Trait RenderBackend 

pub trait RenderBackend: Send {
    type Surface;

    // Required methods
    fn create_surface(
        &self,
        width: u32,
        height: u32,
        bg: &RgbaColor,
    ) -> Self::Surface;
    fn fill_path(
        &mut self,
        surface: &mut Self::Surface,
        ops: &[PathOp],
        fill_rule: FillRule,
        color: &RgbaColor,
        transform: &Matrix,
    );
    fn stroke_path(
        &mut self,
        surface: &mut Self::Surface,
        ops: &[PathOp],
        style: &StrokeStyle,
        color: &RgbaColor,
        transform: &Matrix,
    );
    fn draw_image(
        &mut self,
        surface: &mut Self::Surface,
        image: &DecodedImage,
        transform: &Matrix,
        interpolate: bool,
    );
    fn push_clip(
        &mut self,
        surface: &mut Self::Surface,
        clip: &ClipPath,
        transform: &Matrix,
    );
    fn pop_clip(&mut self, surface: &mut Self::Surface);
    fn push_group(
        &mut self,
        surface: &mut Self::Surface,
        blend_mode: BlendMode,
        opacity: f32,
        isolated: bool,
        knockout: bool,
    );
    fn pop_group(&mut self, surface: &mut Self::Surface);
    fn surface_dimensions(&self, surface: &Self::Surface) -> (u32, u32);
    fn composite_over(&mut self, dst: &mut Self::Surface, src: &Self::Surface);
    fn surface_pixels(&self, surface: &Self::Surface) -> Vec<u8> ;
    fn finish(self, surface: Self::Surface) -> Bitmap;

    // Provided methods
    fn fill_path_no_aa(
        &mut self,
        surface: &mut Self::Surface,
        ops: &[PathOp],
        fill_rule: FillRule,
        color: &RgbaColor,
        transform: &Matrix,
    ) { ... }
    fn set_group_mask(
        &mut self,
        _alpha_data: Vec<u8>,
        _width: u32,
        _height: u32,
    ) { ... }
    fn draw_alpha_bitmap(
        &mut self,
        _surface: &mut Self::Surface,
        _alpha: &[u8],
        _width: u32,
        _height: u32,
        _bearing_x: i32,
        _bearing_y: i32,
        _color: &RgbaColor,
        _transform: &Matrix,
    ) { ... }
    fn set_antialiasing(&mut self, _enabled: bool) { ... }
}

Trait for a 2D rendering backend.

Implementations provide the actual drawing operations (fill, stroke, clip, compositing) using a concrete rendering library (e.g., tiny-skia).

Required Associated Types

type Surface

The surface type used by this backend.

Required Methods

fn create_surface( &self, width: u32, height: u32, bg: &RgbaColor, ) -> Self::Surface

Create a new rendering surface with the given dimensions and background.

fn fill_path( &mut self, surface: &mut Self::Surface, ops: &[PathOp], fill_rule: FillRule, color: &RgbaColor, transform: &Matrix, )

Fill a path with the given color and transform.

fn stroke_path( &mut self, surface: &mut Self::Surface, ops: &[PathOp], style: &StrokeStyle, color: &RgbaColor, transform: &Matrix, )

Stroke a path with the given style, color, and transform.

fn draw_image( &mut self, surface: &mut Self::Surface, image: &DecodedImage, transform: &Matrix, interpolate: bool, )

Draw a decoded image with the given transform.

When interpolate is true, the backend should use bilinear (or higher) filtering instead of nearest-neighbor. This matches PDFium’s auto-bilinear heuristic for upscaled images (see CStretchEngine::UseInterpolateBilinear).

fn push_clip( &mut self, surface: &mut Self::Surface, clip: &ClipPath, transform: &Matrix, )

Push a clipping region onto the clip stack.

fn pop_clip(&mut self, surface: &mut Self::Surface)

Pop the most recent clipping region.

fn push_group( &mut self, surface: &mut Self::Surface, blend_mode: BlendMode, opacity: f32, isolated: bool, knockout: bool, )

Begin a transparency group with the given blend mode, opacity, and transparency group attributes.

fn pop_group(&mut self, surface: &mut Self::Surface)

End the current transparency group, compositing it onto the surface below.

fn surface_dimensions(&self, surface: &Self::Surface) -> (u32, u32)

Return the dimensions (width, height) of the given surface.

fn composite_over(&mut self, dst: &mut Self::Surface, src: &Self::Surface)

Draw the content of src over dst using normal (SourceOver) blending.

This is used to composite rendered content (on a transparent backdrop) onto a background-color surface.

fn surface_pixels(&self, surface: &Self::Surface) -> Vec<u8>

Return the raw pixel data of the surface as premultiplied RGBA bytes.

fn finish(self, surface: Self::Surface) -> Bitmap

Finish rendering and return the final bitmap.

Provided Methods

fn fill_path_no_aa( &mut self, surface: &mut Self::Surface, ops: &[PathOp], fill_rule: FillRule, color: &RgbaColor, transform: &Matrix, )

Fill a path with anti-aliasing forced off.

Used by shading subdivision where upstream PDFium uses full_cover = true to avoid visible seams between adjacent sub-patches.

fn set_group_mask(&mut self, _alpha_data: Vec<u8>, _width: u32, _height: u32)

Set a soft mask on the topmost group entry.

The mask is provided as a single-channel alpha buffer (one byte per pixel, row-major, same dimensions as the surface). Implementations store it so that pop_group can apply the mask during compositing.

fn draw_alpha_bitmap( &mut self, _surface: &mut Self::Surface, _alpha: &[u8], _width: u32, _height: u32, _bearing_x: i32, _bearing_y: i32, _color: &RgbaColor, _transform: &Matrix, )

Draw a pre-rasterized alpha bitmap at the given position with the given color.

The alpha data is a row-major single-channel bitmap. Each pixel in the output should be colored with color modulated by the alpha value.

fn set_antialiasing(&mut self, _enabled: bool)

Set whether anti-aliasing is enabled for subsequent fill/stroke operations.

Backends may ignore this hint. The default implementation is a no-op.

Implementors

impl RenderBackend for TinySkiaBackend

type Surface = SkiaSurface

impl RenderBackend for PsRenderBackend

type Surface = PsSurface