feat: shake cursor to find by magnifying the cursor

src/backend/render/cursor.rs

@@ -8,6 +8,7 @@ use crate::{
     utils::prelude::*,
     wayland::handlers::compositor::FRAME_TIME_FILTER,
 };
+use keyframe::{ease, functions::EaseInOutCubic};
 use smithay::{
     backend::{
         allocator::Fourcc,
@@ -38,7 +39,7 @@ use smithay::{
     wayland::compositor::{get_role, with_states},
 };
 use std::{
-    collections::HashMap,
+    collections::{HashMap, VecDeque},
     io::Read,
     sync::Mutex,
     time::{Duration, Instant},
@@ -270,6 +271,43 @@ pub struct CursorStateInner {
     hidden: bool,
     idle_timer: Option<RegistrationToken>,
     last_armed: Option<Instant>,
+
+    // shake-to-find
+    shake_path: VecDeque<PathSample>,
+    shake_path_position: Point<f64, Logical>,
+    magnify_until: Option<Instant>,
+    magnify_target: f32,
+    magnification: f32,
+    anim_from: f32,
+    anim_start: Option<Instant>,
+}
+
+/// One sampled pointer position on the recent motion path.
+#[derive(Clone, Copy)]
+struct PathSample {
+    position: Point<f64, Logical>,
+    time: Instant,
+}
+
+/// How far back the motion path is considered when looking for a shake.
+const SHAKE_INTERVAL: Duration = Duration::from_millis(1000);
+/// Path-length / bounding-box-diagonal ratio required to count as a shake.
+const SHAKE_SENSITIVITY: f64 = 4.0;
+/// Minimum bounding-box diagonal (logical px) before a shake is considered.
+const SHAKE_DIAGONAL_MIN: f64 = 100.0;
+/// Two deltas count as "the same direction" if both lie within this tolerance.
+const SHAKE_SAME_SIGN_TOLERANCE: f64 = 1.0;
+/// Keep the cursor enlarged for this long after the last detected shake.
+const SHAKE_HOLD: Duration = Duration::from_millis(2000);
+/// Extra magnification added by each shake, growing from the normal cursor size.
+const OVER_MAGNIFICATION: f32 = 1.0;
+/// Duration of the grow/shrink animation.
+const MAGNIFICATION_ANIM: Duration = Duration::from_millis(200);
+
+/// small movement is ignored and direction stays the same
+fn same_direction(a: f64, b: f64) -> bool {
+    (a >= -SHAKE_SAME_SIGN_TOLERANCE && b >= -SHAKE_SAME_SIGN_TOLERANCE)
+        || (a <= SHAKE_SAME_SIGN_TOLERANCE && b <= SHAKE_SAME_SIGN_TOLERANCE)
 }
 
 impl CursorStateInner {
@@ -290,6 +328,116 @@ impl CursorStateInner {
     pub fn size(&self) -> u32 {
         self.cursor_size
     }
+
+    /// Feed one relative-motion event into the shake detector.
+    pub fn detect_shake(&mut self, delta: Point<f64, Logical>, now: Instant) {
+        // Drop samples that have aged out of the time window.
+        while let Some(oldest) = self.shake_path.front() {
+            if now.duration_since(oldest.time) >= SHAKE_INTERVAL {
+                self.shake_path.pop_front();
+            } else {
+                break;
+            }
+        }
+
+        if delta.x != 0.0 || delta.y != 0.0 {
+            self.shake_path_position += delta;
+            let sample = PathSample {
+                position: self.shake_path_position,
+                time: now,
+            };
+
+            if self.shake_path.len() >= 2 {
+                let last = self.shake_path[self.shake_path.len() - 1].position;
+                let prev = self.shake_path[self.shake_path.len() - 2].position;
+                let last_delta = last - prev;
+                if same_direction(last_delta.x, delta.x) && same_direction(last_delta.y, delta.y) {
+                    *self.shake_path.back_mut().unwrap() = sample;
+                } else {
+                    self.shake_path.push_back(sample);
+                }
+            } else {
+                self.shake_path.push_back(sample);
+            }
+        }
+
+        if self.shake_path.len() < 2 {
+            return;
+        }
+
+        let first = self.shake_path[0].position;
+        let (mut left, mut top, mut right, mut bottom) = (first.x, first.y, first.x, first.y);
+        let mut path_length = 0.0;
+        for i in 1..self.shake_path.len() {
+            let p = self.shake_path[i].position;
+            left = left.min(p.x);
+            top = top.min(p.y);
+            right = right.max(p.x);
+            bottom = bottom.max(p.y);
+
+            let step = p - self.shake_path[i - 1].position;
+            path_length += step.x.hypot(step.y);
+        }
+
+        let diagonal = (right - left).hypot(bottom - top);
+        if diagonal < SHAKE_DIAGONAL_MIN {
+            return;
+        }
+
+        // Path noticeably longer than the diagonal => a shake gesture.
+        if path_length / diagonal > SHAKE_SENSITIVITY {
+            self.grow(now);
+            self.shake_path.clear();
+        }
+    }
+
+    /// grow the cursor by one more increment (unbounded)
+    fn grow(&mut self, now: Instant) {
+        self.animate_to(self.magnify_target + OVER_MAGNIFICATION, now);
+        self.magnify_until = Some(now + SHAKE_HOLD);
+    }
+
+    /// Start a 200ms `InOutCubic` tween from the current size to `target`.
+    fn animate_to(&mut self, target: f32, now: Instant) {
+        if (target - self.magnify_target).abs() < f32::EPSILON {
+            return;
+        }
+        self.anim_from = self.magnification;
+        self.anim_start = Some(now);
+        self.magnify_target = target;
+    }
+
+    /// Advance the magnification animation and return the current factor.
+    pub fn animated_magnification(&mut self, now: Instant) -> f32 {
+        // Begin shrinking back once the hold window elapses.
+        if let Some(until) = self.magnify_until
+            && now >= until
+        {
+            self.magnify_until = None;
+            self.animate_to(1.0, now);
+        }
+
+        self.magnification = match self.anim_start {
+            Some(start) => {
+                // `ease` clamps the time to `0.0..=1.0` for us.
+                let t = now.duration_since(start).as_secs_f32() / MAGNIFICATION_ANIM.as_secs_f32();
+                if t >= 1.0 {
+                    self.anim_start = None;
+                }
+                ease(EaseInOutCubic, self.anim_from, self.magnify_target, t)
+            }
+            None => self.magnify_target,
+        };
+        self.magnification
+    }
+
+    /// Whether the cursor is currently magnified or pending; drives continued redraws.
+    pub fn is_magnifying(&self) -> bool {
+        self.magnify_until.is_some()
+            || self.anim_start.is_some()
+            || self.magnification > 1.001
+            || self.magnify_target > 1.001
+    }
 }
 
