Add the basis for a simple STFT example

Right now it doesn't do any FFT operations yet, but all the pieces are
in place using the new STFT helper.

Cargo.lock

@@ -855,6 +855,13 @@ dependencies = [
  "wayland-client",
 ]
 
+[[package]]
+name = "stft"
+version = "0.1.0"
+dependencies = [
+ "nih_plug",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.86"

Cargo.toml

@@ -21,6 +21,7 @@ members = [
   "plugins/examples/gain",
   "plugins/examples/gain-gui",
   "plugins/examples/sine",
+  "plugins/examples/stft",
 
   "plugins/diopser",
 ]

README.md

@@ -77,6 +77,10 @@ examples.
 - [**sine**](plugins/examples/sine) is a simple test tone generator plugin with
   frequency smoothing that can also make use of MIDI input instead of generating
   a static signal based on the plugin's parameters.
+- [**stft**](plugins/examples/stft) shows off some of NIH-plug's other optional
+  helper features, like an adapter to process audio in buffered blocks meant for
+  short-term Fourier transform operations, all using the compositional `Buffer`
+  interface.
 
 ## Licensing
 

plugins/examples/stft/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "stft"
+version = "0.1.0"
+edition = "2021"
+authors = ["Robbert van der Helm <mail@robbertvanderhelm.nl>"]
+license = "ISC"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+nih_plug = { path = "../../../", features = ["assert_process_allocs"] }

plugins/examples/stft/src/lib.rs

@@ -0,0 +1,98 @@
+use nih_plug::prelude::*;
+use std::pin::Pin;
+
+struct Stft {
+    params: Pin<Box<StftParams>>,
+
+    stft: util::StftHelper,
+}
+
+#[derive(Params)]
+struct StftParams {}
+
+impl Default for Stft {
+    fn default() -> Self {
+        Self {
+            params: Box::pin(StftParams::default()),
+
+            stft: util::StftHelper::new(2, 512),
+        }
+    }
+}
+
+impl Default for StftParams {
+    fn default() -> Self {
+        Self {}
+    }
+}
+
+impl Plugin for Stft {
+    const NAME: &'static str = "STFT Example";
+    const VENDOR: &'static str = "Moist Plugins GmbH";
+    const URL: &'static str = "https://youtu.be/dQw4w9WgXcQ";
+    const EMAIL: &'static str = "info@example.com";
+
+    const VERSION: &'static str = "0.0.1";
+
+    const DEFAULT_NUM_INPUTS: u32 = 2;
+    const DEFAULT_NUM_OUTPUTS: u32 = 2;
+
+    const ACCEPTS_MIDI: bool = false;
+
+    fn params(&self) -> Pin<&dyn Params> {
+        self.params.as_ref()
+    }
+
+    fn accepts_bus_config(&self, config: &BusConfig) -> bool {
+        // We'll only do stereo for simplicity's sake
+        config.num_input_channels == config.num_output_channels && config.num_input_channels == 2
+    }
+
+    fn initialize(
+        &mut self,
+        _bus_config: &BusConfig,
+        _buffer_config: &BufferConfig,
+        context: &mut impl ProcessContext,
+    ) -> bool {
+        // Normally we'd also initialize the STFT helper for the correct channel count here, but we
+        // only do stereo so that's not necessary
+        self.stft.set_block_size(512);
+        context.set_latency_samples(self.stft.latency_samples());
+
+        true
+    }
+
+    fn process(
+        &mut self,
+        buffer: &mut Buffer,
+        _context: &mut impl ProcessContext,
+    ) -> ProcessStatus {
+        self.stft.process(buffer, [], |block, _| {
+            for channel_samples in block.iter_mut() {
+                for sample in channel_samples {
+                    // TODO: Use the FFTW bindings and do some STFT operation here instead of
+                    //       reducing the gain at a 512 sample latency...
+                    *sample *= 0.5;
+                }
+            }
+        });
+
+        ProcessStatus::Normal
+    }
+}
+
+impl ClapPlugin for Stft {
+    const CLAP_ID: &'static str = "com.moist-plugins-gmbh.stft";
+    const CLAP_DESCRIPTION: &'static str = "An example plugin using the STFT helper";
+    const CLAP_FEATURES: &'static [&'static str] = &["audio_effect", "stereo", "tool"];
+    const CLAP_MANUAL_URL: &'static str = Self::URL;
+    const CLAP_SUPPORT_URL: &'static str = Self::URL;
+}
+
+impl Vst3Plugin for Stft {
+    const VST3_CLASS_ID: [u8; 16] = *b"StftMoistestPlug";
+    const VST3_CATEGORIES: &'static str = "Fx|Tools";
+}
+
+nih_export_clap!(Stft);
+nih_export_vst3!(Stft);