preset.hpp

Go to the documentation of this file.

// sbl/control/preset.hpp — A voice's settings, kept and recalled by program
//
// A preset is what a controller would have sent: a handful of CC values. It
// is applied by pushing those values through the app's own CcMapper, so a
// preset lands exactly where a knob does — same curves, same merge policies,
// same targets — and an app needs no second path into its parameters.
//
// Presets are generated, never parsed: they are authored in the app's
// `app.sbl.json` (inline, or a file or directory it points at) and sloth
// emits them as `sbl::app::presets`. Nothing reads a file at runtime, and
// hardware and the workbench get the same table.
//
// Program numbers are MIDI's: a Program Change selects a preset, so a MIDI
// file that names a sound gets one. A program the table does not have leaves
// the voice alone; silence is worse than an unchanged voice.
//
// Usage:
//   #include <sbl/hw/config/presets.hpp>   // generated
//   if (const auto* p = sbl::control::find_preset(sbl::app::presets,
//                                                 sbl::app::preset_count, program)) {
//       sbl::control::apply_preset(*p, [](uint8_t cc, uint8_t value) {
//           mapper.on_cc(channel, cc, value, store);
//       });
//   }
 
#ifndef SBL_CONTROL_PRESET_HPP_
#define SBL_CONTROL_PRESET_HPP_
 
#include <cstdint>
 
namespace sbl::control {
 
/// One controller value in a preset.
struct PresetCc {
    uint8_t cc;
    uint8_t value;
};
 
/// A named set of controller values, selected by MIDI program number.
struct Preset {
    uint8_t program;         ///< MIDI program (0–127) that selects it
    const char* name;        ///< what it is called, for logs and displays
    const PresetCc* cc;      ///< the values it sets
    uint8_t count;
};
 
/// The preset a program selects, or nullptr if the table has none.
inline const Preset* find_preset(const Preset* presets, uint8_t count, uint8_t program) {
    if (presets == nullptr) return nullptr;
    for (uint8_t i = 0; i < count; ++i) {
        if (presets[i].program == program) return &presets[i];
    }
    return nullptr;
}
 
/// Send a preset's values wherever a controller's would go.
template<typename Sink>
inline void apply_preset(const Preset& preset, Sink&& sink) {
    for (uint8_t i = 0; i < preset.count; ++i) {
        sink(preset.cc[i].cc, preset.cc[i].value);
    }
}
 
} // namespace sbl::control
 
#endif // SBL_CONTROL_PRESET_HPP_