Jamba Views / Discrete Button

Discrete Button

Discrete Button

A discrete button behaves like a toggle button except that it is on only if the control value (tied to a parameter) is equal to the step value (DiscreteButtonView::getStep() / step property in the xml). Selecting the button will set the underlying parameter to step. This button can be used to implement a radio group button behavior (only one selected at a time).

This view works for any parameter (both Vst and Jmb) that is (or can be interpreted as) a discrete parameter.

In addition to the attributes exposed by CustomDiscreteControlView, this class exposes the following attributes:

Attribute Description
frames The number of frames the image contains. Should be either 2 or 4 (4 includes the pressed state).
on-color When no image is provided, back-color is used for the “off” state and on-color for the “on” state (draws a rectangle with this color).
button-image The image for the button (2 or 4 frames).
inverse Inverses the meaning of “on” and “off” in regards to drawing the view/image.
step The value used to check whether the button is “on” or “off” as well as the value to set the parameter to when the button is selected.

Like the toggle button, it can have 2 or 4 frames (handle depressed state).

The image above shows an example of a vst parameter representing a bank (A through D) of pads. The vst parameter is backed by a discrete value (a VST parameter where step count > 0). The UI shows 4 discrete buttons each one tied to a different step. Because a discrete button is on only when the vst parameter matches its step, selecting one will automatically deselect the others.


The XML defining the 4 buttons (Source)

<view class="jamba::DiscreteButton" control-tag="Param_PadBank" step="0" frames="2" origin="415, 296" size="26, 26" ... />
<view class="jamba::DiscreteButton" control-tag="Param_PadBank" step="1" frames="2" origin="450, 296" size="26, 26" ... />
<view class="jamba::DiscreteButton" control-tag="Param_PadBank" step="2" frames="2" origin="485, 296" size="26, 26" ... />
<view class="jamba::DiscreteButton" control-tag="Param_PadBank" step="3" frames="2" origin="520, 296" size="26, 26" ... />

The vst param is defined this way (discrete parameter => represented by int) (Source)

VstParam<int> fPadBank;

The vst param is initialized this way (Source)

fPadBank =
  vst<DiscreteValueParamConverter<NUM_PAD_BANKS - 1>>(ESampleSplitterParamID::kPadBank,
                                                      STR16("Page %d"), 1)