Add image-scaling property to Images to control how they are scaled

[ryban]

Like CSS image-rendering it has "smooth" and "pixelated" options. Only OpenGL has been tested right now, have not tested WASM or Qt. Right now the first instance of a @image-url() will set the scaling for that specific image. The same image used from memory on the otherhand can all have a different scaling property.

Still need to update documentation, but I wanted to get other backends working, possibly fix the image-url issue, and ask if there is a better way to implement this first.

[CLAassistant]

All committers have signed the CLA.

[ogoffart]

Thanks for your contribution, this is very welcome.

It looks good to me, I just have a few minor point:

• The CI is failing because you added the example in Cargo.toml, but you forgot to git add the examples. I don't think there should be a rust example for that, but if it is just a .60 file it can be added in tests/cases/examples
• it is missing the Qt backend implementation. It should be trivial to add as well (just add the right flag to the painter) But i'd understand if you don't have Qt and i can just add this myself
• As you said, it's missing documentation and changelog entry.

Since the wasm backend is the same as the GL backend, i imagine it should work out of the box.

Then, there is the question of naming.
With CSS, it is called image-rendering https://developer.mozilla.org/en-US/docs/Web/CSS/image-rendering
I think it might make more sense to keep the same name as CSS. Maybe @tronical will have an opinion the name as well.

[ryban]

Yeah, I forgot to remove the example from Cargo.toml because the example was not really interesting. I don't have Qt so I hadn't implemented it, but if someone else can implement it that would help. I did get wasm to compile after working through a perl issue and it does work as expected.

I chose image-scaling instead of image-rendering to be more direct on what the setting is doing, but thinking about it image-scaling could be misinterpreted as a scaling factor. Plus there is value in keeping with what people know.

[tronical]

I very much like the name as proposed in the latest patch set :-) (image-rendering). Nice addition!

[ogoffart]

Looks good to me 👍

Only thing is to fix CI because the test has an error, and one should do cargo fmt

[ogoffart]

Suggested change

import { HorizontalLayout } from "sixtyfps_widgets.60";

Not needed because HorizontalLayout is a builtin element

[ogoffart]

Thank you!

I'll do the Qt backend changes now

[ogoffart]

I done the Qt backend.

Btw, i noticed a bug: the image-rendering property is not properly applied if both image are the same file with the GL backend, because the cached texture contains the image-rendering flag, but it is not part of the cache key.

[ryban]

Thanks for merging and adding Qt support. Yeah, which ever Image instance references a file first "locks in" the image-rendering setting for that image. I wasn't sure how to change the cache key.