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.
SciTE is a SCIntilla based Text Editor. Originally built to demonstrate Scintilla, it has grown to be a generally useful editor with facilities for building and running programs. It is best used for jobs with simple configurations - I use it for building test and demonstration programs as well as SciTE and Scintilla, themselves.
Development of Scintilla started as an effort to improve the text editor in PythonWin. After being frustrated by problems in the Richedit control used by PythonWin, it looked like the best way forward was to write a new edit control. The biggest problem with Richedit and other similar controls is that they treat styling changes as important persistent changes to the document so they are saved into the undo stack and set the document's dirty flag. For source code, styling should not be persisted as it can be mechanically recreated.