feat: Ctrl+Left/Right word navigation and Ctrl+Shift+Left/Right selection (#137)

[YourRobotOverlord]

Copilot Session

[913adbc6-5ccd-4633-b2a6-c0a09b84dc9e]

Fixes #137 — Editor now responds to the modifier keys described in the issue.

What's new

Key	Command	Behaviour
Ctrl+Left	WordLeft	Jump to the previous word start; collapses any selection
Ctrl+Right	WordRight	Jump to the next word start; collapses any selection
Ctrl+Shift+Left	WordLeftExtend	Extend selection to the previous word start
Ctrl+Shift+Right	WordRightExtend	Extend selection to the next word start
Ctrl+Backspace	KillWordLeft	Delete from the previous word start to the caret
Ctrl+Delete	KillWordRight	Delete from the caret to the next word start

Implementation notes

• Word boundary — uses TextUtilities.GetNextCaretPosition with CaretPositioningMode.WordStartOrSymbol, the same mode used by AvaloniaEdit and TG's own TextView for Ctrl+Left/Right. This stops at word starts and between adjacent punctuation/symbol runs, giving intuitive jumps across operators and brackets.
• Selection collapsing — WordLeft collapses to SelectionStart, WordRight collapses to SelectionEnd, matching the behaviour of the plain arrow keys.
• Kill commands — respect ReadOnly; replace any active selection rather than doing a word-boundary delete (consistent with DeleteCharLeft/DeleteCharRight); wrapped in a RunUpdate scope so undo is a single step.
• All six commands are registered in Editor.DefaultKeyBindings and are therefore overridable via Terminal.Gui's ConfigurationManager JSON profile mechanism.

Files changed

• src/Terminal.Gui.Editor/Editor.Selection.cs — GetWordBoundaryOffset, MoveCaretToWordBoundary, KillToWordBoundary helpers
• src/Terminal.Gui.Editor/Editor.Commands.cs — 6 key bindings + 6 AddCommand registrations
• tests/Terminal.Gui.Editor.Tests/EditorWordNavigationTests.cs — 16 new unit tests (new file)
• tests/Terminal.Gui.Editor.Tests/EditorKeyBindingConfigTests.cs — guard assertions for all 6 new commands in the defaults

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[Copilot]

Pull request overview

Adds word-wise navigation, selection extension, and word-kill editing commands to Terminal.Gui.Editor.Editor, aligning editor behavior with common Ctrl-modified key expectations and exposing the bindings via Editor.DefaultKeyBindings for configuration.

Changes:

• Added helpers for word-boundary navigation and deletion using TextUtilities.GetNextCaretPosition(..., CaretPositioningMode.WordStartOrSymbol).
• Registered 6 new commands and default keybindings for Ctrl+Left/Right, Ctrl+Shift+Left/Right, Ctrl+Backspace/Delete.
• Added new unit tests for word navigation/selection/kill behavior and expanded keybinding default assertions.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/Terminal.Gui.Editor/Editor.Selection.cs	Introduces word-boundary helper methods for moving the caret and deleting to word boundaries.
src/Terminal.Gui.Editor/Editor.Commands.cs	Adds default keybindings and command registrations for word navigation/selection/kill.
tests/Terminal.Gui.Editor.Tests/EditorWordNavigationTests.cs	New unit tests covering the new commands’ behavior.
tests/Terminal.Gui.Editor.Tests/EditorKeyBindingConfigTests.cs	Adds assertions ensuring the new commands exist in defaults and have expected keys.

Comments suppressed due to low confidence (1)

tests/Terminal.Gui.Editor.Tests/EditorWordNavigationTests.cs:203

• This test only asserts that the resulting text no longer starts with "hello", which could still pass for incorrect deletions (e.g., deleting too much). Consider asserting the exact expected document text after KillWordRight (and, if relevant, the expected caret position) to make the test more robust.

        editor.InvokeCommand (Command.KillWordRight);

        Assert.False (editor.Document!.Text.StartsWith ("hello"));
        Assert.Equal (0, editor.CaretOffset);

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