Major redesign

[bvssvni]

Example:

graphics::Rectangle::new(color)
    .draw(rect, c, g);

I want to investigate an alternative design, where each drawable shape is a type, such that it can be used without transformation context.

• Add drawable shapes with pub fields
• Context should only contain view and transform matrix

Drawable shapes:

• Ellipse
• Image
• Line
• Polygon
• Rectangle

Todo:

• Create a new branch "newdesign"

[bvssvni]

Perhaps we could use the Get and Modifier convention from piston-current. This can be implemented directly on the drawable shapes. It is possible to use .set as immutable operation if the type is Copy.

[bvssvni]

This reminds me of PistonDevelopers/piston#736 where you blur out the distinction between state and function.

[bvssvni]

One approach is to use context types, but with defaults set to concrete types. The drawback is that you have to use traits:

#![feature(default_type_params)]

pub struct Image<C = [f32, ..4], SR = [i32, ..4]> {
    pub color: C,
    pub source_rectangle: SR
}

pub trait DrawImage {
    fn draw(&self);
}

impl DrawImage for Image {
    fn draw(&self) {}
}

impl DrawImage for Image<(), ()> {
    fn draw(&self) {}
}

fn main() {
    Image { color: (), source_rectangle: () }.draw();
}

[bvssvni]

Another approach is to use Option which lets you use the builder pattern:

pub struct Image {
    pub color: Option<[f32, ..4]>,
    pub source_rectangle: Option<[i32, ..4]>
}

impl Image {
    pub fn draw(&self) {}
}

fn main() {
    Image { color: None, source_rectangle: None }.draw();
}

This could be used like this:

Image::new().set(Color(...)).set(SourceRectangle(...)).draw(texture, c, g);

[bvssvni]

One benefit by separating the shape is that you can reuse and modify how you draw in multiple ways and it does not depend on the type. For example, you can change the color by adding your own ways of modifying it in an ad-hoc way. You can also write a different draw method for another texture type.

[bvssvni]

Done.