Dataframe view update and blueprint API (part 0): introduce view obje…

…ct and improve doc generation (#7515)

### What

This PR introduces a stub blueprint view object for the dataframe view.
It doesn't contain any actual parameters (query, etc.), but is
sufficient to "spawn" a view. This PR also improves doc generation by
special casing the dataframe view (it accepts all archetypes and
inversely).

(Note: the snippet will be much improved in later PRs.)

<img width="673" alt="image"
src="https://github.com/user-attachments/assets/8a945f46-a6a8-44c6-ab88-db8d19e6992a">


![image](https://github.com/user-attachments/assets/0b1b4db5-5afa-41f9-914d-af04c21e34e0)


<hr>

Part of a series to address #6896 and #7498.

All PRs:
- #7515
- #7516
- #7527 
- #7545
- #7551
- #7572
- #7573

### 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/7515?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/7515?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)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7515)
- [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`.

crates/build/re_types_builder/src/codegen/docs/mod.rs

@@ -12,6 +12,8 @@ use crate::{
     ATTR_DOCS_VIEW_TYPES,
 };
 
+pub const DATAFRAME_VIEW_FQNAME: &str = "rerun.blueprint.views.DataframeView";
+
 macro_rules! putln {
     ($o:ident) => ( writeln!($o).ok() );
     ($o:ident, $($tt:tt)*) => ( writeln!($o, $($tt)*).ok() );
@@ -574,9 +576,10 @@ fn write_archetype_fields(
         putln!(page, "**Optional**: {}", optional.join(", "));
     }
 
+    putln!(page);
+    putln!(page, "## Shown in");
+
     if let Some(view_types) = view_per_archetype.get(&object.fqname) {
-        putln!(page);
-        putln!(page, "## Shown in");
         for ViewReference {
             view_name,
             explanation,
@@ -592,6 +595,9 @@ fn write_archetype_fields(
             putln!(page);
         }
     }
+
+    // Special case for dataframe view: it can display anything.
+    putln!(page, "* [DataframeView](../views/dataframe_view.md)");
 }
 
 fn write_visualized_archetypes(
@@ -614,7 +620,7 @@ fn write_visualized_archetypes(
         }
     }
 
-    if archetype_fqnames.is_empty() {
+    if archetype_fqnames.is_empty() && view.fqname != DATAFRAME_VIEW_FQNAME {
         reporter.error(&view.virtpath, &view.fqname, "No archetypes use this view.");
         return;
     }
@@ -624,18 +630,24 @@ fn write_visualized_archetypes(
 
     putln!(page, "## Visualized archetypes");
     putln!(page);
-    for (fqname, explanation) in archetype_fqnames {
-        let object = &objects[&fqname];
-        page.push_str(&format!(
-            "* [`{}`](../{}/{}.md)",
-            object.name,
-            object.kind.plural_snake_case(),
-            object.snake_case_name()
-        ));
-        if let Some(explanation) = explanation {
-            page.push_str(&format!(" ({explanation})"));
+
+    // special case for dataframe view
+    if view.fqname == DATAFRAME_VIEW_FQNAME {
+        putln!(page, "Any data can be displayed by the Dataframe view.");
+    } else {
+        for (fqname, explanation) in archetype_fqnames {
+            let object = &objects[&fqname];
+            page.push_str(&format!(
+                "* [`{}`](../{}/{}.md)",
+                object.name,
+                object.kind.plural_snake_case(),
+                object.snake_case_name()
+            ));
+            if let Some(explanation) = explanation {
+                page.push_str(&format!(" ({explanation})"));
+            }
+            putln!(page);
         }
-        putln!(page);
     }
     putln!(page);
 }

crates/store/re_types/definitions/rerun/blueprint/views/dataframe.fbs

@@ -0,0 +1,13 @@
+namespace rerun.blueprint.views;
+
+/// A view to display any data in a tabular form.
+///
+/// \example views/dataframe title="Use a blueprint to customize a DataframeView."
+//TODO(#6896): add a thumbnail when the example becomes interesting
+table DataframeView (
+    "attr.rerun.view_identifier": "Dataframe"
+) {
+    /// Query of the dataframe.
+    //TODO(#6896): this will be enabled in a later PR in the chain
+    //query: rerun.blueprint.archetypes.DataframeQueryV2 (order: 1000);
+}