Feature Request: progress monitor

[epruesse]

It would be neat to have a progress monitor integrated with spdlog. Something to be used like this:

auto p = spdlog::progress(logger, container, "Doing something");
for (auto& i : container) {
    ...
    ++p
}

or even

for (auto& i :  progress(logger, container, msg)) {
    ...
}

Ideally, it'd use terminal magic from the sink where available to show a pretty bar at the bottom with messages scrolling away above, or minimal output if the sink is a file.

Something like TQDM (which is actually quite fast).

The most basic implementation is so simple, most progress displays are probably home-built. Looking at the above, though, there are quite a few niceties that can't be justified when written for a single project. Loggerhead implements a progress bar using spdlog and might serve as a starting point.

[epruesse]

Hmm. A nice bar is really useful only interactively, so stdout, ansicolor and wincolor sinks.

What it'd need is a way to intercept the line-writes, so that it can issue command codes to move the cursor as needed. Right now those are direct fwrites to a FILE*. The sinks are already templated, though. Any reason why fwrite and fflush can't be moved to the TargetStream, so that an alternate TargetStream might handle interception?

[gabime]

Nice Idea, but I think it is not very easy to achieve (esp. without breaking the existing API).

A possible approach would be a new sink type (e.g. "progress_sink") that destructs when progress is complete:

template<typename Container>
void spdlog::progress(const std::string &logger_name, const Container &container)
{
   progress_sink  the_sink(container.size())  /*total steps */);
   for (auto& i : container)
   {
      the_sink.log_step(...)
  } //progress_sink  dies here. add newline or whatever in its destructor
 }

What it'd need is a way to intercept the line-writes, so that it can issue command codes to move the cursor as needed

I think it can done be in the constructing a formatter with custom eol. Each sink owns its own private formatter instance.

[epruesse]

If I find the time, I may still look into this.