[WIP] New `WindowState` API by m-sasha · Pull Request #2938 · JetBrains/compose-multiplatform-core

m-sasha · 2026-03-30T22:42:28Z

This PR introduces a new WindowState API, and corresponding composable functions.

The main improvements relative to the current API:

Add screen selection and observing.
Add the ability for custom window positioning and sizing.
Add the ability to specify minimum and maximum window size.
Clear API for sizing the window according to its intrinsic/preferred size (previously via DpSize.Unspecified).
Allow sizing the window to its intrinsic size, and have the content fill the window. Previously when using DpSize.Unspecified with a fillMaxSize() top-level modifier would cause the window to fill the screen. Requested in:
- CMP-2923 Add the ability to "pack" a window while allowing its content to match the window size
- CMP-7377 [JVM] Resize Window() size to fit content
Improve WindowState saving/restoring (see CMP-1535 Revisit WindowState/DialogState API).
Improve window position API (see CMP-9260 Design problem with WindowPosition (x, y, isSpecified)).
Allow positioning dialogs relative to their parent window.

Quick-start

The new APIs reside in androidx.compose.ui.window.v2.

Use rememberWindowState(initialScreenProvider=...) or WindowState.requestScreen to specify the screen on which the window may be placed. The actual screen (which may change over time) is observable via WindowState.bounds.
Use rememberWindowState(initialBoundsProvider=...) or WindowState.requestBounds to change the bounds of the window. The actual bounds (which may be different, and which will change over time) are observable via WindowState.bounds.
DialogWindow has a similar API, also in androidx.compose.ui.window.v2.

Plan

The plan is to introduce this API as experimental, gather feedback from users and then deprecate the old one, replacing it with the new one.

Note that currently the PR only includes the window state API, but a similar one will be added for dialogs, once the window one has been generally approved by reviewers.

Fixes https://youtrack.jetbrains.com/issue/CMP-1535
Fixes https://youtrack.jetbrains.com/issue/CMP-9260
Fixes https://youtrack.jetbrains.com/issue/CMP-2923
Fixes https://youtrack.jetbrains.com/issue/CMP-7377
Fixes https://youtrack.jetbrains.com/issue/CMP-1873

Testing

The new API is tested via all the tests of the previous one, plus some additional tests.

This should be tested by QA

Release Notes

Features - Desktop

Implemented a new, experimental, WindowState API.

MatkovIvan · 2026-04-08T09:36:12Z

+internal fun Dimension.toDpSize() = DpSize(width.dp, height.dp)
+internal fun Point.toDpOffset() = DpOffset(x.dp, y.dp)
+internal fun Rectangle.toDpRect() = DpRect(


Any reason to change it? Currently, it's aligned with the similar API across other platforms

To me, Object.asSomething has the connotation of casting, or wrapping an object, like in Arrays.asList().

Object.toSomething(), on the other hand, has the connotation of converting, and creating a completely independent new object. Like in Array.toList()

MatkovIvan · 2026-04-08T09:40:18Z

+ */
+@ExperimentalComposeUiApi
+@Immutable
+class DpInsets(


We must not introduce such API one more time as desktop only. Please reuse the existing one

cc @svastven

The one in ios is internal; this one is public (but experimental).

We could change ios to use this one, but I wouldn't say it's a "must". There are plenty of places where we have internal copies of code because we don't want to create a dependency.

Up to the ios team...

It's public and in skikoMain

compose-multiplatform-core/compose/ui/ui/src/skikoMain/kotlin/androidx/compose/ui/platform/PlatformWindowInsets.skiko.kt

Lines 112 to 116 in 78845ae

/**

* This class represents platform insets.

*/

@InternalComposeUiApi

interface PlatformInsets {

@InternalComposeUiApi is about using only inside our library. If you need really user-faced API - it should be existing foundation/commonMain one

PlatformInsets is not the same as DpInsets.
What I thought you meant was this:

compose-multiplatform-core/compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/platform/UIKitTextInputService.ios.kt

Line 1104 in 78845ae

internal data class DpInsets(val left: Dp, val top: Dp, val right: Dp, val bottom: Dp)

DpInsets is currently internal to iosMain as convenience so that we don’t introduce an API that isn’t used anywhere else unless it’s actually needed.

Personally, I’m fine with having DpInsets as a dp-based convenience type alongside PlatformInsets, which is px-based and also internal API. I don’t see this as duplication, as long as DpInsets remains internal. If moved to skikoMain, then we can remove the one in iosMain.

If this new API is being used for window/platform insets, then I think we should use the existing WindowInsets / PlatformInsets APIs.

If we decide to introduce a public dp-based insets API, then I think it should live in common, at the same level as something like DpRect. But I am not sure this is the case.

