduleApply() {
+        if (suppressApply)
+            return
+        applyTimer.restart()
+    }
+
+    function linToDb(x) {
+        if (x <= 1e-9)
+            return -120
+        return 20 * Math.log(x) / Math.LN10
+    }
+
+    function dbToLin(db) {
+        if (db <= -120)
+            return 0
+        return Math.pow(10, db / 20)
+    }
+
+    function iconUrl(name) {
+        return "file://" + Backend.iconDir + "/" + name + ".svg"
+    }
+
+    component LucideIcon: Kirigami.Icon {
+        property string name
+        source: root.iconUrl(name)
+        color: Kirigami.Theme.textColor
+        isMask: true
+        Layout.preferredWidth: Kirigami.Units.iconSizes.small
+        Layout.preferredHeight: Kirigami.Units.iconSizes.small
+    }
+
+    Timer {
+        id: applyTimer
+        interval: 40
+        onTriggered: Backend.applyLive(root.valuesMap())
+    }
+
+    Connections {
+        target: Backend
+        function onErrorOccurred(title, message) {
+            errorDialog.title = title
+            errorDialog.text = message
+            errorDialog.open()
+        }
+    }
+
+    Component.onCompleted: {
+        const m = Backend.loadConf()
+        if (Object.keys(m).length)
+            applyFromMap(m)
+    }
+
+    pageStack.initialPage: Kirigami.ScrollablePage {
+        id: page
+        title: "Bass Manage 7.1"
+
+        titleDelegate: Item {
+            // Stretch across the header so actions sit on the right of the title
+            Layout.fillWidth: true
+            implicitHeight: row.implicitHeight
+            width: parent ? parent.width : row.implicitWidth
+
+            RowLayout {
+                id: row
+                anchors.fill: parent
+                spacing: Kirigami.Units.smallSpacing
+
+                LucideIcon {
+                    name: "audio-lines"
+                    Layout.preferredWidth: Kirigami.Units.iconSizes.smallMedium
+                    Layout.preferredHeight: Kirigami.Units.iconSizes.smallMedium
+                }
+                Kirigami.Heading {
+                    text: "Bass Manage 7.1"
+                    level: 1
+                }
+
+                Item { Layout.fillWidth: true }
+
+                Controls.ToolButton {
+                    onClicked: {
+                        if (Backend.saveConf(root.valuesMap()))
+                            savedDialog.open()
+                    }
+                    contentItem: RowLayout {
+                        spacing: Kirigami.Units.smallSpacing
+                        LucideIcon { name: "save" }
+                        Controls.Label { text: "Save" }
+                    }
+                    Accessible.name: "Save"
+                    Controls.ToolTip.text: "Save to conf"
+                    Controls.ToolTip.visible: hovered
+                    Controls.ToolTip.delay: Kirigami.Units.toolTipDelay
+                }
+
+                Controls.ToolButton {
+                    onClicked: {
+                        const m = Backend.loadConf()
+                        if (Object.keys(m).length)
+                            root.applyFromMap(m)
+                    }
+                    contentItem: RowLayout {
+                        spacing: Kirigami.Units.smallSpacing
+                        LucideIcon { name: "refresh-cw" }
+                        Controls.Label { text: "Reload" }
+                    }
+                    Accessible.name: "Reload"
+                    Controls.ToolTip.text: "Reload from conf"
+                    Controls.ToolTip.visible: hovered
+                    Controls.ToolTip.delay: Kirigami.Units.toolTipDelay
+                }
+            }
+        }
+
+        ColumnLayout {
+            spacing: Kirigami.Units.largeSpacing
+
+            RowLayout {
+                Layout.fillWidth: true
+                LucideIcon { name: "audio-lines" }
+                Controls.Label {
+                    text: Backend.status
+                    opacity: 0.75
+                    Layout.fillWidth: true
+                    wrapMode: Text.WordWrap
+                }
+            }
+
+            Kirigami.FormLayout {
+                Layout.fillWidth: true
+                wideMode: true
+
