Merge pull request #4945 from Textualize/key-to-character

Add key_to_character function

src/textual/dom.py

@@ -1026,7 +1026,7 @@ def rich_style(self) -> Style:
         )
         return style
 
-    def check_consume_key(self, key: str) -> bool:
+    def check_consume_key(self, key: str, character: str | None) -> bool:
         """Check if the widget may consume the given key.
 
         This should be implemented in widgets that handle [`Key`][textual.events.Key] events and
@@ -1037,6 +1037,7 @@ def check_consume_key(self, key: str) -> bool:
 
         Args:
             key: A key identifier.
+            character: A character associated with the key, or `None` if there isn't one.
 
         Returns:
             `True` if the widget may capture the key in its `Key` event handler, or `False` if it won't.

src/textual/keys.py

@@ -2,6 +2,7 @@
 
 import unicodedata
 from enum import Enum
+from functools import lru_cache
 
 
 # Adapted from prompt toolkit https://github.com/prompt-toolkit/python-prompt-toolkit/blob/master/prompt_toolkit/keys.py
@@ -282,6 +283,7 @@ def _get_key_aliases(key: str) -> list[str]:
     return [key] + KEY_ALIASES.get(key, [])
 
 
+@lru_cache(1024)
 def format_key(key: str) -> str:
     """Given a key (i.e. the `key` string argument to Binding __init__),
     return the value that should be displayed in the app when referring
@@ -303,6 +305,36 @@ def format_key(key: str) -> str:
     return tentative_unicode_name
 
 
+@lru_cache(1024)
+def key_to_character(key: str) -> str | None:
+    """Given a key identifier, return the character associated with it.
+
+    Args:
+        key: The key identifier.
+
+    Returns:
+        A key if one could be found, otherwise `None`.
+    """
+    _, separator, key = key.rpartition("+")
+    if separator:
+        # If there is a separator, then it means a modifier (other than shift) is applied.
+        # Keys with modifiers, don't come from printable keys.
+        return None
+    if len(key) == 1:
+        # Key identifiers with a length of one, are also characters.
+        return key
+    try:
+        return unicodedata.lookup(KEY_TO_UNICODE_NAME[key])
+    except KeyError:
+        pass
+    try:
+        return unicodedata.lookup(key.replace("_", " ").upper())
+    except KeyError:
+        pass
+    # Return None if we couldn't identify the key.
+    return None
+
+
 def _character_to_key(character: str) -> str:
     """Convert a single character to a key value.
 

src/textual/screen.py

@@ -29,6 +29,8 @@
 from rich.console import RenderableType
 from rich.style import Style
 
+from textual.keys import key_to_character
+
 from . import constants, errors, events, messages
 from ._arrange import arrange
 from ._callback import invoke
@@ -330,7 +332,7 @@ def _binding_chain(self) -> list[tuple[DOMNode, BindingsMap]]:
             for filter_namespace in filter_namespaces:
                 check_consume_key = filter_namespace.check_consume_key
                 for key in list(bindings_map.key_to_bindings):
-                    if check_consume_key(key):
+                    if check_consume_key(key, key_to_character(key)):
                         del bindings_map.key_to_bindings[key]
             filter_namespaces.append(namespace)
 

src/textual/widgets/_input.py

@@ -361,18 +361,19 @@ def _cursor_at_end(self) -> bool:
         """Flag to indicate if the cursor is at the end"""
         return self.cursor_position >= len(self.value)
 
-    def check_consume_key(self, key: str) -> bool:
+    def check_consume_key(self, key: str, character: str | None) -> bool:
         """Check if the widget may consume the given key.
 
         As an input we are expecting to capture printable keys.
 
         Args:
             key: A key identifier.
+            character: A character associated with the key, or `None` if there isn't one.
 
         Returns:
             `True` if the widget may capture the key in it's `Key` message, or `False` if it won't.
         """
-        return len(key) == 1 and key.isprintable()
+        return character is not None and character.isprintable()
 
     def validate_cursor_position(self, cursor_position: int) -> int:
         return min(max(0, cursor_position), len(self.value))

src/textual/widgets/_text_area.py

@@ -546,22 +546,26 @@ def _get_builtin_highlight_query(language_name: str) -> str:
 
         return highlight_query
 
-    def check_consume_key(self, key: str) -> bool:
+    def check_consume_key(self, key: str, character: str | None = None) -> bool:
         """Check if the widget may consume the given key.
 
         As a textarea we are expecting to capture printable keys.
 
         Args:
             key: A key identifier.
+            character: A character associated with the key, or `None` if there isn't one.
 
         Returns:
             `True` if the widget may capture the key in it's `Key` message, or `False` if it won't.
         """
         if self.read_only:
+            # In read only mode we don't consume any key events
             return False
         if self.tab_behavior == "indent" and key == "tab":
+            # If tab_behavior is indent, then we consume the tab
             return True
-        return len(key) == 1 and key.isprintable()
+        # Otherwise we capture all printable keys
+        return character is not None and character.isprintable()
 
     def _build_highlight_map(self) -> None:
         """Query the tree for ranges to highlights, and update the internal highlights mapping."""