docs: update Impeller advanced blend docs for framebuffer fetch#185457
Merged
auto-submit[bot] merged 4 commits intoJun 3, 2026
Merged
Conversation
Contributor
There was a problem hiding this comment.
Code Review
This pull request updates the documentation for Impeller's advanced blends to clarify implementation differences based on framebuffer fetch support. It distinguishes between the optimized path used on Metal and Vulkan and the legacy path used on some OpenGL ES devices. A review comment suggests using more general terminology when describing how shaders retrieve backdrop data to accurately reflect both implementation strategies.
d464657 to
c257d0c
Compare
The advanced blend documentation described a three-step cost (end render pass, copy backdrop, blit intermediary) that is no longer accurate on Metal and Vulkan, where framebuffer fetch is now enabled by default. Update the docs to describe both code paths: - Framebuffer fetch path (Metal A8+, most Vulkan): no render pass end, no backdrop copy, no blit — much cheaper than before. - Legacy path (OpenGL ES, iOS simulator, Adreno ≤630, PowerVR): the original three-step path still applies. Fixes flutter#144004
c257d0c to
a11e949
Compare
Contributor
Author
|
Thank you for the review, @gemini-code-assist! "sample the backdrop texture" inaccuracy: Fixed — the introductory sentence now reads "access the backdrop color" which correctly covers both the framebuffer fetch path (reads from the framebuffer attachment, no texture involved) and the legacy path (samples a backdrop texture copy). |
Contributor
|
Thank you for the update, @shivanshu877. The clarification regarding the framebuffer fetch path and the distinction between the framebuffer attachment and the legacy backdrop texture copy makes the documentation much more accurate and easier to follow. I have no further comments on this PR. |
b-luk
approved these changes
Apr 28, 2026
Contributor
|
autosubmit label was removed for flutter/flutter/185457, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label. |
Contributor
|
autosubmit label was removed for flutter/flutter/185457, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label. |
Contributor
|
auto label is removed for flutter/flutter/185457, Failed to enqueue flutter/flutter/185457 with HTTP 400: Pull request Required status check "Merge Queue Guard" is expected.. |
This was referenced Jun 3, 2026
auto-submit Bot
pushed a commit
to flutter/packages
that referenced
this pull request
Jun 5, 2026
Roll Flutter from 2ba5420a7049 to 1bdf4af29076 (43 revisions) flutter/flutter@2ba5420...1bdf4af 2026-06-05 engine-flutter-autoroll@skia.org Roll Packages from 03352b5 to 61bdbb4 (5 revisions) (flutter/flutter#187612) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 6e003d7f69c8 to a47a9a2c8ae5 (1 revision) (flutter/flutter#187610) 2026-06-05 engine-flutter-autoroll@skia.org Roll Dart SDK from aad8be4ce307 to 6a9a0efe66eb (10 revisions) (flutter/flutter#187609) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 494f1bf55f51 to 6e003d7f69c8 (2 revisions) (flutter/flutter#187607) 2026-06-05 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ZE1Jy9CtVVi-tjBAE... to N_LiSaBSUsE2LDZgG... (flutter/flutter#187597) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 59556fdb8c33 to 494f1bf55f51 (2 revisions) (flutter/flutter#187596) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 8eb107046fd5 to 59556fdb8c33 (1 revision) (flutter/flutter#187590) 2026-06-04 34871572+gmackall@users.noreply.github.com Remove `embedded_android_views_integration_test.dart` (flutter/flutter#187465) 2026-06-04 burak.karahan@mail.ru Remove Material imports from rendering editable tests (flutter/flutter#186951) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Wait for the Vulkan device to become idle before destroying Vulkan objects in the AHBSwapchainImplVK destructor (flutter/flutter#187477) 2026-06-04 chris@bracken.jp [iOS] Eliminate unnecessary redeclaration of FlutterDisplayLink (flutter/flutter#187557) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187583) 2026-06-04 34871572+gmackall@users.noreply.github.com Log stdout in adb.dart (flutter/flutter#187531) 2026-06-04 mvincentong@gmail.com Clarify RouterDelegate popRoute bubbling (flutter/flutter#186875) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187584) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add updating-android-sdk agent skill for rolling Android SDK in CIPD (flutter/flutter#187576) 2026-06-04 Rusino@users.noreply.github.com Fixing alignment issue (flutter/flutter#187518) 2026-06-04 brackenavaron@gmail.com [Material Cross Imports] Clean up Material Divider usages (flutter/flutter#187300) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from cecc0e0da9ae to 928ded2a31af (6 revisions) (flutter/flutter#187574) 2026-06-04 31859944+LongCatIsLooong@users.noreply.github.com Use swift demangle to verify internal