Move Build a Desktop Wallet code samples

content/_code-samples/build-a-desktop-wallet/py/2_threaded.py

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+# "Build a Wallet" tutorial, step 2: Watch ledger closes from a worker thread.
+# This step builds an app architecture that keeps the GUI responsive while
+# showing realtime updates to the XRP Ledger.
+# License: MIT. https://github.com/XRPLF/xrpl-dev-portal/blob/master/LICENSE
+
+import xrpl
+import wx
+import asyncio
+from threading import Thread
+
+class XRPLMonitorThread(Thread):
+    """
+    A worker thread to watch for new ledger events and pass the info back to
+    the main frame to be shown in the UI. Using a thread lets us maintain the
+    responsiveness of the UI while doing work in the background.
+    """
+    def __init__(self, url, gui):
+        Thread.__init__(self, daemon=True)
+        # Note: For thread safety, this thread should treat self.gui as
+        # read-only; to modify the GUI, use wx.CallAfter(...)
+        self.gui = gui
+        self.url = url
+        self.loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(self.loop)
+        self.loop.set_debug(True)
+
+    def run(self):
+        """
+        This thread runs a never-ending event-loop that monitors messages coming
+        from the XRPL, sending them to the GUI thread when necessary, and also
+        handles making requests to the XRPL when the GUI prompts them.
+        """
+        self.loop.run_forever()
+
+    async def watch_xrpl(self):
+        """
+        This is the task that opens the connection to the XRPL, then handles
+        incoming subscription messages by dispatching them to the appropriate
+        part of the GUI.
+        """
+
+        async with xrpl.asyncio.clients.AsyncWebsocketClient(self.url) as self.client:
+            await self.on_connected()
+            async for message in self.client:
+                mtype = message.get("type")
+                if mtype == "ledgerClosed":
+                    wx.CallAfter(self.gui.update_ledger, message)
+
+    async def on_connected(self):
+        """
+        Set up initial subscriptions and populate the GUI with data from the
+        ledger on startup. Requires that self.client be connected first.
+        """
+        # Set up a subscriptions for new ledgers
+        response = await self.client.request(xrpl.models.requests.Subscribe(
+            streams=["ledger"]
+        ))
+        # The immediate response contains details for the last validated ledger.
+        # We can use this to fill in that area of the GUI without waiting for a
+        # new ledger to close.
+        wx.CallAfter(self.gui.update_ledger, response.result)
+
+
+class TWaXLFrame(wx.Frame):
+    """
+    Tutorial Wallet for the XRP Ledger (TWaXL)
+    user interface, main frame.
+    """
+    def __init__(self, url):
+        wx.Frame.__init__(self, None, title="TWaXL", size=wx.Size(800,400))
+
+        self.build_ui()
+
+        # Start background thread for updates from the ledger ------------------
+        self.worker = XRPLMonitorThread(url, self)
+        self.worker.start()
+        self.run_bg_job(self.worker.watch_xrpl())
+
+    def build_ui(self):
+        """
+        Called during __init__ to set up all the GUI components.
+        """
+        main_panel = wx.Panel(self)
+        self.ledger_info = wx.StaticText(main_panel, label="Not connected")
+
+        main_sizer = wx.BoxSizer(wx.VERTICAL)
+        main_sizer.Add(self.ledger_info, 1, flag=wx.EXPAND|wx.ALL, border=5)
+        main_panel.SetSizer(main_sizer)
+
+    def run_bg_job(self, job):
+        """
+        Schedules a job to run asynchronously in the XRPL worker thread.
+        The job should be a Future (for example, from calling an async function)
+        """
+        task = asyncio.run_coroutine_threadsafe(job, self.worker.loop)
+
+    def update_ledger(self, message):
+        """
+        Process a ledger subscription message to update the UI with
+        information about the latest validated ledger.
+        """
+        close_time_iso = xrpl.utils.ripple_time_to_datetime(message["ledger_time"]).isoformat()
+        self.ledger_info.SetLabel(f"Latest validated ledger:\n"
+                         f"Ledger Index: {message['ledger_index']}\n"
+                         f"Ledger Hash: {message['ledger_hash']}\n"
+                         f"Close time: {close_time_iso}")
+
+
+if __name__ == "__main__":
+    WS_URL = "wss://s.altnet.rippletest.net:51233" # Testnet
+    app = wx.App()
+    frame = TWaXLFrame(WS_URL)
+    frame.Show()
+    app.MainLoop()