Let users access wgpu resources

[Leif-Rydenfalk]

Background

in Swiftui you can create custom shader effects and apply them to images like so:

Image(systemName: "figure.run.circle.fill")
    .font(.system(size: 300))
    .colorEffect(ShaderLibrary.checkerboard(.float(10), .color(.blue))) 

Proposed changes

• Expose the draw context to the user

What it allows for the user

• GPU Computation for particle systems etc
• Rendering custom ui elements
• Custom renderer

OR / AND

Proposed changes

• Add a way for the user to create a custom wgsl effect. Example api:

let effect = vger::Effect::from_source("examples/gaussian_blur.wgsl");
vger.apply_effect(effect);

or

view.apply_effect(effect)

in use

// draws a blurred white circle. 
fn main() {
    canvas(|_, rect, vger| {
        vger.translate(rect.center() - LocalPoint::zero());
        let radius = 100.0;
        let paint = vger.color_paint(vger::Color {
            r: 1.0,
            g: 1.0,
            b: 1.0,
            a: 1.0,
        });
        vger.fill_circle(LocalPoint::zero(), radius, paint);
	let effect = vger::Effect::from_source("examples/gaussian_blur.wgsl");
	vger.apply_effect(effect);
    })
    .run()
}

What it allows for the user

• Shader effects which could be applied in theory to any view like shadows, color grading, blurs

[wtholliday]

What would the shader look like?

In SwiftUI, it's quite easy to write the shaders due to the [[stitchable]] attribute. See https://www.hackingwithswift.com/quick-start/swiftui/how-to-add-metal-shaders-to-swiftui-views-using-layer-effects

Would apply_effect apply to the entire window? That could be expensive and not desired. How would uniforms be passed to the shaders?