Export GPU symbols for embedder

[jwinarske]

This PR exports GPU symbols for the embedder library.

List which issues are fixed by this PR. You must list at least one issue.
flutter/flutter#153196

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[bdero]

Nice find.

[bdero]

Test-wise, I think adding something that forces one of the symbols to get called in the GLFW embedder smoketest would suffice.

Perhaps just:

diff --git a/examples/glfw/main.dart b/examples/glfw/main.dart
index 557d020a1d..97c81efc6f 100644
--- a/examples/glfw/main.dart
+++ b/examples/glfw/main.dart
@@ -2,11 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

+import '../../lib/gpu/lib/gpu.dart' as gpu;
 import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart'
     show debugDefaultTargetPlatformOverride;

 void main() {
+  // Ensure Flutter GPU symbols are available by forcing the GPU context to instantiate.
+  gpu.gpuContext;
+
   // This is a hack to make Flutter think you are running on Google Fuchsia,
   // otherwise you will get an error about running from an unsupported platform.
   debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;

That's enough to trigger a symbol call.

[bdero]

Ah actually, Impeller isn't enabled in that example, but we can still verify that the symbol is being called properly. Something like this:

diff --git a/examples/glfw/main.dart b/examples/glfw/main.dart
index 557d020a1d..ceb5eda137 100644
--- a/examples/glfw/main.dart
+++ b/examples/glfw/main.dart
@@ -2,11 +2,22 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

+import '../../lib/gpu/lib/gpu.dart' as gpu;
 import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart'
     show debugDefaultTargetPlatformOverride;

 void main() {
+  // Ensure Flutter GPU symbols are available by forcing the GPU context to instantiate.
+  try {
+    // ignore: unnecessary_statements
+    gpu.gpuContext; // Force the context to instantiate.
+  } catch (e) {
+    // If impeller is not enabled, make sure the exception isn't about symbols missing.
+    assert(e.toString().contains(
+        'Flutter GPU requires the Impeller rendering backend to be enabled.'));
+  }
+
   // This is a hack to make Flutter think you are running on Google Fuchsia,
   // otherwise you will get an error about running from an unsupported platform.
   debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;

[jwinarske]

@bdero makes sense

[jwinarske]

The relative path is not working. It should be relative to the myapp/lib folder. I tried all variations, no dice.

Moved to import 'package:flutter_gpu/gpu.dart' as gpu; and added flutter pub add flutter_gpu --sdk=flutter to run.sh.

That part is fine, only the app hits an unrelated problem:

In order to run your application, type:

  $ cd myapp
  $ flutter run

Your application code is in myapp/lib/main.dart.

Resolving dependencies... 
Downloading packages... 
+ flutter_gpu 0.0.0 from sdk flutter
  material_color_utilities 0.11.1 (0.12.0 available)
Changed 1 dependency!
1 package has newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Resolving dependencies... 
Downloading packages... 
  material_color_utilities 0.11.1 (0.12.0 available)
Got dependencies!
1 package has newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.

lib/main.dart:1:1: Error: The specified language version is too high. The highest supported language version is 3.5.
// Copyright 2013 The Flutter Authors. All rights reserved.
^
../../../../../../../../flutter/packages/flutter/lib/src/semantics/semantics.dart:2925:7: Error: No named parameter with the name 'linkUrl'.
      linkUrl: data.linkUrl?.toString() ?? '',
      ^^^^^^^
Target kernel_snapshot_program failed: Exception

[jwinarske]

@bdero
I just wrapped my due diligence; problem was on my end. We are good to go. Assert hits if symbols are not available. This is the happy path output:

Creating project myapp...
Resolving dependencies in `myapp`... 
Downloading packages... 
Got dependencies in `myapp`.
Wrote 18 files.

All done!
You can find general documentation for Flutter at: https://docs.flutter.dev/
Detailed API documentation is available at: https://api.flutter.dev/
If you prefer video documentation, consider: https://www.youtube.com/c/flutterdev

In order to run your application, type:

  $ cd myapp
  $ flutter run

Your application code is in myapp/lib/main.dart.

Resolving dependencies... 
Downloading packages... 
+ flutter_gpu 0.0.0 from sdk flutter
  material_color_utilities 0.11.1 (0.12.0 available)
Changed 1 dependency!
1 package has newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Resolving dependencies... 
Downloading packages... 
  material_color_utilities 0.11.1 (0.12.0 available)
Got dependencies!
1 package has newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.

/home/tcna/workspace-automation/app/engine/src/flutter/examples/glfw/debug
[ERROR:flutter/shell/platform/embedder/embedder_surface_gl_skia.cc(123)] Could not create a resource context for async texture uploads. Expect degraded performance. Set a valid make_resource_current callback on FlutterOpenGLRendererConfig.
[ERROR:flutter/shell/platform/embedder/embedder_surface_gl_skia.cc(123)] Could not create a resource context for async texture uploads. Expect degraded performance. Set a valid make_resource_current callback on FlutterOpenGLRendererConfig.
flutter: The Dart VM service is listening on http://127.0.0.1:34919/E_SicMZ-fEE=/

[bdero]

LGTM