Swift symbols (flutter/flutter#186835) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add android 37 platform and build tools to script for android cipd bundle creation (flutter/flutter#187571) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Increase the precision of the IPSampleWithTileModeOES coords parameter to match the input coordinates in the tiled_texture_fill_external shader (flutter/flutter#187545) 2026-06-04 engine-flutter-autoroll@skia.org Roll Packages from b11504f to 03352b5 (4 revisions) (flutter/flutter#187569) 2026-06-04 iinozemtsev@google.com Roll Dart SDK to Dart 3.13 beta2 (flutter/flutter#187555) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 611e3f8ceb93 to cecc0e0da9ae (1 revision) (flutter/flutter#187562) 2026-06-04 6655696+guidezpl@users.noreply.github.com Add step to bootstrap Flutter tool in coverage workflow (flutter/flutter#187199) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 4fdb859c8da7 to 611e3f8ceb93 (4 revisions) (flutter/flutter#187554) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 0020aae33f63 to 4fdb859c8da7 (2 revisions) (flutter/flutter#187552) 2026-06-04 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ap7MhLX4TdpWRrLS_... to ZE1Jy9CtVVi-tjBAE... (flutter/flutter#187550) 2026-06-04 stuartmorgan@google.com Add vector_math to package issue template (flutter/flutter#187536) 2026-06-04 jason-simmons@users.noreply.github.com Manual roll Dart SDK from d39850bf4a01 to 3b70b98fa7c0 (flutter/flutter#187519) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from d625048c853a to 0020aae33f63 (20 revisions) (flutter/flutter#187539) 2026-06-04 smille2003@yandex.ru [Impeller][Windows] fix black screen on OpenGL fallback (flutter/flutter#187288) 2026-06-04 97480502+b-luk@users.noreply.github.com Fix unintentionally joined path contours (flutter/flutter#187522) 2026-06-03 matt.boetger@gmail.com fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template (flutter/flutter#187127) 2026-06-03 34871572+gmackall@users.noreply.github.com Add a skill for flake analysis (flutter/flutter#187530) 2026-06-03 30870216+gaaclarke@users.noreply.github.com adds linux impeller project flag (flutter/flutter#186982) 2026-06-03 codedoctor@linwood.dev Add support for stylus buttons (flutter/flutter#183369) 2026-06-03 46920873+gabrimatic@users.noreply.github.com Prevent Cubic transform from looping on out-of-range input (flutter/flutter#185875) 2026-06-03 bdero@google.com [Impeller] Reland: Allow attaching specific texture mip levels and slices (flutter/flutter#187470) 2026-06-03 kjlubick@users.noreply.github.com [skia] Update image deserial proc (flutter/flutter#185041) 2026-06-03 112751483+shivanshu877@users.noreply.github.com docs: update Impeller advanced blend docs for framebuffer fetch (flutter/flutter#185457) 2026-06-03 ahmedsameha1@gmail.com Handle#6537 fifth grouped tests (flutter/flutter#183720) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: ...
creatorpiyush
pushed a commit
to creatorpiyush/packages
that referenced
this pull request
Jun 10, 2026
…r#11849) Roll Flutter from 2ba5420a7049 to 1bdf4af29076 (43 revisions) flutter/flutter@2ba5420...1bdf4af 2026-06-05 engine-flutter-autoroll@skia.org Roll Packages from 03352b5 to 61bdbb4 (5 revisions) (flutter/flutter#187612) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 6e003d7f69c8 to a47a9a2c8ae5 (1 revision) (flutter/flutter#187610) 2026-06-05 engine-flutter-autoroll@skia.org Roll Dart SDK from aad8be4ce307 to 6a9a0efe66eb (10 revisions) (flutter/flutter#187609) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 494f1bf55f51 to 6e003d7f69c8 (2 revisions) (flutter/flutter#187607) 2026-06-05 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ZE1Jy9CtVVi-tjBAE... to N_LiSaBSUsE2LDZgG... (flutter/flutter#187597) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 59556fdb8c33 to 494f1bf55f51 (2 revisions) (flutter/flutter#187596) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 8eb107046fd5 to 59556fdb8c33 (1 revision) (flutter/flutter#187590) 2026-06-04 34871572+gmackall@users.noreply.github.com Remove `embedded_android_views_integration_test.dart` (flutter/flutter#187465) 2026-06-04 burak.karahan@mail.ru Remove Material imports from rendering editable tests (flutter/flutter#186951) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Wait for the Vulkan device to become idle before destroying Vulkan objects in the AHBSwapchainImplVK destructor (flutter/flutter#187477) 2026-06-04 chris@bracken.jp [iOS] Eliminate unnecessary redeclaration of FlutterDisplayLink (flutter/flutter#187557) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187583) 2026-06-04 34871572+gmackall@users.noreply.github.com Log stdout in adb.dart (flutter/flutter#187531) 2026-06-04 mvincentong@gmail.com Clarify RouterDelegate popRoute bubbling (flutter/flutter#186875) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187584) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add