Trying to clena the mess opened by plugins

plugins/nih-plug-egui/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "nih_plug_egui"
+version = "0.0.0"
+edition = "2021"
+authors = ["Robbert van der Helm <mail@robbertvanderhelm.nl>"]
+license = "ISC"
+
+description = "An adapter to use egui GUIs with NIH-plug"
+
+[features]
+default = ["opengl", "default_fonts"]
+# `nih_plug_egui` always uses OpenGL since egui's wgpu backend is still unstable
+# depending on the platform
+opengl = ["egui-baseview/opengl"]
+default_fonts = ["egui-baseview/default_fonts"]
+
+[dependencies]
+nih_plug = { git = "https://github.com/robbert-vdh/nih-plug", default-features = false }
+raw-window-handle = "0.5"
+baseview = { path = "../baseview" }
+crossbeam = "0.8"
+egui-baseview = { path = "../egui-baseview" }
+parking_lot = "0.12"
+# To make the state persistable
+serde = { version = "1.0", features = ["derive"] }

plugins/nih-plug-egui/src/editor.rs

@@ -0,0 +1,194 @@
+//! An [`Editor`] implementation for egui.
+
+use crate::egui::Vec2;
+use crate::egui::ViewportCommand;
+use crate::EguiState;
+use baseview::gl::GlConfig;
+use baseview::PhySize;
+use baseview::{Size, WindowHandle, WindowOpenOptions, WindowScalePolicy};
+use crossbeam::atomic::AtomicCell;
+use egui_baseview::egui::Context;
+use egui_baseview::EguiWindow;
+use nih_plug::prelude::{Editor, GuiContext, ParamSetter, ParentWindowHandle};
+use parking_lot::RwLock;
+use raw_window_handle::{HasRawWindowHandle, RawWindowHandle};
+use std::sync::atomic::Ordering;
+use std::sync::Arc;
+
+/// An [`Editor`] implementation that calls an egui draw loop.
+pub(crate) struct EguiEditor<T> {
+    pub(crate) egui_state: Arc<EguiState>,
+    /// The plugin's state. This is kept in between editor openenings.
+    pub(crate) user_state: Arc<RwLock<T>>,
+
+    /// The user's build function. Applied once at the start of the application.
+    pub(crate) build: Arc<dyn Fn(&Context, &mut T) + 'static + Send + Sync>,
+    /// The user's update function.
+    pub(crate) update: Arc<dyn Fn(&Context, &ParamSetter, &mut T) + 'static + Send + Sync>,
+
+    /// The scaling factor reported by the host, if any. On macOS this will never be set and we
+    /// should use the system scaling factor instead.
+    pub(crate) scaling_factor: AtomicCell<Option<f32>>,
+}
+
+/// This version of `baseview` uses a different version of `raw_window_handle than NIH-plug, so we
+/// need to adapt it ourselves.
+struct ParentWindowHandleAdapter(nih_plug::editor::ParentWindowHandle);
+
+unsafe impl HasRawWindowHandle for ParentWindowHandleAdapter {
+    fn raw_window_handle(&self) -> RawWindowHandle {
+        match self.0 {
+            ParentWindowHandle::X11Window(window) => {
+                let mut handle = raw_window_handle::XcbWindowHandle::empty();
+                handle.window = window;
+                RawWindowHandle::Xcb(handle)
+            }
+            ParentWindowHandle::AppKitNsView(ns_view) => {
+                let mut handle = raw_window_handle::AppKitWindowHandle::empty();
+                handle.ns_view = ns_view;
+                RawWindowHandle::AppKit(handle)
+            }
+            ParentWindowHandle::Win32Hwnd(hwnd) => {
+                let mut handle = raw_window_handle::Win32WindowHandle::empty();
+                handle.hwnd = hwnd;
+                RawWindowHandle::Win32(handle)
+            }
+        }
+    }
+}
+
+impl<T> Editor for EguiEditor<T>
+where
+    T: 'static + Send + Sync,
+{
+    fn spawn(
+        &self,
+        parent: ParentWindowHandle,
+        context: Arc<dyn GuiContext>,
+    ) -> Box<dyn std::any::Any + Send> {
+        let build = self.build.clone();
+        let update = self.update.clone();
+        let state = self.user_state.clone();
+        let egui_state = self.egui_state.clone();
+
+        let (unscaled_width, unscaled_height) = self.egui_state.size();
+        let scaling_factor = self.scaling_factor.load();
+        let window = EguiWindow::open_parented(
+            &ParentWindowHandleAdapter(parent),
+            WindowOpenOptions {
+                title: String::from("egui window"),
+                // Baseview should be doing the DPI scaling for us
+                size: Size::new(unscaled_width as f64, unscaled_height as f64),
+                // NOTE: For some reason passing 1.0 here causes the UI to be scaled on macOS but
