1 files changed, 80 insertions, 0 deletions
diff --git a/examples/multimedia/spectrum/levelmeter.h b/examples/multimedia/spectrum/levelmeter.h
new file mode 100644
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+++ b/examples/multimedia/spectrum/levelmeter.h
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+// Copyright (C) 2017 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef LEVELMETER_H
+#define LEVELMETER_H
+
+#include <QElapsedTimer>
+#include <QWidget>
+
+/**
+ * Widget which displays a vertical audio level meter, indicating the
+ * RMS and peak levels of the window of audio samples most recently analyzed
+ * by the Engine.
+ */
+class LevelMeter : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit LevelMeter(QWidget *parent = nullptr);
+    ~LevelMeter();
+
+    void paintEvent(QPaintEvent *event) override;
+
+public slots:
+    void reset();
+    void levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples);
+
+private slots:
+    void redrawTimerExpired();
+
+private:
+    /**
+     * Height of RMS level bar.
+     * Range 0.0 - 1.0.
+     */
+    qreal m_rmsLevel;
+
+    /**
+     * Most recent peak level.
+     * Range 0.0 - 1.0.
+     */
+    qreal m_peakLevel;
+
+    /**
+     * Height of peak level bar.
+     * This is calculated by decaying m_peakLevel depending on the
+     * elapsed time since m_peakLevelChanged, and the value of m_decayRate.
+     */
+    qreal m_decayedPeakLevel;
+
+    /**
+     * Time at which m_peakLevel was last changed.
+     */
+    QElapsedTimer m_peakLevelChanged;
+
+    /**
+     * Rate at which peak level bar decays.
+     * Expressed in level units / millisecond.
+     */
+    qreal m_peakDecayRate;
+
+    /**
+     * High watermark of peak level.
+     * Range 0.0 - 1.0.
+     */
+    qreal m_peakHoldLevel;
+
+    /**
+     * Time at which m_peakHoldLevel was last changed.
+     */
+    QElapsedTimer m_peakHoldLevelChanged;
+
+    QTimer *m_redrawTimer;
+
+    QColor m_rmsColor;
+    QColor m_peakColor;
+};
+
+#endif // LEVELMETER_H