When using multiple windows on webgl, an error is displayed

[zhuliang198754]

Description

When using multiple windows on the WEBGL platform, the rendering position of the non-main window is displayed incorrectly, but WEBGPU is normal

             let second_window = commands
                .spawn((
                    Window {
                        title: "xxx".to_owned(),
                        canvas: Some(canvas_id),
                        transparent: true,
                        composite_alpha_mode: if adapter.backend == wgpu_types::Backend::Gl
                        {
                            bevy::window::CompositeAlphaMode::default()
                        } else {
                            bevy::window::CompositeAlphaMode::PreMultiplied
                        },
                        fit_canvas_to_parent: false,
                        ..default()
                    },
                ))
                .id();

            let second_window_camera = commands
                .spawn((
                    Camera3dBundle {
                        tonemapping: Tonemapping::None,
                        camera: Camera {
                            target: RenderTarget::Window(WindowRef::Entity(second_window)),
                            ..default()
                        },
                        ..default()
                    },
                ))
                .id();

Tested browsers

Chrome, Microsoft Edge

Tested devices

windows

Winit version

0.30

[zhuliang198754]

I haven't found the problem yet, does anyone know the reason?

[daxpedda]

I'm unable to understand the bug report:

• Where is the second "window" in the screenshot?
• This is not the Bevy repository, it is Winit. However if a minimal reproducible example (even with Bevy) is given I'm willing to take a look.
• "the rendering position of the non-main window is displayed incorrectly" what does that mean?
  • Do you mean its not rendered at the correct position?
  • How did you determine or set the position?
  • How is it incorrect?

I'm gonna go ahead and close this, but please tell us if you have any answers to these questions!

[zhuliang198754]

I'm unable to understand the bug report:

• Where is the second "window" in the screenshot?

• This is not the Bevy repository, it is Winit. However if a minimal reproducible example (even with Bevy) is given I'm willing to take a look.

• "the rendering position of the non-main window is displayed incorrectly" what does that mean?

  • Do you mean its not rendered at the correct position?
  • How did you determine or set the position?
  • How is it incorrect?

I'm gonna go ahead and close this, but please tell us if you have any answers to these questions!

@daxpedda

When more than two windows are instantiated and all windows are associated with canvas, the problem of display not being at the canvas position occurs.

[zhuliang198754]

@daxpedda Only webgl is wrong

[daxpedda]

the problem of display not being at the canvas position occurs.

What is a "display"?
Are you saying that what you draw is not drawn at the position of the canvas?

---

It would help if you try to answer the questions directly.

I did try this locally and everything seems to work correctly.
It might be an issue in Wgpu, see gfx-rs/wgpu#2343, I didn't try with Wgpu yet, but I will when I get to it.

[zhuliang198754]

the problem of display not being at the canvas position occurs.

What is a "display"? Are you saying that what you draw is not drawn at the position of the canvas?

It would help if you try to answer the questions directly.

I did try this locally and everything seems to work correctly. It might be an issue in Wgpu, see gfx-rs/wgpu#2343, I didn't try with Wgpu yet, but I will when I get to it.

Thank you so much。It's the same situation gfx-rs/wgpu#2343