Trait piet::RenderContext

pub trait RenderContextwhere
    Self::Brush: IntoBrush<Self>,{
    type Brush: Clone;
    type Text: Text<TextLayout = Self::TextLayout>;
    type TextLayout: TextLayout;
    type Image: Image;

    fn status(&mut self) -> Result<(), Error>;
    fn solid_brush(&mut self, color: Color) -> Self::Brush;
    fn gradient(
        &mut self,
        gradient: impl Into<FixedGradient>
    ) -> Result<Self::Brush, Error>;
    fn clear(&mut self, region: impl Into<Option<Rect>>, color: Color);
    fn stroke(
        &mut self,
        shape: impl Shape,
        brush: &impl IntoBrush<Self>,
        width: f64
    );
    fn stroke_styled(
        &mut self,
        shape: impl Shape,
        brush: &impl IntoBrush<Self>,
        width: f64,
        style: &StrokeStyle
    );
    fn fill(&mut self, shape: impl Shape, brush: &impl IntoBrush<Self>);
    fn fill_even_odd(&mut self, shape: impl Shape, brush: &impl IntoBrush<Self>);
    fn clip(&mut self, shape: impl Shape);
    fn text(&mut self) -> &mut Self::Text;
    fn draw_text(&mut self, layout: &Self::TextLayout, pos: impl Into<Point>);
    fn save(&mut self) -> Result<(), Error>;
    fn restore(&mut self) -> Result<(), Error>;
    fn finish(&mut self) -> Result<(), Error>;
    fn transform(&mut self, transform: Affine);
    fn make_image(
        &mut self,
        width: usize,
        height: usize,
        buf: &[u8],
        format: ImageFormat
    ) -> Result<Self::Image, Error>;
    fn draw_image(
        &mut self,
        image: &Self::Image,
        dst_rect: impl Into<Rect>,
        interp: InterpolationMode
    );
    fn draw_image_area(
        &mut self,
        image: &Self::Image,
        src_rect: impl Into<Rect>,
        dst_rect: impl Into<Rect>,
        interp: InterpolationMode
    );
    fn capture_image_area(
        &mut self,
        src_rect: impl Into<Rect>
    ) -> Result<Self::Image, Error>;
    fn blurred_rect(
        &mut self,
        rect: Rect,
        blur_radius: f64,
        brush: &impl IntoBrush<Self>
    );
    fn current_transform(&self) -> Affine;

    fn with_save(
        &mut self,
        f: impl FnOnce(&mut Self) -> Result<(), Error>
    ) -> Result<(), Error> { ... }
}

The main trait for rendering graphics.

This trait provides an API for drawing 2D graphics. In basic usage, it wraps a surface of some kind, so that drawing commands paint onto the surface. It can also be a recording context, creating a display list for playback later.

The intent of the design is to be general so that any number of back-ends can implement this trait.

Code that draws graphics will in general take &mut impl RenderContext.

Required Associated Types

type Brush: Clone

The type of a “brush”.

Represents solid colors and gradients.

type Text: Text<TextLayout = Self::TextLayout>

An associated factory for creating text layouts and related resources.

type TextLayout: TextLayout

The type use to represent text layout objects.

type Image: Image

The associated type of an image.

Required Methods

fn status(&mut self) -> Result<(), Error>

Report an internal error.

Drawing operations may cause internal errors, which may also occur asynchronously after the drawing command was issued. This method reports any such error that has been detected.

fn solid_brush(&mut self, color: Color) -> Self::Brush

Create a new brush resource.

TODO: figure out how to document lifetime and rebuilding requirements. Should that be the responsibility of the client, or should the back-end take responsibility? We could have a cache that is flushed when the Direct2D render target is rebuilt. Solid brushes are super lightweight, but other potentially retained objects will be heavier.

fn gradient(
    &mut self,
    gradient: impl Into<FixedGradient>
) -> Result<Self::Brush, Error>

Create a new gradient brush.

fn clear(&mut self, region: impl Into<Option<Rect>>, color: Color)

Replace a region of the canvas with the provided Color.

The region can be omitted, in which case it will apply to the entire canvas.

This operation ignores any existing clipping and transforations.