updating-android-sdk agent skill for rolling Android SDK in CIPD (flutter/flutter#187576) 2026-06-04 Rusino@users.noreply.github.com Fixing alignment issue (flutter/flutter#187518) 2026-06-04 brackenavaron@gmail.com [Material Cross Imports] Clean up Material Divider usages (flutter/flutter#187300) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from cecc0e0da9ae to 928ded2a31af (6 revisions) (flutter/flutter#187574) 2026-06-04 31859944+LongCatIsLooong@users.noreply.github.com Use swift demangle to verify internal Swift symbols (flutter/flutter#186835) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add android 37 platform and build tools to script for android cipd bundle creation (flutter/flutter#187571) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Increase the precision of the IPSampleWithTileModeOES coords parameter to match the input coordinates in the tiled_texture_fill_external shader (flutter/flutter#187545) 2026-06-04 engine-flutter-autoroll@skia.org Roll Packages from b11504f to 03352b5 (4 revisions) (flutter/flutter#187569) 2026-06-04 iinozemtsev@google.com Roll Dart SDK to Dart 3.13 beta2 (flutter/flutter#187555) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 611e3f8ceb93 to cecc0e0da9ae (1 revision) (flutter/flutter#187562) 2026-06-04 6655696+guidezpl@users.noreply.github.com Add step to bootstrap Flutter tool in coverage workflow (flutter/flutter#187199) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 4fdb859c8da7 to 611e3f8ceb93 (4 revisions) (flutter/flutter#187554) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 0020aae33f63 to 4fdb859c8da7 (2 revisions) (flutter/flutter#187552) 2026-06-04 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ap7MhLX4TdpWRrLS_... to ZE1Jy9CtVVi-tjBAE... (flutter/flutter#187550) 2026-06-04 stuartmorgan@google.com Add vector_math to package issue template (flutter/flutter#187536) 2026-06-04 jason-simmons@users.noreply.github.com Manual roll Dart SDK from d39850bf4a01 to 3b70b98fa7c0 (flutter/flutter#187519) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from d625048c853a to 0020aae33f63 (20 revisions) (flutter/flutter#187539) 2026-06-04 smille2003@yandex.ru [Impeller][Windows] fix black screen on OpenGL fallback (flutter/flutter#187288) 2026-06-04 97480502+b-luk@users.noreply.github.com Fix unintentionally joined path contours (flutter/flutter#187522) 2026-06-03 matt.boetger@gmail.com fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template (flutter/flutter#187127) 2026-06-03 34871572+gmackall@users.noreply.github.com Add a skill for flake analysis (flutter/flutter#187530) 2026-06-03 30870216+gaaclarke@users.noreply.github.com adds linux impeller project flag (flutter/flutter#186982) 2026-06-03 codedoctor@linwood.dev Add support for stylus buttons (flutter/flutter#183369) 2026-06-03 46920873+gabrimatic@users.noreply.github.com Prevent Cubic transform from looping on out-of-range input (flutter/flutter#185875) 2026-06-03 bdero@google.com [Impeller] Reland: Allow attaching specific texture mip levels and slices (flutter/flutter#187470) 2026-06-03 kjlubick@users.noreply.github.com [skia] Update image deserial proc (flutter/flutter#185041) 2026-06-03 112751483+shivanshu877@users.noreply.github.com docs: update Impeller advanced blend docs for framebuffer fetch (flutter/flutter#185457) 2026-06-03 ahmedsameha1@gmail.com Handle#6537 fifth grouped tests (flutter/flutter#183720) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: ...
via-guy
pushed a commit
to via-guy/flutter
that referenced
this pull request
Jun 26, 2026
…ter#185457) ## Description The advanced blend section of `blending.md` described a three-step cost (end render pass → copy backdrop → blit intermediary) that is no longer accurate on Metal and Vulkan, where framebuffer fetch is now the default. ### Changes - **`docs/engine/impeller/docs/blending.md`**: Rewrites the cost model for advanced blends to describe both code paths: - **Framebuffer fetch supported** (Metal / Vulkan default): no render pass end, no backdrop copy, no intermediary blit — the shader reads the backdrop directly from the framebuffer. Only the source snapshot is required. Still more expensive than a pipeline blend, but significantly cheaper than the legacy path. - **Framebuffer fetch not supported** (some OpenGL ES devices): the original three-step path still applies. Fixes flutter#144004 Co-authored-by: gaaclarke <30870216+gaaclarke@users.noreply.github.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Description
The advanced blend section of
blending.mddescribed a three-step cost (end render pass → copy backdrop → blit intermediary) that is no longer accurate on Metal and Vulkan, where framebuffer fetch is now the default.Changes
docs/engine/impeller/docs/blending.md: Rewrites the cost model for advanced blends to describe both code paths:Fixes #144004