+                Kirigami.Separator {
+                    Kirigami.FormData.isSection: true
+                    Kirigami.FormData.label: "Center → fronts (add)"
+                }
+
+                SliderRow {
+                    Kirigami.FormData.label: "FC into FL/FR"
+                    iconName: "align-center-horizontal"
+                    from: 0; to: 1.5; stepSize: 0.01
+                    kind: "gain"
+                    value: root.fcFold
+                    onValueEdited: (v) => { root.fcFold = v; root.scheduleApply() }
+                }
+                SliderRow {
+                    Kirigami.FormData.label: "FL/FR dry"
+                    iconName: "volume-2"
+                    from: 0; to: 1.5; stepSize: 0.01
+                    kind: "gain"
+                    value: root.dry
+                    onValueEdited: (v) => { root.dry = v; root.scheduleApply() }
+                }
+
+                Kirigami.Separator {
+                    Kirigami.FormData.isSection: true
+                    Kirigami.FormData.label: "LFE mix"
+                }
+
+                SliderRow {
+                    Kirigami.FormData.label: "Mains → LFE"
+                    iconName: "sliders-horizontal"
+                    from: 0; to: 1.5; stepSize: 0.01
+                    kind: "gain"
+                    value: root.lfeMains
+                    onValueEdited: (v) => { root.lfeMains = v; root.scheduleApply() }
+                }
+                SliderRow {
+                    Kirigami.FormData.label: "Discrete LFE"
+                    iconName: "speaker"
+                    from: 0; to: 1.5; stepSize: 0.01
+                    kind: "gain"
+                    value: root.lfeDisc
+                    onValueEdited: (v) => { root.lfeDisc = v; root.scheduleApply() }
+                }
+                SliderRow {
+                    Kirigami.FormData.label: "LFE delay"
+                    iconName: "timer"
+                    from: 0; to: 0.05; stepSize: 0.001
+                    kind: "delay"
+                    value: root.lfeDelay
+                    onValueEdited: (v) => { root.lfeDelay = v; root.scheduleApply() }
+                }
+            }
+
+            Controls.Label {
+                Layout.fillWidth: true
+                wrapMode: Text.WordWrap
+                opacity: 0.7
+                text: "Type a value and press Enter (gains: 0.707 or -3dB; delay: ms). Reload resets from conf. Save writes conf."
+            }
+        }
+    }
+
+    component SliderRow: RowLayout {
+        id: row
+        property real from
+        property real to
+        property real stepSize
+        property real value
+        property string kind: "gain"
+        property string iconName
+        signal valueEdited(real v)
+
+        Layout.fillWidth: true
+        spacing: Kirigami.Units.smallSpacing
+
+        Kirigami.Icon {
+            source: root.iconUrl(row.iconName)
+            color: Kirigami.Theme.textColor
+            isMask: true
+            Layout.preferredWidth: Kirigami.Units.iconSizes.small
+            Layout.preferredHeight: Kirigami.Units.iconSizes.small
+        }
+
+        Controls.Slider {
+            id: slider
+            Layout.fillWidth: true
+            from: row.from
+            to: row.to
+            stepSize: row.stepSize
+            value: row.value
+            onMoved: row.valueEdited(value)
+        }
+
+        Controls.TextField {
+            id: field
+            Layout.preferredWidth: Kirigami.Units.gridUnit * 4
+            horizontalAlignment: Text.AlignRight
+
+            function formatValue(v) {
+                return row.kind === "delay"
+                    ? Number(v * 1000).toFixed(2).replace(/\.?0+$/, "")
+                    : Number(v).toPrecision(4)
+            }
+
+            Component.onCompleted: text = formatValue(row.value)
+
+            Connections {
+                target: row
+                function onValueChanged() {
+                    if (!field.activeFocus)
+                        field.text = field.formatValue(row.value)
+                }
+            }
+
+            function commit() {
+                let s = text.trim().toLowerCase().replace(",", ".")
