Slider `scale` metadata not interpreted

[hatchjaw]

Steps to Reproduce

• Run the plugin or standalone
• Enter the following code

import("stdfaust.lib");
freq = hslider("freq [scale:log]", 400, 20, 20000, .01);
gate = button("gate");
gain = hslider("gain", .5, 0, 1, .01);
process = os.square(freq),en.ar(.05, 1, gate) : *,gain : *;

• Click compile (view switches to Parameters tab)

Expected Behaviour

• freq slider has logarithmic range.

Actual behaviour

• freq slider has linear range.

Here's how the freq slider looks in the Faust Web IDE:

Thanks to the [scale:log] metadata, 400 (Hz) lies somewhere toward the middle of the slider.

Here's the equivalent for Amati++:

NB. [scale:exp] and numerical metadata for setting the order of parameters in the UI (e.g. hslider("[10] myparam...) are also apparently not interpreted.

System

OS: Manjaro Linux Kernel: Linux 6.5.13-7-MANJARO Audio system: Pipewire (libpipewire 1.0.7)

Builds tested

• Standalone
• VST3 (hosts: Reaper, AudioPluginHost)
• CLAP (hosts: Reaper)

[sletz]

Since the code used the APIUI helper class, I've just realised that the ratio related functions (which take the scale mapping in account) have to be used and not the setParamValue/getParamValueones.

Proper documentation added this morning in https://github.com/grame-cncm/faust/commit/c5d114f8ee61ab09445d50738b7099e9993c723f

And look at the new documentation here: https://github.com/grame-cncm/faust/blob/c5d114f8ee61ab09445d50738b7099e9993c723f/architecture/faust/gui/APIUI.h#L549

[hatchjaw]

Could juce::Slider::setSkewFactor help here?

[sletz]

Well the problem is to exactly reproduce what the Faust conversion functions currently do (see https://github.com/grame-cncm/faust/blob/master-dev/architecture/faust/gui/ValueConverter.h). So I think we should better use them to get a homogenous behaviour on every platform.