QT host

[redtide]

I started to create a Qt host for elements but I'm not sure if this is really doable with the current status of Cairo Qt backend.
I made a custom QWidget where to forward all required signals/events to elements but I'm not sure how to access the host_view (mainly for the Cairo surface). Any advice?

[djowel]

I am not familiar with QT. I'm not sure how I can help. What do you mean by accessing the host_view?

[redtide]

The host_view class is declared in base_view.cpp, IIUC that is the one to use for cairo access to the surface.
But I see there are some problems to interface cairo with Qt, there was some work years ago but it seems it's still a work in progress.
How is going the Artist port? I saw Skia has some more documentation and examples to use with Qt.

[djowel]

Are you working on something like @jpcima's PR here: #111 ?

Artist is fine. I just need some time to integrate it. It's a bandwidth issue for me at the moment. But I'll get time one way or another.

[redtide]

Just trying to make a Qt5 host implementation, to be able to add elements over a view implemented in a QWidget, inside a QMainWindow.

[djowel]

Just trying to make a Qt5 host implementation, to be able to add elements over a view implemented in a QWidget, inside a QMainWindow.

That's certainly a good use-case!

[djowel]

Ok, let's see... There's actually an artist branch already (https://github.com/cycfi/elements/tree/artist_port). It's not by any means in a good state yet. I'm really tempted to have artist into elements sooner rather than later. My worry is that it will require a lot of time from me, which I do not have for the moment. The issue is not actually the port itself, but the maintenance of it after the port. The plan was to back-port element's cairo based canvas into artist first. Then have the cairo ported artist in elements as default 'canvas' backend. That would prevent a big disruption.

There's talk of a roadmap in another "issue". I'll start a draft and add this there.

In the meantime, do you have a simple example project for creating a qt window and widget I can look at, and we can discuss? I'm not a QT user, but that might inspire some ideas.

[jpcima]

If I may add to this discussion, there are multiple strategies to go for the implementation.

• create an intermediate image surface, paint on it, and transfer pixels to the qt widget
  (slow, but tolerable if UI doesn't move too much)
• extract the platform-dependent draw context (HDC/Quartz port/Xlib drawable) if possible, and make cairo paint on it
• create an OpenGL widget, setup a 2d context, and create a cairo painter to target OpenGL

[redtide]

I'm not sure what you requested is a simple Qt example or a basic Qt elements host case, on which I have only implemented the application and window classes, not having a view yet I can't provide a widget.