[PATCH yew-widget-toolkit 1/3] state: event: add helpers for custom DOM events

[Dominik Csapak <d.csapak@proxmox.com>]

Creating and dispatching custom events is currently open coded, e.g. for
the `pwt-theme-changed` event. Provide small wrappers so that further
users do not have to repeat the window/document lookup and the JS error
conversion.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/state/event.rs | 24 ++++++++++++++++++++++++
 src/state/mod.rs   |  3 +++
 2 files changed, 27 insertions(+)
 create mode 100644 src/state/event.rs

diff --git a/src/state/event.rs b/src/state/event.rs
new file mode 100644
index 0000000..8566071
--- /dev/null
+++ b/src/state/event.rs
@@ -0,0 +1,24 @@
+//! Helpers to create and dispatch custom DOM events.
+
+use anyhow::{Error, format_err};
+use web_sys::Event;
+
+/// Create a custom [Event] with the given name.
+pub fn create_custom_event(name: &str) -> Result<Event, Error> {
+    Event::new(name).map_err(crate::convert_js_error)
+}
+
+/// Dispatch a custom event with the given name on the document.
+///
+/// The event is only delivered to listeners in the current document, so listeners in other
+/// browser tabs or windows are not notified.
+pub fn dispatch_custom_event(name: &str) -> Result<(), Error> {
+    let document = web_sys::window()
+        .and_then(|window| window.document())
+        .ok_or_else(|| format_err!("no document available"))?;
+
+    document
+        .dispatch_event(&create_custom_event(name)?)
+        .map(|_| ())
+        .map_err(crate::convert_js_error)
+}
diff --git a/src/state/mod.rs b/src/state/mod.rs
index 86d6b7f..6f99c7e 100644
--- a/src/state/mod.rs
+++ b/src/state/mod.rs
@@ -7,6 +7,9 @@ use serde::{Serialize, de::DeserializeOwned};
 mod data_store;
 pub use data_store::{DataNode, DataNodeDerefGuard, DataStore};
 
+mod event;
+pub use event::{create_custom_event, dispatch_custom_event};
+
 mod loader;
 pub use loader::{Loader, LoaderState};
 
-- 
2.47.3