+                //       not the mouse events.
+                scale: scaling_factor
+                    .map(|factor| WindowScalePolicy::ScaleFactor(factor as f64))
+                    .unwrap_or(WindowScalePolicy::SystemScaleFactor),
+
+                #[cfg(feature = "opengl")]
+                gl_config: Some(GlConfig {
+                    version: (3, 2),
+                    red_bits: 8,
+                    blue_bits: 8,
+                    green_bits: 8,
+                    alpha_bits: 8,
+                    depth_bits: 24,
+                    stencil_bits: 8,
+                    samples: None,
+                    srgb: true,
+                    double_buffer: true,
+                    vsync: true,
+                    ..Default::default()
+                }),
+            },
+            Default::default(),
+            state,
+            move |egui_ctx, _queue, state| build(egui_ctx, &mut state.write()),
+            move |egui_ctx, queue, state| {
+                let setter = ParamSetter::new(context.as_ref());
+
+                // If the window was requested to resize
+                if let Some(new_size) = egui_state.requested_size.swap(None) {
+                    // Ask the plugin host to resize to self.size()
+                    if context.request_resize() {
+                        // Resize the content of egui window
+                        queue.resize(PhySize::new(new_size.0, new_size.1));
+                        egui_ctx.send_viewport_cmd(ViewportCommand::InnerSize(Vec2::new(
+                            new_size.0 as f32,
+                            new_size.1 as f32,
+                        )));
+
+                        // Update the state
+                        egui_state.size.store(new_size);
+                    }
+                }
+
+                // For now, just always redraw. Most plugin GUIs have meters, and those almost always
+                // need a redraw. Later we can try to be a bit more sophisticated about this. Without
+                // this we would also have a blank GUI when it gets first opened because most DAWs open
+                // their GUI while the window is still unmapped.
+                egui_ctx.request_repaint();
+                (update)(egui_ctx, &setter, &mut state.write());
+            },
+        );
+
+        self.egui_state.open.store(true, Ordering::Release);
+        Box::new(EguiEditorHandle {
+            egui_state: self.egui_state.clone(),
+            window,
+        })
+    }
+
+    /// Size of the editor window
+    fn size(&self) -> (u32, u32) {
+        let new_size = self.egui_state.requested_size.load();
+        // This method will be used to ask the host for new size.
+        // If the editor is currently being resized and new size hasn't been consumed and set yet, return new requested size.
+        if let Some(new_size) = new_size {
+            new_size
+        } else {
+            self.egui_state.size()
+        }
+    }
+
+    fn set_scale_factor(&self, factor: f32) -> bool {
+        // If the editor is currently open then the host must not change the current HiDPI scale as
+        // we don't have a way to handle that. Ableton Live does this.
+        if self.egui_state.is_open() {
+            return false;
+        }
+
+        self.scaling_factor.store(Some(factor));
+        true
+    }
+
+    fn param_value_changed(&self, _id: &str, _normalized_value: f32) {
+        // As mentioned above, for now we'll always force a redraw to allow meter widgets to work
+        // correctly. In the future we can use an `Arc<AtomicBool>` and only force a redraw when
+        // that boolean is set.
+    }
+
+    fn param_modulation_changed(&self, _id: &str, _modulation_offset: f32) {}
+
+    fn param_values_changed(&self) {
+        // Same
+    }
+}
+
+/// The window handle used for [`EguiEditor`].
+struct EguiEditorHandle {
+    egui_state: Arc<EguiState>,
+    window: WindowHandle,
+}
+
+/// The window handle enum stored within 'WindowHandle' contains raw pointers. Is there a way around
+/// having this requirement?
+unsafe impl Send for EguiEditorHandle {}
+
+impl Drop for EguiEditorHandle {
+    fn drop(&mut self) {
+        self.egui_state.open.store(false, Ordering::Release);
+        // XXX: This should automatically happen when the handle gets dropped, but apparently not
+        self.window.close();
+    }
+}

