x11: ignore mouse scroll button release events

winit-x11/src/event_processor.rs

@@ -1020,7 +1020,8 @@ impl EventProcessor {
             // those. In practice, even clicky scroll wheels appear to be reported by
             // evdev (and XInput2 in turn) as axis motion, so we don't otherwise
             // special-case these button presses.
-            4..=7 => WindowEvent::MouseWheel {
+            4..=7 => match state {
+                ElementState::Pressed => WindowEvent::MouseWheel {
                     device_id,
                     delta: match event.detail {
                         4 => MouseScrollDelta::LineDelta(0.0, 1.0),
@@ -1031,6 +1032,8 @@ impl EventProcessor {
                     },
                     phase: TouchPhase::Moved,
                 },
+                ElementState::Released => return,
+            },
             8 => WindowEvent::PointerButton {
                 device_id,
                 primary: true,

winit/src/changelog/unreleased.md

@@ -269,3 +269,4 @@ changelog entry.
 - On Windows 11, prevent incorrect shifting when dragging window onto a monitor with different DPI.
 - On Web, device events are emitted regardless of cursor type.
 - On Wayland, `axis_value120` scroll events now generate `MouseScrollDelta::LineDelta`
+- On X11, mouse scroll button events no longer cause duplicated `WindowEvent::MouseWheel` events.