Make better use of space in task detail screen

[hds]

What problem are you trying to solve?

In the task detail screen, there are two panels which split the width of the screen in half. The Task panel and the Waker panel.

The task panel is 7 or 8 lines high (depending on whether the task has a name defined). The Waker panel is just 2 lines high. Additionally, the location of the task can sometimes overflow the width of the Task panel, causing the beginning of the location to not be visible.

See the screenshot below which illustrates how the location can't be seen yet we have plenty of space elsewhere:

Additionally, if the task doesn't have a name, we don't list the name line at all, which results in an empty line at the bottom of the Task panel:

How should the problem be solved?

The space on that panel should be better optimised.

The Waker panel could be split onto more lines. So instead of looking like this:

╭Waker─────────────────────────────────────────────────────────────────────────╮
│Current wakers: 1 (clones: 10461, drops: 10460)                               │
│Woken: 5230 times, last woken: 75.831727ms ago                                │
│                                                                              │
│                                                                              │
│                                                                              │
│                                                                              │
│                                                                              │
│                                                                              │
╰──────────────────────────────────────────────────────────────────────────────╯

It could be split onto multiple lines:

╭Waker─────────────────────────────────────────────────────────────────────────╮
│Current wakers: 1                                                             |
|  Clones: 10461                                                               |
|  Drops: 10460                                                                │
│Woken: 5230 times,                                                            │
│Last woken: 75.831727ms ago                                                   │
│                                                                              │
│                                                                              │
│                                                                              │
╰──────────────────────────────────────────────────────────────────────────────╯

This would free up more horizontal space. Then the Task panel could be made wider and the Waker panel narrower.

Additionally, the hight should depend on how many lines are actually needed. If the task has no name, then we can make the Task and Waker panels one line shorter.

For bonus points, the Location field in the Task panel could be split onto multiple lines (up to some reasonable maximum like 2 or 3) in case it still doesn't fit into the space provided. If done, it would make sense to submit this change as a separate PR.

This could end up with the two panels looking like this:

╭Task─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮╭Waker──────────────────────╮
│ID: 22 ⏸                                                                                                                         ││Current wakers: 1          |
│Name: my favorite task                                                                                                           │|  Clones: 10461            |
│Target: tokio::task                                                                                                              │|  Drops: 10460             │
│Location: src/tokio-with-the-console/src/a_very_long_module_name/yet_another_very_long_module_name/finally_one_more_long_module_n││Woken: 5230 times,         │
|          ame.rs:6:10                                                                                                            ││Last woken: 75.831727ms ago│
│Total Time: 15m22s                                                                                                               ││                           |
│Busy: 5.76s (0.63%)                                                                                                              ││                           │
│Scheduled: 497.29ms (0.05%)                                                                                                      ││                           │
│Idle: 15m15s (99.32%)                                                                                                            ││                           │
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯╰───────────────────────────╯

However, if the location isn't so long, we should probably not squash the Waker panel up any more than necessary:

╭Task──────────────────────────────────────────────────────────────────────────╮╭Waker─────────────────────────────────────────────────────────────────────────╮
│ID: 22 ⏸                                                                      ││Current wakers: 1                                                             |
│Name: my favorite task                                                        │|  Clones: 10461                                                               |
│Target: tokio::task                                                           │|  Drops: 10460                                                                │
│Location: src/main.rs:21:11                                                   ││Woken: 5230 times,                                                            │
│Total Time: 15m22s                                                            ││Last woken: 75.831727ms ago                                                   │
│Busy: 5.76s (0.63%)                                                           ││                                                                              │
│Scheduled: 497.29ms (0.05%)                                                   ││                                                                              │
│Idle: 15m15s (99.32%)                                                         ││                                                                              │
╰──────────────────────────────────────────────────────────────────────────────╯╰──────────────────────────────────────────────────────────────────────────────╯

Implementation hints

Currently we hard code the height of the Task and Waker panels here in two places depending on whether there is an active warning for the task being viewed. That happens here:

console/tokio-console/src/view/task.rs

Line 86 in 28a27fc

layout::Constraint::Length(10),

and here:

console/tokio-console/src/view/task.rs

Line 108 in 28a27fc

layout::Constraint::Length(10),

We could make that height dependent on the real height of those panels.