plugins/nih-plug-egui/src/lib.rs

@@ -0,0 +1,119 @@
+//! [egui](https://github.com/emilk/egui) editor support for NIH plug.
+//!
+//! TODO: Proper usage example, for now check out the gain_gui example
+
+// See the comment in the main `nih_plug` crate
+#![allow(clippy::type_complexity)]
+
+use crossbeam::atomic::AtomicCell;
+use egui::Context;
+use nih_plug::params::persist::PersistentField;
+use nih_plug::prelude::{Editor, ParamSetter};
+use parking_lot::RwLock;
+use serde::{Deserialize, Serialize};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+
+#[cfg(not(feature = "opengl"))]
+compile_error!("There's currently no software rendering support for egui");
+
+/// Re-export for convenience.
+pub use egui_baseview::egui;
+
+mod editor;
+pub mod resizable_window;
+pub mod widgets;
+
+/// Create an [`Editor`] instance using an [`egui`][::egui] GUI. Using the user state parameter is
+/// optional, but it can be useful for keeping track of some temporary GUI-only settings. See the
+/// `gui_gain` example for more information on how to use this. The [`EguiState`] passed to this
+/// function contains the GUI's intitial size, and this is kept in sync whenever the GUI gets
+/// resized. You can also use this to know if the GUI is open, so you can avoid performing
+/// potentially expensive calculations while the GUI is not open. If you want this size to be
+/// persisted when restoring a plugin instance, then you can store it in a `#[persist = "key"]`
+/// field on your parameters struct.
+///
+/// See [`EguiState::from_size()`].
+pub fn create_egui_editor<T, B, U>(
+    egui_state: Arc<EguiState>,
+    user_state: T,
+    build: B,
+    update: U,
+) -> Option<Box<dyn Editor>>
+where
+    T: 'static + Send + Sync,
+    B: Fn(&Context, &mut T) + 'static + Send + Sync,
+    U: Fn(&Context, &ParamSetter, &mut T) + 'static + Send + Sync,
+{
+    Some(Box::new(editor::EguiEditor {
+        egui_state,
+        user_state: Arc::new(RwLock::new(user_state)),
+        build: Arc::new(build),
+        update: Arc::new(update),
+
+        // TODO: We can't get the size of the window when baseview does its own scaling, so if the
+        //       host does not set a scale factor on Windows or Linux we should just use a factor of
+        //       1. That may make the GUI tiny but it also prevents it from getting cut off.
+        #[cfg(target_os = "macos")]
+        scaling_factor: AtomicCell::new(None),
+        #[cfg(not(target_os = "macos"))]
+        scaling_factor: AtomicCell::new(Some(1.0)),
+    }))
+}
+
+/// State for an `nih_plug_egui` editor.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct EguiState {
+    /// The window's size in logical pixels before applying `scale_factor`.
+    #[serde(with = "nih_plug::params::persist::serialize_atomic_cell")]
+    size: AtomicCell<(u32, u32)>,
+
+    /// The new size of the window, if it was requested to resize by the GUI.
+    #[serde(skip)]
+    requested_size: AtomicCell<Option<(u32, u32)>>,
+
+    /// Whether the editor's window is currently open.
+    #[serde(skip)]
+    open: AtomicBool,
+}
+
+impl<'a> PersistentField<'a, EguiState> for Arc<EguiState> {
+    fn set(&self, new_value: EguiState) {
+        self.size.store(new_value.size.load());
+    }
+
+    fn map<F, R>(&self, f: F) -> R
+    where
+        F: Fn(&EguiState) -> R,
+    {
+        f(self)
+    }
+}
+
+impl EguiState {
+    /// Initialize the GUI's state. This value can be passed to [`create_egui_editor()`]. The window
+    /// size is in logical pixels, so before it is multiplied by the DPI scaling factor.
+    pub fn from_size(width: u32, height: u32) -> Arc<EguiState> {
+        Arc::new(EguiState {
+            size: AtomicCell::new((width, height)),
+            requested_size: Default::default(),
+            open: AtomicBool::new(false),
+        })
+    }
+
+    /// Returns a `(width, height)` pair for the current size of the GUI in logical pixels.
+    pub fn size(&self) -> (u32, u32) {
+        self.size.load()
+    }
+
+    /// Whether the GUI is currently visible.
+    // Called `is_open()` instead of `open()` to avoid the ambiguity.
+    pub fn is_open(&self) -> bool {
+        self.open.load(Ordering::Acquire)
+    }
+
+    /// Set the new size that will be used to resize the window if the host allows.
+    pub fn set_requested_size(&self, new_size: (u32, u32)) {
+        self.requested_size.store(Some(new_size));
+    }
+}

