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Updating the windowing API for sized to content regular and dialog windows + removing the decorated flag#184977

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Updating the windowing API for sized to content regular and dialog windows + removing the decorated flag#184977
mattkae merged 18 commits into
flutter:masterfrom
canonical:sized-to-content-regular-and-dialog

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@mattkae mattkae commented Apr 13, 2026 •
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closes #183560
closes #183559
closes #185123

What's new?

  • Adding sizedToContent factory methods for RegularWindowController and DialogWindowController
  • Adding a resizable boolean for sizedToContent windows (the assumption being that windows with a specified size area always resizable?)
  • Remove decorated flag on windows but left it as an option on Linux

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@github-actions github-actions Bot added a: tests "flutter test", flutter_test, or one of our tests framework flutter/packages/flutter repository. See also f: labels. labels Apr 13, 2026
@mattkae mattkae changed the title Updating the windowing API for sized to content regular and dialog wi… Updating the windowing API for sized to content regular and dialog windows Apr 15, 2026
@mattkae mattkae marked this pull request as ready for review April 15, 2026 18:48
@mattkae mattkae added the CICD Run CI/CD label Apr 15, 2026
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Code Review

This pull request introduces sizedToContent factory constructors for RegularWindowController and DialogWindowController to support content-based window sizing, makes preferredSize a required parameter in default constructors, and adds a resizable parameter to the windowing API. Review feedback recommends adding isWindowingEnabled checks and WidgetsFlutterBinding.ensureInitialized() calls to the new constructors for consistency, and expanding the documentation for the resizable parameter in DialogWindowController.sizedToContent.

Comment thread packages/flutter/lib/src/widgets/_window.dart
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justinmc
justinmc previously approved these changes Apr 16, 2026
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LGTM with nits 👍 . Generally splitting controllers up like this helps in simplifying a complex API, we've done it a bunch of times in the framework before. Was the motivation just to make it easier to understand for users?

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Comment thread packages/flutter/lib/src/widgets/_window.dart
///
/// {@macro flutter.widgets.windowing.experimental}
@internal
factory RegularWindowController.sizedToContent({

@loic-sharma loic-sharma Apr 18, 2026

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Maybe consider the name .contentSized since it's a bit shorter? I don't feel strongly either ways, just another option for you to consider :)

@mattkae mattkae Apr 20, 2026

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I like sizedToContent but I don't feel strongly either way too :)

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Comment thread packages/flutter/lib/src/widgets/_window.dart Outdated
/// {@macro flutter.widgets.windowing.experimental}
@internal
factory RegularWindowController.sizedToContent({
bool resizable = true,

@loic-sharma loic-sharma Apr 18, 2026 •
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FYI, previously we made content-sizing easier by requiring that a view can be either be content-sized or user-resizable, but not both at the same time. This limitation isn't strictly necessary, but it does make things a bit easier. For example, imagine a scenario where a window is user-resizable and content-sizable at the same time:

  1. The user resizes a content-sized window from 100x100 to 200x200. The embedder blocks until it receives a frame that is 200x200
  2. The app decides to ignore the 200x200 size and produces a 100x100 frame.

I think this scenario is still broken today.

I'm not opposed to adding a resizable flag, but this does mean we'll need to figure out how to resolve "conflicts" between user-resizing and content-sizing.

Would y'all be OK with punting the resizable flag from content-sized window controllers?

@knopp knopp Apr 19, 2026 •
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I am against punting this. RegularWindowController.sizedToContent with resizable=true simply means window is sized to content on first frame, after that the window is freely resizable. I have a working implementation of this and it's pretty straightforward to implement.

The reason why we decided to have sizedToContent as separate opt-in constructor is that most flutter applications unfortunately do not behave well in unconstrained environments. And we don't want first thing user sees being a layout exceptions.

@loic-sharma loic-sharma Apr 20, 2026 •
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Ah I didn't realize that if resizable=true only the first frame is content-sized. That addresses my initial concern.

