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/*! * This library serves as an event interpretation library. * To use, you will need to take the raw events you recieve * on your platform and adapt it to a compatible input * interface. You are expected to call get_pan() once on every frame. * It expects an estimation of the next frametime as well as how * long until the current frame will be rendered. This allows overshoot * calculation to take place. */ extern crate num; use std::f64; mod circular_backqueue; use std::ops; //#[macro_use] //extern crate smart_default; // configs /// Determines how much "smoothing" happens, at a direct cost to responsiveness to an action /// A large number means more past events will be counted in the current velocity, /// which avoids skipping over or being "hitched" by anomalies, but also means /// that changes to velocity after the initial touch are responded to slower const MAX_EVENTS_CONSIDERED: u32 = 5; /// Determines whether the prior config (MAX_EVENTS_CONSIDERED) is used. /// If false, no smoothing occurs and the velocity is simply the most recent event /// Equivalent to setting MAX_EVENTS_CONSIDERED to 1, but allows a performance shortcut const ENABLE_VELOCITY_SMOOTHING: bool = true; const FLING_FRICTION_FACTOR: f64 = 0.998; const PAN_ACCELERATION_FACTOR_TOUCHPAD: f64 = 1.34; /// Used to specify over what window (in number of frames) the ratio of input events to frames /// should be derived. The ratio is then used to interpolate/extrapolate input events const SAMPLE_OVER_X_FRAMES: usize = 10; type Millis = f64; #[derive(Default)] pub struct Scrollview { content_height: u64, content_width: u64, viewport_height: u64, viewport_width: u64, current_velocity: AxisVector<f64>, current_position: AxisVector<f64>, current_source: Source, frametime: Millis, time_to_pageflip: Millis, current_timestamp: u64, interpolation_ratio: f64, input_per_frame_log: circular_backqueue::ForgetfulLogQueue<u32>, // pairing of a (timestamp, magnitude) for pan events pan_log_x: circular_backqueue::ForgetfulLogQueue<(u64, f64)>, pan_log_y: circular_backqueue::ForgetfulLogQueue<(u64, f64)>, } /// Describes a vector in terms of its 2 2d axis magnitudes, /// used often to describe transforms and offsets #[derive(Copy)] #[derive(Clone)] #[derive(Default)] pub struct AxisVector<T> where T: num::Num, T: PartialOrd, T: Copy { pub x: T, pub y: T, x_threshold: T, y_threshold: T, decaying: bool, } impl<T> AxisVector<T> where T: num::Num, T: PartialOrd, T: Copy { fn difference(self, other: AxisVector<T>) -> AxisVector<T> { AxisVector { x: self.x - other.x, y: self.y - other.y, ..self } } fn replace(&mut self, axis: Axis, magnitude: T) { match axis { Axis::Horizontal => self.x = magnitude, Axis::Vertical => self.y = magnitude, } } fn get_at(&self, axis: Axis) -> T { match axis { Axis::Horizontal => self.x, Axis::Vertical => self.y } } fn update(&mut self, axis: Axis, magnitude: T) { match axis { Axis::Horizontal => self.x = magnitude + self.x, Axis::Vertical => self.y = magnitude + self.y, } } } impl AxisVector<f64> { fn decay_active(&self) -> bool { self.decaying && self.x > self.x_threshold && self.y > self.y_threshold } fn decay_start(&mut self) { self.decaying = true; } fn step_frame(&mut self, device: Source) { if self.decay_active() { self.x = Scrollview::fling_decay(self.x, device); self.y = Scrollview::fling_decay(self.y, device); } if self.x < self.x_threshold && self.y < self.y_threshold { self.decaying = false; } } } // TODO: consider naming, doing pythagorean add on + may make more sense, with alternative op to // simply add elems impl<T> ops::Add<AxisVector<T>> for AxisVector<T> where T: num::Num, T: PartialOrd, T: Copy { type Output = AxisVector<T>; fn add(self, rhs: AxisVector<T>) -> AxisVector<T> { AxisVector { x: self.x + rhs.x, y: self.y + rhs.y, ..self } } } #[derive(Copy)] #[derive(Clone)] pub enum Axis { Horizontal, Vertical, } #[derive(Copy)] #[derive(Clone)] pub enum Source { Undefined, Touchscreen, Touchpad, Mousewheel, PreciseMousewheel, Passthrough, KineticPassthrough, Previous, } impl Default for Source { fn default() -> Self { Source::Undefined } } /*pub enum Event { Pan { timestamp: u64, axis: Axis, amount: i32 }, // doesn't use AxisVector since some platforms only send one pan axis at once // TODO: consider AxisVector[Optional] Fling { timestamp: u64 }, Interrupt { timestamp: u64 }, //Zoom? }*/ // pub interface impl Scrollview { /// Create a new scrollview with default settings /// /// Warning: these settings are unlikely to be /// particularly useful, so set_geometry(), set_avg_frametime(), and any /// other relevant initialization functions still need to be used pub fn new() -> Scrollview { Scrollview { input_per_frame_log: circular_backqueue::ForgetfulLogQueue::new(SAMPLE_OVER_X_FRAMES), ..Default::default() } } /// Deletes/deinitializes the current scrollview /// /// Primarily intended for ffi use, Scrollview implements Drop /// where deinitialization is required, so this is only useful /// for ffi use /// /// NOTE: likely will be removed, not sure why I put this in here to begin with pub fn del(_: Scrollview) {} /// Set the geometry for the given scrollview /// /// Can be used both on scrollview initialization and on scrollview resize pub fn set_geometry( &mut self, content_height: u64, content_width: u64, viewport_height: u64, viewport_width: u64, ) { self.content_height = content_height; self.content_width = content_width; self.viewport_height = viewport_height; self.viewport_width = viewport_width; } /// Add an event to the queue to be processed for the next call to /// step_frame() /// NOTE: doesn't simplify usage much and hurts ffi interop, so currently exposing the /// individual push_... functions instead (impl complexity is similar/same between both /// methods) /*pub fn push_event( &mut self, event: &Event ) { match event { Event::Pan { timestamp, axis, amount } => self.push_pan(*timestamp, *axis, *amount), Event::Fling {..