plugins/nih-plug-egui/src/resizable_window.rs

@@ -0,0 +1,81 @@
+//! Resizable window wrapper for Egui editor.
+
+use egui_baseview::egui::emath::GuiRounding;
+use egui_baseview::egui::{InnerResponse, UiBuilder};
+
+use crate::egui::{pos2, CentralPanel, Context, Id, Rect, Response, Sense, Ui, Vec2};
+use crate::EguiState;
+
+/// Adds a corner to the plugin window that can be dragged in order to resize it.
+/// Resizing happens through plugin API, hence a custom implementation is needed.
+pub struct ResizableWindow {
+    id: Id,
+    min_size: Vec2,
+}
+
+impl ResizableWindow {
+    pub fn new(id_source: impl std::hash::Hash) -> Self {
+        Self {
+            id: Id::new(id_source),
+            min_size: Vec2::splat(16.0),
+        }
+    }
+
+    /// Won't shrink to smaller than this
+    #[inline]
+    pub fn min_size(mut self, min_size: impl Into<Vec2>) -> Self {
+        self.min_size = min_size.into();
+        self
+    }
+
+    pub fn show<R>(
+        self,
+        context: &Context,
+        egui_state: &EguiState,
+        add_contents: impl FnOnce(&mut Ui) -> R,
+    ) -> InnerResponse<R> {
+        CentralPanel::default().show(context, move |ui| {
+            let ui_rect = ui.clip_rect();
+            let mut content_ui =
+                ui.new_child(UiBuilder::new().max_rect(ui_rect).layout(*ui.layout()));
+
+            let ret = add_contents(&mut content_ui);
+
+            let corner_size = Vec2::splat(ui.visuals().resize_corner_size);
+            let corner_rect = Rect::from_min_size(ui_rect.max - corner_size, corner_size);
+
+            let corner_response = ui.interact(corner_rect, self.id.with("corner"), Sense::drag());
+
+            if let Some(pointer_pos) = corner_response.interact_pointer_pos() {
+                let desired_size = (pointer_pos - ui_rect.min + 0.5 * corner_response.rect.size())
+                    .max(self.min_size);
+
+                if corner_response.dragged() {
+                    egui_state.set_requested_size((
+                        desired_size.x.round() as u32,
+                        desired_size.y.round() as u32,
+                    ));
+                }
+            }
+
+            paint_resize_corner(&content_ui, &corner_response);
+
+            ret
+        })
+    }
+}
+
+pub fn paint_resize_corner(ui: &Ui, response: &Response) {
+    let stroke = ui.style().interact(response).fg_stroke;
+
+    let painter = ui.painter();
+    let rect = response.rect.translate(-Vec2::splat(2.0)); // move away from the corner
+    let cp = rect.max.round_to_pixels(painter.pixels_per_point());
+
+    let mut w = 2.0;
+
+    while w <= rect.width() && w <= rect.height() {
+        painter.line_segment([pos2(cp.x - w, cp.y), pos2(cp.x, cp.y - w)], stroke);
+        w += 4.0;
+    }
+}

plugins/nih-plug-egui/src/widgets.rs

@@ -0,0 +1,12 @@
+//! Custom egui widgets for displaying parameter values.
+//!
+//! # Note
+//!
+//! None of these widgets are finalized, and their sizes or looks can change at any point. Feel free
+//! to copy the widgets and modify them to your personal taste.
+
+pub mod generic_ui;
+mod param_slider;
+pub mod util;
+
+pub use param_slider::ParamSlider;

