Add an(int) $resumeAt argument forProgressBar#start(), so that the progress bar is initialized at a specific progress level, with a new property so thatgetEstimated() andgetRemaining() report the right number.

As pointed out on a recently postedSO question), when working on a longish task one may want to create a progress bar for aresumed task.

Callingadvance() works to increase the progress bar counter, but the results ofgetRemaining() andgetEstimated() will be "broken", since whatever steps one "skipped" will be considered to have taken 0 seconds. For a longer running task, the estimation will bevery inaccurate, and will remain so for a long while. Using the example code from the linked question:

$itemCount =1_000_000;$startItem =150_000;$progressBar =newProgressBar($output,$itemCount);$progressBar->setFormat($progressBar->getFormatDefinition(ProgressBar::FORMAT_DEBUG));$progressBar->start();if ($startItem !==0) {// unfortunately taken into account in ETA calculation$progressBar->advance($startItem);}for ($i =$startItem;$i <$itemCount;$i++) {usleep(50_000);$progressBar->advance();}

This will output this to begin with:

150038/1000000 [====>-----------------------]  15% 2 secs/13 secs 20.0 MiB

The estimated time will keep growing as the tasks progresses, but the estimation won't be remotely useful for a long while.

This PR adds a$resumeAt parameter toProgresBar#start(), so that's possible to write:

$bar =newProgressBar($output,1_200_000,0);$bar->start(null,300_000);

And calls to$bar->getEstimated() and$bar->getRemaining() will return sane results (and calling the initial->advance() would be no longer necessary).

TODO:

• submit changes to the documentation (if the PR is well received)