source code editor

What's a source code editor?

Let's first exclude, what it is not. It is not a textprocessor, i.e.

• uses an single monospaced western font of unique size and spacing [Courier].
• lines have a unique height and spacing.
• does not add hidden properties to the stored text.
• text attributes are used only for syntax highliting or similar predefined purposes.
• has left justified tabstops [of unique width?]
• does not normally wrap long lines.
• has no document, page or paragraph formatting or layout.

Some common and desireable features are:

• adjustable tab expansion.
• right margin marker (soft).
• block selection and processing (single block).
• read-only, insert and overwrite input modes.
• rich choice of keyboard commands.
• scrollbars, mouse and mousewheel support.
• undo/redo support.
• clipboard support.
• line number and special marker display (gutter).

Additional useful extensions:

• syntax highlighting.
• bookmarks.
• hyperlink and block navigation.
• code completion.
• visualization of white characters.
• display and editing of embedded Unicode literals.
• macro capabilites.
• block folding.
• block movement.
• EOL adjustment.
• tab replacement.
• smart indentation.
• multiple text windows, easy content switch, multiple display of same text source.
• persistent user settings.
• context menu.

Also desireable, but not for source code editing:

• word wrap.
• Unicode support.
• hexdump of binary sources.