I'm looking a tool that will display details of syntax errors in my code as I'm typing it, in the same way that Visual Studio does. I'm currently using Gedit, but am not adverse to acquiring a new text editor. I'm using C++ and HTML/CSS right now, but will be branching out to more languages in the future, so it needs to have support for as many languages as possible. I'd also like to avoid using an IDE as I feel more productive using a text editor and the GNU toolchain. Any suggestions?
vim does syntax highlighting well. As far as I know, however, it doesn't have the ability to display the details of the syntax errors in the editor. The constant "hands on keyboard" does speed up programming, though.
You will likely have difficulty finding a simple one-file editor that can do this. An IDE is virtually a necessity, since it integrates with a compiler to detect errors/warnings.
If you use an IDE (and I would recommend Eclipse or maybe KDevelop), you can continue to use the GNU toolchain; you don't need to build your project from the IDE if you don't want to. I regularly use Eclipse for programming and then Ant or Make in a terminal for building.
vim
with the pyflakes plugin does this for python, but I don't know about other languages.