Scintilla is a free source code editing component. As well as features found in
standard text editing components, Scintilla includes features especially useful
when editing and debugging source code. These include support for syntax
styling, error indicators, code completion and call tips. The selection margin
can contain markers like those used in debuggers to indicate breakpoints and the
current line. Styling choices are more open than with many editors, allowing the
use of proportional fonts, bold and italics, multiple foreground and background
colours and multiple fonts. It comes with complete source code and may be used
in any free project or commercial product.

WWW: https://www.scintilla.org/