[−][src]Trait graphics::Graphics

pub trait Graphics: Sized {
    type Texture: ImageSize;
    fn clear_color(&mut self, color: Color);
    fn clear_stencil(&mut self, value: u8);
    fn tri_list<F>(&mut self, draw_state: &DrawState, color: &[f32; 4], f: F)
    where
        F: FnMut(&mut dyn FnMut(&[[f32; 2]]));
    fn tri_list_uv<F>(
        &mut self, 
        draw_state: &DrawState, 
        color: &[f32; 4], 
        texture: &Self::Texture, 
        f: F
    )
    where
        F: FnMut(&mut dyn FnMut(&[[f32; 2]], &[[f32; 2]]));

    fn rectangle<R: Into<Rectangle>>(
        &mut self, 
        r: &Rectangle, 
        rectangle: R, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn polygon(
        &mut self, 
        p: &Polygon, 
        polygon: Polygon<'_>, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn polygon_tween_lerp(
        &mut self, 
        p: &Polygon, 
        polygons: Polygons<'_>, 
        tween_factor: Scalar, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn image(
        &mut self, 
        image: &Image, 
        texture: &Self::Texture, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn ellipse<R: Into<Rectangle>>(
        &mut self, 
        e: &Ellipse, 
        rectangle: R, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn line<L: Into<Line>>(
        &mut self, 
        l: &Line, 
        line: L, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
    fn circle_arc<R: Into<Rectangle>>(
        &mut self, 
        c: &CircleArc, 
        rectangle: R, 
        draw_state: &DrawState, 
        transform: Matrix2d
    ) { ... }
}

Implemented by all graphics back-ends.

An example back-end using raw OpenGL

By default, this design uses triangles as graphics primitives. This is supported by all GPUs and easy to implement in shader languages.

Default trait methods can be overridden for better performance or higher quality.

When drawing, use this trait as generic constraint:

use graphics::{Graphics, Context};

fn draw<G: Graphics>(c: &Context, g: &mut G) {
    //...
}

Color space is sRGB.

Notice for back-end authors

When sRGB is enabled for a back-end shader, the gamma must be converted to linear space when used as vertex color or uniform parameter. To convert gamma, use color::gamma_srgb_to_linear.

For more information, see https://github.com/PistonDevelopers/piston/issues/1014.

Associated Types

`type Texture: ImageSize`

The texture type associated with the back-end.

In generic code, this type is often unknown. This might lead to more boilerplate code:

use graphics::{Graphics, Context, ImageSize};

fn draw_texture<G, T>(c: &Context, g: &mut G)
    where G: Graphics<Texture = T>, T: ImageSize {
    //...
}

Code written specifically for one back-end can be easier to write. Later, when the code is done, it can be refactored into generic code.

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Required methods

`fn clear_color(&mut self, color: Color)`

Clears background with a color.

The color should replace the values in the buffer.

Color space is sRGB.

`fn clear_stencil(&mut self, value: u8)`

Clears stencil buffer with a value, usually 0.

A stencil buffer contains values that are not visible on the screen. These values are used to test against the pixel to paint.

If you are drawing a shape for clipping and forgot to clear the stencil buffer, then the clipping shape will carry over in next frame and cause artifacts.

`fn tri_list<F>(&mut self, draw_state: &DrawState, color: &[f32; 4], f: F) where F: FnMut(&mut dyn FnMut(&[[f32; 2]])),`

Renders list of 2d triangles using a solid color.

All vertices share the same color.

The back-end calls the closure with a closure to receive vertices. First, the back-end sets up shaders and such to prepare. Then it calls the closure, which calls back with chunks of vertices. The number of vertices per chunk never exceeds BACK_END_MAX_VERTEX_COUNT. Vertex positions are encoded [[x0, y0], [x1, y1], ...].

Color space is sRGB.

`fn tri_list_uv<F>( &mut self, draw_state: &DrawState, color: &[f32; 4], texture: &Self::Texture, f: F ) where F: FnMut(&mut dyn FnMut(&[[f32; 2]], &[[f32; 2]])),`

Renders list of 2d triangles using a color and a texture.

All vertices share the same color.

Tip: For objects of different colors, use grayscale textures. The texture color gets multiplied with the color.

A texture coordinate is assigned per vertex (from [0, 0] to [1, 1]).

The back-end calls the closure with a closure to receive vertices. First, the back-end sets up shaders and such to prepare. Then it calls the closure, which calls back with chunks of vertices. The number of vertices per chunk never exceeds BACK_END_MAX_VERTEX_COUNT. Vertex positions are encoded [[x0, y0], [x1, y1], ...]. Texture coordinates are encoded [[u0, v0], [u1, v1], ...].

Chunks uses separate buffer for vertex positions and texture coordinates. Arguments are |vertices: &[f32], texture_coords: &[f32].

Color space is sRGB.

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Provided methods

`fn rectangle<R: Into<Rectangle>>( &mut self, r: &Rectangle, rectangle: R, draw_state: &DrawState, transform: Matrix2d )`

Draws a rectangle.

Can be overriden in the back-end for higher performance.

Instead of calling this directly, use Rectangle::draw.