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50
51#ifndef LEVELMETER_H
52#define LEVELMETER_H
53
54#include <QElapsedTimer>
55#include <QWidget>
56
57/**
58 * Widget which displays a vertical audio level meter, indicating the
59 * RMS and peak levels of the window of audio samples most recently analyzed
60 * by the Engine.
61 */
62class LevelMeter : public QWidget
63{
64 Q_OBJECT
65
66public:
67 explicit LevelMeter(QWidget *parent = 0);
68 ~LevelMeter();
69
70 void paintEvent(QPaintEvent *event) override;
71
72public slots:
73 void reset();
74 void levelChanged(qreal rmsLevel, qreal peakLevel, int numSamples);
75
76private slots:
77 void redrawTimerExpired();
78
79private:
80 /**
81 * Height of RMS level bar.
82 * Range 0.0 - 1.0.
83 */
84 qreal m_rmsLevel;
85
86 /**
87 * Most recent peak level.
88 * Range 0.0 - 1.0.
89 */
90 qreal m_peakLevel;
91
92 /**
93 * Height of peak level bar.
94 * This is calculated by decaying m_peakLevel depending on the
95 * elapsed time since m_peakLevelChanged, and the value of m_decayRate.
96 */
97 qreal m_decayedPeakLevel;
98
99 /**
100 * Time at which m_peakLevel was last changed.
101 */
102 QElapsedTimer m_peakLevelChanged;
103
104 /**
105 * Rate at which peak level bar decays.
106 * Expressed in level units / millisecond.
107 */
108 qreal m_peakDecayRate;
109
110 /**
111 * High watermark of peak level.
112 * Range 0.0 - 1.0.
113 */
114 qreal m_peakHoldLevel;
115
116 /**
117 * Time at which m_peakHoldLevel was last changed.
118 */
119 QElapsedTimer m_peakHoldLevelChanged;
120
121 QTimer *m_redrawTimer;
122
123 QColor m_rmsColor;
124 QColor m_peakColor;
125
126};
127
128#endif // LEVELMETER_H
129

source code of qtmultimedia/examples/multimedia/spectrum/app/levelmeter.h