Starts flipping content on windows to avoid full screen renders by gaaclarke · Pull Request #193133 · flutter/flutter

gaaclarke · 2026-09-21T23:06:06Z

This is glue code to hook us up to the optimization we've created in ANGLE at https://chromium-review.git.corp.google.com/c/angle/angle/+/8436859

This removes a temporary full screen texture and a full screen render pass, allowing us to MSAA resolve directly into the swapchain.

fixes: #192496

screenshot of afterwards capture

Notice the last thing is a resolve.

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renders.

gaaclarke · 2026-09-25T22:17:19Z

+      attributes.push_back(EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE);
+      attributes.push_back(EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE);


This sounds counter intuitive but looking at the gpu captures, this wasn't helping us. EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE only helps when rendering directly to the swapchain. We render to offscreen MSAA and resolve it to the swapchain.

gemini-code-assist

Code Review

This pull request introduces support for a top-left default framebuffer origin in Impeller's GLES backend, allowing embedders (such as ANGLE on Windows with EGL_SURFACE_ORIENTATION_INVERT_Y_ANGLE) to use an inverted Y-axis window surface. This avoids a full-screen shader pass for flipping during presentation by keeping the pipeline in a single orientation. Feedback on these changes suggests downgrading a warning log to a debug log when the surface orientation extension is unavailable to prevent noisy production logs, and refactoring a test helper function to remove an unused context parameter.

gemini-code-assist · 2026-09-28T20:22:20Z

+        FML_LOG(WARNING) << "EGL_ANGLE_surface_orientation is unavailable. "
+                            "Falling back to a bottom-left surface origin.";


This warning is logged on any hardware/driver configuration that does not support EGL_ANGLE_surface_orientation. Since this is a completely expected fallback path and rendering remains fully correct, logging a WARNING can be unnecessarily noisy for production applications. Consider changing this to a debug-only log (FML_DLOG(INFO)) or a verbose log (FML_VLOG(1)).

Suggested change

FML_LOG(WARNING) << "EGL_ANGLE_surface_orientation is unavailable. "

"Falling back to a bottom-left surface origin.";

FML_DLOG(INFO) << \"EGL_ANGLE_surface_orientation is unavailable. \"\n \"Falling back to a bottom-left surface origin.\";

gemini-code-assist · 2026-09-28T20:22:20Z

+std::shared_ptr<RenderPass> CreateWrappedFBORenderPass(
+    const std::shared_ptr<ContextGLES>& context,
+    const std::shared_ptr<ReactorGLES>& reactor,
+    const std::shared_ptr<CommandBuffer>& command_buffer) {


The context parameter is not used anywhere inside the CreateWrappedFBORenderPass helper function. Removing it simplifies the helper's signature and improves maintainability.

std::shared_ptr<RenderPass> CreateWrappedFBORenderPass(\n const std::shared_ptr<ReactorGLES>& reactor,\n const std::shared_ptr<CommandBuffer>& command_buffer) {

gemini-code-assist · 2026-09-28T20:22:21Z

+  std::shared_ptr<RenderPass> render_pass =
+      CreateWrappedFBORenderPass(ctx.context, reactor, ctx.command_buffer);


Update the call to CreateWrappedFBORenderPass to match the simplified signature by removing the unused ctx.context argument.

std::shared_ptr<RenderPass> render_pass =\n CreateWrappedFBORenderPass(reactor, ctx.command_buffer);

gemini-code-assist · 2026-09-28T20:22:21Z

+  std::shared_ptr<RenderPass> render_pass =
+      CreateWrappedFBORenderPass(ctx.context, reactor, ctx.command_buffer);


Update the call to CreateWrappedFBORenderPass to match the simplified signature by removing the unused ctx.context argument.

std::shared_ptr<RenderPass> render_pass =\n CreateWrappedFBORenderPass(reactor, ctx.command_buffer);

b-luk

Looks good except for one comment that I think could be clearer.

b-luk · 2026-09-29T23:54:46Z

-  const bool flip_y = !is_wrapped_fbo;
+  //
+  // When the embedder's default framebuffer already has a top-left origin
+  // there is nothing to leave alone: every target, wrapped or not, is stored


As someone new to this code, I think this comment and the existing comment above was a bit confusing. Particularly the phrasing of "nothing to leave alone" in the new comment, and the terms "offscreen FBO" and "swapchain" vs "wrapped" and "non-wrapped".

