If you are a student, you can get a free student license for Sigasi. This is an eclipse-based vhdl development environment with all the modern IDE features such as error checking on the fly, formatting, freezes ...
It has integration with Modelsim, ISim and riviera, Sigasi compiles vhdl files for you in the background, and you can run the simulator with 1 click. This is not a 100% IDE experience, but it is as close to VHDL as possible.
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