+                let parsed = NaN
+                if (row.kind === "delay") {
+                    if (s.endsWith("ms"))
+                        parsed = parseFloat(s.slice(0, -2)) / 1000
+                    else if (s.endsWith("s"))
+                        parsed = parseFloat(s.slice(0, -1))
+                    else
+                        parsed = parseFloat(s) / 1000
+                } else {
+                    if (s.endsWith("db"))
+                        parsed = root.dbToLin(parseFloat(s.slice(0, -2)))
+                    else if (s.startsWith("+") || (s.startsWith("-") && s.indexOf("e") < 0))
+                        parsed = root.dbToLin(parseFloat(s))
+                    else
+                        parsed = parseFloat(s)
+                }
+                if (isNaN(parsed)) {
+                    text = formatValue(row.value)
+                    return
+                }
+                parsed = Math.min(row.to, Math.max(row.from, parsed))
+                row.valueEdited(parsed)
+            }
+
+            onEditingFinished: commit()
+            Keys.onReturnPressed: commit()
+            Keys.onEnterPressed: commit()
+        }
+
+        Controls.Label {
+            Layout.preferredWidth: Kirigami.Units.gridUnit * 5
+            text: row.kind === "delay"
+                  ? "ms"
+                  : "(" + (root.linToDb(row.value) >= 0 ? "+" : "")
+                    + root.linToDb(row.value).toFixed(1) + " dB)"
+            opacity: 0.7
+        }
+    }
+
+    Controls.Dialog {
+        id: errorDialog
+        property alias text: errorLabel.text
+        modal: true
+        standardButtons: Controls.Dialog.Ok
+        anchors.centerIn: parent
+        Controls.Label {
+            id: errorLabel
+            wrapMode: Text.WordWrap
+            width: errorDialog.availableWidth
+        }
+    }
+
+    Controls.Dialog {
+        id: savedDialog
+        title: "Saved"
+        modal: true
+        standardButtons: Controls.Dialog.Ok
+        anchors.centerIn: parent
+        Controls.Label {
+            wrapMode: Text.WordWrap
+            width: savedDialog.availableWidth
+            text: "Wrote " + Backend.confPath + "\nLive params applied."
+        }
+    }
+}

src/backend.cpp

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+#include "backend.h"
+
+#include <QCoreApplication>
+#include <QDir>
+#include <QFile>
+#include <QJsonArray>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QProcess>
+#include <QProcessEnvironment>
+#include <QRegularExpression>
+
+#include <unistd.h>
+
+namespace {
+
+QString confFilePath()
+{
+    return QDir::homePath()
+        + QStringLiteral("/.config/pipewire/filter-chain.conf.d/50-bass-manage-lfe.conf");
+}
+
+double toDouble(const QVariant &v, double fallback)
+{
+    bool ok = false;
+    const double d = v.toDouble(&ok);
+    return ok ? d : fallback;
+}
+
+QString runCapture(const QStringList &args)
+{
+    QProcess p;
+    p.setProcessChannelMode(QProcess::MergedChannels);
+    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    if (!env.contains(QStringLiteral("XDG_RUNTIME_DIR")))
+        env.insert(QStringLiteral("XDG_RUNTIME_DIR"),
+                   QStringLiteral("/run/user/%1").arg(getuid()));
+    p.setProcessEnvironment(env);
+    p.start(args.value(0), args.mid(1));
+    if (!p.waitForFinished(8000))
+        return {};
+    return QString::fromUtf8(p.readAllStandardOutput());
+}
+
+QString mixerBlock(const QString &text, const QString &name)
+{
+    const QRegularExpression re(
+        QStringLiteral(
+            R"(name\s*=\s*%1\s*\n\s*type\s*=\s*builtin\s*\n\s*label\s*=\s*mixer\s*\n\s*control\s*=\s*\{(.*?)\n\s*\})")
+            .arg(QRegularExpression::escape(name)),
