add logging support (#219)

* add logging support

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

README.md

@@ -28,14 +28,26 @@ example notebook.
 from zndraw import ZnDraw
 import ase
 
-zndraw = ZnDraw()
+vis = ZnDraw()
 
-zndraw.socket.sleep(2) # give it some time to fully connect
-zndraw[0] = ase.Atoms(
+vis.socket.sleep(2) # give it some time to fully connect
+vis[0] = ase.Atoms(
   "H2O", positions=[[0.75, -0.75, 0], [0.75, 0.75, 0], [0, 0, 0]]
   )
 ```
 
+ZnDraw also provides an interface to the Python
+[logging](https://docs.python.org/3/library/logging.html) library, including
+support for formatters and different logging levels.
+
+```python
+import logging
+
+log = logging.getLogger(__name__)
+log.addHandler(vis.get_logging_handler())
+log.critical("Critical Message")
+```
+
 ## User Interface
 
 ![ZnDraw UI](https://raw.githubusercontent.com/zincware/ZnDraw/main/misc/zndraw_ui.png "ZnDraw UI")

zndraw/app.py

@@ -348,3 +348,8 @@ def delete_atoms(data):
 @io.on("atoms:insert")
 def insert_atoms(data):
     emit("atoms:insert", data, broadcast=True, include_self=False)
+
+
+@io.on("message:log")
+def log(data):
+    emit("message:log", data, broadcast=True, include_self=False)

zndraw/static/main.js

@@ -41,6 +41,10 @@ function main() {
   socket.emit("atoms:request", window.location.href, () => {
     displayIncomingAtoms();
   });
+
+  socket.on("message:log", (msg) => {
+    console.log(msg);
+  });
 }
 
 main();

zndraw/zndraw.py

@@ -1,6 +1,7 @@
 import collections.abc
 import contextlib
 import dataclasses
+import logging
 import pathlib
 import threading
 import time
@@ -19,6 +20,23 @@
 from zndraw.utils import get_port
 
 
+class ZnDrawLoggingHandler(logging.Handler):
+    """Logging handler which emits log messages to the ZnDraw server."""
+
+    def __init__(self, socket):
+        super().__init__()
+        self.socket = socket
+
+    def emit(self, record):
+        try:
+            msg = self.format(record)
+            self.socket.emit("message:log", msg)
+        except RecursionError:  # See StreamHandler
+            raise
+        except Exception:
+            self.handleError(record)
+
+
 @dataclasses.dataclass
 class ZnDraw(collections.abc.MutableSequence):
     url: str = None
@@ -187,6 +205,13 @@ def extend(self, values: list[ase.Atoms]) -> None:
         if self.display_new:
             self.display(len(self) - 1)
 
+    def log(self, message: str) -> None:
+        """Log a message to the console"""
+        self.socket.emit("message:log", message)
+
+    def get_logging_handler(self) -> ZnDrawLoggingHandler:
+        return ZnDrawLoggingHandler(self.socket)
+
     def read(self, filename: str, start: int, stop: int, step: int):
         """Read atoms from file and return a list of atoms dicts.