As for PlatformInsets it is a px-based API. Its purpose is to represent the platform backing to WindowInsets, which are also px-based. The developer can then choose the PlatformInsets behavior they need for their particular case, for example dynamic getters, packed values, introduce new ones, etc.

I moved DpInsets to skikoMain. Not sure what else should be done here.

compose-multiplatform-core/compose/foundation/foundation-layout/src/commonMain/kotlin/androidx/compose/foundation/layout/WindowInsets.kt

Lines 35 to 45 in 78845ae

/**

* A representation of window insets that tracks access to enable recomposition, relayout, and

* redrawing when values change. These values should not be read during composition to avoid doing

* composition for every frame of an animation. Use methods like [Modifier.windowInsetsPadding],

* [Modifier.systemBarsPadding], and [Modifier.windowInsetsTopHeight] for Modifiers that will not

* cause recomposition when values change.

*

* Use the [WindowInsets.Companion] extensions to retrieve [WindowInsets] for the current window.

*/

@Stable

interface WindowInsets {

compose-multiplatform-core/compose/ui/ui/src/commonMain/kotlin/androidx/compose/ui/layout/WindowInsetsRulers.kt

Lines 34 to 40 in 78845ae

/**

* Contains rulers used for window insets. The [current] values are available as well as values when

* the insets are [fully visible][maximum].

*

* Other animation properties can be retrieved with [getAnimation].

*/

sealed interface WindowInsetsRulers {

WindowInsets is related to DpInsets mostly just by name, and WindowRulers is even less related.

These are types for a concrete purpose, not generic geometry types like, for example, DpRect.

So I see no reason to forcibly use WindowInsets instead of a simple holder of 4 named Dp values. Also, WindowInsets is in foundation, while this new API is in ui.

If we have an issue with DpInsets, there is an option to remove it and keep only availableBounds public - insets can be derived from it.

I am also fine with keeping the current DpInsets public.

Another option is to rename them to DpScreenInsets

I don't see anything wrong with DpInsets.

MatkovIvan · 2026-04-16T12:30:17Z

+     *
+     * Note that the actual placement is set asynchronously.
+     */
+    fun requestPlacement(placement: WindowPlacement) {


How does it work with Wayland?

In the end, the implementation goes through the same API as the old Window API, so it works the same way...

MatkovIvan · 2026-04-16T12:35:53Z

+    /**
+     * The list of screens on which the window can be placed.
+     */
+    val screens: List<Screen> = devices.map { Screen(it) }


Shouldn't it be state-backed? How to be notified about a new screen appearing?

This is part of WindowScreenProviderScope, which is a very short-lived object. It's created for, and only exists, during the call to WindowScreenProvider.getScreen().

Also, there's no AWT API to monitor screens...

igordmn · 2026-04-24T13:38:48Z

+ *
+ * @see androidx.compose.ui.window.v2.Window
+ */
+@ExperimentalComposeUiApi


Please add a KDoc note to each function that it is planned to be moved to androidx.compose.ui.awt after stabilization.

You mean to every v2 function/class?

Actually, we probably have to keep classes under "v2".

What we discussed earlier was about Composable functions

Discussed that keeping it forever in "v2" is also an option.

igordmn

Approve for the current public API.

I also looked at the implementation, but not deeply.

… and `SwingWindow`

…nt size

… providers

… can be used.

…metryProviderScope

…oseUiApi

…AWT.

…when closed`

…e and position separately

…owBoundsProvider`.

…ate to avoid accidentally using it. Add size and position properties to WindowState and DialogState.

…and functions.

m-sasha marked this pull request as draft March 30, 2026 22:46

m-sasha requested a review from kropp March 31, 2026 14:11

m-sasha force-pushed the m-sasha/rework-window-state branch 2 times, most recently from 5f80465 to 44d9b6c Compare April 2, 2026 21:15

m-sasha requested a review from MatkovIvan April 7, 2026 10:54

kropp reviewed Apr 7, 2026

View reviewed changes

Comment thread compose/ui/ui/src/desktopMain/kotlin/androidx/compose/ui/window/v2/WindowState.desktop.kt Outdated

MatkovIvan reviewed Apr 8, 2026

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m-sasha force-pushed the m-sasha/rework-window-state branch 2 times, most recently from 7abe766 to d0f6910 Compare April 8, 2026 18:43

MatkovIvan reviewed Apr 9, 2026

View reviewed changes

Comment thread compose/ui/ui/src/skikoMain/kotlin/androidx/compose/ui/scene/ComposeScene.skiko.kt Outdated

m-sasha force-pushed the m-sasha/rework-window-state branch from 48f8bc8 to fb106d0 Compare April 10, 2026 07:39

MatkovIvan reviewed Apr 16, 2026

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svastven mentioned this pull request Apr 20, 2026

