From 2dae807c4f797712c3c56342f694b74956d69a07 Mon Sep 17 00:00:00 2001
From: John Nunley <dev@notgull.net>
Date: Fri, 1 Mar 2024 01:11:28 -0800
Subject: [PATCH] On X11, filter out tiny device mouse events

Usually, if mouse events are equal to (0, 0) we filter them out.
However, if the event is very close to zero it will still be given to
the user. In some cases this can be caused by bad float math on the X11
server side.

Fix it by filtering absolute values smaller than floating point epsilon.

Signed-off-by: John Nunley <dev@notgull.net>
Closes: #3500
---
 CHANGELOG.md                                  |  2 +
 .../linux/x11/event_processor.rs              | 16 +++---
 src/platform_impl/linux/x11/util/mod.rs       |  3 +-
 src/platform_impl/linux/x11/util/mouse.rs     | 52 +++++++++++++++++++
 4 files changed, 64 insertions(+), 9 deletions(-)
 create mode 100644 src/platform_impl/linux/x11/util/mouse.rs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 622ad2bbd9..0531c281e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@ Unreleased` header.
 
 # Unreleased
 
+- On X11, filter close to zero values in mouse device events
+
 # 0.29.11
 
 - On Wayland, fix DeviceEvent::Motion not being sent
diff --git a/src/platform_impl/linux/x11/event_processor.rs b/src/platform_impl/linux/x11/event_processor.rs
index b809768443..6882f21489 100644
--- a/src/platform_impl/linux/x11/event_processor.rs
+++ b/src/platform_impl/linux/x11/event_processor.rs
@@ -1502,8 +1502,8 @@ impl<T: 'static> EventProcessor<T> {
         let mask =
             unsafe { slice::from_raw_parts(xev.valuators.mask, xev.valuators.mask_len as usize) };
         let mut value = xev.raw_values;
-        let mut mouse_delta = (0.0, 0.0);
-        let mut scroll_delta = (0.0, 0.0);
+        let mut mouse_delta = util::Delta::default();
+        let mut scroll_delta = util::Delta::default();
         for i in 0..xev.valuators.mask_len * 8 {
             if !xinput2::XIMaskIsSet(mask, i) {
                 continue;
@@ -1513,10 +1513,10 @@ impl<T: 'static> EventProcessor<T> {
             // We assume that every XInput2 device with analog axes is a pointing device emitting
             // relative coordinates.
             match i {
-                0 => mouse_delta.0 = x,
-                1 => mouse_delta.1 = x,
-                2 => scroll_delta.0 = x as f32,
-                3 => scroll_delta.1 = x as f32,
+                0 => mouse_delta.set_x(x),
+                1 => mouse_delta.set_y(x),
+                2 => scroll_delta.set_x(x as f32),
+                3 => scroll_delta.set_y(x as f32),
                 _ => {}
             }
 
@@ -1532,7 +1532,7 @@ impl<T: 'static> EventProcessor<T> {
             value = unsafe { value.offset(1) };
         }
 
-        if mouse_delta != (0.0, 0.0) {
+        if let Some(mouse_delta) = mouse_delta.consume() {
             let event = Event::DeviceEvent {
                 device_id: did,
                 event: DeviceEvent::MouseMotion { delta: mouse_delta },
@@ -1540,7 +1540,7 @@ impl<T: 'static> EventProcessor<T> {
             callback(&self.target, event);
         }
 
-        if scroll_delta != (0.0, 0.0) {
+        if let Some(scroll_delta) = scroll_delta.consume() {
             let event = Event::DeviceEvent {
                 device_id: did,
                 event: DeviceEvent::MouseWheel {
diff --git a/src/platform_impl/linux/x11/util/mod.rs b/src/platform_impl/linux/x11/util/mod.rs
index 937671aa58..f33dc763ca 100644
--- a/src/platform_impl/linux/x11/util/mod.rs
+++ b/src/platform_impl/linux/x11/util/mod.rs
@@ -15,13 +15,14 @@ mod icon;
 mod input;
 pub mod keys;
 pub(crate) mod memory;
+mod mouse;
 mod randr;
 mod window_property;
 mod wm;
 mod xmodmap;
 
 pub use self::{
-    geometry::*, hint::*, input::*, window_property::*, wm::*, xmodmap::ModifierKeymap,
+    geometry::*, hint::*, input::*, mouse::*, window_property::*, wm::*, xmodmap::ModifierKeymap,
 };
 
 use super::{atoms::*, ffi, VoidCookie, X11Error, XConnection, XError};
diff --git a/src/platform_impl/linux/x11/util/mouse.rs b/src/platform_impl/linux/x11/util/mouse.rs
new file mode 100644
index 0000000000..212ea57267
--- /dev/null
+++ b/src/platform_impl/linux/x11/util/mouse.rs
@@ -0,0 +1,52 @@
+//! Utilities for handling mouse events.
+
+/// Recorded mouse delta designed to filter out noise.
+pub struct Delta<T> {
+    x: T,
+    y: T,
+}
+
+impl<T: Default> Default for Delta<T> {
+    fn default() -> Self {
+        Self {
+            x: Default::default(),
+            y: Default::default(),
+        }
+    }
+}
+
+impl<T: Default> Delta<T> {
+    pub(crate) fn set_x(&mut self, x: T) {
+        self.x = x;
+    }
+
+    pub(crate) fn set_y(&mut self, y: T) {
+        self.y = y;
+    }
+}
+
+macro_rules! consume {
+    ($this:expr, $ty:ty) => {{
+        let this = $this;
+        let (x, y) = match (this.x.abs() < <$ty>::EPSILON, this.y.abs() < <$ty>::EPSILON) {
+            (true, true) => return None,
+            (true, false) => (this.x, 0.0),
+            (false, true) => (0.0, this.y),
+            (false, false) => (this.x, this.y),
+        };
+
+        Some((x, y))
+    }};
+}
+
+impl Delta<f32> {
+    pub(crate) fn consume(self) -> Option<(f32, f32)> {
+        consume!(self, f32)
+    }
+}
+
+impl Delta<f64> {
+    pub(crate) fn consume(self) -> Option<(f64, f64)> {
+        consume!(self, f64)
+    }
+}