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Experimental WebAPI

OffscreenCanvas

Values

addEventListener

Appends an event listener for events whose type attribute value is type. The callback argument sets the callback that will be invoked when the event is dispatched.

The options argument sets listener-specific options. For compatibility this can be a boolean, in which case the method behaves exactly as if the value was specified as options's capture.

When set to true, options's capture prevents callback from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE. When false (or not present), callback will not be invoked when event's eventPhase attribute value is CAPTURING_PHASE. Either way, callback will be invoked if event's eventPhase attribute value is AT_TARGET.

When set to true, options's passive indicates that the callback will not cancel the event by invoking preventDefault(). This is used to enable performance optimizations described in § 2.8 Observing event listeners.

When set to true, options's once indicates that the callback will only be invoked once after which the event listener will be removed.

If an AbortSignal is passed for options's signal, then the event listener will be removed when signal is aborted.

The event listener is appended to target's event listener list and is not appended if it has the same type, callback, and capture. Read more on MDN

let addEventListener: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~type_: WebAPI.EventAPI.eventType,
  ~callback: WebAPI.EventAPI.eventListener<'event>,
  ~options: WebAPI.EventAPI.addEventListenerOptions=?,
) => unit

Parameters

WebAPI.CanvasAPI.offscreenCanvas WebAPI.EventAPI.eventType WebAPI.EventAPI.eventListener option< WebAPI.EventAPI.addEventListenerOptions >

Return type

unit

addEventListener_useCapture

Appends an event listener for events whose type attribute value is type. The callback argument sets the callback that will be invoked when the event is dispatched.

The options argument sets listener-specific options. For compatibility this can be a boolean, in which case the method behaves exactly as if the value was specified as options's capture.

When set to true, options's capture prevents callback from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE. When false (or not present), callback will not be invoked when event's eventPhase attribute value is CAPTURING_PHASE. Either way, callback will be invoked if event's eventPhase attribute value is AT_TARGET.

When set to true, options's passive indicates that the callback will not cancel the event by invoking preventDefault(). This is used to enable performance optimizations described in § 2.8 Observing event listeners.

When set to true, options's once indicates that the callback will only be invoked once after which the event listener will be removed.

If an AbortSignal is passed for options's signal, then the event listener will be removed when signal is aborted.

The event listener is appended to target's event listener list and is not appended if it has the same type, callback, and capture. Read more on MDN

let addEventListener_useCapture: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~type_: WebAPI.EventAPI.eventType,
  ~callback: WebAPI.EventAPI.eventListener<'event>,
) => unit

Parameters

WebAPI.CanvasAPI.offscreenCanvas WebAPI.EventAPI.eventType WebAPI.EventAPI.eventListener

Return type

unit

asEventTarget

let asEventTarget: WebAPI.CanvasAPI.offscreenCanvas => WebAPI.EventAPI.eventTarget

Parameters

WebAPI.CanvasAPI.offscreenCanvas

Return type

WebAPI.EventAPI.eventTarget

convertToBlob

Returns a promise that will fulfill with a new Blob object representing a file containing the image in the OffscreenCanvas object.

The argument, if provided, is a dictionary that controls the encoding options of the image file to be created. The type field specifies the file format and has a default value of "image/png"; that type is also used if the requested type isn't supported. If the image format supports variable quality (such as "image/jpeg"), then the quality field is a number in the range 0.0 to 1.0 inclusive indicating the desired quality level for the resulting image. Read more on MDN

let convertToBlob: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~options: WebAPI.CanvasAPI.imageEncodeOptions=?,
) => Promise.t<WebAPI.FileAPI.blob>

Parameters

WebAPI.CanvasAPI.offscreenCanvas option< WebAPI.CanvasAPI.imageEncodeOptions >

Return type

Promise.t< WebAPI.FileAPI.blob >

dispatchEvent

Dispatches a synthetic event event to target and returns true if either event's cancelable attribute value is false or its preventDefault() method was not invoked, and false otherwise. Read more on MDN

let dispatchEvent: (
  WebAPI.CanvasAPI.offscreenCanvas,
  WebAPI.EventAPI.event,
) => bool

Parameters

WebAPI.CanvasAPI.offscreenCanvas WebAPI.EventAPI.event

Return type

bool

getContext_2D

Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.

