How to setup pager in dart console - dart

Question

It is popular to show output per page at one time when content is huge in many console applications: git log/diff, more/less; but how do I do in a dart programming application?
I find a setup_pager method in git diff source code, but could not figure it out, do I have to do some linux programming? or start an other process to pass output to less command? Thanks!

Answer 1

If it's something simple like the more command then use the console package to get the no of rows for the terminal.
Enter a for loop from 1 to the row count - 1
Print a row of text on each iteration.
Then prompt the user to hit the space key.
When they do, restart the for loop.
Rinse and repeat.
If you want to scroll up then again the console package is you friend.
Similar process but when you prompt the user ask which direction.
If the direction is up then clear the screen and print the prior page of text.
The tricky bit is reading backwards through the file.
Have a look at the File class and the seek method. It will let you move backward in the file but you will have to find the line brakes yourself.
A very crude implementation:
#! /usr/bin/env dcli
// ignore: prefer_relative_imports
import 'dart:math';
import 'package:dcli/dcli.dart';
/// dcli script generated by:
/// dcli create %scriptname%
///
/// See
/// https://pub.dev/packages/dcli#-installing-tab-
///
/// For details on installing dcli.
///
void main(List<String> args) {
// -1 to allow for the 'Hit enter to continue' message
var rows = Terminal().rows - 1;
final lines = read('/var/log/syslog').toList();
rows = min(lines.length, rows);
var shown = 0;
while (shown < lines.length) {
for (var row = 0; row < rows; row++) {
print(lines[shown]);
shown++;
}
ask('Hit enter to continue', required: false);
}
print(orange('Done'));
}