feat: release keyPress automatically (#796)

* feat: release keyPress automatically

* send keepalive when pressing the key

* remove logging

* clean up logging

* chore: use unreliable channel to send keepalive events

* chore: use ordered unreliable channel for pointer events

* chore: adjust auto release key interval

* chore: update logging for kbdAutoReleaseLock

* chore: update comment for KEEPALIVE_INTERVAL

* fix: should cancelAutorelease when pressed is true

* fix: handshake won't happen if webrtc reconnects

* chore: add trace log for writeWithTimeout

* chore: add timeout for KeypressReport

* chore: use the proper key to send release command

* refactor: simplify HID RPC keyboard input handling and improve key state management

- Updated `handleHidRPCKeyboardInput` to return errors directly instead of keys down state.
- Refactored `rpcKeyboardReport` and `rpcKeypressReport` to return errors instead of states.
- Introduced a queue for managing key down state updates in the `Session` struct to prevent input handling stalls.
- Adjusted the `UpdateKeysDown` method to handle state changes more efficiently.
- Removed unnecessary logging and commented-out code for clarity.

* refactor: enhance keyboard auto-release functionality and key state management

* fix: correct Windows default auto-repeat delay comment from 1ms to 1s

* refactor: send keypress as early as possible

* refactor: replace console.warn with console.info for HID RPC channel events

* refactor: remove unused NewKeypressKeepAliveMessage function from HID RPC

* fix: handle error in key release process and log warnings

* fix: log warning on keypress report failure

* fix: update auto-release keyboard interval to 225

* refactor: enhance keep-alive handling and jitter compensation in HID RPC

- Implemented staleness guard to ignore outdated keep-alive packets.
- Added jitter compensation logic to adjust timer extensions based on packet arrival times.
- Introduced new methods for managing keep-alive state and reset functionality in the Session struct.
- Updated auto-release delay mechanism to use dynamic durations based on keep-alive timing.
- Adjusted keep-alive interval in the UI to improve responsiveness.

* gofmt

* clean up code

* chore: use dynamic duration for scheduleAutoRelease

* Use harcoded timer reset value for now

* fix: prevent nil pointer dereference when stopping timers in Close method

* refactor: remove nil check for kbdAutoReleaseTimers in DelayAutoReleaseWithDuration

* refactor: optimize dependencies in useHidRpc hooks

* refactor: streamline keep-alive timer management in useKeyboard hook

* refactor: clarify comments in useKeyboard hook for resetKeyboardState function

* refactor: reduce keysDownStateQueueSize

* refactor: close and reset keysDownStateQueue in newSession function

* chore: resolve conflicts

* resolve conflicts

---------

Co-authored-by: Adam Shiervani <adam.shiervani@gmail.com>

internal/usbgadget/usbgadget.go

@@ -68,6 +68,9 @@ type UsbGadget struct {
 	keyboardState byte          // keyboard latched state (NumLock, CapsLock, ScrollLock, Compose, Kana)
 	keysDownState KeysDownState // keyboard dynamic state (modifier keys and pressed keys)
 
+	kbdAutoReleaseLock   sync.Mutex
+	kbdAutoReleaseTimers map[byte]*time.Timer
+
 	keyboardStateLock   sync.Mutex
 	keyboardStateCtx    context.Context
 	keyboardStateCancel context.CancelFunc
@@ -85,6 +88,7 @@ type UsbGadget struct {
 
 	onKeyboardStateChange *func(state KeyboardState)
 	onKeysDownChange      *func(state KeysDownState)
+	onKeepAliveReset      *func()
 
 	log *zerolog.Logger
 
@@ -118,23 +122,24 @@ func newUsbGadget(name string, configMap map[string]gadgetConfigItem, enabledDev
 	keyboardCtx, keyboardCancel := context.WithCancel(context.Background())
 
 	g := &UsbGadget{
-		name:                name,
-		kvmGadgetPath:       path.Join(gadgetPath, name),
-		configC1Path:        path.Join(gadgetPath, name, "configs/c.1"),
-		configMap:           configMap,
-		customConfig:        *config,
-		configLock:          sync.Mutex{},
-		keyboardLock:        sync.Mutex{},
-		absMouseLock:        sync.Mutex{},
-		relMouseLock:        sync.Mutex{},
-		txLock:              sync.Mutex{},
-		keyboardStateCtx:    keyboardCtx,
-		keyboardStateCancel: keyboardCancel,
-		keyboardState:       0,
-		keysDownState:       KeysDownState{Modifier: 0, Keys: []byte{0, 0, 0, 0, 0, 0}}, // must be initialized to hidKeyBufferSize (6) zero bytes
-		enabledDevices:      *enabledDevices,
-		lastUserInput:       time.Now(),
-		log:                 logger,
+		name:                 name,
+		kvmGadgetPath:        path.Join(gadgetPath, name),
+		configC1Path:         path.Join(gadgetPath, name, "configs/c.1"),
+		configMap:            configMap,
+		customConfig:         *config,
+		configLock:           sync.Mutex{},
+		keyboardLock:         sync.Mutex{},
+		absMouseLock:         sync.Mutex{},
+		relMouseLock:         sync.Mutex{},
+		txLock:               sync.Mutex{},
+		keyboardStateCtx:     keyboardCtx,
+		keyboardStateCancel:  keyboardCancel,
+		keyboardState:        0,
+		keysDownState:        KeysDownState{Modifier: 0, Keys: []byte{0, 0, 0, 0, 0, 0}}, // must be initialized to hidKeyBufferSize (6) zero bytes
+		kbdAutoReleaseTimers: make(map[byte]*time.Timer),
+		enabledDevices:       *enabledDevices,
+		lastUserInput:        time.Now(),
+		log:                  logger,
 
 		strictMode: config.strictMode,
 
@@ -149,3 +154,37 @@ func newUsbGadget(name string, configMap map[string]gadgetConfigItem, enabledDev
 
 	return g
 }
+
+// Close cleans up resources used by the USB gadget
+func (u *UsbGadget) Close() error {
+	// Cancel keyboard state context
+	if u.keyboardStateCancel != nil {
+		u.keyboardStateCancel()
+	}
+
+	// Stop auto-release timer
+	u.kbdAutoReleaseLock.Lock()
+	for _, timer := range u.kbdAutoReleaseTimers {
+		if timer != nil {
+			timer.Stop()
+		}
+	}
+	u.kbdAutoReleaseTimers = make(map[byte]*time.Timer)
+	u.kbdAutoReleaseLock.Unlock()
+
+	// Close HID files
+	if u.keyboardHidFile != nil {
+		u.keyboardHidFile.Close()
+		u.keyboardHidFile = nil
+	}
+	if u.absMouseHidFile != nil {
+		u.absMouseHidFile.Close()
+		u.absMouseHidFile = nil
+	}
+	if u.relMouseHidFile != nil {
+		u.relMouseHidFile.Close()
+		u.relMouseHidFile = nil
+	}
+
+	return nil
+}