This specification defines the "2d" context below, which is similar but distinct from the "2d" context that is created from a canvas element. The WebGL specifications define the "webgl" and "webgl2" contexts. [WEBGL]

Returns null if the canvas has already been initialized with another context type (e.g., trying to get a "2d" context after getting a "webgl" context). Read more on MDN

let getContext_2D: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~options: JSON.t=?,
) => WebAPI.CanvasAPI.offscreenCanvasRenderingContext2D

Parameters

WebAPI.CanvasAPI.offscreenCanvas option< JSON.t >

Return type

WebAPI.CanvasAPI.offscreenCanvasRenderingContext2D

getContext_BitmapRenderer

Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.

This specification defines the "2d" context below, which is similar but distinct from the "2d" context that is created from a canvas element. The WebGL specifications define the "webgl" and "webgl2" contexts. [WEBGL]

Returns null if the canvas has already been initialized with another context type (e.g., trying to get a "2d" context after getting a "webgl" context). Read more on MDN

let getContext_BitmapRenderer: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~options: WebAPI.CanvasAPI.imageBitmapRenderingContextSettings=?,
) => WebAPI.CanvasAPI.imageBitmapRenderingContext

Parameters

WebAPI.CanvasAPI.offscreenCanvas option< WebAPI.CanvasAPI.imageBitmapRenderingContextSettings >

Return type

WebAPI.CanvasAPI.imageBitmapRenderingContext

getContext_WebGL

Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.

This specification defines the "2d" context below, which is similar but distinct from the "2d" context that is created from a canvas element. The WebGL specifications define the "webgl" and "webgl2" contexts. [WEBGL]

Returns null if the canvas has already been initialized with another context type (e.g., trying to get a "2d" context after getting a "webgl" context). Read more on MDN

let getContext_WebGL: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~options: WebAPI.CanvasAPI.webGLContextAttributes=?,
) => WebAPI.CanvasAPI.webGLRenderingContext

Parameters

WebAPI.CanvasAPI.offscreenCanvas option< WebAPI.CanvasAPI.webGLContextAttributes >

Return type

WebAPI.CanvasAPI.webGLRenderingContext

getContext_WebGL2

Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.

This specification defines the "2d" context below, which is similar but distinct from the "2d" context that is created from a canvas element. The WebGL specifications define the "webgl" and "webgl2" contexts. [WEBGL]

Returns null if the canvas has already been initialized with another context type (e.g., trying to get a "2d" context after getting a "webgl" context). Read more on MDN

let getContext_WebGL2: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~options: WebAPI.CanvasAPI.webGLContextAttributes=?,
) => WebAPI.CanvasAPI.webGL2RenderingContext

Parameters

WebAPI.CanvasAPI.offscreenCanvas option< WebAPI.CanvasAPI.webGLContextAttributes >

Return type

WebAPI.CanvasAPI.webGL2RenderingContext

make

Read more on MDN

let make: (
  ~width: int,
  ~height: int,
) => WebAPI.CanvasAPI.offscreenCanvas

Parameters

int int

Return type

WebAPI.CanvasAPI.offscreenCanvas

removeEventListener

Removes the event listener in target's event listener list with the same type, callback, and options. Read more on MDN

let removeEventListener: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~type_: WebAPI.EventAPI.eventType,
  ~callback: WebAPI.EventAPI.eventListener<'event>,
  ~options: WebAPI.EventAPI.eventListenerOptions=?,
) => unit

Parameters

WebAPI.CanvasAPI.offscreenCanvas WebAPI.EventAPI.eventType WebAPI.EventAPI.eventListener option< WebAPI.EventAPI.eventListenerOptions >

Return type

unit

removeEventListener_useCapture

Removes the event listener in target's event listener list with the same type, callback, and options. Read more on MDN

let removeEventListener_useCapture: (
  WebAPI.CanvasAPI.offscreenCanvas,
  ~type_: WebAPI.EventAPI.eventType,
  ~callback: WebAPI.EventAPI.eventListener<'event>,
) => unit

Parameters

WebAPI.CanvasAPI.offscreenCanvas WebAPI.EventAPI.eventType WebAPI.EventAPI.eventListener

Return type

unit

transferToImageBitmap

Returns a newly created ImageBitmap object with the image in the OffscreenCanvas object. The image in the OffscreenCanvas object is replaced with a new blank image. Read more on MDN

let transferToImageBitmap: WebAPI.CanvasAPI.offscreenCanvas => WebAPI.CanvasAPI.imageBitmap

Parameters

WebAPI.CanvasAPI.offscreenCanvas

Return type

WebAPI.CanvasAPI.imageBitmap