plugins/nih-plug-egui/src/widgets/generic_ui.rs

@@ -0,0 +1,72 @@
+//! A simple generic UI widget that renders all parameters in a [`Params`] object as a scrollable
+//! list of sliders and labels.
+
+use std::sync::Arc;
+
+use egui_baseview::egui::{self, TextStyle, Ui, Vec2};
+use nih_plug::prelude::{Param, ParamFlags, ParamPtr, ParamSetter, Params};
+
+use super::ParamSlider;
+
+/// A widget that can be used to create a generic UI with. This is used in conjuction with empty
+/// structs to emulate existential types.
+pub trait ParamWidget {
+    fn add_widget<P: Param>(&self, ui: &mut Ui, param: &P, setter: &ParamSetter);
+
+    /// The same as [`add_widget()`][Self::add_widget()], but for a `ParamPtr`.
+    ///
+    /// # Safety
+    ///
+    /// Undefined behavior of the `ParamPtr` does not point to a valid parameter.
+    unsafe fn add_widget_raw(&self, ui: &mut Ui, param: &ParamPtr, setter: &ParamSetter) {
+        match param {
+            ParamPtr::FloatParam(p) => self.add_widget(ui, &**p, setter),
+            ParamPtr::IntParam(p) => self.add_widget(ui, &**p, setter),
+            ParamPtr::BoolParam(p) => self.add_widget(ui, &**p, setter),
+            ParamPtr::EnumParam(p) => self.add_widget(ui, &**p, setter),
+        }
+    }
+}
+
+/// Create a generic UI using [`ParamSlider`]s.
+pub struct GenericSlider;
+
+/// Create a scrollable generic UI using the specified widget. Takes up all the remaining vertical
+/// space.
+pub fn create(
+    ui: &mut Ui,
+    params: Arc<impl Params>,
+    setter: &ParamSetter,
+    widget: impl ParamWidget,
+) {
+    let padding = Vec2::splat(ui.text_style_height(&TextStyle::Body) * 0.2);
+    egui::containers::ScrollArea::vertical()
+        // Take up all remaining space, use a wrapper container to adjust how much space that is
+        .auto_shrink([false, false])
+        .show(ui, |ui| {
+            let mut first_widget = true;
+            for (_, param_ptr, _) in params.param_map().into_iter() {
+                let flags = unsafe { param_ptr.flags() };
+                if flags.contains(ParamFlags::HIDE_IN_GENERIC_UI) {
+                    continue;
+                }
+
+                // This list looks weird without a little padding
+                if !first_widget {
+                    ui.allocate_space(padding);
+                }
+
+                ui.label(unsafe { param_ptr.name() });
+                unsafe { widget.add_widget_raw(ui, &param_ptr, setter) };
+
+                first_widget = false;
+            }
+        });
+}
+
+impl ParamWidget for GenericSlider {
+    fn add_widget<P: Param>(&self, ui: &mut Ui, param: &P, setter: &ParamSetter) {
+        // Make these sliders a bit wider, else they look a bit odd
+        ui.add(ParamSlider::for_param(param, setter).with_width(100.0));
+    }
+}

