Implement using conditions

[gaborcsardi]

That will allow debugging subprocesses.

[krlmlr]

Can you elaborate?

[gaborcsardi]

Instead of cat(), we use message() with a custom class, and support top level handlers. E.g. you can have a top level handler that can do something special with the debug messages, put them on an RStudio pane, etc.

[krlmlr]

What about color?

[gaborcsardi]

That's fine. If the condition is not muffled, then we still cat(), with color.