Code Editor - Must-Have features? [closed]

Question

I've been coding for almost 18 years, and having migrated to Macs for the last year or so, it was inevitable to start thinking about writing a code editor from scratch - probably, just to try this thing out, or to make something that perfectly suits my needs.

And I was wondering :

What are the absolute MUST-HAVEs of a good code editor? (by order of priority, if possible) If we're talking about a not-so-conventional feature, could you give me an example of actual implementation of that particular feature? ("xxxxx" like in Notepad++ on Windows). Looking forward to see your answers...

*Well, there is sometimes a thin line between what could be considered as an "Editor" and an "IDE", but let's just not exclude more... IDE-oriented ones...

Answer 1

In my honest opinion, the really great code editors have your basic features plus they are designed almost exclusively for a single language. The more specific (and less generic) the editor is designed the better it will implement all of the tiny little details of Python or Java or C++...

• FAST (read ... faster than Netbeans or Eclipse, even if that means compromising features)
• Show line numbers all the time
• Syntax Highlighting
• Allow Tab Indent or spaces, allow representing tabs as any number of spaces.
• Document outline (what functions/classes are in this file?)
• Support multiple languages at once (php, html, javascript) in the same file.
• Mark lines / highlight lines (allow jumping to code segments / marked functions / classes)
• Auto-save periodically
• Save open-files / reopen to last open files
• Save historical versions of the edited file (optionally)
• Show hidden/special characters (A button that shows symbols over tabs, newlines, etc)
• Switch between *Nix, Mac, Windows file-formats.
• Indent multiple highlighted lines
• Writing the code highlighter as a stand-alone library that can be maintained independent of your application and is specific to that language.
• Writing the code highlighter so it's stupid fast (sparingly use regex)
• Automatic Indentation (when I hit the enter key and I'm indented four spaces you should optionally start the next line at the same indentation)
• Highlighting Keywords properly (like True, False, None in Python)
• Autocomplete (classes, functions, built-ins, etc) .. (but keep it fast ... driven by a Ternary Search Tree not some verbose XML data structure)
• Not attempting to perform syntax error checking on every key stroke (man that is annoying, and often really slow!)
• Scope Awareness (rarely seen, but the ability to prioritize name suggestions based on the current line's scope)
• Built-in Support for remote file systems (ftp, sftp)