plugins/nih-plug-egui/src/widgets/param_slider.rs

@@ -0,0 +1,357 @@
+use std::sync::{Arc, LazyLock};
+
+use egui_baseview::egui::emath::GuiRounding;
+use egui_baseview::egui::{
+    self, emath, vec2, Key, Response, Sense, Stroke, TextEdit, TextStyle, Ui, Vec2, Widget,
+    WidgetText,
+};
+use nih_plug::prelude::{Param, ParamSetter};
+use parking_lot::Mutex;
+
+use super::util;
+
+/// When shift+dragging a parameter, one pixel dragged corresponds to this much change in the
+/// noramlized parameter.
+const GRANULAR_DRAG_MULTIPLIER: f32 = 0.0015;
+
+static DRAG_NORMALIZED_START_VALUE_MEMORY_ID: LazyLock<egui::Id> =
+    LazyLock::new(|| egui::Id::new((file!(), 0)));
+static DRAG_AMOUNT_MEMORY_ID: LazyLock<egui::Id> = LazyLock::new(|| egui::Id::new((file!(), 1)));
+static VALUE_ENTRY_MEMORY_ID: LazyLock<egui::Id> = LazyLock::new(|| egui::Id::new((file!(), 2)));
+
+/// A slider widget similar to [`egui::widgets::Slider`] that knows about NIH-plug parameters ranges
+/// and can get values for it. The slider supports double click and control click to reset,
+/// shift+drag for granular dragging, text value entry by clicking on the value text.
+///
+/// TODO: Vertical orientation
+/// TODO: Check below for more input methods that should be added
+/// TODO: Decouple the logic from the drawing so we can also do things like nobs without having to
+///       repeat everything
+/// TODO: Add WidgetInfo annotations for accessibility
+#[must_use = "You should put this widget in an ui with `ui.add(widget);`"]
+pub struct ParamSlider<'a, P: Param> {
+    param: &'a P,
+    setter: &'a ParamSetter<'a>,
+
+    draw_value: bool,
+    slider_width: Option<f32>,
+
+    /// Will be set in the `ui()` function so we can request keyboard input focus on Alt+click.
+    keyboard_focus_id: Option<egui::Id>,
+}
+
+impl<'a, P: Param> ParamSlider<'a, P> {
+    /// Create a new slider for a parameter. Use the other methods to modify the slider before
+    /// passing it to [`Ui::add()`].
+    pub fn for_param(param: &'a P, setter: &'a ParamSetter<'a>) -> Self {
+        Self {
+            param,
+            setter,
+
+            draw_value: true,
+            slider_width: None,
+
+            keyboard_focus_id: None,
+        }
+    }
+
+    /// Don't draw the text slider's current value after the slider.
+    pub fn without_value(mut self) -> Self {
+        self.draw_value = false;
+        self
+    }
+
+    /// Set a custom width for the slider.
+    pub fn with_width(mut self, width: f32) -> Self {
+        self.slider_width = Some(width);
+        self
+    }
+
+    fn plain_value(&self) -> P::Plain {
+        self.param.modulated_plain_value()
+    }
+
+    fn normalized_value(&self) -> f32 {
+        self.param.modulated_normalized_value()
+    }
+
+    fn string_value(&self) -> String {
+        self.param.to_string()
+    }
+
+    /// Enable the keyboard entry part of the widget.
+    fn begin_keyboard_entry(&self, ui: &Ui) {
+        ui.memory_mut(|mem| mem.request_focus(self.keyboard_focus_id.unwrap()));
+
+        // Always initialize the field to the current value, that seems nicer than having to
+        // being typing from scratch
+        let value_entry_mutex = ui.memory_mut(|mem| {
+            mem.data
+                .get_temp_mut_or_default::<Arc<Mutex<String>>>(*VALUE_ENTRY_MEMORY_ID)
+                .clone()
+        });
+        *value_entry_mutex.lock() = self.string_value();
+    }
+
+    fn keyboard_entry_active(&self, ui: &Ui) -> bool {
+        ui.memory(|mem| mem.has_focus(self.keyboard_focus_id.unwrap()))
+    }
+
+    fn begin_drag(&self) {
+        self.setter.begin_set_parameter(self.param);
+    }
+
+    fn set_normalized_value(&self, normalized: f32) {
+        // This snaps to the nearest plain value if the parameter is stepped in some way.
+        // TODO: As an optimization, we could add a `const CONTINUOUS: bool` to the parameter to
+        //       avoid this normalized->plain->normalized conversion for parameters that don't need
+        //       it
+        let value = self.param.preview_plain(normalized);
+        if value != self.plain_value() {
+            self.setter.set_parameter(self.param, value);
+        }
+    }
+
+    /// Begin and end drag still need to be called when using this. Returns `false` if the string
+    /// could no tbe parsed.
+    fn set_from_string(&self, string: &str) -> bool {
+        match self.param.string_to_normalized_value(string) {
+            Some(normalized_value) => {
+                self.set_normalized_value(normalized_value);
+                true
+            }
+            None => false,
+        }
+    }
+
+    /// Begin and end drag still need to be called when using this..
+    fn reset_param(&self) {
+        self.setter
+            .set_parameter(self.param, self.param.default_plain_value());
+    }
+
+    fn granular_drag(&self, ui: &Ui, drag_delta: Vec2) {
