Show Welcome Screen after closing recording even with `--skip-welcome…

…-screen` (#3035)

### What

Fixes #3018 


https://github.com/rerun-io/rerun/assets/49431240/af2d69e0-921d-4f11-8ca0-b6f6957f7599

### 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/3035) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/3035)
- [Docs
preview](https://rerun.io/preview/pr%3Aantoine%2Foverride-skip-welcome-screen/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Aantoine%2Foverride-skip-welcome-screen/examples)

crates/re_viewer/src/app.rs

@@ -868,17 +868,23 @@ impl App {
     /// The welcome screen can be displayed only when a blueprint is available (and no recording is
     /// loaded). This function implements the heuristic which determines when the welcome screen
     /// should show up.
-    fn handle_default_blueprint(&mut self, store_hub: &mut StoreHub) {
-        if store_hub.current_recording().is_some()
-            || store_hub.selected_application_id().is_some()
-            || self.startup_options.skip_welcome_screen
+    fn should_show_welcome_screen(&mut self, store_hub: &mut StoreHub) -> bool {
+        // Don't show the welcome screen if we have actual data to display.
+        if store_hub.current_recording().is_some() || store_hub.selected_application_id().is_some()
         {
-            return;
+            return false;
+        }
+
+        // Don't show the welcome screen if the `--skip-welcome-screen` flag was used (e.g. by the
+        // Python SDK), until some data has been loaded and shown. This way, we *still* show the
+        // welcome screen when the user closes all recordings after, e.g., running a Python example.
+        if self.startup_options.skip_welcome_screen && !store_hub.was_recording_active() {
+            return false;
         }
 
         // Here, we use the type of Receiver as a proxy for which kind of workflow the viewer is
         // being used in.
-        let welcome = match self.rx.source() {
+        match self.rx.source() {
             // These source are typically "finite". We want the loading screen so long as data is
             // coming in.
             SmartChannelSource::Files { .. } | SmartChannelSource::RrdHttpStream { .. } => {
@@ -894,10 +900,6 @@ impl App {
             // where it's not the case, including Python/C++ SDKs and possibly other, advanced used,
             // scenarios. In this cases, `--skip-welcome-screen` should be used.
             SmartChannelSource::TcpServer { .. } => true,
-        };
-
-        if welcome {
-            store_hub.set_app_id(StoreHub::welcome_screen_app_id());
         }
     }
 }
@@ -1014,7 +1016,9 @@ impl eframe::App for App {
 
         // Heuristic to set the app_id to the welcome screen blueprint.
         // Must be called before `read_context` below.
-        self.handle_default_blueprint(&mut store_hub);
+        if self.should_show_welcome_screen(&mut store_hub) {
+            store_hub.set_app_id(StoreHub::welcome_screen_app_id());
+        }
 
         let store_context = store_hub.read_context();
 

crates/re_viewer/src/store_hub.rs

@@ -28,6 +28,9 @@ pub struct StoreHub {
     blueprint_by_app_id: HashMap<ApplicationId, StoreId>,
     store_dbs: StoreBundle,
 
+    /// Was a recording ever activated? Used by the heuristic controlling the welcome screen.
+    was_recording_active: bool,
+
     // The [`StoreGeneration`] from when the [`StoreDb`] was last saved
     #[cfg(not(target_arch = "wasm32"))]
     blueprint_last_save: HashMap<StoreId, StoreGeneration>,
@@ -69,6 +72,8 @@ impl StoreHub {
             blueprint_by_app_id: blueprints,
             store_dbs: Default::default(),
 
+            was_recording_active: false,
+
             #[cfg(not(target_arch = "wasm32"))]
             blueprint_last_save: Default::default(),
         }
@@ -114,6 +119,13 @@ impl StoreHub {
             })
     }
 
+    /// Keeps track if a recording was every activated.
+    ///
+    /// This useful for the heuristic controlling the welcome screen.
+    pub fn was_recording_active(&self) -> bool {
+        self.was_recording_active
+    }
+
     /// Change the selected/visible recording id.
     /// This will also change the application-id to match the newly selected recording.
     pub fn set_recording_id(&mut self, recording_id: StoreId) {
@@ -128,6 +140,7 @@ impl StoreHub {
         }
 
         self.selected_rec_id = Some(recording_id);
+        self.was_recording_active = true;
     }
 
     pub fn remove_recording_id(&mut self, recording_id: &StoreId) {