Skip to content

Fix: Multitouch data handling memory safety #117

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
NullPointerDepressiveDisorder merged 2 commits into from
Mar 5, 2026
Merged

Fix: Multitouch data handling memory safety #117

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
a1e7588
Fix: Multitouch data handling memory safety
sentry[bot] Mar 5, 2026
c1f6d3b
Update MiddleDrag/Managers/MultitouchManager.swift
NullPointerDepressiveDisorder Mar 5, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 14 additions & 12 deletions MiddleDrag/Managers/MultitouchManager.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -855,25 +855,27 @@ extension MultitouchManager: DeviceMonitorDelegate {
let modifierFlags = CGEventSource.flagsState(.hidSystemState)

// The touches pointer is only valid for the duration of this callback.
// Copy touch data via raw memcpy — much cheaper than Swift Array allocation
// + map closure that was causing per-frame GC pressure and jitter at 100Hz+.
// Copy touch data into a Data value — Swift manages its lifetime automatically,
// eliminating the use-after-free / double-free risk of manual raw pointer
// allocation that can occur when rapid sleep/wake cycles cause concurrent
// restart() calls while async closures are still queued on gestureQueue.
let touchCount = Int(count)
nonisolated(unsafe) let touchesPtr: UnsafeMutableRawPointer?
let touchData: Data?
if touchCount > 0 {
let byteCount = touchCount * MemoryLayout<MTTouch>.stride
let buffer = UnsafeMutableRawPointer.allocate(
byteCount: byteCount, alignment: MemoryLayout<MTTouch>.alignment)
unsafe buffer.copyMemory(from: touches, byteCount: byteCount)
unsafe touchesPtr = unsafe buffer
touchData = unsafe Data(bytes: touches, count: byteCount)
} else {
unsafe touchesPtr = nil
touchData = nil
}

gestureQueue.async { [weak self] in
if let buffer = unsafe touchesPtr {
defer { unsafe buffer.deallocate() }
unsafe self?.gestureRecognizer.processTouches(
buffer, count: touchCount, timestamp: timestamp, modifierFlags: modifierFlags)
if var data = touchData {
data.withUnsafeMutableBytes { rawBuffer in
guard let ptr = rawBuffer.baseAddress else { return }
let buffer = UnsafeMutableRawPointer(ptr)
unsafe self?.gestureRecognizer.processTouches(
buffer, count: touchCount, timestamp: timestamp, modifierFlags: modifierFlags)
}
} else {
// Zero touches — still notify so gesture recognizer can end via stableFrameCount
unsafe self?.gestureRecognizer.processTouches(
Expand Down
Loading