Support sizing of Compose hosting views on iOS #2984

Draft

svastven reviewed Apr 20, 2026

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m-sasha force-pushed the m-sasha/rework-window-state branch from 92a59f1 to f23f001 Compare April 20, 2026 11:54

m-sasha mentioned this pull request Apr 20, 2026

Expose ComposeScene.measurableContent to allow querying the scene for its size properties #2986

Merged

m-sasha force-pushed the m-sasha/rework-window-state branch from f23f001 to 146a6be Compare April 20, 2026 16:12

igordmn reviewed Apr 24, 2026

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igordmn approved these changes Apr 24, 2026

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m-sasha force-pushed the m-sasha/rework-window-state branch 2 times, most recently from 49a2341 to 5502d13 Compare April 27, 2026 16:56

m-sasha added 9 commits April 28, 2026 16:20

[WIP] Proposal for reworking WindowState and related types

0ea4d0e

Add onBoundsChanged argument to Window, singleWindowApplication…

74f764b

… and `SwingWindow`

Use WindowState.bounds as initial bounds if it's not null

0774fec

Prevent setting WindowState.bounds to null

e115078

Replace bounds setter with a function

f9a1a08

Fix v2.WindowState Saver

91e3dc2

Change new WindowState.bounds to be DpRect

521002a

Enhance initial window positioning; allow selecting the screen.

e039cd3

Added fun WindowState.awtBounds()

61d8682

m-sasha added 29 commits April 28, 2026 16:20

Added @immutable annotation to DpInsets

aa74998

Add WindowSizeLimits and corresponding Window parameter

d75ff24

Add more @ExperimentalComposeUiApi where appropriate

43d65d6

Add offset parameter in WindowBoundsProvider.AlignedToScreen

210d0d2

Add the ability to size windows according to the real intrinsic conte…

6eb2909

…nt size

Address PR feedback

94dcf6c

Add MinWidthMatchingHeight and MinHeightMatchingWidth window size…

6ace75f

… providers

Expose MeasurableRootContent in WindowGeometryProviderScope

e44b59a

Make sure to make the window displayable before MeasurableRootContent…

e450a1a

… can be used.

Unconditionally make the window displayable before creating WindowGeo…

c482db4

…metryProviderScope

Correctly mark ComposeWindow.measurableContent as @ExperimentalComp…

b0957d9

…oseUiApi

Removed MeasuredRootContent in favor of Measured.

fc74eb7

Added unit tests for the new WindowSizeProviders

4f943e2

Add more flexible WindowSizeProviders

015d808

Return simple versions of intrinsic WindowSizeProviders

680532a

Minor improvement in tests

e8d97b5

Make sure to round up the requested window size before passing it to …

7d6d461

…AWT.

Add sizeLimits argument to singleWindowApplication.

d851391

Add link to ticket for supporting window focus management

92be283

Minor refactoring of WindowSizeProviders

e5b1752

Fix flakiness of v2 window test of `window does not flash background …

dcaf8c1

…when closed`

Initial implementation of new Dialog State API

8a4f3c8

Add Current window position/size providers to allow setting the siz…

fc5bda2

…e and position separately

Make AlignedToScreen a WindowPositionProvider rather than a `Wind…

423b7ce

…owBoundsProvider`.

Remove unused imports

729910a

Hide constructor which creates uninitialized WindowState and DialogSt…

b253816

…ate to avoid accidentally using it. Add size and position properties to WindowState and DialogState.

Add WindowV2StateTest

2056893

Added a note about being moved to a package below for all "v2" types …

8b8aa1c

…and functions.

Allow positioning dialogs relative to the parent window

7619a90

m-sasha force-pushed the m-sasha/rework-window-state branch from 5502d13 to 7619a90 Compare April 28, 2026 13:42

	/**
	* This class represents platform insets.
	*/
	@InternalComposeUiApi
	interface PlatformInsets {

	/**
	* A representation of window insets that tracks access to enable recomposition, relayout, and
	* redrawing when values change. These values should not be read during composition to avoid doing
	* composition for every frame of an animation. Use methods like [Modifier.windowInsetsPadding],
	* [Modifier.systemBarsPadding], and [Modifier.windowInsetsTopHeight] for Modifiers that will not
	* cause recomposition when values change.
	*
	* Use the [WindowInsets.Companion] extensions to retrieve [WindowInsets] for the current window.
	*/
	@Stable
	interface WindowInsets {

	/**
	* Contains rulers used for window insets. The [current] values are available as well as values when
	* the insets are [fully visible][maximum].
	*
	* Other animation properties can be retrieved with [getAnimation].
	*/
	sealed interface WindowInsetsRulers {

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m-sasha commented Mar 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Quick-start

Plan

Testing

Release Notes

Features - Desktop

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svastven Apr 8, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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m-sasha commented Mar 30, 2026 •

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svastven Apr 8, 2026 •

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