I'm wondering if this behavior would be clearer through an enum. Perhaps:

  • ContentSizedMode.once. The window is content-sized for its initial frame. The user can resize the window, if the window supports resizing (e.g. regular windows, but not popup windows).
  • ContentSizedMode.always. The window is always content-sized. The user cannot resize the window.

@knopp knopp Apr 20, 2026

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I don't mind the enum not sure about the name / values. The fact that I had to explain this could very well mean that the API is not obvious enough. But it could also be just that you're seeing into the implementation details most users don't. @mattkae, any suggestion?

@mattkae mattkae Apr 20, 2026

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I prefer the boolean personally. I think it should be fairly straightforward after reading the documentation what the behavior is going to be.

That being said, I think that the sane default for sizedToContent is resizable=false instead of resizable=true. If I am explicitly setting resizable to true, I will probably have questions about how that will behave, at which point I will read the docs. The default case will be completely obvious however, which is a good thing 😄

@knopp

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I think we should use this PR to clean-up the interface a little bit. We should remove decorated from controllers and windowing owner, also I think resizable shouldn't have a default value and it should be required.

@knopp knopp mentioned this pull request Apr 19, 2026
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LGTM with one comment on the content-sized constructor docs explaining resizable twice

@mattkae mattkae dismissed stale reviews from loic-sharma and knopp via d36f36a April 23, 2026 11:58
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Re-LGTM!

@mattkae mattkae added this pull request to the merge queue Apr 23, 2026
Merged via the queue into flutter:master with commit 09380fe Apr 23, 2026
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@mattkae mattkae deleted the sized-to-content-regular-and-dialog branch April 23, 2026 23:27
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2026-04-23 jason-simmons@users.noreply.github.com Check for overflow when computing the pixel buffer size for an animated PNG frame (flutter/flutter#185442)
2026-04-23 reinar@crypt.ws Impeller: Recreate Vulkan transients on surface size change (flutter/flutter#185122)
2026-04-23 matt.kosarek@canonical.com Updating the windowing API for sized to content regular and dialog windows + removing the decorated flag (flutter/flutter#184977)
2026-04-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 634991935e9a to 70665fc3fd2e (2 revisions) (flutter/flutter#185488)
2026-04-23 louisehsu@google.com Updating ios triage link (flutter/flutter#185437)
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2026-04-23 1961493+harryterkelsen@users.noreply.github.com fix(web): Fix LateInitializationError in CkSurface and SkwasmSurface (flutter/flutter#185116)
2026-04-23 1961493+harryterkelsen@users.noreply.github.com [web] Implement stepped image downscaling for CanvasKit and Skwasm (flutter/flutter#184741)
2026-04-23 30870216+gaaclarke@users.noreply.github.com Made wide_gamut_macos only run on arm64 machines (flutter/flutter#185486)
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flutter/flutter@5e4f169...aeb9623