+        // Remember the intial position when we started with the granular drag. This value gets
+        // reset whenever we have a normal itneraction with the slider.
+        let start_value = if Self::get_drag_amount_memory(ui) == 0.0 {
+            Self::set_drag_normalized_start_value_memory(ui, self.normalized_value());
+            self.normalized_value()
+        } else {
+            Self::get_drag_normalized_start_value_memory(ui)
+        };
+
+        let total_drag_distance = drag_delta.x + Self::get_drag_amount_memory(ui);
+        Self::set_drag_amount_memory(ui, total_drag_distance);
+
+        self.set_normalized_value(
+            (start_value + (total_drag_distance * GRANULAR_DRAG_MULTIPLIER)).clamp(0.0, 1.0),
+        );
+    }
+
+    fn end_drag(&self) {
+        self.setter.end_set_parameter(self.param);
+    }
+
+    fn get_drag_normalized_start_value_memory(ui: &Ui) -> f32 {
+        ui.memory(|mem| {
+            mem.data
+                .get_temp(*DRAG_NORMALIZED_START_VALUE_MEMORY_ID)
+                .unwrap_or(0.5)
+        })
+    }
+
+    fn set_drag_normalized_start_value_memory(ui: &Ui, amount: f32) {
+        ui.memory_mut(|mem| {
+            mem.data
+                .insert_temp(*DRAG_NORMALIZED_START_VALUE_MEMORY_ID, amount)
+        });
+    }
+
+    fn get_drag_amount_memory(ui: &Ui) -> f32 {
+        ui.memory(|mem| mem.data.get_temp(*DRAG_AMOUNT_MEMORY_ID).unwrap_or(0.0))
+    }
+
+    fn set_drag_amount_memory(ui: &Ui, amount: f32) {
+        ui.memory_mut(|mem| mem.data.insert_temp(*DRAG_AMOUNT_MEMORY_ID, amount));
+    }
+
+    fn slider_ui(&self, ui: &Ui, response: &mut Response) {
+        // Handle user input
+        // TODO: Optionally (since it can be annoying) add scrolling behind a builder option
+        if response.drag_started() {
+            // When beginning a drag or dragging normally, reset the memory used to keep track of
+            // our granular drag
+            self.begin_drag();
+            Self::set_drag_amount_memory(ui, 0.0);
+        }
+        if let Some(click_pos) = response.interact_pointer_pos() {
+            if ui.input(|i| i.modifiers.command) {
+                // Like double clicking, Ctrl+Click should reset the parameter
+                self.reset_param();
+                response.mark_changed();
+            // // FIXME: This releases the focus again when you release the mouse button without
+            // //        moving the mouse a bit for some reason
+            // } else if ui.input().modifiers.alt && self.draw_value {
+            //     // Allow typing in the value on an Alt+Click. Right now this is shown as part of the
+            //     // value field, so it only makes sense when we're drawing that.
+            //     self.begin_keyboard_entry(ui);
+            } else if ui.input(|i| i.modifiers.shift) {
+                // And shift dragging should switch to a more granulra input method
+                self.granular_drag(ui, response.drag_delta());
+                response.mark_changed();
+            } else {
+                let proportion =
+                    emath::remap_clamp(click_pos.x, response.rect.x_range(), 0.0..=1.0) as f64;
+                self.set_normalized_value(proportion as f32);
+                response.mark_changed();
+                Self::set_drag_amount_memory(ui, 0.0);
+            }
+        }
+        if response.double_clicked() {
+            self.reset_param();
+            response.mark_changed();
+        }
+        if response.drag_stopped() {
+            self.end_drag();
+        }
+
+        // And finally draw the thing
+        if ui.is_rect_visible(response.rect) {
+            // We'll do a flat widget with background -> filled foreground -> slight border
+            ui.painter()
+                .rect_filled(response.rect, 0.0, ui.visuals().widgets.inactive.bg_fill);
+
+            let filled_proportion = self.normalized_value();
+            if filled_proportion > 0.0 {
+                let mut filled_rect = response.rect;
+                filled_rect.set_width(response.rect.width() * filled_proportion);
+                let filled_bg = if response.dragged() {
+                    util::add_hsv(ui.visuals().selection.bg_fill, 0.0, -0.1, 0.1)
+                } else {
+                    ui.visuals().selection.bg_fill
+                };
+                ui.painter().rect_filled(filled_rect, 0.0, filled_bg);
+            }
+
+            ui.painter().rect_stroke(
+                response.rect,
+                0.0,
+                Stroke::new(1.0, ui.visuals().widgets.active.bg_fill),
+                egui::StrokeKind::Middle,
+            );
+        }
+    }
+
+    fn value_ui(&self, ui: &mut Ui) {
+        let visuals = ui.visuals().widgets.inactive;
+        let should_draw_frame = ui.visuals().button_frame;
+        let padding = ui.spacing().button_padding;
+
+        // Either show the parameter's label, or show a text entry field if the parameter's label