} => self.push_fling(), Event::Interrupt {..} => self.push_interrupt(), } }*/ /// True if scrollview should continue to be polled /// even in absence of events (fling or other /// animation in progress) pub fn animating(&self) -> bool { self.current_velocity.decay_active() } /// Advances scrollview state by a frame, /// Serves to step through animations one frame at a time /// /// After any event, continue to call this on every /// page-flip (new frame) until animating() returns false pub fn step_frame(&mut self, timestamp: Option<u64>) { self.interpolation_ratio = self.input_per_frame_log.all().iter().sum::<u32>() as f64 / self.input_per_frame_log.size() as f64; self.current_timestamp = timestamp.unwrap_or(1); //self.current_velocity = self.current_velocity.clone().step_frame(&self); self.current_velocity.step_frame(self.current_source); self.update_velocity(); // update position with interpolated velocity self.current_position.x += Self::accelerate(self.current_velocity.x, self.current_source) * self.interpolation_ratio * self.frametime; self.current_position.y += Self::accelerate(self.current_velocity.y, self.current_source) * self.interpolation_ratio * self.frametime; self.input_per_frame_log.push(0); // add new frame for events to pile into } /// Should be called at scrollview initialization time. /// Will internally flush any active events or animations, /// so should only be used when scrollview is inactive or /// when absolutely necessary (monitor refresh rate changes) /// /// Used for position prediction (better pan tracking) pub fn set_avg_frametime(&mut self, milliseconds: f64) { self.frametime = milliseconds; } /// Indicate how long there is until the next frame will be rendered /// to the screen. /// /// Used for position prediction (better pan tracking) pub fn set_next_frame_predict(&mut self, milliseconds: f64) { self.time_to_pageflip = milliseconds; } /// Get the position of the content's top-left corner relative to /// the top-left corner of the viewport /// /// NOTE: either axis may be negative. This indicates an overscroll is occurring. /// Recommended way of handling this is to checkerboard that area visually /// and draw true to the provided geometry. This matches platform behavior for OSX and Windows, /// as well as some Linux programs, and is often called the "rubber band effect" pub fn get_position_absolute(&self) -> AxisVector<f64> { self.current_position + self.get_overshoot() } // Get the position of the content's top-left corner relative to // its position before the most recent step_frame(), saying how much // the content should be moved from its last position // // Note: may support in future, but unclear if this provides any benefits currently, and is // difficult to support with prediction. Currently not provided. /*pub fn get_position_relative(&self) -> AxisVector<f64> { self.current_position.difference(self.prior_position) }*/ pub fn push_pan(&mut self, timestamp: Option<u64>, axis: Axis, amount: f64) { match axis { Axis::Horizontal => self.pan_log_x.push((timestamp.unwrap_or(self.current_timestamp), amount)), Axis::Vertical => self.pan_log_y.push((timestamp.unwrap_or(self.current_timestamp), amount)), } } pub fn push_fling(&mut self) { self.current_velocity.decay_start(); } pub fn push_interrupt(&mut self) { self.pan_log_x.clear(); self.pan_log_y.clear(); self.current_velocity = AxisVector { x: 0.0, y: 0.0, ..self.current_velocity }; } /// Set what device type is going to be providing any events that follow until the next source /// is declared pub fn set_source(&mut self, source: Source) { self.current_source = source; } } // private impl impl Scrollview { fn get_overshoot(&self) -> AxisVector<f64> { let time_to_target = (self.frametime / 2.0) + self.time_to_pageflip; AxisVector { x: self.current_velocity.x * time_to_target, y: self.current_velocity.y * time_to_target, decaying: false, ..Default::default() } } // Uses backlog and input acceleration curve to smooth recent pan deltas fn update_velocity(&mut self) { if ENABLE_VELOCITY_SMOOTHING == false { // last input vector on each axis is unsmoothed velocity self.current_velocity = AxisVector { x: self.pan_log_x.get_or_avg(0).1, y: self.pan_log_y.get_or_avg(0).1, ..self.current_velocity } } else { // sum total weights let mut sum_x = 0.0; let mut sum_y = 0.0; // end divisor for calculating weighting let mut weight_x = 0.0; let mut weight_y = 0.0; let axes = vec![(&self.pan_log_x, &mut sum_x, &mut weight_x), (&self.pan_log_y, &mut sum_y, &mut weight_y)]; // need to do weighted averages for (log, sum, weight) in axes { for i in 0..(MAX_EVENTS_CONSIDERED - 1) { match log.get(i as usize) { None => (), Some((timestamp, magnitude)) => { let staleness = self.current_timestamp - timestamp; let staleness_mult_factor = 1.0 / (staleness as f64); *weight += staleness_mult_factor; *sum += magnitude * staleness_mult_factor; } } } } let avg_x = sum_x / weight_x; let avg_y = sum_y / weight_y; self.current_velocity = AxisVector { x: avg_x, y: avg_y, ..self.current_velocity } } } // TODO: move to pref fn accelerate(from: f64, device: Source) -> f64 { match device { Source::Touchpad => from.powf(PAN_ACCELERATION_FACTOR_TOUCHPAD), _ => from, } } // should be changed later to allow different curves, fn fling_decay(from: f64, device: Source) -> f64 { match device { Source::Touchpad | Source::KineticPassthrough => from.powf(FLING_FRICTION_FACTOR), _ => 0.0, } } }