Syscalls

PYUI is a hybrid framework thst uses JS and Python. To eshtablish a proper communication protocol between both the runtimes I have made Syscalls. This are core to all messages sent from JS to Python or from Python to JS. Howerver PYUI support developers to register there own Syscalls and add functionallity to PYUI. In this page we will talk about Custom Syscall

Why Custom Syscall ?

Custom Syscalls help developer to communicate to and fro between JS and Python runtime, without touching the websocket directly.Custom Syscalls were added to keep developers abstracted from touching sockets, and to enforce the proper messenging format. Developers not touching the syscalls explicitly keeps the message JSON coherent and interpretable in both Python or JS side.

JS File in PYUI

Before we tell how to make our first syscall it is important to know how to make js file in PYUI.

Go to layouts/JS folder
Make the js file of exacly same name as your form name with .js extension. For example if your form is profile.xml so make profile.js. Also it supports nested folders. Like if you have form in auth/profile.xml you have to make js file in auth/profile.js

Making a custom syscall

Let us see the following example

Example

// JS side
function add(message)
{
    // The message contains several things .msg is the actual content sent by Python
    const token = JSON.parse(message.msg);

    let a = token.a; 
    let b = token.b;

    const r = {"result":a+b};

    // send back result to Python
    sendSyscall('ADD',r);

}

bind('ADD',add); // <= bind the function to syscall

and then in Python side

// Python side

// Register the syscall to Python PYUi
self.pyui.RegisterSyscall('ADD')

// register the callback for the syscall this is triggered when JS event come
self.pyui.RegisterSyscallCallback('ADD',self.callback_result)

// send callback
toSend = {"a":10,"b":20}
self.pyui.sendSyscall('ADD',toSend)


def callback_result(self,pyui_instance,message):

    print(message)

    # Expected: {"result":30}

We bind a function in JS side using bind() function.
We can use sendSyscall() function in JS side to send syscall.
```
sendSyscall('SYSCALL_NAME',function)
```
In Python side we need to first register the syscall.
```
self.pyui.RegisterSyscall('SYSCALL_NAME')
```

Then add a callback to it if you exepect some return response from JS side

self.pyui.RegisterSyscallCallback('SYSCALL_NAME',func)

# use args= to supply arguments

Send the syscall to JS whenever needed

self.pyui.sendSyscall('SYSCALL_NAME',message)

# message in string or json serialzeable objects

Make the callback function to accept the value from JS side
```
def func(self,pyui_instance,message):
    .....
```

Unregister a Syscall Callback or Remove a Syscall

Unregister a Syscall callback

    self.pyui.UnSyscallRegisterCallBack("syscall_name")

Remove a syscall

    self.pyui.RemoveSyscall('syscall_name')