controllers: add helper to control "waveform_zoom" with potmeters

res/controllers/common-controller-scripts.js

@@ -32,7 +32,6 @@ String.prototype.toInt = function() {
 
 /**
  * Prints a message to the terminal and the log file.
- *
  * @param {string} message - The log message.
  * @deprecated Use console.log()/console.warn()/console.debug() instead.
  */
@@ -380,6 +379,20 @@ script.crossfaderCurve = function(value, min, max) {
     }
 };
 
+/* -------- ------------------------------------------------------
+     script.waveformZoom
+   Purpose: Adjusts the wavform zoom level with a pot (0 <= value <= 127)
+            "waveform_zoom" behaves like a ControlPotmeter but is actually
+            a ControlObject (no min, max or default), so we need to calculate
+            the scaled with script.absoluteLin().
+   Input:   Deck group, current value of the hardware control
+   Output:  none
+   -------- ------------------------------------------------------ */
+script.waveformZoom = function(group, value) {
+    const scaledValue = script.absoluteLin(value, 0, 10, 0, 127);
+    engine.setValue(group, "waveform_zoom", scaledValue);
+};
+
 /* -------- ------------------------------------------------------
      script.posMod
    Purpose: Computes the euclidean modulo of m % n. The result is always

src/mixer/basetrackplayer.cpp

@@ -140,9 +140,12 @@ BaseTrackPlayerImpl::BaseTrackPlayerImpl(
             this,
             &BaseTrackPlayerImpl::slotLoadTrackFromSampler);
 
-    // Waveform controls
-    // This acts somewhat like a ControlPotmeter, but the normal _up/_down methods
-    // do not work properly with this CO.
+    // Waveform zoom controls
+    // This acts somewhat like a ControlPotmeter, but the normal ControlPotmeter's
+    // _up/_down methods would not work properly with this CO. Instead, _up/_down,
+    // scroll wheel ticks sent to the waveform widget and the default zoom level
+    // combobox in the waveform preferences page set discrete zoom levels
+    // (integer values of "waveform_zoom").
     m_pWaveformZoom =
             std::make_unique<ControlObject>(ConfigKey(getGroup(), "waveform_zoom"));
     m_pWaveformZoom->connectValueChangeRequest(this,

src/waveform/renderers/waveformwidgetrenderer.cpp

@@ -10,6 +10,8 @@
 #include "waveform/visualplayposition.h"
 #include "waveform/waveform.h"
 
+// When changing these zoom values remember to also adjust the range in
+// script.waveformZoom in /res/controllers/common-controller-scripts.js
 const double WaveformWidgetRenderer::s_waveformMinZoom = 1.0;
 const double WaveformWidgetRenderer::s_waveformMaxZoom = 10.0;
 const double WaveformWidgetRenderer::s_waveformDefaultZoom = 3.0;