Windows as `Entities` #4947

Weibye · 2022-06-06T16:26:15Z

This is going to be both large and controversial, so I would very much appreciate feedback and input on this initial direction so that this turns out the best it can be.

I will update the PR description with more details as I progress.

Current Status: Check todo list at the bottom.

Objective

Make windows be Entities as that would allow users to operate on windows the same as they would already be doing with commands, systems and components
Fixes Windows as entities #4530

Solution

High Level Overview

Windows in Bevy has now become entities with components. The user can query these components to read information about the windows. The user can use change detection to check if various components has changed. These components are 'readony'-ish for the user.

To mutate the windows, the user will now use WindowCommands and apply Commands to the Entity with the window. The window backend is responsible handling these commands and updating the data on the components accordingly.

`bevy_window` changes

`Window_id`

WindowId has been replaced by Entity throughout the entire project

`Window`

Window has been split into multiple components:
- Window (marker)
- WindowCursor
- WindowCursorPosition
- WindowHandle
- WindowPresentation
- WindowModeComponent
- WindowPosition
- WindowResolution
- WindowTitle
- WindowCanvas
- WindowDecoraded (marker)
- WindowCurrentlyFocused (marker)
- WindowResizable (marker)
- WindowTransparent (marker)
- WindowMinimized (marker)
- WindowMaximized (marker)
It is the responsibility of the window backend (bevy_winit) to create, update and remove these components
All fields on these components are private
The user should get data from the fields using the various getter methods exposed
All setter methods are named update_x_from_backend() or similar and should only be used by the window backend.

`Windows`

Windows has been removed completely
Getting all windows should now be done by querying for entities with the Window marker component
- Query<Entity, With<Window>>

`WindowCommandsExtension`

Created WindowCommandsExtensions so that we can commands.window(entity) to get WindowCommands
- Similar to how ÈntityCommands work

`WindowCommand`

Is no longer an enum
Has been split into structs that all impl Command
These commands will send themselves as events on command.write() for the window backend to handle

`PrimaryWindow`

PrimaryWindow is a new resource that the bevy_window plugin is responsible for creating when setting up the initial window.
It contains the Entity of the window that is considered the primary window
TODO: Consider if this should be a marker instead of a resource.

`bevy_winit` changes

TODO

`bevy_render` changes

TODO

`bevy_text`

Internal changes: Res -> Query

`bevy_ui`

Internal changes:

Res<Windows> -> Query
window.

Changelog

TODO: User facing changes to Window
- Creating windows
- Reading from windows
- Writing / making changes to windows
TODO: User facing changes to Winit (This probably does not affect most users)
TODO: User facing changes to bevy_render

Migration Guide

WindowId -> Entity
window: Res<Window> -> windows: Query<&RelevantWindowComponent, With<Window>>
windows: Res<Windows> -> windows: Query<&RelevantWindowComponent, With<Window>>

Remaining Tasks

Changes compiles :)
Fix timing issues between bevy_window, bevy_winit and bevy_render when it comes to window handle creation.
Check for system order ambiguities in Winit systems
Double check that we aren't regressing any features
Clear out remaining TODOs
Write tests that covers these changes / systems
Add documentation
Write changelog
Write migration guide

…ndow`

…Command`s

crates/bevy_winit/src/lib.rs

Weibye · 2022-06-06T17:54:50Z

crates/bevy_winit/src/lib.rs

+                CoreStage::PostUpdate,
+                SystemSet::new()
+                    .label(ModifiesWindows)
+                    .with_system(update_title)
+                    .with_system(update_window_mode)
+                    .with_system(update_decorations)
+                    .with_system(update_scale_factor)
+                    .with_system(update_resizable)
+                    .with_system(update_position)
+                    .with_system(update_minimized)
+                    .with_system(update_maximized)
+                    .with_system(update_resolution)
+                    .with_system(update_cursor_icon)
+                    .with_system(update_cursor_lock_mode)
+                    .with_system(update_cursor_visibility)
+                    .with_system(update_cursor_position)
+                    .with_system(update_resize_contraints)
+                    .with_system(update_present_mode)
+                    .with_system(destroy_windows), // TODO: This should probably go last?