2026-04-24 robert.ancell@canonical.com Fix leak on error case (flutter/flutter#185516)
2026-04-24 engine-flutter-autoroll@skia.org Roll Skia from 04c6c369cfd0 to 1c9b0b9141e9 (2 revisions) (flutter/flutter#185529)
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2026-04-24 chris@bracken.jp [ios] Extract SplashScreenManager from FlutterViewController (flutter/flutter#185405)
2026-04-24 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from j3UCWZhWx7zSl9Asy... to 9fPnyEo9PaNdXtasl... (flutter/flutter#185523)
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2026-04-24 engine-flutter-autoroll@skia.org Roll Skia from e8d00d634c22 to ea20c73ac72c (8 revisions) (flutter/flutter#185500)
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2026-04-23 rmolivares@renzo-olivares.dev update team-text-input pr triage link to filter out "waiting for response" label (flutter/flutter#185499)
2026-04-23 jason-simmons@users.noreply.github.com Check for overflow when computing the pixel buffer size for an animated PNG frame (flutter/flutter#185442)
2026-04-23 reinar@crypt.ws Impeller: Recreate Vulkan transients on surface size change (flutter/flutter#185122)
2026-04-23 matt.kosarek@canonical.com Updating the windowing API for sized to content regular and dialog windows + removing the decorated flag (flutter/flutter#184977)
2026-04-23 engine-flutter-autoroll@skia.org Roll Dart SDK from 634991935e9a to 70665fc3fd2e (2 revisions) (flutter/flutter#185488)
2026-04-23 louisehsu@google.com Updating ios triage link (flutter/flutter#185437)
2026-04-23 34871572+gmackall@users.noreply.github.com Revert "Preprovision Android NDK for flavored builds and reuse matchi… (flutter/flutter#185439)
2026-04-23 1961493+harryterkelsen@users.noreply.github.com fix(web): Fix LateInitializationError in CkSurface and SkwasmSurface (flutter/flutter#185116)
2026-04-23 1961493+harryterkelsen@users.noreply.github.com [web] Implement stepped image downscaling for CanvasKit and Skwasm (flutter/flutter#184741)
2026-04-23 30870216+gaaclarke@users.noreply.github.com Made wide_gamut_macos only run on arm64 machines (flutter/flutter#185486)
2026-04-23 chris@bracken.jp [ios] Update documentation for FlutterAppDelegate.pluginRegistrant (flutter/flutter#185201)
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2026-04-23 ishaquehassan@gmail.com Add disposal guidance to CurvedAnimation and CurveTween docs (flutter/flutter#184569)
2026-04-23 ishaquehassan@gmail.com Add `clipBehavior` parameter to `AnimatedCrossFade` (flutter/flutter#184545)
2026-04-23 rmacnak@google.com [fuchsia] Ask for only VMEX, not ambient-replace-as-executable. (flutter/flutter#185099)
2026-04-23 47866232+chunhtai@users.noreply.github.com Unify SemanticUpdateBuilder API for web and non-web (flutter/flutter#185433)
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pull Bot pushed a commit to TheRakeshPurohit/flutter that referenced this pull request Jun 11, 2026
@mattkae
Sized to content for regular and dialog windows on win32 (flutter#186829
6414603 
)

## What's new?
- This implements the sized to content windowing API introduced by
flutter#184977
- Implements size-to-content for regular windows
- Implements size-to-content for dialog windows
- Update the example application to include "size to content" and
"resizable" as windowing settings
- Added unit tets

## How to test?
1. Run the `multiple_windows` example app on win32
2. Go to the window settings dialog and change the "sized to content"
boolean for dialogs and regulars
3. Open up a dialog or a regular window and see that they are sized to
their content

Caveat: The example app does not strictly size dialogs and regulars, so
they will open up at the current screen dimensions.


## 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 documentation (doc comments with `///`).
- [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.
via-guy pushed a commit to via-guy/flutter that referenced this pull request Jun 26, 2026
@mattkae @via-guy
Sized to content for regular and dialog windows on win32 (flutter#186829
1201e1e 
)

## What's new?
- This implements the sized to content windowing API introduced by
flutter#184977
- Implements size-to-content for regular windows
- Implements size-to-content for dialog windows
- Update the example application to include "size to content" and
"resizable" as windowing settings
- Added unit tets

## How to test?
1. Run the `multiple_windows` example app on win32
2. Go to the window settings dialog and change the "sized to content"
boolean for dialogs and regulars
3. Open up a dialog or a regular window and see that they are sized to
their content

Caveat: The example app does not strictly size dialogs and regulars, so
they will open up at the current screen dimensions.


## 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 documentation (doc comments with `///`).
- [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.
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@knopp knopp knopp approved these changes
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Unable to create RegularWindow on Windows when preferredSize not set Support undecorated windows on macOS Support undecorated windows on Windows

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