+        QRegularExpression::DotMatchesEverythingOption);
+    const auto m = re.match(text);
+    return m.hasMatch() ? m.captured(1) : QString();
+}
+
+QMap<QString, double> parseGains(const QString &block)
+{
+    QMap<QString, double> out;
+    const QRegularExpression re(QString::fromUtf8(R"re("([^"]+)"\s*=\s*([0-9.]+))re"));
+    auto it = re.globalMatch(block);
+    while (it.hasNext()) {
+        const auto m = it.next();
+        out.insert(m.captured(1), m.captured(2).toDouble());
+    }
+    return out;
+}
+
+bool replaceMixer(QString &text, const QString &name, const QMap<QString, double> &gains)
+{
+    const QRegularExpression re(
+        QStringLiteral(
+            R"((name\s*=\s*%1\s*\n\s*type\s*=\s*builtin\s*\n\s*label\s*=\s*mixer\s*\n\s*control\s*=\s*\{)(.*?)(\n\s*\}))")
+            .arg(QRegularExpression::escape(name)),
+        QRegularExpression::DotMatchesEverythingOption);
+    const auto m = re.match(text);
+    if (!m.hasMatch())
+        return false;
+    QStringList lines;
+    for (auto it = gains.begin(); it != gains.end(); ++it)
+        lines << QStringLiteral("                            \"%1\" = %2")
+                     .arg(it.key())
+                     .arg(it.value(), 0, 'g', 6);
+    const QString block = m.captured(1) + QLatin1Char('\n') + lines.join(QLatin1Char('\n'))
+        + m.captured(3);
+    text.replace(m.capturedStart(), m.capturedLength(), block);
+    return true;
+}
+
+} // namespace
+
+QString bassManageDataRoot()
+{
+#ifdef BASS_MANAGE_SOURCE_DIR
+    {
+        const QString src = QString::fromUtf8(BASS_MANAGE_SOURCE_DIR);
+        if (QDir(src + QStringLiteral("/qml")).exists())
+            return src;
+    }
+#endif
+    // Installed layout: <prefix>/bin/bass-manage-gui → <prefix>/share/bass-manage
+    {
+        QDir bin(QCoreApplication::applicationDirPath());
+        if (bin.cd(QStringLiteral("../share/bass-manage"))
+            && QDir(bin.filePath(QStringLiteral("qml"))).exists())
+            return bin.absolutePath();
+    }
+    // Running from build/ inside the source tree
+    {
+        QDir dir(QCoreApplication::applicationDirPath());
+        if (dir.cdUp() && QDir(dir.filePath(QStringLiteral("qml"))).exists())
+            return dir.absolutePath();
+    }
+    return QDir::homePath() + QStringLiteral("/dev/bass-manage");
+}
+
+Backend::Backend(QObject *parent)
+    : QObject(parent)
+{
+    setStatus(QStringLiteral("Looking for bass_manage.7.1…"));
+    refreshNode();
+}
+
+QString Backend::iconDir() const
+{
+    return bassManageDataRoot() + QStringLiteral("/icons");
+}
+
+QString Backend::confPath() const
+{
+    return confFilePath();
+}
+
+void Backend::setStatus(const QString &s)
+{
+    if (m_status == s)
+        return;
+    m_status = s;
+    emit statusChanged();
+}
+
+void Backend::refreshNode()
+{
+    const bool was = connected();
+    m_nodeId = findNodeId();
+    if (connected() != was)
+        emit connectedChanged();
+    if (m_nodeId < 0)
+        setStatus(QStringLiteral("bass_manage.7.1 not found (is filter-chain running?)"));
+    else if (!m_status.contains(QStringLiteral("Applied"))
+             && !m_status.contains(QStringLiteral("Reloaded"))
+             && !m_status.contains(QStringLiteral("Saved")))
+        setStatus(QStringLiteral("Connected · node %1").arg(m_nodeId));
+}
+
+int Backend::findNodeId() const
+{
+    const QString out = runCapture({QStringLiteral("pw-dump")});
+    if (out.isEmpty())
+        return -1;
+    const QJsonDocument doc = QJsonDocument::fromJson(out.toUtf8());
+    if (!doc.isArray())
+        return -1;
+    for (const QJsonValue &v : doc.array()) {
+        const QJsonObject o = v.toObject();
+        if (o.value(QStringLiteral("type")).toString()
