Simplify Welcome Screen and use card-based layout for examples (#5699)

### What

* Closes #5452 

Note: the "Source code" links are functional but disabled, as the
example manifest must be updated to include the corresponding URL, see
follow-up issues.

Follow-up:
- #5700 
- #5701 

Before/After:

<img width="844" alt="image"
src="https://github.com/rerun-io/rerun/assets/49431240/ded75ce3-600d-4c0c-bfa0-7742e9fad503">

<img width="1043" alt="image"
src="https://github.com/rerun-io/rerun/assets/49431240/87f33dc9-154f-42b0-bdda-3647c71a6c90">



### 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/5699/index.html)
* Using examples from latest `main` build:
[app.rerun.io](https://app.rerun.io/pr/5699/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/5699/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](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/5699)
- [Docs
preview](https://rerun.io/preview/6766af1787603295c4d4970a1c98849677409942/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/6766af1787603295c4d4970a1c98849677409942/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_ui/src/design_tokens.rs

@@ -84,21 +84,21 @@ fn apply_design_tokens(ctx: &egui::Context) -> DesignTokens {
     // TODO(ab): font sizes should come from design tokens
     egui_style
         .text_styles
-        .insert(ReUi::welcome_screen_h1(), egui::FontId::proportional(28.0));
+        .insert(ReUi::welcome_screen_h1(), egui::FontId::proportional(41.0));
     egui_style
         .text_styles
-        .insert(ReUi::welcome_screen_h2(), egui::FontId::proportional(24.0));
-    egui_style
-        .text_styles
-        .insert(ReUi::welcome_screen_h3(), egui::FontId::proportional(15.0));
+        .insert(ReUi::welcome_screen_h2(), egui::FontId::proportional(27.0));
     egui_style.text_styles.insert(
         ReUi::welcome_screen_example_title(),
-        egui::FontId::proportional(16.0),
+        egui::FontId::proportional(13.0),
     );
     egui_style.text_styles.insert(
         ReUi::welcome_screen_body(),
-        egui::FontId::proportional(13.0),
+        egui::FontId::proportional(15.0),
     );
+    egui_style
+        .text_styles
+        .insert(ReUi::welcome_screen_tag(), egui::FontId::proportional(10.5));
 
     let panel_bg_color = get_aliased_color(&json, "{Alias.Color.Surface.Default.value}");
     // let floating_color = get_aliased_color(&json, "{Alias.Color.Surface.Floating.value}");

crates/re_ui/src/icons.rs

@@ -144,18 +144,4 @@ pub const LINK: Icon = Icon::new("link", include_bytes!("../data/icons/link.png"
 pub const COMPONENT: Icon = Icon::new("component", include_bytes!("../data/icons/component.png"));
 
 pub const STORE: Icon = Icon::new("store", include_bytes!("../data/icons/store.png"));
-
-pub const WELCOME_SCREEN_CONFIGURE: Icon = Icon::new(
-    "welcome_screen_configure",
-    include_bytes!("../data/images/configure-card.png"),
-);
-
-pub const WELCOME_SCREEN_LIVE_DATA: Icon = Icon::new(
-    "welcome_screen_live_data",
-    include_bytes!("../data/images/live-data-card.png"),
-);
-
-pub const WELCOME_SCREEN_RECORDED_DATA: Icon = Icon::new(
-    "welcome_screen_recorded_data",
-    include_bytes!("../data/images/recorded-data-card.png"),
-);
+pub const GITHUB: Icon = Icon::new("github", include_bytes!("../data/icons/github.png"));

crates/re_ui/src/lib.rs

@@ -114,11 +114,6 @@ impl ReUi {
         egui::TextStyle::Name("welcome-screen-h2".into())
     }
 
-    #[inline]
-    pub fn welcome_screen_h3() -> egui::TextStyle {
-        egui::TextStyle::Name("welcome-screen-h3".into())
-    }
-
     #[inline]
     pub fn welcome_screen_example_title() -> egui::TextStyle {
         egui::TextStyle::Name("welcome-screen-example-title".into())
@@ -129,6 +124,11 @@ impl ReUi {
         egui::TextStyle::Name("welcome-screen-body".into())
     }
 
+    #[inline]
+    pub fn welcome_screen_tag() -> egui::TextStyle {
+        egui::TextStyle::Name("welcome-screen-tag".into())
+    }
+
     pub fn welcome_screen_tab_bar_style(ui: &mut egui::Ui) {
         ui.spacing_mut().item_spacing.x = 16.0;
         ui.visuals_mut().selection.bg_fill = egui::Color32::TRANSPARENT;

crates/re_viewer/src/app_state.rs

@@ -362,7 +362,7 @@ impl AppState {
                     .frame(viewport_frame)
                     .show_inside(ui, |ui| {
                         if show_welcome {
-                            welcome_screen.ui(ui, re_ui, rx, command_sender);
+                            welcome_screen.ui(ui, re_ui, command_sender);
                         } else {
                             viewport.viewport_ui(ui, &ctx);
                         }

crates/re_viewer/src/ui/top_panel.rs

@@ -292,11 +292,9 @@ fn website_link_ui(ui: &mut egui::Ui) {
         .on_hover_cursor(egui::CursorIcon::PointingHand)
         .on_hover_text(url);
     if response.clicked() {
-        ui.ctx().output_mut(|o| {
-            o.open_url = Some(egui::output::OpenUrl {
-                url: url.to_owned(),
-                new_tab: true,
-            });
+        ui.ctx().open_url(egui::output::OpenUrl {
+            url: url.to_owned(),
+            new_tab: true,
         });
     }
 }