Fixes for Input widget cursor visual glitches (#4773)

* Updates to the Input widget cursor

* Remove redundant code

* Fixing Input widget cursor to match TextArea and remove jankiness

* Unit test updates

* Fixing more Input tests

* Update CHANGELOG

* Remove debugging prints

Author: darrenburns

CHANGELOG.md

@@ -5,6 +5,15 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Changed
+
+- Input cursor will no longer jump to the end on focus https://github.com/Textualize/textual/pull/4773
+
+### Fixed
+
+- Input cursor blink effect will now restart correctly when any action is performed on the input https://github.com/Textualize/textual/pull/4773
 
 ## [0.75.1] - 2024-08-02
 

src/textual/widgets/_input.py

@@ -23,7 +23,7 @@
 from ..events import Blur, Focus, Mount
 from ..geometry import Offset, Size
 from ..message import Message
-from ..reactive import reactive, var
+from ..reactive import Reactive, reactive, var
 from ..suggester import Suggester, SuggestionReady
 from ..timer import Timer
 from ..validation import ValidationResult, Validator
@@ -174,7 +174,7 @@ class Input(Widget, can_focus=True):
     cursor_blink = reactive(True, init=False)
     value = reactive("", layout=True, init=False)
     input_scroll_offset = reactive(0)
-    cursor_position = reactive(0)
+    cursor_position: Reactive[int] = reactive(0)
     view_position = reactive(0)
     placeholder = reactive("")
     complete = reactive("")
@@ -335,8 +335,11 @@ def __init__(
             elif self.type == "number":
                 self.validators.append(Number())
 
+        self._initial_value = True
+        """Indicates if the value has been set for the first time yet."""
         if value is not None:
             self.value = value
+
         if tooltip is not None:
             self.tooltip = tooltip
 
@@ -391,8 +394,8 @@ def _watch_cursor_blink(self, blink: bool) -> None:
             if blink:
                 self._blink_timer.resume()
             else:
+                self._pause_blink_cycle()
                 self._cursor_visible = True
-                self._blink_timer.pause()
 
     @property
     def cursor_screen_offset(self) -> Offset:
@@ -412,6 +415,11 @@ def _watch_value(self, value: str) -> None:
         )
         self.post_message(self.Changed(self, value, validation_result))
 
+        # If this is the first time the value has been updated, set the cursor position to the end
+        if self._initial_value:
+            self.cursor_position = len(self.value)
+            self._initial_value = False
+
     def _watch_valid_empty(self) -> None:
         """Repeat validation when valid_empty changes."""
         self._watch_value(self.value)
@@ -506,32 +514,25 @@ def _toggle_cursor(self) -> None:
         """Toggle visibility of cursor."""
         self._cursor_visible = not self._cursor_visible
 
-    def _on_mount(self, _: Mount) -> None:
+    def _on_mount(self, event: Mount) -> None:
         self._blink_timer = self.set_interval(
             0.5,
             self._toggle_cursor,
             pause=not (self.cursor_blink and self.has_focus),
         )
 
-    def _on_blur(self, _: Blur) -> None:
-        assert self._blink_timer is not None
-        self._blink_timer.pause()
+    def _on_blur(self, event: Blur) -> None:
+        self._pause_blink_cycle()
         if "blur" in self.validate_on:
             self.validate(self.value)
 
-    def _on_focus(self, _: Focus) -> None:
-        assert self._blink_timer is not None
-        self.cursor_position = len(self.value)
-        if self.cursor_blink:
-            self._blink_timer.resume()
+    def _on_focus(self, event: Focus) -> None:
+        self._restart_blink_cycle()
         self.app.cursor_position = self.cursor_screen_offset
         self._suggestion = ""
 
     async def _on_key(self, event: events.Key) -> None:
-        assert self._blink_timer is not None
-        self._cursor_visible = True
-        if self.cursor_blink:
-            self._blink_timer.reset()
+        self._restart_blink_cycle()
 
         if event.is_printable:
             event.stop()
@@ -562,11 +563,29 @@ async def _on_click(self, event: events.Click) -> None:
         else:
             self.cursor_position = len(self.value)
 
+    async def _on_mouse_down(self, event: events.MouseDown) -> None:
+        self._pause_blink_cycle()
+
+    async def _on_mouse_up(self, event: events.MouseUp) -> None:
+        self._restart_blink_cycle()
+
     async def _on_suggestion_ready(self, event: SuggestionReady) -> None:
         """Handle suggestion messages and set the suggestion when relevant."""
         if event.value == self.value:
             self._suggestion = event.suggestion
 
+    def _restart_blink_cycle(self) -> None:
+        """Restart the cursor blink cycle."""
+        self._cursor_visible = True
+        if self.cursor_blink and self._blink_timer:
+            self._blink_timer.reset()
+
+    def _pause_blink_cycle(self) -> None:
+        """Hide the blinking cursor and pause the blink cycle."""
+        self._cursor_visible = False
+        if self.cursor_blink and self._blink_timer:
+            self._blink_timer.pause()
+
     def insert_text_at_cursor(self, text: str) -> None:
         """Insert new text at the cursor, move the cursor to the end of the new text.
 
