Move hold key handling into Go backend analogous to https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt

internal/usbgadget/hid_keyboard.go

@@ -74,7 +74,7 @@ func (u *UsbGadget) keyboardWriteHidFile(data []byte) error {
 	return nil
 }
 
-func (u *UsbGadget) KeyboardReport(modifier uint8, keys []uint8) error {
+func (u *UsbGadget) KeyboardReport(modifier uint8, keys []uint8, hold bool) error {
 	u.keyboardLock.Lock()
 	defer u.keyboardLock.Unlock()
 
@@ -90,6 +90,13 @@ func (u *UsbGadget) KeyboardReport(modifier uint8, keys []uint8) error {
 		return err
 	}
 
+	if !hold {
+		err := u.keyboardWriteHidFile(make([]uint8, 8))
+		if err != nil {
+			return err
+		}
+	}
+
 	u.resetUserInputTime()
 	return nil
 }

jsonrpc.go

@@ -980,7 +980,7 @@ var rpcHandlers = map[string]RPCHandler{
 	"getNetworkSettings":     {Func: rpcGetNetworkSettings},
 	"setNetworkSettings":     {Func: rpcSetNetworkSettings, Params: []string{"settings"}},
 	"renewDHCPLease":         {Func: rpcRenewDHCPLease},
-	"keyboardReport":         {Func: rpcKeyboardReport, Params: []string{"modifier", "keys"}},
+	"keyboardReport":         {Func: rpcKeyboardReport, Params: []string{"modifier", "keys", "hold"}},
 	"absMouseReport":         {Func: rpcAbsMouseReport, Params: []string{"x", "y", "buttons"}},
 	"relMouseReport":         {Func: rpcRelMouseReport, Params: []string{"dx", "dy", "buttons"}},
 	"wheelReport":            {Func: rpcWheelReport, Params: []string{"wheelY"}},

ui/src/components/popovers/PasteModal.tsx

@@ -13,8 +13,8 @@ import { keys, modifiers } from "@/keyboardMappings";
 import { layouts, chars } from "@/keyboardLayouts";
 import notifications from "@/notifications";
 
-const hidKeyboardPayload = (keys: number[], modifier: number) => {
-  return { keys, modifier };
+const hidKeyboardPayload = (keys: number[], modifier: number, hold: boolean) => {
+  return { keys, modifier, hold };
 };
 
 const modifierCode = (shift?: boolean, altRight?: boolean) => {
@@ -82,13 +82,10 @@ export default function PasteModal() {
           await new Promise<void>((resolve, reject) => {
             send(
               "keyboardReport",
-              hidKeyboardPayload([kei], modz[index]),
+              hidKeyboardPayload([kei], modz[index], false),
               params => {
                 if ("error" in params) return reject(params.error);
-                send("keyboardReport", hidKeyboardPayload([], 0), params => {
-                  if ("error" in params) return reject(params.error);
-                  resolve();
-                });
+                resolve();
               },
             );
           });

ui/src/hooks/useKeyboard.ts

@@ -4,6 +4,10 @@ import { useHidStore, useRTCStore } from "@/hooks/stores";
 import { useJsonRpc } from "@/hooks/useJsonRpc";
 import { keys, modifiers } from "@/keyboardMappings";
 
+const hidKeyboardPayload = (keys: number[], modifier: number, hold: boolean) => {
+  return { keys, modifier, hold };
+};
+
 export default function useKeyboard() {
   const [send] = useJsonRpc();
 
@@ -17,7 +21,7 @@ export default function useKeyboard() {
       if (rpcDataChannel?.readyState !== "open") return;
       const accModifier = modifiers.reduce((acc, val) => acc + val, 0);
 
-      send("keyboardReport", { keys, modifier: accModifier });
+      send("keyboardReport", hidKeyboardPayload(keys, accModifier, true));
 
       // We do this for the info bar to display the currently pressed keys for the user
       updateActiveKeysAndModifiers({ keys: keys, modifiers: modifiers });

usb.go

@@ -26,8 +26,8 @@ func initUsbGadget() {
 	}()
 }
 
-func rpcKeyboardReport(modifier uint8, keys []uint8) error {
-	return gadget.KeyboardReport(modifier, keys)
+func rpcKeyboardReport(modifier uint8, keys []uint8, hold bool) error {
+	return gadget.KeyboardReport(modifier, keys, hold)
 }
 
 func rpcAbsMouseReport(x, y int, buttons uint8) error {