Add vorpal.ui.clear command to API

[mamboer]

hi,
I implemented a clear command in one of my vorpal application following your answers in this post http://stackoverflow.com/questions/8813142/clear-terminal-window-in-node-js-readline-shell/32871585#32871585?newreg=0fd7e6b366544c72b82496cd4c077973

The problem is that the cursor lost in the console after executing the clear command, as the screenshots below:

Before clear,

After clear,

Notice that the grey cursor had gone.

[dthree]

Thanks.

The API on this changed a bit since that post. Could you possibly paste your code?

[mamboer]

hi, here's my code in my clear command,

'use strict';
module.exports = (vorpal, config) => {
    return vorpal
        .command('clear', 'Clear the outputs.')
        .action(function(args, cbk) {
            let blank = '';
            for (var i = 0; i < process.stdout.rows; ++i) {
              blank += '\n';
            }
            vorpal.ui.redraw(blank);
            vorpal.ui.redraw('');
            cbk();
        });
};

[mamboer]

It will be very nice that vorpal could add a built-in clear command along with the help and exit.
Viewing the help, doing some works, clear the screen and doing some other works, daily CLI working routine.

[dthree]

For sure!

In the immediate, check out this for a much better way to solve your problem!

https://github.com/dthree/cash/blob/master/src/commands/clear.js

[mamboer]

Cool! Thanks so much!

I'm confused on the \u001b[2J\u001b[0;0H in the source code, can you explain a little bit about it?

[eistaa]

@mamboer: It's ANSI escape codes. A breakdown of \u001b[2J\u001b[0;0H is:

• \u001b is the escape character, together with [ it becomes a Control Sequence Introducer (CSI)
• CSI 2J is the sequence for clearing the entire screen
• CSI 0;0H is the sequence for moving the cursor to row 0, column 0

[dthree]

No problem.

I'm renaming this issue to turn it into a feature request.

[mamboer]

@eistaa @dthree thanks guys

[subk]

Just to point out the ansi-escapes package which implements a clearScreen method and many other useful sequences.

[Maxtoros]

Hey guys am using this command to 'clean' the screen , especially after a messy execution :
vorpal
.command('clean')
.action(function (args,cb) {
process.stdout.write ("\u001B[2J\u001B[0;0f");
cb();
});

[dthree]

@Maxtoros nice idea!

[jimbuck]

Should we use @Maxtoros's process.stdout.write(...) or @dthree's this.log(...) for that?

[jimbuck]

I just tried this on Windows 10 and it exits my app completely. Any ideas?

[Maxtoros]

@JimmyBoh I used Windows 10 while working with my solution ( ConEmu with 2 tabs : Cygwin Bash + CMD)

[dthree]

@JimmyBoh probably this.log.

---

What exactly exits your app? Is there an exception?

[jimbuck]

@Maxtoros exact recommendation:

vorpal
  .command('clean')
  .action(function (args,cb) {
    process.stdout.write ("\u001B[2J\u001B[0;0f");
    cb();
  });

There was no exception, it just instantly cleared everything and exiting the vorpal context (returned back to regular cmd.exe).

[jimbuck]

I actually just tried the same thing with vorpal.ui.redraw.clear and even that made my app immediately exit without any error or other indication of failure. This is in cmd.exe with Windows 10, and also happens in Cmder on Windows 10.