+            != QLatin1String("PipeWire:Interface:Node"))
+            continue;
+        const QJsonObject props = o.value(QStringLiteral("info")).toObject()
+                                      .value(QStringLiteral("props")).toObject();
+        if (props.value(QStringLiteral("node.name")).toString()
+            == QLatin1String("bass_manage.7.1"))
+            return o.value(QStringLiteral("id")).toInt(-1);
+    }
+    return -1;
+}
+
+QVariantMap Backend::logicalToPipewire(const QVariantMap &values) const
+{
+    return {
+        {QStringLiteral("mixFL:Gain 1"), toDouble(values.value(QStringLiteral("fl_dry")), 1.0)},
+        {QStringLiteral("mixFR:Gain 1"), toDouble(values.value(QStringLiteral("fr_dry")), 1.0)},
+        {QStringLiteral("mixFL:Gain 2"), toDouble(values.value(QStringLiteral("fc_to_fl")), 0.707)},
+        {QStringLiteral("mixFR:Gain 2"), toDouble(values.value(QStringLiteral("fc_to_fr")), 0.707)},
+        {QStringLiteral("mixLFE:Gain 1"), toDouble(values.value(QStringLiteral("lfe_fl")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 2"), toDouble(values.value(QStringLiteral("lfe_fr")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 3"), toDouble(values.value(QStringLiteral("lfe_fc")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 4"), toDouble(values.value(QStringLiteral("lfe_lfe")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 5"), toDouble(values.value(QStringLiteral("lfe_rl")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 6"), toDouble(values.value(QStringLiteral("lfe_rr")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 7"), toDouble(values.value(QStringLiteral("lfe_sl")), 0.99)},
+        {QStringLiteral("mixLFE:Gain 8"), toDouble(values.value(QStringLiteral("lfe_sr")), 0.99)},
+        {QStringLiteral("delayLFE:Delay (s)"), toDouble(values.value(QStringLiteral("lfe_delay")), 0.01)},
+    };
+}
+
+bool Backend::setParams(int nodeId, const QVariantMap &pipewireParams) const
+{
+    if (nodeId < 0 || pipewireParams.isEmpty())
+        return false;
+    QStringList parts;
+    for (auto it = pipewireParams.begin(); it != pipewireParams.end(); ++it) {
+        parts << QStringLiteral("\"%1\"").arg(it.key());
+        parts << QString::number(it.value().toDouble(), 'g', 6);
+    }
+    const QString body = QStringLiteral("{ params = [ %1 ] }").arg(parts.join(QLatin1Char(' ')));
+    QProcess p;
+    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    if (!env.contains(QStringLiteral("XDG_RUNTIME_DIR")))
+        env.insert(QStringLiteral("XDG_RUNTIME_DIR"),
+                   QStringLiteral("/run/user/%1").arg(getuid()));
+    p.setProcessEnvironment(env);
+    p.start(QStringLiteral("pw-cli"),
+            {QStringLiteral("set-param"), QString::number(nodeId), QStringLiteral("Props"), body});
+    return p.waitForFinished(5000) && p.exitCode() == 0;
+}
+
+QVariantMap Backend::loadConf()
+{
+    QFile f(confFilePath());
+    if (!f.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        emit errorOccurred(QStringLiteral("Reload failed"),
+                           QStringLiteral("Missing conf: %1").arg(confFilePath()));
+        return {};
+    }
+    const QString text = QString::fromUtf8(f.readAll());
+    const auto fl = parseGains(mixerBlock(text, QStringLiteral("mixFL")));
+    const auto fr = parseGains(mixerBlock(text, QStringLiteral("mixFR")));
+    const auto lfe = parseGains(mixerBlock(text, QStringLiteral("mixLFE")));
+    const QRegularExpression delayRe(QString::fromUtf8(R"re("Delay \(s\)"\s*=\s*([0-9.]+))re"));
+    const auto dm = delayRe.match(text);
+    if (fl.isEmpty() || fr.isEmpty() || lfe.isEmpty() || !dm.hasMatch()) {
+        emit errorOccurred(QStringLiteral("Reload failed"),
+                           QStringLiteral("Could not parse %1").arg(confFilePath()));