+        // has been clicked on
+        let keyboard_focus_id = self.keyboard_focus_id.unwrap();
+        if self.keyboard_entry_active(ui) {
+            let value_entry_mutex = ui.memory_mut(|mem| {
+                mem.data
+                    .get_temp_mut_or_default::<Arc<Mutex<String>>>(*VALUE_ENTRY_MEMORY_ID)
+                    .clone()
+            });
+            let mut value_entry = value_entry_mutex.lock();
+
+            ui.add(
+                TextEdit::singleline(&mut *value_entry)
+                    .id(keyboard_focus_id)
+                    .font(TextStyle::Monospace),
+            );
+            if ui.input(|i| i.key_pressed(Key::Escape)) {
+                // Cancel when pressing escape
+                ui.memory_mut(|mem| mem.surrender_focus(keyboard_focus_id));
+            } else if ui.input(|i| i.key_pressed(Key::Enter)) {
+                // And try to set the value by string when pressing enter
+                self.begin_drag();
+                self.set_from_string(&value_entry);
+                self.end_drag();
+
+                ui.memory_mut(|mem| mem.surrender_focus(keyboard_focus_id));
+            }
+        } else {
+            let text = WidgetText::from(self.string_value()).into_galley(
+                ui,
+                None,
+                ui.available_width() - (padding.x * 2.0),
+                TextStyle::Button,
+            );
+
+            let response = ui.allocate_response(text.size() + (padding * 2.0), Sense::click());
+            if response.clicked() {
+                self.begin_keyboard_entry(ui);
+            }
+
+            if ui.is_rect_visible(response.rect) {
+                if should_draw_frame {
+                    let fill = visuals.bg_fill;
+                    let stroke = visuals.bg_stroke;
+                    ui.painter().rect(
+                        response.rect.expand(visuals.expansion),
+                        visuals.corner_radius,
+                        fill,
+                        stroke,
+                        egui::StrokeKind::Middle,
+                    );
+                }
+
+                let text_pos = ui
+                    .layout()
+                    .align_size_within_rect(text.size(), response.rect.shrink2(padding))
+                    .min;
+
+                ui.painter().add(egui::epaint::TextShape::new(
+                    text_pos,
+                    text,
+                    visuals.fg_stroke.color,
+                ));
+            }
+        }
+    }
+}
+
+impl<P: Param> Widget for ParamSlider<'_, P> {
+    fn ui(mut self, ui: &mut Ui) -> Response {
+        let slider_width = self
+            .slider_width
+            .unwrap_or_else(|| ui.spacing().slider_width);
+
+        ui.horizontal(|ui| {
+            // Allocate space, but add some padding on the top and bottom to make it look a bit slimmer.
+            let height = ui
+                .text_style_height(&TextStyle::Body)
+                .max(ui.spacing().interact_size.y * 0.8);
+            let slider_height = (height * 0.8).round_to_pixels(ui.painter().pixels_per_point());
+            let mut response = ui
+                .vertical(|ui| {
+                    ui.allocate_space(vec2(slider_width, (height - slider_height) / 2.0));
+                    let response = ui.allocate_response(
+                        vec2(slider_width, slider_height),
+                        Sense::click_and_drag(),
+                    );
+                    let (kb_edit_id, _) =
+                        ui.allocate_space(vec2(slider_width, (height - slider_height) / 2.0));
+                    // Allocate an automatic ID for keeping track of keyboard focus state
+                    // FIXME: There doesn't seem to be a way to generate IDs in the public API, not sure how
+                    //        you're supposed to do this
+                    self.keyboard_focus_id = Some(kb_edit_id);
+
+                    response
+                })
+                .inner;
+
+            self.slider_ui(ui, &mut response);
+            if self.draw_value {
+                self.value_ui(ui);
+            }
+
+            response
+        })
+        .inner
+    }
+}

plugins/nih-plug-egui/src/widgets/util.rs

@@ -0,0 +1,21 @@
+//! Utilities for creating these widgets.
+
+use egui_baseview::egui::{self, Color32};
+
+/// Additively modify the hue, saturation, and lightness [0, 1] values of a color.
+pub fn add_hsv(color: Color32, h: f32, s: f32, v: f32) -> Color32 {
+    let mut hsv = egui::epaint::Hsva::from(color);
+    hsv.h += h;
+    hsv.s += s;
+    hsv.v += v;
+    hsv.into()
+}
+
+/// Multiplicatively modify the hue, saturation, and lightness [0, 1] values of a color.
+pub fn scale_hsv(color: Color32, h: f32, s: f32, v: f32) -> Color32 {
+    let mut hsv = egui::epaint::Hsva::from(color);
+    hsv.h *= h;
+    hsv.s *= s;
+    hsv.v *= v;
+    hsv.into()
+}