Markdown support in TextDocument (#3343)

### What
```rs
    rec.log(
        "markdown",
        &TextDocument::new(
            "# Hello\n\
             Markdown with `code`!\n\
             \n\
             A random image:\n\
             \n\
             ![A random image](https://picsum.photos/640/480)",
        )
        .with_media_type(MediaType::markdown()),
    )?;
```

<img width="809" alt="image"
src="https://github.com/rerun-io/rerun/assets/1148717/d4cbf9a3-e3c9-4aba-be35-8921dae001e7">

This will let us add nice documentation explaining our examples.

### Not yet supported
* Syntax highlighting of code blocks
* `egui_commomark` uses `syntect` which is too big of a dependency imho,
see lampsitter/egui_commonmark#13
* Embedding references to images in the data store
* We should support something like `![](entity://my/image/entity)` where
`my/image/entity` is the entity path to an image you have logged.

### 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 [demo.rerun.io](https://demo.rerun.io/pr/3343) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/3343)
- [Docs
preview](https://rerun.io/preview/8b743c5708382aef1841a364442762a2abc80db3/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/8b743c5708382aef1841a364442762a2abc80db3/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://ref.rerun.io/dev/bench/)
- [Wasm size tracking](https://ref.rerun.io/dev/sizes/)

Cargo.toml

@@ -91,8 +91,9 @@ egui = { version = "0.22.0", features = [
   "log",
   "puffin",
 ] }
+egui_commonmark = { version = "0.7", default-features = false }
 egui_extras = { version = "0.22.0", features = ["http", "image", "puffin"] }
-egui_plot = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
+egui_plot = { git = "https://github.com/emilk/egui", rev = "d949eaf" } # egui_lot is not yet published on crates.io
 egui_tiles = { version = "0.2" }
 egui-wgpu = "0.22.0"
 ehttp = { version = "0.3" }
@@ -165,14 +166,17 @@ debug = true
 # ALWAYS document what PR the commit hash is part of, or when it was merged into the upstream trunk.
 
 # Temporary patch until next egui release
-ecolor = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-eframe = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-egui-wgpu = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-egui-winit = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-egui = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-egui_extras = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-emath = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
-epaint = { git = "https://github.com/emilk/egui", rev = "2bbceb856b8c26cd7d7a749baba13cb7ffe41d89" }
+ecolor = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+eframe = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+egui-wgpu = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+egui-winit = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+egui = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+egui_extras = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+emath = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+epaint = { git = "https://github.com/emilk/egui", rev = "d949eaf" }
+
+# Temporary patch until next egui_commonmark release
+egui_commonmark = { git = "https://github.com/lampsitter/egui_commonmark.git", rev = "a133564f26a95672e756079ac5583817e0cdaa1f" }
 
 # Temporary patch until next egui_tiles release
 egui_tiles = { git = "https://github.com/rerun-io/egui_tiles", rev = "c66d6cba7ddb5b236be614d1816be4561260274e" }

crates/re_space_view_text_document/Cargo.toml

@@ -15,14 +15,28 @@ include = ["../../LICENSE-APACHE", "../../LICENSE-MIT", "**/*.rs", "Cargo.toml"]
 [package.metadata.docs.rs]
 all-features = true
 
+[features]
+default = ["markdown"]
+## Show `text/markdown` as Markdown.
+markdown = ["dep:egui_commonmark"]
+
 [dependencies]
 re_arrow_store.workspace = true
 re_log.workspace = true
 re_query.workspace = true
 re_renderer.workspace = true
+re_tracing.workspace = true
 re_types.workspace = true
 re_ui.workspace = true
 re_viewer_context.workspace = true
 
 egui.workspace = true
+itertools.workspace = true
 vec1.workspace = true
+
+# Optional dependencies:
+
+# egui_commonmark is a 3rd party crate.
+# By making it an optional dependency we can easily drop it if we need to,
+# .e.g if isn't release a new version quickly enough after an egui release.
+egui_commonmark = { workspace = true, optional = true, default-features = false }

crates/re_space_view_text_document/src/space_view_class.rs

@@ -1,24 +1,33 @@
 use egui::Label;
+
 use re_viewer_context::{
     external::re_log_types::EntityPath, SpaceViewClass, SpaceViewClassName,
     SpaceViewClassRegistryError, SpaceViewId, SpaceViewState, SpaceViewSystemExecutionError,
     ViewContextCollection, ViewPartCollection, ViewQuery, ViewerContext,
 };
 
+use crate::view_part_system::TextDocumentEntry;
+
 use super::view_part_system::TextDocumentSystem;
 
