The Code Editor

Lumide's editor is built on a custom Rope data structure and GPU-accelerated text layout.

Edits made while a file is opening remain in the buffer and are backed up. Reloading or reopening with another encoding applies only while the same session remains unchanged; typing, renaming or closing the tab cancels an outdated load. Reopening with a UTF-8 BOM or UTF-16 BOM encoding preserves the first characters when the file has no BOM.

Editor Features#

Large File Handling#

• O(log n) Operations: Insertions, deletions, and splits touch only affected Rope nodes.
• Virtualized Viewport: Only visible lines are measured and rendered. Opening files with 100,000+ lines does not block the UI.
• Memory Efficiency: Memory scales with edits, not file size.

Soft Wrap#

• Toggle via the Command Palette (Toggle Soft Wrap).
• Setting: editor.soft_wrap (default: false).
• Wraps long lines to the viewport width while preserving line indentation.
• Line numbers only increment on logical line breaks.

Line Numbers#

• Toggle via Settings -> Editor -> Show Line Numbers (editor.show_line_numbers).
• Vim relative line numbers can be enabled separately under Settings -> Editor -> Vim Relative Line Numbers (editor.vim_mode.relative_line_numbers).

Cursor Shapes#

Cursor shape adapts to mode:

• Bar: Insert mode.
• Block: Vim Normal and Visual modes.
• Underline: Replace mode.

Bracket Matching#

When the cursor sits next to (), [], or {}, both brackets highlight.

• Jump to matching bracket: Ctrl + M (macOS) / Ctrl + Shift + M (Windows/Linux) or % in Vim mode.

Undo#

Undo steps follow how you edit, as in IntelliJ:

• Typing groups by word: a space after a word starts a new step, and Enter goes with the word you type after it.
• Backspaces group, and so do forward deletes; one that joins two lines starts a new step.
• Pasting, commands such as formatting, a pause of over a second, or moving the caret start a new step.
• Undo and Redo put the caret back where it was. In a shared workspace, Undo reverts only your own edits, and the caret follows everyone else's.

Binary Files#

A file holding binary data, such as an archive or a font, opens as a placeholder with its type and size instead of garbled text. Open with Default App and Reveal in Finder (Reveal in File Manager) show for files on this machine; Open Anyway as Text loads it into the editor, from the host in a remote or shared workspace, with the unsaved edits you made the last time you opened it as text. Saving never writes over a binary file you have not opened as text, and a file that turns binary on disk while open shows the placeholder. UTF-16 text without a byte order mark opens as text.

Common Editing Shortcuts#

Shortcuts below reflect Lumide's default JetBrains keymap preset. If you choose another preset (such as VS Code or Sublime) in Settings, shortcuts adapt accordingly.

Next Steps#

• Multi-Cursor Editing — Multiple cursors and column selection.
• Code Folding — Collapse syntax blocks and imports.
• Find & Replace — In-buffer search and regex replace.
• Markdown Live Preview — Synchronized split preview for Markdown.