Further fixes; improve error handling

Makefile

@@ -1,7 +1,7 @@
 CPPFLAGS += -I $(GPHOTO2PREFIX)/include
 
 libapi.mjs: api.cpp
-	libtool --verbose --mode=link --tag=CXX $(CC) -std=c++17 $+ --bind -s ASYNCIFY -fexceptions -g -O2 -s ALLOW_MEMORY_GROWTH -s DYNAMIC_EXECUTION=0 -o $@ \
+	libtool --verbose --mode=link --tag=CXX $(CC) -std=c++17 $+ --bind -s ASYNCIFY -fexceptions -Os -s ALLOW_MEMORY_GROWTH -s DYNAMIC_EXECUTION=0 -o $@ \
 	  $(GPHOTO2PREFIX)/lib/libltdl.la \
 	  $(GPHOTO2PREFIX)/lib/libgphoto2.la \
 	  -dlpreopen $(GPHOTO2PREFIX)/lib/libgphoto2/2.5.27.1/ptp2.la \

package-lock.json

@@ -8,6 +8,18 @@
       "integrity": "sha512-DIOOg+POSrYl+OlNRHQuIEqCd8DCtynG57H862UCce16nXJX7J8eWxNGgOcf8Eyge8zXeSs27mz1UcFu8L/L7g==",
       "dev": true
     },
+    "@types/requestidlecallback": {
+      "version": "0.3.4",
+      "resolved": "https://registry.npmjs.org/@types/requestidlecallback/-/requestidlecallback-0.3.4.tgz",
+      "integrity": "sha512-aTSyiZuRemRLTQkJPb25L7A4/eR2Teo5l4yJ1V6P3+MFxEZckTDkNKNtr/V1zEOMzS6H8DgxF22U6jPAPrzQvw==",
+      "dev": true
+    },
+    "@types/stats.js": {
+      "version": "0.17.0",
+      "resolved": "https://registry.npmjs.org/@types/stats.js/-/stats.js-0.17.0.tgz",
+      "integrity": "sha512-9w+a7bR8PeB0dCT/HBULU2fMqf6BAzvKbxFboYhmDtDkKPiyXYbjoe2auwsXlEFI7CFNMF1dCv3dFH5Poy9R1w==",
+      "dev": true
+    },
     "preact": {
       "version": "10.5.14",
       "resolved": "https://registry.npmjs.org/preact/-/preact-10.5.14.tgz",

package.json

@@ -1,6 +1,8 @@
 {
   "devDependencies": {
     "@types/emscripten": "^1.39.5",
+    "@types/requestidlecallback": "^0.3.4",
+    "@types/stats.js": "^0.17.0",
     "preact": "^10.5.14"
   }
 }

ui/index.js

@@ -1,6 +1,6 @@
 import { h, render, Component } from 'preact';
 import { CaptureButton } from './capture-button.js';
-import { connect } from './ops.js';
+import { connect, rethrowIfCritical } from './ops.js';
 import { Preview } from './preview.js';
 import { Widget } from './widget.js';
 
@@ -69,6 +69,7 @@ class App extends Component {
     }
     // We should reach this only once.
     while (this.connection) {
+      try {
         let config = await this.connection.schedule(context =>
           context.configToJS()
         );
@@ -80,16 +81,25 @@ class App extends Component {
           type: 'Config',
           config
         });
+      } catch (err) {
+        rethrowIfCritical(err);
+        console.error('Could not refresh config:', err);
+      }
       while (true) {
         await new Promise(resolve =>
           requestIdleCallback(resolve, { timeout: 500 })
         );
+        try {
           let hadEvents = await this.connection.schedule(context =>
             context.consumeEvents()
           );
           if (hadEvents) {
             break;
           }
+        } catch (err) {
+          rethrowIfCritical(err);
+          console.error('Could not consume events:', err);
+        }
       }
     }
   }

ui/ops.js

@@ -4,29 +4,31 @@ import initModule from '../libapi.mjs';
 
 const ModulePromise = initModule();
 
+export function rethrowIfCritical(err) {
+  // If it's precisely Error, it's a custom error; anything else - SyntaxError,
+  // WebAssembly.RuntimeError, TypeError, etc. - is treated as critical here.
+  if (err.constructor !== Error) {
+    throw err;
+  }
+}
+
 export async function connect() {
   const Module = await ModulePromise;
 
   let context = await new Module.Context();
   let supportedOps = await context.supportedOps();
 
+  /** @type {Promise<unknown>} */
   let queue = Promise.resolve();
 
   /** Schedules an exclusive async operation on the global context.
-   * @template T
+   * @template T,T2
    * @param {(ctx: Context) => Promise<T>} op
    * @returns {Promise<T>}
    */
   function schedule(op) {
     let res = queue.then(() => op(context));
-
+    queue = res.catch(rethrowIfCritical);
-    // Queue should ignore result values as well as errors from singular ops.
-    queue = res.then(
-      () => {},
-      () => {}
-    );
-
-    // Result should contain the unwrapped value or error.
     return res;
   }
 

ui/preview.js

@@ -1,4 +1,5 @@
 import { h, Component, createRef } from 'preact';
+import { rethrowIfCritical } from './ops.js';
 
 export const isDebug = new URLSearchParams(location.search).has('debug');
 
@@ -87,8 +88,9 @@ export class Preview extends Component {
           updateCanvasSize();
         }
         canvasCtx.transferFromImageBitmap(img);
-      } catch (error) {
+      } catch (err) {
-        console.error(error);
+        rethrowIfCritical(err);
+        console.error('Could not refresh preview:', err);
       }
       await new Promise(resolve => requestAnimationFrame(resolve));
       this.stats?.update();