Splitting this into multiple systems seemed like the natural thing to do once the commands are their own events. Having many small systems instead of a big one should make the plugin more approachable to new users wanting to contribute so I hope this does not cause a lot of timing or race-condition issues

We should scan for and resolve system order ambiguities before merging this. That said, I very much appreciate this design.

Weibye · 2022-06-06T17:55:46Z

crates/bevy_window/src/windows.rs

-
-/// A collection of [`Window`]s with unique [`WindowId`]s.
-#[derive(Debug, Default)]
-pub struct Windows {


All places that previously used Windows should now instead do a Query<Entity, With<Window>>

Weibye · 2022-06-06T17:57:52Z

crates/bevy_window/src/window_commands.rs

+#[derive(Debug)]
+pub struct SetTitleCommand {
+    pub entity: Entity,
+    pub title: String,
+}
+
+impl Command for SetTitleCommand {
+    fn write(self, world: &mut World) {
+        if let Some(_) = world.get::<Window>(self.entity) {
+            let mut event = world.resource_mut::<Events<SetTitleCommand>>();
+            event.send(self);
+        } else {
+            panic!("Trying to enact window commands on an entity without a window-component");
+        }
+    }
+}


All window commands now look like this: They are a Command that sends itself as an event that the window backend will pick up

Weibye · 2022-06-06T18:00:59Z

crates/bevy_ecs/src/system/commands/mod.rs

+    // TODO: Can this be solved in any other way?
+    /// Returns true if this commands has the entity present
+    pub fn has_entity(&self, entity: Entity) -> bool {
+        return self.entities.contains(entity);
+    }


This is needed to be able to not grant WindowCommands on an entity that does not exist, see: https://github.com/bevyengine/bevy/pull/4947/files#diff-9e0af223dcea6a0265d880b70764a4362c0c84438fb28f5f558a369cda91021cR27

crates/bevy_render/src/lib.rs

crates/bevy_winit/src/lib.rs

Weibye · 2022-06-26T21:49:47Z

crates/bevy_window/src/lib.rs

+            // if not we'll regress on this
            let window_descriptor = app
                .world
                .get_resource::<WindowDescriptor>()
                .map(|descriptor| (*descriptor).clone())
                .unwrap_or_default();
-            let mut create_window_event = app.world.resource_mut::<Events<CreateWindow>>();
-            create_window_event.send(CreateWindow {
-                id: WindowId::primary(),
-                descriptor: window_descriptor,
-            });
+
+            let window_id = app.world.spawn().id();
+
+            let mut system_state: SystemState<(Commands, ResMut<PrimaryWindow>)> = SystemState::new(&mut app.world);
+            let (mut commands, mut primary_window) = system_state.get_mut(&mut app.world);
+            primary_window.window = Some(window_id);
+            // create_primary_window(commands, primary_window);
+
+
+            let command = CreateWindowCommand { entity: window_id, descriptor: window_descriptor };
+            // Apply the command directly on the world
+            // I wonder if this causes timing issue: this will trigger a CreateWindowCommand event, but will bevy_winit exist in time to listen to the event?
+            command.write(&mut app.world);


TODO: Replace with systemState api

Weibye · 2022-08-06T10:08:52Z

Status: Work has been picked up by @Aceeri over at #5589 as I have shifted focus onto other UI priorities. Will leave this up for now then we close this when #5589 get merged

Nilirad · 2022-08-06T14:30:23Z

@Weibye I think you can just close this, since you can reopen it with just a click if needed.

Weibye · 2022-08-06T18:01:03Z

@Weibye I think you can just close this, since you can reopen it with just a click if needed.