 pub fn load_cursor_env() -> (String, u32) {
@@ -324,6 +472,14 @@ impl Default for CursorStateInner {
             hidden: false,
             idle_timer: None,
             last_armed: None,
+
+            shake_path: VecDeque::new(),
+            shake_path_position: Point::from((0.0, 0.0)),
+            magnify_until: None,
+            magnify_target: 1.0,
+            magnification: 1.0,
+            anim_from: 1.0,
+            anim_start: None,
         }
     }
 }

src/backend/render/element.rs

@@ -41,7 +41,9 @@ where
     Workspace(
         RelocateRenderElement<CropRenderElement<RescaleRenderElement<WorkspaceRenderElement<R>>>>,
     ),
-    Cursor(RescaleRenderElement<RelocateRenderElement<CursorRenderElement<R>>>),
+    Cursor(
+        RescaleRenderElement<RescaleRenderElement<RelocateRenderElement<CursorRenderElement<R>>>>,
+    ),
     Dnd(SurfaceRenderElement<R>),
     MoveGrab(RescaleRenderElement<CosmicMappedRenderElement<R>>),
     Postprocess(

src/backend/render/mod.rs

@@ -510,22 +510,35 @@ pub fn cursor_elements<'a, 'frame, R>(
         };
         let location = pointer.current_location() - output.current_location().to_f64();
 
+        // Shake-to-find magnification, applied around the pointer tip.
+        let cursor_magnification = seat
+            .user_data()
+            .get::<cursor::CursorState>()
+            .map_or(1.0, |s| {
+                s.lock().unwrap().animated_magnification(Instant::now())
+            });
+        let cursor_center = location.to_physical(scale).to_i32_round();
+
         if mode != CursorMode::None {
             cursor::draw_cursor(
                 renderer,
                 seat,
                 location,
                 scale.into(),
-                zoom_scale,
+                zoom_scale * cursor_magnification as f64,
                 now,
                 blur_strength,
                 mode != CursorMode::NotDefault,
                 &mut |elem, hotspot| {
                     push(CosmicElement::Cursor(RescaleRenderElement::from_element(
-                        RelocateRenderElement::from_element(
-                            elem,
-                            Point::from((-hotspot.x, -hotspot.y)),
-                            Relocate::Relative,
+                        RescaleRenderElement::from_element(
+                            RelocateRenderElement::from_element(
+                                elem,
+                                Point::from((-hotspot.x, -hotspot.y)),
+                                Relocate::Relative,
+                            ),
+                            cursor_center,
+                            cursor_magnification as f64,
                         ),
                         focal_point
                             .as_logical()

src/config/mod.rs

@@ -969,6 +969,10 @@ fn config_changed(config: cosmic_config::Config, keys: Vec<String>, state: &mut
                     }
                 }
             }
+            "cursor_shake_to_find" => {
+                let new = get_config::<bool>(&config, "cursor_shake_to_find");
+                state.common.config.cosmic_conf.cursor_shake_to_find = new;
+            }
             "cursor_hide_timeout" => {
                 let new = get_config::<Option<u32>>(&config, "cursor_hide_timeout");
                 if new != state.common.config.cosmic_conf.cursor_hide_timeout {

src/input/mod.rs

@@ -337,6 +337,21 @@ impl State {
                     notify_cursor_activity(self, &seat);
                     let current_output = seat.active_output();
 
+                    if self.common.config.cosmic_conf.cursor_shake_to_find
+                        && let Some(cursor_state) =
+                            seat.user_data()
+                                .get::<crate::backend::render::cursor::CursorState>()
+                    {
+                        let active = {
+                            let mut cursor = cursor_state.lock().unwrap();
+                            cursor.detect_shake(event.delta(), std::time::Instant::now());
+                            cursor.is_magnifying()
+                        };
+                        if active {
+                            self.backend.schedule_render(&current_output);
+                        }
+                    }
+
                     let mut position = seat.get_pointer().unwrap().current_location().as_global();
 
                     let under = State::surface_under(position, &current_output, &shell)

src/shell/mod.rs

@@ -2286,6 +2286,11 @@ impl Shell {
                         .is_some_and(|state| state.lock().unwrap().is_animating())
                 })
             })
+            || self.seats.iter().any(|seat| {
+                seat.user_data()
+                    .get::<crate::backend::render::cursor::CursorState>()
+                    .is_some_and(|state| state.lock().unwrap().is_magnifying())
+            })
     }
 
     pub fn update_animations(&mut self) -> HashMap<ClientId, Client> {