nih-plug/src/wrapper/clap/context.rs

use atomic_refcell::AtomicRefMut;
use crossbeam::channel;
use std::collections::VecDeque;
use std::sync::atomic::Ordering;
use std::sync::Arc;

use super::wrapper::{OutputParamEvent, Task, Wrapper};
use crate::context::{GuiContext, ProcessContext, Transport};
use crate::event_loop::EventLoop;
use crate::param::internals::ParamPtr;
use crate::plugin::{ClapPlugin, NoteEvent};

/// A [`GuiContext`] implementation for the wrapper. This is passed to the plugin in
/// [`Editor::spawn()`][crate::prelude::Editor::spawn()] so it can interact with the rest of the plugin and
/// with the host for things like setting parameters.
pub(crate) struct WrapperGuiContext<P: ClapPlugin> {
    pub(super) wrapper: Arc<Wrapper<P>>,
}

/// A [`ProcessContext`] implementation for the wrapper. This is a separate object so it can hold on
/// to lock guards for event queues. Otherwise reading these events would require constant
/// unnecessary atomic operations to lock the uncontested RwLocks.
pub(crate) struct WrapperProcessContext<'a, P: ClapPlugin> {
    pub(super) wrapper: &'a Wrapper<P>,
    pub(super) input_events_guard: AtomicRefMut<'a, VecDeque<NoteEvent>>,
    pub(super) transport: Transport,
}

impl<P: ClapPlugin> GuiContext for WrapperGuiContext<P> {
    fn request_resize(&self) -> bool {
        // Bitwig and the CLAP test host require this resize to be done from the main thread, so
        // we'll use a channel as a substitute for a promise here.
        let (result_sender, result_receiver) = channel::bounded(1);
        if !self
            .wrapper
            .do_maybe_async(Task::RequestResize(result_sender))
        {
            nih_debug_assert_failure!("The task queue is full, dropping task...");
            return false;
        }

        // FIXME: Waiting for this can be very slow when this function gets called many times in
        //        rapid succession because the X11 GUI thread is not the same as the host's GUI
        //        thread and both Bitwig and CLAP will reject (or outright SIGABRT) if this gets
        //        called from any other thread
        result_receiver.recv().expect("Main thread died?")
    }

    // All of these functions are supposed to be called from the main thread, so we'll put some
    // trust in the caller and assume that this is indeed the case
    unsafe fn raw_begin_set_parameter(&self, param: ParamPtr) {
        match self.wrapper.param_ptr_to_hash.get(&param) {
            Some(hash) => {
                let success = self
                    .wrapper
                    .queue_parameter_event(OutputParamEvent::BeginGesture { param_hash: *hash });

                nih_debug_assert!(success, "Parameter output event queue was full, parameter change will not be sent to the host");
            }
            None => nih_debug_assert_failure!("Unknown parameter: {:?}", param),
        }
    }

    unsafe fn raw_set_parameter_normalized(&self, param: ParamPtr, normalized: f32) {
        match self.wrapper.param_ptr_to_hash.get(&param) {
            Some(hash) => {
                // We queue the parameter change event here, and it will be sent to the host either
                // at the end of the current processing cycle or after requesting an explicit flush
                // (when the plugin isn't processing audio). The parameter's actual value will only
                // be changed when the output event is written to prevent changing parameter values
                // in the middle of processing audio.
                let clap_plain_value = normalized as f64 * param.step_count().unwrap_or(1) as f64;
                let success = self
                    .wrapper
                    .queue_parameter_event(OutputParamEvent::SetValue {
                        param_hash: *hash,
                        clap_plain_value,
                    });

                nih_debug_assert!(success, "Parameter output event queue was full, parameter change will not be sent to the host");
            }
            None => nih_debug_assert_failure!("Unknown parameter: {:?}", param),
        }
    }

    unsafe fn raw_end_set_parameter(&self, param: ParamPtr) {
        match self.wrapper.param_ptr_to_hash.get(&param) {
            Some(hash) => {
                let success = self
                    .wrapper
                    .queue_parameter_event(OutputParamEvent::EndGesture { param_hash: *hash });

                nih_debug_assert!(success, "Parameter output event queue was full, parameter change will not be sent to the host");
            }
            None => nih_debug_assert_failure!("Unknown parameter: {:?}", param),
        }
    }
}

impl<P: ClapPlugin> ProcessContext for WrapperProcessContext<'_, P> {
    fn transport(&self) -> &Transport {
        &self.transport
    }

    fn next_midi_event(&mut self) -> Option<NoteEvent> {
        self.input_events_guard.pop_front()
    }

    fn set_latency_samples(&self, samples: u32) {
        // Only make a callback if it's actually needed
        // XXX: For CLAP we could move this handling to the Plugin struct, but it may be worthwhile
        //      to keep doing it this way to stay consistent with VST3.
        let old_latency = self.wrapper.current_latency.swap(samples, Ordering::SeqCst);
        if old_latency != samples {
            let task_posted = self.wrapper.do_maybe_async(Task::LatencyChanged);
            nih_debug_assert!(task_posted, "The task queue is full, dropping task...");
        }
    }
}