+        return {};
+    }
+
+    QVariantMap values{
+        {QStringLiteral("fl_dry"), fl.value(QStringLiteral("Gain 1"), 1.0)},
+        {QStringLiteral("fr_dry"), fr.value(QStringLiteral("Gain 1"), 1.0)},
+        {QStringLiteral("fc_to_fl"), fl.value(QStringLiteral("Gain 2"), 0.707)},
+        {QStringLiteral("fc_to_fr"), fr.value(QStringLiteral("Gain 2"), 0.707)},
+        {QStringLiteral("lfe_fl"), lfe.value(QStringLiteral("Gain 1"), 0.99)},
+        {QStringLiteral("lfe_fr"), lfe.value(QStringLiteral("Gain 2"), 0.99)},
+        {QStringLiteral("lfe_fc"), lfe.value(QStringLiteral("Gain 3"), 0.99)},
+        {QStringLiteral("lfe_lfe"), lfe.value(QStringLiteral("Gain 4"), 0.99)},
+        {QStringLiteral("lfe_rl"), lfe.value(QStringLiteral("Gain 5"), 0.99)},
+        {QStringLiteral("lfe_rr"), lfe.value(QStringLiteral("Gain 6"), 0.99)},
+        {QStringLiteral("lfe_sl"), lfe.value(QStringLiteral("Gain 7"), 0.99)},
+        {QStringLiteral("lfe_sr"), lfe.value(QStringLiteral("Gain 8"), 0.99)},
+        {QStringLiteral("lfe_delay"), dm.captured(1).toDouble()},
+    };
+
+    refreshNode();
+    if (m_nodeId >= 0) {
+        setParams(m_nodeId, logicalToPipewire(values));
+        setStatus(QStringLiteral("Reloaded from conf · node %1").arg(m_nodeId));
+    } else {
+        setStatus(QStringLiteral("Loaded from conf · sink not running"));
+    }
+    return values;
+}
+
+bool Backend::saveConf(const QVariantMap &values)
+{
+    QFile f(confFilePath());
+    if (!f.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        emit errorOccurred(QStringLiteral("Save failed"),
+                           QStringLiteral("Missing conf: %1").arg(confFilePath()));
+        return false;
+    }
+    QString text = QString::fromUtf8(f.readAll());
+    f.close();
+
+    QMap<QString, double> mixFL{
+        {QStringLiteral("Gain 1"), toDouble(values.value(QStringLiteral("fl_dry")), 1.0)},
+        {QStringLiteral("Gain 2"), toDouble(values.value(QStringLiteral("fc_to_fl")), 0.707)},
+    };
+    QMap<QString, double> mixFR{
+        {QStringLiteral("Gain 1"), toDouble(values.value(QStringLiteral("fr_dry")), 1.0)},
+        {QStringLiteral("Gain 2"), toDouble(values.value(QStringLiteral("fc_to_fr")), 0.707)},
+    };
+    QMap<QString, double> mixLFE{
+        {QStringLiteral("Gain 1"), toDouble(values.value(QStringLiteral("lfe_fl")), 0.99)},
+        {QStringLiteral("Gain 2"), toDouble(values.value(QStringLiteral("lfe_fr")), 0.99)},
+        {QStringLiteral("Gain 3"), toDouble(values.value(QStringLiteral("lfe_fc")), 0.99)},
+        {QStringLiteral("Gain 4"), toDouble(values.value(QStringLiteral("lfe_lfe")), 0.99)},
+        {QStringLiteral("Gain 5"), toDouble(values.value(QStringLiteral("lfe_rl")), 0.99)},
+        {QStringLiteral("Gain 6"), toDouble(values.value(QStringLiteral("lfe_rr")), 0.99)},
+        {QStringLiteral("Gain 7"), toDouble(values.value(QStringLiteral("lfe_sl")), 0.99)},
+        {QStringLiteral("Gain 8"), toDouble(values.value(QStringLiteral("lfe_sr")), 0.99)},
+    };
+
+    if (!replaceMixer(text, QStringLiteral("mixFL"), mixFL)
+        || !replaceMixer(text, QStringLiteral("mixFR"), mixFR)
+        || !replaceMixer(text, QStringLiteral("mixLFE"), mixLFE)) {
+        emit errorOccurred(QStringLiteral("Save failed"),
+                           QStringLiteral("Could not update mixer blocks"));
+        return false;
+    }
+
+    const double delay = toDouble(values.value(QStringLiteral("lfe_delay")), 0.01);
+    const QRegularExpression delayRe(
+        QString::fromUtf8(R"re((control\s*=\s*\{\s*"Delay \(s\)"\s*=\s*)([0-9.]+))re"));
+    const auto dm = delayRe.match(text);
+    if (!dm.hasMatch()) {
+        emit errorOccurred(QStringLiteral("Save failed"),
