package adsr sliders into an envelopeGenerator widget

src/ui/widgets/EnvelopeGenerator/EnvelopeGenerator.h

@@ -0,0 +1,37 @@
+
+#pragma once
+
+#include <QWidget>
+
+QT_BEGIN_NAMESPACE
+namespace Ui { class EnvelopeGenerator; }
+QT_END_NAMESPACE
+
+// this is for the widget, not the synth object named Envelope
+class EnvelopeGenerator : public QWidget {
+    Q_OBJECT
+public:
+    explicit EnvelopeGenerator(QWidget* parent = nullptr);
+    ~EnvelopeGenerator();
+
+    void setAttack(float v);
+    void setDecay(float v);
+    void setSustain(float v);
+    void setRelease(float v);
+
+    void setRanges(float minA, float maxA, float minD, float maxD, float minS, float maxS, float minR, float maxR);
+
+    float attack() const;
+    float decay() const;
+    float sustain() const;
+    float release() const;
+
+signals:
+    void envelopeChanged(double a, double d, double s, double r);
+
+private:
+
+    Ui::EnvelopeGenerator* ui_;
+
+    void emitEnvelope();
+};