codify "platform" into resolution logic, server-fn/fullstack overhaul (#4596)

overhaul dioxus fullstack using a new implementation of server_fn

This PR is a complete rewrite of dioxus fullstack designed to improve compatibility with axum and to fix a number of compilation errors based on feature flag unification plumbing through macros.

examples/08-apis/control_focus.rs

@@ -0,0 +1,65 @@
+//! Managing focus
+//!
+//! This example shows how to manage focus in a Dioxus application. We implement a "roulette" that focuses on each input
+//! in the grid every few milliseconds until the user interacts with the inputs.
+
+use std::rc::Rc;
+
+use async_std::task::sleep;
+use dioxus::prelude::*;
+
+const STYLE: Asset = asset!("/examples/assets/roulette.css");
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    // Element data is stored as Rc<MountedData> so we can clone it and pass it around
+    let mut elements = use_signal(Vec::<Rc<MountedData>>::new);
+    let mut running = use_signal(|| true);
+
+    use_future(move || async move {
+        let mut focused = 0;
+
+        loop {
+            sleep(std::time::Duration::from_millis(50)).await;
+
+            if !running() {
+                continue;
+            }
+
+            if let Some(element) = elements.with(|f| f.get(focused).cloned()) {
+                _ = element.set_focus(true).await;
+            } else {
+                focused = 0;
+            }
+
+            focused += 1;
+        }
+    });
+
+    rsx! {
+        Stylesheet { href: STYLE }
+        h1 { "Input Roulette" }
+        button { onclick: move |_| running.toggle(), "Toggle roulette" }
+        div { id: "roulette-grid",
+            // Restart the roulette if the user presses escape
+            onkeydown: move |event| {
+                if event.code().to_string() == "Escape" {
+                    running.set(true);
+                }
+            },
+
+            // Draw the grid of inputs
+            for i in 0..100 {
+                input {
+                    r#type: "number",
+                    value: "{i}",
+                    onmounted: move |cx| elements.write().push(cx.data()),
+                    oninput: move |_| running.set(false),
+                }
+            }
+        }
+    }
+}