SHEdit is a VCL based syntax highlight text editor component written "from scratch" as a semestral project (for school; in C++). Currently it is in a "not entirely finished" state, which though is already usable (but with a lot of "should be extended/rewritten" points). It is tested and written under the BCB XE.

FEATURES/CAPABILITIES
Is written to handle large amounts of data
Syntax highlight is implemented as part of rendering engine. More complicated grammars are to be specified as automatons using a bit awkward syntax (the basis is a push-down automaton with stack for the automaton states and a single register that can be used to remember some trivial in formation). (Currenly common language constructs are more-or-less supported, but tokens cannot be specified using regular expressions). The syntax highlighter supports recursive dictionaries.
The standard windows like keyboard shortcuts are used. Undo/redo working. Line numbers optional.
Explicit formatting (foreground/background color + font style) besides the syntax highlight.
Text wrapping is currently NOT supported.
Integration with vcl aware IDEs.
Rendering is written so that it redraws just what has to be redrawn.
Buffer is implemented as a linear two-level linked list, which allows comfortable continuous movement using iterators.
Note that API is not complete. If you decide to use this component in your project you most likely will have to extend it yourself.