How about something like:

// Offscreen (non-wrapped) FBOs always flip in the vertex shader so they are // stored with a top-left origin, matching Impeller's coordinate system. See // https://github.com/flutter/flutter/issues/186554. // // Wrapped FBOs match the embedder's default framebuffer origin: // - Bottom-left (the OpenGL default): no flip. // - Top-left (currently only the Windows embedder, via ANGLE's // EGL_SURFACE_ORIENTATION_INVERT_Y_ANGLE): flip, like offscreen FBOs. // The whole pipeline is then in one orientation, so the blit that // presents a wrapped framebuffer to the swapchain is a straight 1:1 copy, // which lets the driver resolve or DMA it instead of running a // full-screen shader pass to flip it.

andywolff

LGTM with some nits

andywolff · 2026-10-01T21:17:27Z

Building on @b-luk's comment on lines 362-369, this comment still states that the swapchain always keeps the top-down to bottom-up conversion. We could update this note so it reflects that flip_y can now be true for swapchain targets when the default framebuffer has a top-left origin.

One option for this:

My comment at #193133 (comment) also suggested a change for this line

// Offscreen (non-wrapped) FBOs always flip in the vertex shader so they are // stored with a top-left origin, matching Impeller's coordinate system. See // https://github.com/flutter/flutter/issues/186554.

That way the first paragraph of this comment block is only about offscreen/non-wrapped FBOs and doesn't mention the swapchain at all. And the second paragraph (which is already changed) is only about the swapchain/wrapped FBOs.

missed this, done

auto-submit · 2026-10-02T19:01:44Z

autosubmit label was removed for flutter/flutter/193133, because - The status or check suite Dashboard Checks has failed. Please fix the issues identified (or deflake) before re-applying this label.

Resolve the EGL manager and Windows engine conflicts from flutter#193133 by passing both the upstream surface-orientation flag and the optional program cache. Keep cache installation after eglInitialize and before context creation. Validation: clang-format checks on resolved ranges, whitespace checks, call-site review, and unchanged cache implementation/tests. Native Windows build and unit tests were not run on this macOS host.

…ter#193133) This is glue code to hook us up to the optimization we've created in ANGLE at https://chromium-review.git.corp.google.com/c/angle/angle/+/8436859 This removes a temporary full screen texture and a full screen render pass, allowing us to MSAA resolve directly into the swapchain. fixes: flutter#192496 ## screenshot of afterwards capture Notice the last thing is a resolve. <img width="1674" height="903" alt="Screenshot 2026-09-25 133558" src="https://github.com/user-attachments/assets/599449e8-57be-40c2-9cc9-fd1fc1c9217e" /> ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant in-code documentation (doc comments with `///`). - [x] If this PR introduces a new feature or capability, I created and linked a website documentation issue or PR in [flutter/website] (or verified none is needed). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. If this change needs to override an active code freeze, provide a comment explaining why. The code freeze workflow can be overridden by code reviewers. See pinned issues for any active code freezes with guidance. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [AI contribution guidelines]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#ai-contribution-guidelines [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [flutter/website]: https://github.com/flutter/website [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

github-actions Bot added engine flutter/engine related. See also e: labels. platform-windows Building on or for Windows specifically a: desktop Running on desktop e: impeller Impeller rendering backend issues and features requests team-windows Owned by the Windows platform team labels Sep 21, 2026

Started flipping content on windows to avoid full screen flipping

538a303

renders.

gaaclarke force-pushed the no-flip-windows branch from 87311a0 to 538a303 Compare September 25, 2026 20:37

gaaclarke added the CICD Run CI/CD label Sep 25, 2026

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Merge branch 'master' into no-flip-windows

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mdebbar mentioned this pull request Oct 8, 2026

[gn] Use python3 as script_executable in engine/src/.gn #193954

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Flutter Notable Commits - 2026 #181433

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dbebawy mentioned this pull request Oct 14, 2026

Support soft hyphen (U+00AD) rendering with a Hyphens API #185152

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		attributes.push_back(EGL_EXPERIMENTAL_PRESENT_PATH_ANGLE);
		attributes.push_back(EGL_EXPERIMENTAL_PRESENT_PATH_FAST_ANGLE);

		FML_LOG(WARNING) << "EGL_ANGLE_surface_orientation is unavailable. "
		"Falling back to a bottom-left surface origin.";

	FML_LOG(WARNING) << "EGL_ANGLE_surface_orientation is unavailable. "
	"Falling back to a bottom-left surface origin.";
	FML_DLOG(INFO) << \"EGL_ANGLE_surface_orientation is unavailable. \"\n \"Falling back to a bottom-left surface origin.\";

		std::shared_ptr<RenderPass> render_pass =
		CreateWrappedFBORenderPass(ctx.context, reactor, ctx.command_buffer);

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screenshot of afterwards capture

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