@@ -739,7 +758,8 @@ def action_delete_left_word(self) -> None:
                 self.cursor_position = 0
             else:
                 self.cursor_position = hit.start()
-            self.value = f"{self.value[: self.cursor_position]}{after}"
+            new_value = f"{self.value[: self.cursor_position]}{after}"
+            self.value = new_value
 
     def action_delete_left_all(self) -> None:
         """Delete all characters to the left of the cursor position."""

tests/input/test_input_key_modification_actions.py

@@ -25,6 +25,7 @@ async def test_delete_left_from_home() -> None:
     """Deleting left from home should do nothing."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_left()
             assert input.cursor_position == 0
             assert input.value == TEST_INPUTS[input.id]
@@ -44,6 +45,7 @@ async def test_delete_left_word_from_home() -> None:
     """Deleting word left from home should do nothing."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_left_word()
             assert input.cursor_position == 0
             assert input.value == TEST_INPUTS[input.id]
@@ -68,7 +70,6 @@ async def test_delete_left_word_from_end() -> None:
             "multi-and-hyphenated": "Long as she does it quiet-",
         }
         for input in pilot.app.query(Input):
-            input.action_end()
             input.action_delete_left_word()
             assert input.cursor_position == len(input.value)
             assert input.value == expected[input.id]
@@ -78,7 +79,6 @@ async def test_password_delete_left_word_from_end() -> None:
     """Deleting word left from end of a password input should delete everything."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
-            input.action_end()
             input.password = True
             input.action_delete_left_word()
             assert input.cursor_position == 0
@@ -89,6 +89,7 @@ async def test_delete_left_all_from_home() -> None:
     """Deleting all left from home should do nothing."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_left_all()
             assert input.cursor_position == 0
             assert input.value == TEST_INPUTS[input.id]
@@ -108,6 +109,7 @@ async def test_delete_right_from_home() -> None:
     """Deleting right from home should delete one character (if there is any to delete)."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_right()
             assert input.cursor_position == 0
             assert input.value == TEST_INPUTS[input.id][1:]
@@ -117,7 +119,6 @@ async def test_delete_right_from_end() -> None:
     """Deleting right from end should not change the input's value."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
-            input.action_end()
             input.action_delete_right()
             assert input.cursor_position == len(input.value)
             assert input.value == TEST_INPUTS[input.id]
@@ -133,6 +134,7 @@ async def test_delete_right_word_from_home() -> None:
             "multi-and-hyphenated": "as she does it quiet-like",
         }
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_right_word()
             assert input.cursor_position == 0
             assert input.value == expected[input.id]
@@ -142,6 +144,7 @@ async def test_password_delete_right_word_from_home() -> None:
     """Deleting word right from home of a password input should delete everything."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.password = True
             input.action_delete_right_word()
             assert input.cursor_position == 0
@@ -162,6 +165,7 @@ async def test_delete_right_all_from_home() -> None:
     """Deleting all right home should remove everything in the input."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_delete_right_all()
             assert input.cursor_position == 0
             assert input.value == ""

tests/input/test_input_key_movement_actions.py

@@ -43,6 +43,7 @@ async def test_input_right_from_home() -> None:
     """Going right should always land at the next position, if there is one."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_cursor_right()
             assert input.cursor_position == (1 if input.value else 0)
 
@@ -60,6 +61,7 @@ async def test_input_left_from_home() -> None:
     """Going left from home should stay put."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_cursor_left()
             assert input.cursor_position == 0
 
@@ -77,6 +79,7 @@ async def test_input_left_word_from_home() -> None:
     """Going left one word from the start should do nothing."""
     async with InputTester().run_test() as pilot:
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_cursor_left_word()
             assert input.cursor_position == 0
 
@@ -118,6 +121,7 @@ async def test_input_right_word_from_home() -> None:
             "multi-and-hyphenated": 5,
         }
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             input.action_cursor_right_word()
             assert input.cursor_position == expected_at[input.id]
 
@@ -151,6 +155,7 @@ async def test_input_right_word_to_the_end() -> None:
             "multi-and-hyphenated": 7,
         }
         for input in pilot.app.query(Input):
+            input.cursor_position = 0
             hops = 0
             while input.cursor_position < len(input.value):
                 input.action_cursor_right_word()