+                           QStringLiteral("Could not update delay"));
+        return false;
+    }
+    text.replace(dm.capturedStart(), dm.capturedLength(),
+                 dm.captured(1) + QString::number(delay, 'g', 6));
+
+    if (!f.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate)) {
+        emit errorOccurred(QStringLiteral("Save failed"), f.errorString());
+        return false;
+    }
+    f.write(text.toUtf8());
+    f.close();
+
+    applyLive(values);
+    setStatus(QStringLiteral("Saved · %1").arg(confFilePath()));
+    return true;
+}
+
+bool Backend::applyLive(const QVariantMap &values)
+{
+    refreshNode();
+    if (m_nodeId < 0) {
+        setStatus(QStringLiteral("bass_manage.7.1 not found"));
+        return false;
+    }
+    const bool ok = setParams(m_nodeId, logicalToPipewire(values));
+    setStatus(ok ? QStringLiteral("Applied · node %1").arg(m_nodeId)
+                 : QStringLiteral("Apply failed · node %1").arg(m_nodeId));
+    return ok;
+}

src/backend.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <QObject>
+#include <QString>
+#include <QVariantMap>
+
+/** Project / install data root (contains qml/ and icons/). */
+QString bassManageDataRoot();
+
+class Backend : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(QString status READ status NOTIFY statusChanged)
+    Q_PROPERTY(bool connected READ connected NOTIFY connectedChanged)
+    Q_PROPERTY(QString iconDir READ iconDir CONSTANT)
+    Q_PROPERTY(QString confPath READ confPath CONSTANT)
+
+public:
+    explicit Backend(QObject *parent = nullptr);
+
+    QString status() const { return m_status; }
+    bool connected() const { return m_nodeId >= 0; }
+    QString iconDir() const;
+    QString confPath() const;
+
+    Q_INVOKABLE QVariantMap loadConf();
+    Q_INVOKABLE bool saveConf(const QVariantMap &values);
+    Q_INVOKABLE bool applyLive(const QVariantMap &values);
+    Q_INVOKABLE void refreshNode();
+
+signals:
+    void statusChanged();
+    void connectedChanged();
+    void errorOccurred(const QString &title, const QString &message);
+
+private:
+    int findNodeId() const;
+    bool setParams(int nodeId, const QVariantMap &pipewireParams) const;
+    QVariantMap logicalToPipewire(const QVariantMap &values) const;
+    void setStatus(const QString &s);
+
+    int m_nodeId = -1;
+    QString m_status;
+};

src/main.cpp

@@ -0,0 +1,41 @@
+#include "backend.h"
+
+#include <QGuiApplication>
+#include <QIcon>
+#include <QQmlApplicationEngine>
+#include <QQmlContext>
+#include <QQuickStyle>
+#include <QTimer>
+#include <QUrl>
+
+int main(int argc, char *argv[])
+{
+    qputenv("QT_QPA_PLATFORM", "wayland;xcb");
+
+    QGuiApplication app(argc, argv);
+    app.setOrganizationName(QStringLiteral("local"));
+    app.setApplicationName(QStringLiteral("bass-manage"));
+    app.setDesktopFileName(QStringLiteral("bass-manage-gui"));
+    app.setWindowIcon(QIcon::fromTheme(QStringLiteral("bass-manage-gui"),
+                                       QIcon::fromTheme(QStringLiteral("audio-card"))));
+
+    // Plasma / system style (not Material/Fusion override)
+    if (qEnvironmentVariableIsEmpty("QT_QUICK_CONTROLS_STYLE"))
+        QQuickStyle::setStyle(QStringLiteral("org.kde.desktop"));
+
+    Backend backend;
+
+    QQmlApplicationEngine engine;
+    engine.rootContext()->setContextProperty(QStringLiteral("Backend"), &backend);
+
+    const QString qmlPath = bassManageDataRoot() + QStringLiteral("/qml/Main.qml");
+    engine.load(QUrl::fromLocalFile(qmlPath));
+    if (engine.rootObjects().isEmpty())
+        return 1;
+
+    QTimer nodeWatch;
+    QObject::connect(&nodeWatch, &QTimer::timeout, &backend, &Backend::refreshNode);
+    nodeWatch.start(2000);
+
+    return app.exec();
+}