What is the fastest way to create a cross-platform IDE for a new programming language?

Question

The title already says most of what I'm after, but let me state some of the requirements explicitly:

• The language is not widely used, so writing a new language tokenizer etc is assumed to probably be required.
• Cross-platform, means at least Linux, Mac OS and Windows
• Minimal features: Syntax highlighting and Code-completion (aka "IntelliSense")
• Preferrable features: Interactive debugging
• Assumption: The developer is not an expert in any one programming language (although mediocre in a few, and eager to learn new techniques), so the focus on an environment / tools that quickly gets a developer up to speed, and is productive enough to reach the goal as fast as possible.

Answer 1

Xtext would be the perfect fit for these requirements. All you need to do is to define your grammar and you have your parser, linker, editor, etc. Of course all of this can be customized to your needs.

If your language compiles down to Java, you also get expressions and debugging out of the box.

Answer 2

Lazarus + SynEdit + SynCompletion (cross platform + syntax highlighting + autocompletion), interactive debugging is way to difficult I guess.