Notepad

What is it?

Notepad is the plain-text editor: open a text file, edit it, save it. This roadmap plans it as a desktop program under src/apps/notepad/, built on a gap buffer, with TrueType rendering and a caret, a 200-step undo history, a File menu with open and save dialogs, mouse selection and clipboard, find and replace, go to line, and optional line numbers, syntax colouring and zoom. Nothing is implemented yet: there is no editor program and no Start menu entry for one.

How does it work?

Today. No text editor exists; type in the shell is the only way to read a text file, and there is no way to edit one. The building blocks it will use have shipped:

Text. ttf_draw_string(), ttf_measure_width() and ttf_get() draw and measure TrueType text, and FONT_MONO selects the monospace face (font_mgr.h).
Files. vfs_open(), vfs_read(), vfs_write(), vfs_stat() and vfs_create() (vfs.h).
Memory. pmm_alloc_contiguous() for buffers larger than 4 KB (pmm.h).

What it needs and does not have yet: a menu bar, a status bar, file open and save dialogs, context menus and the clipboard. The control library has only buttons, labels, text boxes and scroll bars (controls.h), and the Start menu has no Notepad entry (desktop.c).

Planned design.

Gap buffer. text_buffer_t: the text with a movable gap at the caret, so typing is a constant-time insert. It grows by reallocating, and loads and saves whole files.
Rendering and caret. Line-by-line TrueType drawing, an I-beam caret, and arrow, Home, End, Page Up and Page Down navigation.
Undo and redo. A stack of 200 insert and delete actions on Ctrl+Z and Ctrl+Y, with a whole paste recorded as one action.
File menu. New, Open, Save and Save As through the menu bar and the file dialogs, with an asterisk in the title while there are unsaved changes and a prompt before discarding them.
Editing. Mouse and Shift selection, Ctrl+A, cut, copy and paste, a scroll bar, and a status bar with the line and column.
Find and replace. A find bar that slides in without blocking the text, replace and replace all, and Go to Line.
Extras. A line-number gutter, colouring for C, assembly and Markdown, and Ctrl+scroll zoom.

The window follows the window chrome, menu bar and dialog designs.

What are its interfaces?

Interface	Status
`ttf_draw_string()`, `ttf_measure_width()`, `ttf_get(FONT_MONO, ...)`	Shipped
`vfs_open()`, `vfs_read()`, `vfs_write()`	Shipped
`text_buffer_t`, `notepad.exe`	Planned
`CTRL_MENUBAR`, `CTRL_STATUSBAR`, `dialog_file_open()`, `dialog_file_save()`	Planned by Complex Controls and Dialogs

How do I use it?

It cannot be used yet. Read a text file with type <file> in the terminal.

What is not implemented yet?

Gap Buffer
Text Rendering and Cursor
Undo/Redo
File Menu, which needs the menu bar and file dialogs
Editing Features, which needs the Clipboard
Find and Replace
Stretch Features

A second roadmap, Notepad in the applications domain, covers the same program and refers back to this one for the editor core.

How does it compare with Windows 11 and Linux?

Windows 11 Notepad has unlimited undo, a full File menu, an inline find bar and Ctrl+scroll zoom, but no syntax colouring. gedit and Kate use piece-table buffers, unlimited undo and syntax colouring through GtkSourceView or KSyntaxHighlighting. Impossible OS has no editor yet. The plan keeps the editor small (a gap buffer and a 200-step undo ring) and adds syntax colouring for C, assembly and Markdown, which Windows Notepad lacks.