Fair point!

Weibye added 10 commits June 6, 2022 18:20

Replacing Window_id with Entity

3e5ff59

Adding WindowCommandsExtensions for Commands

07da9f5

Exploding Window into multiple coponents

0c11956

Adding WindowCommands to replace methods previously existing on `Wi…

ee35b2a

…ndow`

Adding new ExitCondition

f9a4529

Updating bevy_window to follow new pattern more

0e0c43c

Deleting Windows as this should now be replaced by a query

9325098

Split change_window system into multiple system that handle `Window…

b1f57bb

…Command`s

Start reworking winit_runner()

29453d7

Add initial sketch of example

b64d741

Weibye commented Jun 6, 2022

View reviewed changes

bjorn3 added the M-Needs-Migration-Guide A breaking change to Bevy's public API that needs to be noted in a migration guide label Jun 6, 2022

Weibye force-pushed the windows-as-entities branch from f9b3c3e to b64d741 Compare June 6, 2022 19:12

Weibye added 13 commits June 6, 2022 22:55

Adding notes

1e1599b

Fully implement spawning of created window

00cee99

Start updating bevy_render to new patterns

7c4b815

More cleanup of winit main loop

317fef3

minor fix

28944d5

And more tweaks

1d95cdb

continuing refactor of winit-loop

8df34dc

Finish setting up components for new windows

537e4b0

cleanup

c97365a

Start attempting to get rendering to compile again

0e05569

Updating bevy_text

d852a55

Fixing up bevy_ui

dc6875c

Cleanup

0696336

Weibye added 6 commits June 10, 2022 20:19

Fixing up bevy_ui

aca8773

fixing examples

f6f793a

Fixing up more examples

c2b99cd

Every finally compiles!

98da3ce

Fixing runtime bugs

60e81be

Wrangling with timing issues in render

5099960

Weibye commented Jun 13, 2022

View reviewed changes

crates/bevy_render/src/lib.rs Show resolved Hide resolved

Weibye added 2 commits June 14, 2022 08:48

Window setup operations need to happen during build-time

6182f9f

Further attempts at spawning components in build-time

c409ceb

Weibye commented Jun 26, 2022

View reviewed changes

crates/bevy_winit/src/lib.rs Outdated Show resolved Hide resolved

Using system-state apply

542660a

Weibye commented Jun 26, 2022

View reviewed changes

Weibye self-assigned this Jul 28, 2022

Weibye mentioned this pull request Jul 31, 2022

Split UI Style into multiple components #5511

Open

alice-i-cecile closed this Aug 6, 2022

Weibye deleted the windows-as-entities branch August 18, 2022 19:29

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Windows as `Entities` #4947

Windows as `Entities` #4947

Weibye commented Jun 6, 2022 •

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Nilirad commented Aug 6, 2022

Weibye commented Aug 6, 2022

Windows as Entities #4947

Windows as Entities #4947

Conversation

Weibye commented Jun 6, 2022 • edited Loading

Objective

Solution

High Level Overview

bevy_window changes

Window_id

Window

Windows

WindowCommandsExtension

WindowCommand

PrimaryWindow

bevy_winit changes

bevy_render changes

bevy_text

bevy_ui

Changelog

Migration Guide

Remaining Tasks

Weibye Jun 6, 2022 • edited Loading

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Weibye commented Aug 6, 2022 • edited Loading

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Weibye commented Aug 6, 2022

Windows as `Entities` #4947

Windows as `Entities` #4947

Weibye commented Jun 6, 2022 •

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`bevy_window` changes

`Window_id`

`Window`

`Windows`

`WindowCommandsExtension`

`WindowCommand`

`PrimaryWindow`

`bevy_winit` changes

`bevy_render` changes

`bevy_text`

`bevy_ui`

Weibye Jun 6, 2022 •

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Weibye commented Aug 6, 2022 •

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