Note:

You probably don’t want to call this. It is essentially a specialized fill method that can be used in GUI contexts for things like clearing damage regions. It does not have a good cross-platform implementation, and eventually should be deprecated when support is added for blend modes, at which point it will be easier to just use fill for everything.

fn stroke(&mut self, shape: impl Shape, brush: &impl IntoBrush<Self>, width: f64)

Stroke a Shape, using the default StrokeStyle.

fn stroke_styled(
    &mut self,
    shape: impl Shape,
    brush: &impl IntoBrush<Self>,
    width: f64,
    style: &StrokeStyle
)

Stroke a Shape, providing a custom StrokeStyle.

fn fill(&mut self, shape: impl Shape, brush: &impl IntoBrush<Self>)

Fill a Shape, using the non-zero fill rule.

fn fill_even_odd(&mut self, shape: impl Shape, brush: &impl IntoBrush<Self>)

Fill a shape, using the even-odd fill rule.

fn clip(&mut self, shape: impl Shape)

Clip to a Shape.

All subsequent drawing operations up to the next restore are clipped by the shape.

fn text(&mut self) -> &mut Self::Text

Returns a reference to a shared Text object.

This provides access to the text API.

fn draw_text(&mut self, layout: &Self::TextLayout, pos: impl Into<Point>)

Draw a TextLayout.

The pos parameter specifies the upper-left corner of the layout object (even for right-to-left text). To draw on a baseline, you can use TextLayout::line_metric to get the baseline position of a specific line.

fn save(&mut self) -> Result<(), Error>

Save the context state.

Pushes the current context state onto a stack, to be popped by restore.

Prefer with_save if possible, as that statically enforces balance of save/restore pairs.

The context state currently consists of a clip region and an affine transform, but is expected to grow in the near future.

fn restore(&mut self) -> Result<(), Error>

Restore the context state.

Pop a context state that was pushed by save. See that method for details.

fn finish(&mut self) -> Result<(), Error>

Finish any pending operations.

This will generally be called by a shell after all user drawing operations but before presenting. Not all back-ends will handle this the same way.

fn transform(&mut self, transform: Affine)

Apply a transform.

Apply an affine transformation. The transformation remains in effect until a restore operation.

fn make_image(
    &mut self,
    width: usize,
    height: usize,
    buf: &[u8],
    format: ImageFormat
) -> Result<Self::Image, Error>

Create a new Image from a pixel buffer.

This takes raw pixel data and attempts create an object that the platform knows how to draw.

The generated image can be cached and reused. This is a good idea for images that are used frequently, because creating the image type may be expensive.

To draw the generated image, pass it to draw_image. To draw a portion of the image, use draw_image_area.

If you are trying to create an image from the contents of this RenderContext, see capture_image_area.

fn draw_image(
    &mut self,
    image: &Self::Image,
    dst_rect: impl Into<Rect>,
    interp: InterpolationMode
)

Draw an Image into the provided Rect.

The image is scaled to fit the provided Rect; it will be squashed if the aspect ratios don’t match.

fn draw_image_area(
    &mut self,
    image: &Self::Image,
    src_rect: impl Into<Rect>,
    dst_rect: impl Into<Rect>,
    interp: InterpolationMode
)

Draw a specified area of an Image.

The src_rect area of image is scaled to the provided dst_rect. It will be squashed if the aspect ratios don’t match.

fn capture_image_area(
    &mut self,
    src_rect: impl Into<Rect>
) -> Result<Self::Image, Error>

Create an Image of the specified region of the context.

The src_rect area of the current render context will be captured as a copy and returned.

This can be used for things like caching expensive drawing operations.

fn blurred_rect(
    &mut self,
    rect: Rect,
    blur_radius: f64,
    brush: &impl IntoBrush<Self>
)

Draw a rectangle with Gaussian blur.

The blur radius is sometimes referred to as the “standard deviation” of the blur.

fn current_transform(&self) -> Affine

Returns the transformations currently applied to the context.

Provided Methods

fn with_save(
    &mut self,
    f: impl FnOnce(&mut Self) -> Result<(), Error>
) -> Result<(), Error>

Do graphics operations with the context state saved and then restored.

Equivalent to save, calling f, then restore. See those methods for more details.

Implementors