The Task and Waker panel contents are created inline in the render function. This is done after the constraints have already been calculated. Instead of that, the creation of each panel could be factored out into separate functions (or actual widget implementations). If the creation of each panel contents also returns the minimum area that it needs (width and height), then the "chunking" of the total area could be performed a bit more dynamically.

Task panel:

console/tokio-console/src/view/task.rs

Lines 142 to 187 in 28a27fc

	let mut overview = Vec::with_capacity(8);
	overview.push(Spans::from(vec![
	bold("ID: "),
	Span::raw(format!("{} ", task.id_str())),
	task.state().render(styles),
	]));
	if let Some(name) = task.name() {
	overview.push(Spans::from(vec![bold("Name: "), Span::raw(name)]));
	}
	overview.push(Spans::from(vec![
	bold("Target: "),
	Span::raw(task.target()),
	]));
	let title = "Location: ";
	let location_max_width = stats_area[0].width as usize - 2 - title.len(); // NOTE: -2 for the border
	let location = if task.location().len() > location_max_width {
	let ellipsis = styles.if_utf8("\u{2026}", "...");
	let start = task.location().len() - location_max_width + ellipsis.chars().count();
	format!("{}{}", ellipsis, &task.location()[start..])
	} else {
	task.location().to_string()
	};
	overview.push(Spans::from(vec![bold(title), Span::raw(location)]));
	let total = task.total(now);
	let dur_percent = |name: &'static str, amt: Duration| -> Spans {
	let percent = amt.as_secs_f64().percent_of(total.as_secs_f64());
	Spans::from(vec![
	bold(name),
	styles.time_units(amt, view::DUR_LIST_PRECISION, None),
	Span::from(format!(" ({:.2}%)", percent)),
	])
	};
	overview.push(Spans::from(vec![
	bold("Total Time: "),
	styles.time_units(total, view::DUR_LIST_PRECISION, None),
	]));
	overview.push(dur_percent("Busy: ", task.busy(now)));
	overview.push(dur_percent("Scheduled: ", task.scheduled(now)));
	overview.push(dur_percent("Idle: ", task.idle(now)));

Waker panel:

console/tokio-console/src/view/task.rs

Lines 189 to 222 in 28a27fc

	let mut waker_stats = vec![Spans::from(vec![
	bold("Current wakers: "),
	Span::from(format!("{} (", task.waker_count())),
	bold("clones: "),
	Span::from(format!("{}, ", task.waker_clones())),
	bold("drops: "),
	Span::from(format!("{})", task.waker_drops())),
	])];
	let mut wakeups = vec![
	bold("Woken: "),
	Span::from(format!("{} times", task.wakes())),
	];
	// If the task has been woken, add the time since wake to its stats as well.
	if let Some(since) = task.since_wake(now) {
	wakeups.reserve(3);
	wakeups.push(Span::raw(", "));
	wakeups.push(bold("last woken:"));
	wakeups.push(Span::from(format!(" {:?} ago", since)));
	}
	waker_stats.push(Spans::from(wakeups));
	if task.self_wakes() > 0 {
	waker_stats.push(Spans::from(vec![
	bold("Self Wakes: "),
	Span::from(format!(
	"{} times ({}%)",
	task.self_wakes(),
	task.self_wake_percent()
	)),
	]));
	}

Keep in mind that the self wakes count is optional, the waker panel will have a different minimum height if it is present!

console/tokio-console/src/view/task.rs

Line 213 in 28a27fc

if task.self_wakes() > 0 {

Any alternatives you've considered?

We could only split the Location field onto multiple lines, and leave the rest of the layout where it is.

[devanbenz]

lol whoops! meant to have this one assigned @hds 😅 I was mobile when I commented on the other issue 😆