Input bar at console bottom in C

Question

Window bottom

Some applications like vim, mutt, aptitude contain

• a top window section for output and
• a bottom section for the user to type in

Answer 1

This answer suggests a slightly different approach, but it avoids a lot of complication you'd introduce by using the current method. I hope it is possible to implement these simplifications.

Use termio to turn off canonical mode.

Sample code (here) will show you exactly how to set up such an input loop. This sample 'polls-and-sleeps' which could mean a delay unless you reduce the sleep. Also I think you can use termio to set a timeout (wait a second and return 'no input' or give me the input NOW if it comes earlier). But if you are really going to monitor another process, polling might be the more flexible option.. You can really poll 30x a second and live with the .00001% processor hit it is going to cause, but you will love the simplicity and bug prevention it gives.

Avoid multiple threads and processes like the plague

You don't need to use 2 processes/threads if the only problem you are trying to solve is the fact that getch() blocks. That would be required if it were impossible to prevent the input functions from blocking. 'Canonical' (rules based) means all sorts of handy 'rules' are in effect, like, 'don't give the input to the program until ENTER is hit'. For a full screen console app you want to turn off all the rules and do everything yourself.

Put the main thread in charge of the window...

... Then you can just use the ansi escape csi codes to position the cursor back to where you want it. Caveat: you can't write to the lower-right box in the screen. Everything will scroll.

There is an annoying thing in MS windows programming where only the thread that creates a window can safely update it. There is actually a reason for this. Whether you're talking console, or windowing system. sooner or later, if you have multiple threads/processing hitting one output device, you'll interrupt an escape sequence (or have to make extra code to manage this which is a bad thing), be fighting for the output 'port', etc. you need one thread to manage the output.

if you really care about what some other thread or process is doing, just check it in your main console management loop. For example of you have another process that you just want to report its progress, start it from your program and capture its stdouput and look at that; another thread, just lock something shared you can check in your polling routine. Heck if it's just a byte and it's only used for statuses, don't even lock the damn thing. You can throw in a couple of GOTO's too, just to show your individuality :-)

caveat I don't know that ncurses would play well with you if you are manually messing with termio? I would guess it wants to do that itself. Never tried mixing. If your app is simple you could go it alone without the help, especially if you can wrestle ncurses into doing what you want. I'm no expert on those apps you mention but I'd bet they are micromanaging everything.