Add beginChangeGesture/endChangeGesture support to audio demo plug-in

examples/audio plugin demo/Source/PluginEditor.cpp

@@ -102,16 +102,28 @@ void JuceDemoPluginAudioProcessorEditor::timerCallback()
 // This is our Slider::Listener callback, when the user drags a slider.
 void JuceDemoPluginAudioProcessorEditor::sliderValueChanged (Slider* slider)
 {
-    if (slider == &gainSlider)
+    if (AudioProcessorParameter* param = getParameterFromSlider (slider))
     {
         // It's vital to use setValueNotifyingHost to change any parameters that are automatable
         // by the host, rather than just modifying them directly, otherwise the host won't know
         // that they've changed.
-        getProcessor().gain->setValueNotifyingHost ((float) gainSlider.getValue());
+        param->setValueNotifyingHost ((float) slider->getValue());
     }
-    else if (slider == &delaySlider)
+}
+
+void JuceDemoPluginAudioProcessorEditor::sliderDragStarted (Slider* slider)
+{
+    if (AudioProcessorParameter* param = getParameterFromSlider (slider))
+    {
+        param->beginChangeGesture();
+    }
+}
+
+void JuceDemoPluginAudioProcessorEditor::sliderDragEnded (Slider* slider)
+{
+    if (AudioProcessorParameter* param = getParameterFromSlider (slider))
     {
-        getProcessor().delay->setValueNotifyingHost ((float) delaySlider.getValue());
+        param->endChangeGesture();
     }
 }
 
@@ -153,6 +165,20 @@ static String ppqToBarsBeatsString (double ppq, double /*lastBarPPQ*/, int numer
     return s;
 }
 
+AudioProcessorParameter* JuceDemoPluginAudioProcessorEditor::getParameterFromSlider (const Slider* slider) const
+{
+    if (slider == &gainSlider)
+    {
+        return getProcessor().gain;
+    }
+    else if (slider == &delaySlider)
+    {
+        return getProcessor().delay;
+    }
+
+    return nullptr;
+}
+
 // Updates the text in our position label.
 void JuceDemoPluginAudioProcessorEditor::displayPositionInfo (const AudioPlayHead::CurrentPositionInfo& pos)
 {

examples/audio plugin demo/Source/PluginEditor.h

@@ -31,6 +31,8 @@ public:
     void paint (Graphics&) override;
     void resized() override;
     void sliderValueChanged (Slider*) override;
+    void sliderDragStarted  (Slider*) override;
+    void sliderDragEnded    (Slider*) override;
 
 private:
     MidiKeyboardComponent midiKeyboard;
@@ -41,11 +43,14 @@ private:
 
     AudioPlayHead::CurrentPositionInfo lastDisplayedPosition;
 
+    //==============================================================================
     JuceDemoPluginAudioProcessor& getProcessor() const
     {
         return static_cast<JuceDemoPluginAudioProcessor&> (processor);
     }
 
+    AudioProcessorParameter* getParameterFromSlider (const Slider*) const;
+
     void displayPositionInfo (const AudioPlayHead::CurrentPositionInfo& pos);
 };