Add table.changed event emitter (#209)

* add callback on table cell change

* fix tests

* fix event test

examples/table.py

@@ -58,4 +58,7 @@
 # table.data.to_numpy()
 # table.to_dataframe()
 
+# the table.changed event emits a dict of information on any cell change
+# e.g. {'data': 'sdfg', 'row': 1, 'column': 0, 'column_header': '1', 'row_header': '1'}
+table.changed.connect(lambda e: print(e.value))
 table.show(run=True)

magicgui/backends/_qtpy/widgets.py

@@ -821,12 +821,21 @@ def _mgui_bind_column_headers_change_callback(self, callback) -> None:
         """Bind callback to column headers change event."""
         raise NotImplementedError()
 
-    def _mgui_bind_cell_change_callback(self, callback) -> None:
-        """Bind callback to column headers change event."""
-        raise NotImplementedError()
-
     def _mgui_bind_change_callback(self, callback):
-        # FIXME: this currently reads out the WHOLE table every time we change ANY cell.
-        # nonsense.
-        # self._qwidget.itemChanged.connect(lambda i: callback(self._mgui_get_value()))
-        pass
+        """Bind callback to event of changing any cell."""
+
+        def _item_callback(item, callback=callback):
+            col_head = item.tableWidget().horizontalHeaderItem(item.column())
+            col_head = col_head.text() if col_head is not None else ""
+            row_head = item.tableWidget().verticalHeaderItem(item.row())
+            row_head = row_head.text() if row_head is not None else ""
+            data = {
+                "data": item.data(self._DATA_ROLE),
+                "row": item.row(),
+                "column": item.column(),
+                "column_header": col_head,
+                "row_header": row_head,
+            }
+            callback(data)
+
+        self._qwidget.itemChanged.connect(_item_callback)

magicgui/events.py

@@ -661,8 +661,11 @@ def __call__(self, *args, **kwargs) -> Event:
                 self.disconnect(cb)
         finally:
             self._emitting = False
-            if event._pop_source() != self.source:
-                raise RuntimeError("Event source-stack mismatch.")
+            evsource = event._pop_source()
+            if evsource is not self.source:
+                raise RuntimeError(
+                    f"Event source-stack mismatch. ({evsource} is not {self.source}"
+                )
 
         return event
 

magicgui/widgets/_protocols.py

@@ -272,8 +272,8 @@ def _mgui_bind_column_headers_change_callback(
         raise NotImplementedError()
 
     @abstractmethod
-    def _mgui_bind_cell_change_callback(self, callback: Callable[[Any], None]) -> None:
-        """Bind callback to column headers change event."""
+    def _mgui_bind_change_callback(self, callback: Callable[[Any], Any]) -> None:
+        """Bind callback to value change event."""
         raise NotImplementedError()
 
 

magicgui/widgets/_table.py

@@ -23,6 +23,7 @@
 from typing_extensions import Literal
 
 from magicgui.application import use_app
+from magicgui.events import EventEmitter
 from magicgui.widgets._bases import Widget
 from magicgui.widgets._protocols import TableWidgetProtocol
 
@@ -195,6 +196,14 @@ class Table(Widget, MutableMapping[TblKey, list]):
     to_dict(orient='dict')
         Return one of many different dict-like representations of table and header data.
         See docstring of :meth:`to_dict` for details.
+
+    Events
+    ------
+    changed
+        Emitted whenever a cell in the table changes.  the `event.value` will have a
+        dict of information regarding the cell that changed:
+        {'data': x, 'row': int, 'column': int, 'column_header': str, 'row_header': str}
+        CURRENTLY: only emitted on changes in the GUI. not programattic changes.
     """
 
     _widget: TableWidgetProtocol
@@ -230,6 +239,13 @@ def __init__(
             "columns": columns if columns is not None else _columns,
         }
 
+    def _post_init(self):
+        super()._post_init()
+        self.changed = EventEmitter(source=self, type="changed")
+        self._widget._mgui_bind_change_callback(
+            lambda *x: self.changed(value=x[0] if x else None)
+        )
+
     @property
     def value(self) -> dict[TblKey, Collection]:
         """Return dict with current `data`, `index`, and `columns` of the widget."""

tests/conftest.py

@@ -0,0 +1,9 @@
+import pytest
+
+
+# for now, the only backend is qt, and pytest-qt's qapp provides some nice pre-post
+# test cleanup that prevents some segfaults.  Once we start testing multiple backends
+# this will need to change.
+@pytest.fixture(autouse=True, scope="session")
+def always_qapp(qapp):
+    return qapp

tests/test_events.py

@@ -395,7 +395,7 @@ def cb(ev):
     try:
         em()
     except RuntimeError as err:
-        if str(err) != "Event source-stack mismatch.":
+        if "Event source-stack mismatch." not in str(err):
             raise
 
     em.disconnect()