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[web] Ensure Flutter adds a generator meta-tag. #55714

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Oct 14, 2024
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[web] Ensure Flutter adds a generator meta-tag. #55714

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[web] Ensure Flutter adds a generator meta-tag.
ditman Oct 7, 2024
4bfc920
Merge branch 'main' into web-add-generator-meta
ditman Oct 8, 2024
7cb76f1
Merge branch 'main' into web-add-generator-meta
ditman Oct 9, 2024
f41e078
Merge branch 'main' into web-add-generator-meta
ditman Oct 11, 2024
9c3274d
Merge branch 'main' into web-add-generator-meta
ditman Oct 14, 2024
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3 changes: 3 additions & 0 deletions lib/web_ui/lib/src/engine/initialization.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -229,6 +229,9 @@ Future<void> initializeEngineUi() async {
RawKeyboard.initialize(onMacOs: ui_web.browser.operatingSystem == ui_web.OperatingSystem.macOs);
KeyboardBinding.initInstance();

// Ensures Flutter renders a global "generator" meta-tag.
ensureMetaTag('generator', 'Flutter');
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@yjbanov yjbanov Oct 7, 2024

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Can we do this in flutter.js so it's loaded asap?

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@yjbanov yjbanov Oct 7, 2024

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Oh, just saw your comment:

Added it here, instead of flutter.js so we can have a proper test for the feature.

I think we should add it to flutter.js if it's the more appropriate place for it. For testing, I think we have a couple of flutter.js tests already that we can steal ideas from. Alternatively, we can write an integration test on the flutter/flutter side. We're merging repos soon anyway, so the disadvantages of cross-repo testing will go away.

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@mdebbar mdebbar Oct 8, 2024

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I agree that flutter.js has the advantage of injecting the meta tag earlier, but I would like us to keep in mind that flutter.js is optional (is this not the case anymore?). So we still need to ensureMetaTag here to guarantee that the tag is always added.

If we want to add the meta tag in the absolute earliest moment, we could add it in index.html. But again, we still need to do it in initializeEngineUi as a backup.


if (!configuration.multiViewEnabled) {
final EngineFlutterWindow implicitView =
ensureImplicitViewInitialized(hostElement: configuration.hostElement);
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13 changes: 13 additions & 0 deletions lib/web_ui/lib/src/engine/util.dart
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Expand Up @@ -722,6 +722,19 @@ void setThemeColor(ui.Color? color) {
}
}

/// Ensure a "meta" tag with [name] and [content] is set on the page.
void ensureMetaTag(String name, String content) {
final DomElement? existingTag =
domDocument.querySelector('meta[name=$name][content=$content]');

if (existingTag == null) {
final DomHTMLMetaElement meta = createDomHTMLMetaElement()
..name = name
..content = content;
domDocument.head!.append(meta);
}
}

bool? _ellipseFeatureDetected;

/// Draws CanvasElement ellipse with fallback.
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5 changes: 5 additions & 0 deletions lib/web_ui/test/engine/initialization_test.dart
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Expand Up @@ -8,6 +8,7 @@ import 'package:js/js_util.dart' as js_util;
import 'package:test/bootstrap/browser.dart';
import 'package:test/test.dart';
import 'package:ui/src/engine.dart' as engine;
import 'package:ui/src/engine/dom.dart';
import 'package:ui/ui_web/src/ui_web.dart' as ui_web;

@JS('_flutter')
Expand Down Expand Up @@ -76,6 +77,10 @@ void testMain() {
// Check that the object we captured is actually a loader
expect(pluginsRegistered, isTrue, reason: 'Plugins should be immediately registered in autoStart mode.');
expect(appRan, isTrue, reason: 'App should run immediately in autoStart mode');

// After starting the engine, the meta-generator tag should be on the page
final DomElement? meta = domDocument.querySelector('meta[name=generator][content=Flutter]');
expect(meta, isNotNull, reason: 'The generator meta-tag should be added when Flutter initializes its UI.');
});

// We cannot test anymore, because by now the engine has registered some stuff that can't be rewound back.
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