Chunkify time panel data density graphs

[jprochazk]

What

Part 1 of:

• Optimize TimeHistogram #6065

This adds a new option, Chunk-based data density graph, which when enabled switches the timeline from rendering using TimeHistogram to rendering chunks directly, using range queries in the UI code.

To test, enable Options -> Chunk-based data density graph

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

• PR Build Summary
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[emilk]

Looks like a good first step! But I think we should consider entity-level APIs for Chunks to make this code less awkward and more performant

[emilk]

I think it would be great with some test code for this, testing different scenarios:

• A lot of tiny chunks
• A few huge, sorted chunks
• A few huge, unsorted chunks
• An examples with gaps

Of course, to properly test this, one has to turn off the compaction in the viewer somehow

[teh-cmc]

Of course, to properly test this, one has to turn off the compaction in the viewer somehow

Compaction can be disabled either via ChunkStoreConfig or the associated environment variables:

rerun/crates/store/re_chunk_store/src/store.rs

Lines 96 to 115 in 2342e2b

	pub const DEFAULT: Self = Self {
	enable_changelog: true,
	chunk_max_bytes: 8 * 1024 * 1024,
	chunk_max_rows: 1024,
	chunk_max_rows_if_unsorted: 256,
	};
	/// Environment variable to configure [`Self::enable_changelog`].
	pub const ENV_STORE_ENABLE_CHANGELOG: &'static str = "RERUN_STORE_ENABLE_CHANGELOG";
	/// Environment variable to configure [`Self::chunk_max_bytes`].
	pub const ENV_CHUNK_MAX_BYTES: &'static str = "RERUN_CHUNK_MAX_BYTES";
	/// Environment variable to configure [`Self::chunk_max_rows`].
	pub const ENV_CHUNK_MAX_ROWS: &'static str = "RERUN_CHUNK_MAX_ROWS";
	/// Environment variable to configure [`Self::chunk_max_rows_if_unsorted`].
	//
	// NOTE: Shared with the same env-var on the batcher side, for consistency.
	pub const ENV_CHUNK_MAX_ROWS_IF_UNSORTED: &'static str = "RERUN_CHUNK_MAX_ROWS_IF_UNSORTED";

[teh-cmc]

I'm not sure I understand the UX here.

I open https://rerun.io/viewer/pr/6847?url=https%3A%2F%2Fapp.rerun.io%2Fversion%2Fnightly%2Fexamples%2Fnuscenes_dataset.rrd and then hover randomly over the time panel and I cannot quite make sense of the behaviour. Sometimes I get an hover pop-up, sometimes not, I'm not sure why?
I expect to always have a hover pop-up no matter what, if only to tell me that I can only see very coarse data because <reasons>.

24-07-11_15.07.47.patched.mp4

Am I missing something?

[jprochazk]

Updated after design call with Katya and @emilk:

• The "timeline cursor preview" that used to only show when hovering over the timeline rect now shows when hovering anywhere in the time area
• Set the "timeline cursor preview" to use a brighter color, it should be more visible now
• Clicking anywhere in the time area now takes you to that point on the timeline (as the preview suggests)
• Removed the range highlight
• Removed num_events from the tooltip

For testing, I added tests/rust/test_data_density_graph, based on #6847 (comment)

[emilk]

Double-clicking to reset the pan/zoom of the streams panel view no longer works

[emilk]

When hovering something in a chunk I want to know when in time the thing I hover is at.

I think the individual time-point of the latest-at query should be shown in the tooltip, but also visually.

For the visually part I think either that's where the time-cursor snaps to on hover, or we add a circle or something to highlight when that time-point is.

Both these can wait for a later PR though, but definitely before we switch to the new chunk design.

[jprochazk]

Double-clicking to reset the pan/zoom of the streams panel view no longer works

Should be working now. I also feature-gated the new behavior, should've been done from the start. This feels like something that should eventually be added to the release checklist. I tested:

• Click/drag on the timeline: Sets time + starts dragging
• Shift+drag on the timeline: Creates loop section
• Click on the time area (streams area?): Sets time
• Double click on the time area: Sets time, then resets the zoom/pan

The last part is new and slightly strange, because previously you couldn't just click anywhere on the time area to set time. Now you can, which has this side effect. I don't dislike it, but I don't know how I'd get it working as it did previously if it is an issue.