Move blueprint tree UI to new re_blueprint_tree crate (rerun-io#6427)

### What

- Fixes rerun-io#6415

Straightforward refactor overall. Made two calls:
- Create a `ui` sub-module in `re_viewport_blueprint` to host the
`add_space_view_or_container` modal (used by both the blueprint tree and
the selection panel).
- Moved down two small utility functions in `re_viewer_context` (in
`lib.rs`).
- There was a weird double-buffering of the drop target container ID
going through `TreeAction`. This is gone in favour of a much simpler
approach (still double-buffered though).

(Chained to rerun-io#6423)


![](https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/1200w.png)

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/6427?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/6427?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/6427)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

ARCHITECTURE.md

@@ -88,11 +88,11 @@ Of course, this will only take us so far. In the future we plan on caching queri
 Here is an overview of the crates included in the project:
 
 <picture>
-  <img src="https://static.rerun.io/crates/1681e343ee14bb8a72c32e818447cdf853683d64/full.png" alt="">
-  <source media="(max-width: 480px)" srcset="https://static.rerun.io/crates/1681e343ee14bb8a72c32e818447cdf853683d64/480w.png">
-  <source media="(max-width: 768px)" srcset="https://static.rerun.io/crates/1681e343ee14bb8a72c32e818447cdf853683d64/768w.png">
-  <source media="(max-width: 1024px)" srcset="https://static.rerun.io/crates/1681e343ee14bb8a72c32e818447cdf853683d64/1024w.png">
-  <source media="(max-width: 1200px)" srcset="https://static.rerun.io/crates/1681e343ee14bb8a72c32e818447cdf853683d64/1200w.png">
+  <img src="https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/full.png" alt="">
+  <source media="(max-width: 480px)" srcset="https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/480w.png">
+  <source media="(max-width: 768px)" srcset="https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/768w.png">
+  <source media="(max-width: 1024px)" srcset="https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/1024w.png">
+  <source media="(max-width: 1200px)" srcset="https://static.rerun.io/crates/1b123b5323a7d1366bdbd6c2fd5a788f46d20caf/1200w.png">
 </picture>
 
 
@@ -127,6 +127,7 @@ Update instructions:
 
 | Crate                       | Description                                                                            |
 |-----------------------------|----------------------------------------------------------------------------------------|
+| re_blueprint_tree           | The UI for the blueprint tree in the left panel.                                       |
 | re_viewer                   | The Rerun Viewer                                                                       |
 | re_viewport                 | The central viewport panel of the Rerun viewer.                                        |
 | re_time_panel               | The time panel of the Rerun Viewer, allowing to control the displayed timeline & time. |

Cargo.lock

@@ -4150,6 +4150,25 @@ dependencies = [
  "simdutf8",
 ]
 
+[[package]]
+name = "re_blueprint_tree"
+version = "0.17.0-alpha.2"
+dependencies = [
+ "egui",
+ "itertools 0.12.0",
+ "re_context_menu",
+ "re_data_ui",
+ "re_entity_db",
+ "re_log",
+ "re_log_types",
+ "re_tracing",
+ "re_types",
+ "re_ui",
+ "re_viewer_context",
+ "re_viewport_blueprint",
+ "smallvec",
+]
+
 [[package]]
 name = "re_build_info"
 version = "0.17.0-alpha.2"
@@ -5025,6 +5044,7 @@ dependencies = [
  "once_cell",
  "poll-promise",
  "re_analytics",
+ "re_blueprint_tree",
  "re_build_info",
  "re_build_tools",
  "re_context_menu",
@@ -5141,7 +5161,6 @@ dependencies = [
  "re_ui",
  "re_viewer_context",
  "re_viewport_blueprint",
- "smallvec",
 ]
 
 [[package]]
@@ -5153,6 +5172,8 @@ dependencies = [
  "egui_tiles",
  "itertools 0.12.0",
  "nohash-hasher",
+ "once_cell",
+ "parking_lot",
  "re_data_store",
  "re_entity_db",
  "re_log",
@@ -5161,6 +5182,7 @@ dependencies = [
  "re_types",
  "re_types_blueprint",
  "re_types_core",
+ "re_ui",
  "re_viewer_context",
  "slotmap",
  "smallvec",

Cargo.toml

@@ -29,6 +29,7 @@ version = "0.17.0-alpha.2"
 # In particular: if we compile rerun 0.3.0-alpha.0 we only want it to use
 # re_log_types 0.3.0-alpha.0, NOT 0.3.0-alpha.4 even though it is newer and semver-compatible.
 re_analytics = { path = "crates/re_analytics", version = "=0.17.0-alpha.2", default-features = false }
+re_blueprint_tree = { path = "crates/re_blueprint_tree", version = "=0.17.0-alpha.2", default-features = false }
 re_build_info = { path = "crates/re_build_info", version = "=0.17.0-alpha.2", default-features = false }
 re_build_tools = { path = "crates/re_build_tools", version = "=0.17.0-alpha.2", default-features = false }
 re_crash_handler = { path = "crates/re_crash_handler", version = "=0.17.0-alpha.2", default-features = false }

crates/re_blueprint_tree/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+authors.workspace = true
+description = "The UI for the blueprint tree in the left panel."
+edition.workspace = true
+homepage.workspace = true
+license.workspace = true
+name = "re_blueprint_tree"
+publish = true
+readme = "README.md"
+repository.workspace = true
+rust-version.workspace = true
+version.workspace = true
+include = ["../../LICENSE-APACHE", "../../LICENSE-MIT", "**/*.rs", "Cargo.toml"]
+
+[lints]
+workspace = true
+
+[package.metadata.docs.rs]
+all-features = true
+
+[dependencies]
+re_context_menu.workspace = true
+re_data_ui.workspace = true
+re_entity_db = { workspace = true, features = ["serde"] }
+re_log_types.workspace = true
+re_log.workspace = true
+re_tracing.workspace = true
+re_types.workspace = true
+re_ui.workspace = true
+re_viewer_context.workspace = true
+re_viewport_blueprint.workspace = true
+
+egui.workspace = true
+itertools.workspace = true
+smallvec.workspace = true

crates/re_blueprint_tree/README.md

@@ -0,0 +1,10 @@
+# re_blueprint_tree
+
+Part of the [`rerun`](https://github.com/rerun-io/rerun) family of crates.
+
+[![Latest version](https://img.shields.io/crates/v/re_blueprint_tree.svg)](https://crates.io/crates/re_blueprint_tree?speculative-link)
+[![Documentation](https://docs.rs/re_blueprint_tree/badge.svg)](https://docs.rs/re_blueprint_tree?speculative-link)
+![MIT](https://img.shields.io/badge/license-MIT-blue.svg)
+![Apache](https://img.shields.io/badge/license-Apache-blue.svg)
+
+The UI for the blueprint tree in the left panel.