From 0d98b4016c6296b38a4d081991ccd223f2109fc4 Mon Sep 17 00:00:00 2001
From: Matthew Gordon <matthew@gordon.earth>
Date: Thu, 12 Jun 2025 10:53:10 -0300
Subject: [PATCH] Add some error handling

---
 src/lib.rs            |  2 +-
 src/wasm/mod.rs       | 34 +++++++++++++++++++++++++---------
 web/pteropus-frame.js | 23 ++++++++++++++++++-----
 3 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index f7359f0..98df44e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -23,6 +23,6 @@ pub fn main() {
 
 #[cfg(target_arch = "wasm32")]
 #[wasm_bindgen]
-pub async fn init_pteropus() -> wasm::PteropusCanvas {
+pub async fn init_pteropus() -> Result<wasm::PteropusCanvas, wasm::PteropusInitError> {
     run(App::new(), Rc::new(Model::new())).await
 }
diff --git a/src/wasm/mod.rs b/src/wasm/mod.rs
index 9dba6ee..e423d97 100644
--- a/src/wasm/mod.rs
+++ b/src/wasm/mod.rs
@@ -9,7 +9,7 @@ use {
 use crate::{
     app::{App, Model},
     mvu,
-    mvu::{Event, File, MvuApp, Size2i},
+    mvu::{Event, MvuApp, Size2i},
 };
 
 struct FrameTimer {
@@ -52,9 +52,23 @@ pub struct PteropusCanvas {
     model: Rc<Model>,
 }
 
+#[wasm_bindgen(getter_with_clone)]
+#[derive(Clone)]
+pub struct PteropusInitError {
+    pub message: String,
+}
+
+impl PteropusInitError {
+    fn new<M: Into<String>>(message: M) -> Self {
+        Self {
+            message: message.into(),
+        }
+    }
+}
+
 #[wasm_bindgen]
 impl PteropusCanvas {
-    async fn init(&self) {
+    async fn init(&self) -> Result<(), PteropusInitError> {
         let html_canvas = self.get_canvas();
         let size = Size2i {
             width: html_canvas.client_width() as u32,
@@ -62,15 +76,17 @@ impl PteropusCanvas {
         };
         let instance = wgpu::Instance::default();
         let surface_target = SurfaceTarget::Canvas(html_canvas);
-        let surface = instance
-            .create_surface(surface_target)
-            .expect("create graphics surface for canvas");
-
+        let surface = instance.create_surface(surface_target).map_err(|_| {
+            PteropusInitError::new(
+                "Could not initialize canvas. This browser may not support WebGPU.",
+            )
+        })?;
         self.app
             .lock()
             .expect("get app mutex")
             .init(&instance, surface, size, Box::new(FrameTimer::new()))
             .await;
+        Ok(())
     }
 
     #[wasm_bindgen]
@@ -134,11 +150,11 @@ impl PteropusCanvas {
     }
 }
 
-pub async fn run(app: App, model: Rc<Model>) -> PteropusCanvas {
+pub async fn run(app: App, model: Rc<Model>) -> Result<PteropusCanvas, PteropusInitError> {
     let app = Rc::new(Mutex::new(app));
     std::panic::set_hook(Box::new(console_error_panic_hook::hook));
     console_log::init_with_level(log::Level::Info).expect("Couldn't initialize logger");
     let pteropus_canvas = PteropusCanvas { app, model };
-    pteropus_canvas.init().await;
-    pteropus_canvas
+    pteropus_canvas.init().await?;
+    Ok(pteropus_canvas)
 }
diff --git a/web/pteropus-frame.js b/web/pteropus-frame.js
index 5977c99..427f120 100644
--- a/web/pteropus-frame.js
+++ b/web/pteropus-frame.js
@@ -1,4 +1,4 @@
-import init, {init_pteropus} from '../pkg/pteropus.js';
+import init, {init_pteropus, PteropusInitError} from '../pkg/pteropus.js';
 
 function fileDragOverHandler(event) {
     event.preventDefault();
@@ -7,13 +7,26 @@ function fileDragOverHandler(event) {
 async function run() {
     await init();
 
-    let pteropus = await init_pteropus();
+    try {
+        let pteropus = await init_pteropus();
+    } catch(e) {
+        const errorParagraph = document.createElement("p");
+        if(e instanceof PteropusInitError) {
+            const errorMessage = document.createTextNode(e.message);
+            errorParagraph.appendChild(errorMessage);
+        } else {
+            const errorMessage = document.createTextNode("Something unexpected happened.");
+            errorParagraph.appendChild(errorMessage);
+        }
+        document.getElementById("whole-window").replaceWith(errorParagraph);
+        return;
+    }
 
     let test_file_data = null;
     let needs_resize = true;
     let clear_scene = false;
 
-    let mainCanvas = document.getElementById("pteropus-canvas");
+    const mainCanvas = document.getElementById("pteropus-canvas");
     mainCanvas.addEventListener("drop", async (event) => {
         event.preventDefault();
         test_file_data = event.dataTransfer.files[0]
@@ -24,7 +37,7 @@ async function run() {
     });
     resizeObserver.observe(mainCanvas);
 
-    let fileUploadButton = document.getElementById("file-upload-file-input");
+    const fileUploadButton = document.getElementById("file-upload-file-input");
     fileUploadButton.addEventListener("change", () => {
         const files = fileUploadButton.files;
         if(files.length > 0) {
@@ -32,7 +45,7 @@ async function run() {
         }
     });
 
-    let clearSceneButton = document.getElementById("clear-scene-button");
+    const clearSceneButton = document.getElementById("clear-scene-button");
     clearSceneButton.addEventListener("click", () => {
         clear_scene = true;
     });