Windowless

[psivasubramanian]

No description provided.

[philn]

What is the use-case for this?

[psivasubramanian]

Windowless backend support with Keyboard and Mouse events

[zdobersek]

"Windowless" in what way?

Why enabling PLATFORM(WAYLAND) then?

What's the point of this backend?

[psivasubramanian]

It's Wayland backend only and the name windowless is since webprocess itself is used for rendering.

[kraj]

is windowless'ness related to compositor here since you are using wayland backend so it can be another backend I hope.

[psivasubramanian]

Thanks @zdobersek for taking pain to answer. Here are some of the questions

1. Dummy viewbackend implementation is not required? Does bypassing Viewbackend mean that?
2. All these changes including key & mouse event support should be under Source/WPE only?

[zdobersek]

1. ViewBackend implementation is required, but it would only ever send the frameComplete() call back to the client in the commitBuffer() function. See the IntelCE backend, but ignore the GDL initialization.
   https://github.com/Metrological/WebKitForWayland/blob/master/Source/WPE/Source/ViewBackend/IntelCE/ViewBackendIntelCE.cpp
2. No big changes should be done outside Source/WPE, and definitely not anything under PLATFORM(WAYLAND) -- we shouldn't use that code in any configuration.

Input events are are problematic in this setup, because they must be piped to the client that ViewBackend provides in setInputClient() -- that's set in stone, and can't be changed or worked around. But the Wayland client is now running in the WebProcess so you have to somehow pipe the events back to the client that's in the UIProcess.

[psivasubramanian]

@zdobersek@kraj
Here are the review changes approach to get this code merged.

1. Modifying our current ViewBackend (Windowless implementation) commitBuffer method to actually send only the frameComplete() callback.
2. Moving all changes (outside of Source/WPE including input event handling) to our new RenderingBackend implementation.
3. Sending the input events from RenderingBackend to ViewBackend through IPC like
   CompositorManager (Webprocess) ---------> CompositorManagerProxy (UIProcess) and then to ViewBackend. Of course this messaging implementation(Webprocess to UIProcess) will be outside Source/WPE.
4. Modifying ViewBackend implementation to add input events handler methods which will send those events to input client.
5. Planning to rename this backend since current name "windowless" is confusing.
   Kindly comment on this approach steps.

[zdobersek]

1, 2, and 5 are fine. I recommend doing these first.

In the next two weeks I expect to switch over various ViewBackend and RenderingBackend implementations to the new WPE library:
https://github.com/WebKitForWayland/webkit/tree/wpe-ng
https://github.com/WebKitForWayland/webkit/tree/wpe-ng/Source/ThirdParty/WPE

This infrastructure would allow constructing additional IPC channels between the ViewBackend (in the future wpe_view_backend) and the RenderingBackend (in the future wpe_renderer_backend_egl), not being limited only to WK2 IPC. It's through these additional IPCs that buffer management will be done, and it would also be possible to communicate events from the WebProcess to the UIProcess through there.

So I'd recommend holding off 3 and 4 until that work is completed (I hope to be done in 2 weeks), after which point the event routing will be possible outside of WebKit.

[psivasubramanian]

Thanks @zdobersek
We started implementing the changes mentioned in my comment namely point 1,2 & 5 first.

[psivasubramanian]

@zdobersek@kraj & others
I have implemented review changes 1,2 & 5 as you suggested. Can you kindly guide on upstreaming it to the same pull request. I tried few experiments, but not able to upstream.

[psivasubramanian]

Closing this as new review #57 is merged to mainstream. Thanks @zdobersek@kraj and others.