Struct CanvasBackend

pub struct CanvasBackend { /* private fields */ }

The backend that is drawing on the HTML canvas TODO: Support double buffering

Implementations

impl CanvasBackend

pub fn new(elem_id: &str) -> Option<Self>

Create a new drawing backend backed with an HTML5 canvas object with given Id

• elem_id The element id for the canvas
• Return either some drawing backend has been created, or none in error case

pub fn with_canvas_object(canvas: HtmlCanvasElement) -> Option<Self>

Create a new drawing backend backend with a HTML5 canvas object passed in

• canvas The object we want to use as backend
• Return either the drawing backend or None for error

Trait Implementations

impl DrawingBackend for CanvasBackend

type ErrorType = CanvasError

The error type reported by the backend

fn get_size(&self) -> (u32, u32)

Get the dimension of the drawing backend in pixels

fn ensure_prepared(&mut self) -> Result<(), DrawingErrorKind<CanvasError>>

Ensure the backend is ready to draw

fn present(&mut self) -> Result<(), DrawingErrorKind<CanvasError>>

Finalize the drawing step and present all the changes. This is used as the real-time rendering support. The backend may implement in the following way, when ensure_prepared is called it checks if it needs a fresh buffer and present is called rendering all the pending changes on the screen.

fn draw_pixel( &mut self, point: BackendCoord, style: BackendColor, ) -> Result<(), DrawingErrorKind<CanvasError>>

Draw a pixel on the drawing backend

fn draw_line<S: BackendStyle>( &mut self, from: BackendCoord, to: BackendCoord, style: &S, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Draw a line on the drawing backend

fn draw_rect<S: BackendStyle>( &mut self, upper_left: BackendCoord, bottom_right: BackendCoord, style: &S, fill: bool, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Draw a rectangle on the drawing backend

fn draw_path<S: BackendStyle, I: IntoIterator<Item = BackendCoord>>( &mut self, path: I, style: &S, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Draw a path on the drawing backend

fn fill_polygon<S: BackendStyle, I: IntoIterator<Item = BackendCoord>>( &mut self, path: I, style: &S, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

fn draw_circle<S: BackendStyle>( &mut self, center: BackendCoord, radius: u32, style: &S, fill: bool, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Draw a circle on the drawing backend

fn draw_text<S: BackendTextStyle>( &mut self, text: &str, style: &S, pos: BackendCoord, ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Draw a text on the drawing backend

fn estimate_text_size<TStyle>( &self, text: &str, style: &TStyle, ) -> Result<(u32, u32), DrawingErrorKind<Self::ErrorType>>

where TStyle: BackendTextStyle,

Estimate the size of the horizontal text if rendered on this backend. This is important because some of the backend may not have font ability. Thus this allows those backend reports proper value rather than ask the font rasterizer for that.

fn blit_bitmap( &mut self, pos: (i32, i32), _: (u32, u32), src: &[u8], ) -> Result<(), DrawingErrorKind<Self::ErrorType>>

Blit a bitmap on to the backend.