Do not allow adding Horizontal/Vertical containers inside of containe…

…rs with the same type (#5091)

### What

- Fixes #5082

*Note*: due to emilk/egui#3997, the tooltip
shows up immediately, which is slightly annoying.

<img width="1898" alt="image"
src="https://github.com/rerun-io/rerun/assets/49431240/ef64fa2f-7a5b-41f0-aec5-31b2e55c8efc">

<img width="681" alt="image"
src="https://github.com/rerun-io/rerun/assets/49431240/5ace80d5-eb49-4a1e-9440-6debb54d7d4f">


### 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 newly built examples:
[app.rerun.io](https://app.rerun.io/pr/5091/index.html)
* Using examples from latest `main` build:
[app.rerun.io](https://app.rerun.io/pr/5091/index.html?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[app.rerun.io](https://app.rerun.io/pr/5091/index.html?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](tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/5091)
- [Docs
preview](https://rerun.io/preview/57a22b0a289369057acc1000af69df20df9e3d23/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/57a22b0a289369057acc1000af69df20df9e3d23/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

crates/re_viewport/src/add_space_view_or_container_modal.rs

@@ -2,6 +2,7 @@
 
 use itertools::Itertools;
 
+use crate::container::blueprint_id_to_tile_id;
 use crate::{icon_for_container_kind, ViewportBlueprint};
 use re_log_types::{EntityPath, EntityPathFilter};
 use re_space_view::{DataQueryBlueprint, SpaceViewBlueprint};
@@ -70,7 +71,34 @@ fn modal_ui(
     ];
 
     for (title, subtitle, kind) in container_data {
-        if row_ui(ui, icon_for_container_kind(&kind), title, subtitle).clicked() {
+        let target_container_kind = target_container
+            .and_then(|container_id| {
+                viewport
+                    .tree
+                    .tiles
+                    .get(blueprint_id_to_tile_id(&container_id))
+            })
+            .and_then(|tile| tile.container_kind());
+
+        // We disallow creating "linear" containers (horizontal/vertical) inside containers of the same kind, because
+        // it's not useful and is automatically simplified away.
+        let disabled = Some(kind) == target_container_kind
+            && matches!(
+                kind,
+                egui_tiles::ContainerKind::Horizontal | egui_tiles::ContainerKind::Vertical
+            );
+
+        let resp = ui
+            .add_enabled_ui(!disabled, |ui| {
+                row_ui(ui, icon_for_container_kind(&kind), title, subtitle)
+            })
+            .inner
+            .on_disabled_hover_text(format!(
+                "Nested {title} containers in containers of the same type are disallowed and automatically simplified \
+                away as they are not useful."
+            ));
+
+        if resp.clicked() {
             viewport.add_container(kind, target_container);
             viewport.mark_user_interaction(ctx);
             *keep_open = false;