 // TODO(andreas): This should be a blueprint component.
-#[derive(Clone, PartialEq, Eq)]
+
 pub struct TextDocumentSpaceViewState {
     monospace: bool,
     word_wrap: bool,
+
+    #[cfg(feature = "markdown")]
+    commonmark_cache: egui_commonmark::CommonMarkCache,
 }
 
 impl Default for TextDocumentSpaceViewState {
     fn default() -> Self {
         Self {
             monospace: false,
             word_wrap: true,
+
+            #[cfg(feature = "markdown")]
+            commonmark_cache: Default::default(),
         }
     }
 }
@@ -104,21 +113,39 @@ impl SpaceViewClass for TextDocumentSpaceView {
                 egui::ScrollArea::both()
                     .auto_shrink([false, false])
                     .show(ui, |ui| {
-                        // TODO(jleibs): better handling for multiple results
                         if text_document.text_entries.is_empty() {
-                            ui.label("No TextDocument entries found.");
+                            // We get here if we scroll back time to before the first text document was logged.
+                            ui.weak("(empty)");
                         } else if text_document.text_entries.len() == 1 {
-                            let mut text =
-                                egui::RichText::new(text_document.text_entries[0].body.as_str());
+                            let TextDocumentEntry { body, media_type } =
+                                &text_document.text_entries[0];
+
+                            #[cfg(feature = "markdown")]
+                            {
+                                if media_type == &re_types::components::MediaType::markdown() {
+                                    re_tracing::profile_scope!("egui_commonmark");
+                                    egui_commonmark::CommonMarkViewer::new("markdown_viewer")
+                                        .max_image_width(Some(ui.available_width().floor() as _))
+                                        .show(ui, &mut state.commonmark_cache, body);
+                                    return;
+                                }
+                            }
+                            #[cfg(not(feature = "markdown"))]
+                            {
+                                _ = media_type;
+                            }
+
+                            let mut text = egui::RichText::new(body.as_str());
 
                             if state.monospace {
                                 text = text.monospace();
                             }
 
                             ui.add(Label::new(text).wrap(state.word_wrap));
                         } else {
+                            // TODO(jleibs): better handling for multiple results
                             ui.label(format!(
-                                "Unexpected number of text entries: {}. Limit your query to 1.",
+                                "Can only show one text document at a time; was given {}.",
                                 text_document.text_entries.len()
                             ));
                         }

crates/re_space_view_text_document/src/view_part_system.rs

@@ -1,6 +1,9 @@
 use re_arrow_store::LatestAtQuery;
 use re_query::{query_archetype, QueryError};
-use re_types::{archetypes::TextDocument, Archetype as _, ComponentNameSet};
+use re_types::{
+    archetypes::{self, TextDocument},
+    components, Archetype as _, ComponentNameSet,
+};
 use re_viewer_context::{
     NamedViewSystem, SpaceViewSystemExecutionError, ViewContextCollection, ViewPartSystem,
     ViewQuery, ViewerContext,
@@ -10,7 +13,8 @@ use re_viewer_context::{
 
 #[derive(Debug, Clone)]
 pub struct TextDocumentEntry {
-    pub body: re_types::datatypes::Utf8,
+    pub body: components::Text,
+    pub media_type: components::MediaType,
 }
 
 /// A text scene, with everything needed to render it.
@@ -50,17 +54,16 @@ impl ViewPartSystem for TextDocumentSystem {
         for (ent_path, _props) in query.iter_entities_for_system(Self::name()) {
             // TODO(jleibs): this match can go away once we resolve:
             // https://github.com/rerun-io/rerun/issues/3320
-            match query_archetype::<re_types::archetypes::TextDocument>(
-                store,
-                &timeline_query,
-                ent_path,
-            ) {
+            match query_archetype::<archetypes::TextDocument>(store, &timeline_query, ent_path) {
                 Ok(arch_view) => {
-                    for text_entry in
-                        arch_view.iter_required_component::<re_types::components::Text>()?
-                    {
-                        let re_types::components::Text(text) = text_entry;
-                        self.text_entries.push(TextDocumentEntry { body: text });
+                    let bodies = arch_view.iter_required_component::<components::Text>()?;
+                    let media_types =
+                        arch_view.iter_optional_component::<components::MediaType>()?;
+
+                    for (body, media_type) in itertools::izip!(bodies, media_types) {
+                        let media_type = media_type.unwrap_or(components::MediaType::plain_text());
+                        self.text_entries
+                            .push(TextDocumentEntry { body, media_type });
                     }
                 }
                 Err(QueryError::PrimaryNotFound(_)) => {}

crates/re_string_interner/src/lib.rs

@@ -260,24 +260,35 @@ macro_rules! declare_new_type {
         }
 
         impl std::fmt::Debug for $StructName {
+            #[inline]
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 self.as_str().fmt(f)
             }
         }
 
         impl std::fmt::Display for $StructName {
+            #[inline]
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 self.as_str().fmt(f)
             }
         }
 
         impl<'a> PartialEq<&'a str> for $StructName {
+            #[inline]
+            fn eq(&self, other: &&'a str) -> bool {
+                self.as_str() == *other
+            }
+        }
+
+        impl<'a> PartialEq<&'a str> for &$StructName {
+            #[inline]
             fn eq(&self, other: &&'a str) -> bool {
                 self.as_str() == *other
             }
         }
 
         impl<'a> PartialEq<$StructName> for &'a str {
+            #[inline]
             fn eq(&self, other: &$StructName) -> bool {
                 *self == other.as_str()
             }

crates/re_types/definitions/rerun/archetypes/text_document.fbs

@@ -14,5 +14,12 @@ table TextDocument (
 ) {
   body: rerun.components.Text ("attr.rerun.component_required", order: 100);
 
-  // TODO(emilk): text_format: rerun.components.TextFormat # (txt, md, …)
+  /// The Media Type of the text.
+  ///
+  /// For instance:
+  /// * `text/plain`
+  /// * `text/markdown`
+  ///
+  /// If omitted, `text/plain` is assumed.
+  media_type: rerun.components.MediaType ("attr.rerun.component_optional", nullable, order: 100);
 }