Implement proper decorationless popups by specifying the type of the child window with with_type()
With this commit, different kind of child windows can be created
- Popups: Special windows without any decoration which can be positioned relative to the parent
- Window: Normal window with a parent or not
The type can be specified during creation of the Window using the window_attributes and the with_type() function. As default a normal Window is used. If Popup is choosen a parent must be specified, otherwise the Popup creation fails with an Error returned by the new() function.
Related issues: #403 and #4256
This commit implements a new API for drag and drop, with a `DataTransfer` type which abstracts over the various clipboard/drag and drop APIs across different platforms. I built this on top of #2429 although admittedly I ended up removing pretty much all of their work while I was reworking the design.
This is being built in order to help support [drag-and-drop work](https://github.com/slint-ui/slint/issues/1967) in Slint's winit backend. As part of that work, I did extensive research on how drag-and-drop and clipboard APIs are implemented across different platforms, and wrote a (still WIP) research document that can be found [here](https://gist.github.com/eira-fransham/06750cf8d25ade08d362a0ca8dfafe06).
The new API is inspired by the browser's [`DataTransfer`](https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer) API.
Allow updating IME state atomically to make it easier for platforms
where it's atomic by its nature, like Wayland. The old API is marked
as deprecated and is routed to the new atomic API.
Co-authored-by: dcz <gilapfco.dcz@porcupinefactory.org>
