Iced is a lower level GUI library, similar to what GDK is to GTK. We built our own COSMIC-themed GUI toolkit around iced, which is called libcosmic. As we've gotten more and more widgets and application logic developed, actual application development with libcosmic is a breeze. Even if you do have to create a custom widget, it's much easier to creating custom widgets in GTK. We're able to develop much faster than we ever could with GTK now.
Yew and Leptos aren't comparable since they're not native GUI toolkits. These are for web developers rather than application development. It wouldn't be possible to use this for developing layer shell applets for COSMIC, either.
Btw, is this the only reason that cosmic isn't gtk, or are there other reasons? Because afiak gtk uses/can use rust.
The GTK4 project was cancelled for multiple reasons. We originally began working on Relm4 to use GTK4 for COSMIC applets. While others on the team were also experimenting with alternative Rust GUI libraries.
It required a lot of effort to patch GTK4 to support the Wayland layer shell protocol. Getting those patches merged into GTK4 was also taking a much longer time. There were long delays between code reviews; and they also wanted a series of much larger refactoring changes to be made to GTK4 before exposing the layer shell feature. It was much easier to get layer-shell working with iced, as it is a much leaner and concise code base.
GTK does not support fractional scaling, which is something we want our applets to support on day one. This was one of our major concerns. A concern that didn't apply to iced.
It was also exceedingly difficult to create custom widgets with GTK in Rust. Even those of us with years of experience considered it to be unreasonably difficult. So it was not feasible to expect new hires on the team to be able to comfortably develop COSMIC components with it. In comparison, our team was able to develop custom widgets with iced with much less effort and with greater flexibility, so the demand for iced grew stronger.
At the end of the day, GTK is not a Rust toolkit, and its API is cumbersome to adapt to Rust. Use of GTK would always be a compromise that lessens the developer experience for COSMIC app and applet development. A compromise that would eventually require us to rewrite everything in a native Rust GUI library the moment it would become possible to do so.
Since we are developing a desktop environment from the ground up anyway, we decided that there would be much more value for our time if we contribute to the Rust ecosystem and utilize iced to make a fully featured GUI library for application development.
Makes sense, thank you for the detailed answer! By the way, I saw that gtk apps will be automatically themed, is that only gtk3 or also gtk4?
Edit: typo
We will be adding integrations to our theme engine to automatically generate themes for GTK3, GTK4, and libadwaita.
Great! Cant wait to try out cosmic, thank you for all the great work you guys have been doing!
Why develop libcosmic around iced instead of going with something else modern that's easy to develop in such as Flutter? Iced/libcosmic is probably a bit more efficient resource-wise but that probably wasn't a huge point.
That would compromise our vision of a GUI platform built from the ground up in Rust. It would also not be feasible to use Flutter for applet development. We can easily make modifications directly to iced for all the Wayland integrations that we need in COSMIC, as the iced code base is very lean, and written in Rust.
Got it. So being written in Rust is one of the requirements. Makes sense. Flutter is great for self-contained applications but we can definitely use another sane native toolkit besides Qt that has wider applicability.
Iced is a lower level GUI library, similar to what GDK is to GTK. We built our own COSMIC-themed GUI toolkit around iced, which is called libcosmic. As we've gotten more and more widgets and application logic developed, actual application development with libcosmic is a breeze. Even if you do have to create a custom widget, it's much easier to creating custom widgets in GTK. We're able to develop much faster than we ever could with GTK now.
Yew and Leptos aren't comparable since they're not native GUI toolkits. These are for web developers rather than application development. It wouldn't be possible to use this for developing layer shell applets for COSMIC, either.
Btw, is this the only reason that cosmic isn't gtk, or are there other reasons? Because afiak gtk uses/can use rust.
The GTK4 project was cancelled for multiple reasons. We originally began working on Relm4 to use GTK4 for COSMIC applets. While others on the team were also experimenting with alternative Rust GUI libraries.
It required a lot of effort to patch GTK4 to support the Wayland layer shell protocol. Getting those patches merged into GTK4 was also taking a much longer time. There were long delays between code reviews; and they also wanted a series of much larger refactoring changes to be made to GTK4 before exposing the layer shell feature. It was much easier to get layer-shell working with iced, as it is a much leaner and concise code base.
GTK does not support fractional scaling, which is something we want our applets to support on day one. This was one of our major concerns. A concern that didn't apply to iced.
It was also exceedingly difficult to create custom widgets with GTK in Rust. Even those of us with years of experience considered it to be unreasonably difficult. So it was not feasible to expect new hires on the team to be able to comfortably develop COSMIC components with it. In comparison, our team was able to develop custom widgets with iced with much less effort and with greater flexibility, so the demand for iced grew stronger.
At the end of the day, GTK is not a Rust toolkit, and its API is cumbersome to adapt to Rust. Use of GTK would always be a compromise that lessens the developer experience for COSMIC app and applet development. A compromise that would eventually require us to rewrite everything in a native Rust GUI library the moment it would become possible to do so.
Since we are developing a desktop environment from the ground up anyway, we decided that there would be much more value for our time if we contribute to the Rust ecosystem and utilize iced to make a fully featured GUI library for application development.
Makes sense, thank you for the detailed answer! By the way, I saw that gtk apps will be automatically themed, is that only gtk3 or also gtk4? Edit: typo
We will be adding integrations to our theme engine to automatically generate themes for GTK3, GTK4, and libadwaita.
Great! Cant wait to try out cosmic, thank you for all the great work you guys have been doing!
Why develop libcosmic around iced instead of going with something else modern that's easy to develop in such as Flutter? Iced/libcosmic is probably a bit more efficient resource-wise but that probably wasn't a huge point.
That would compromise our vision of a GUI platform built from the ground up in Rust. It would also not be feasible to use Flutter for applet development. We can easily make modifications directly to iced for all the Wayland integrations that we need in COSMIC, as the iced code base is very lean, and written in Rust.
Got it. So being written in Rust is one of the requirements. Makes sense. Flutter is great for self-contained applications but we can definitely use another sane native toolkit besides Qt that has wider applicability.