script/dom/html/
htmlcanvaselement.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use std::cell::{Cell, RefCell};
6use std::rc::Rc;
7
8use canvas_traits::webgl::{GLContextAttributes, WebGLVersion};
9use constellation_traits::BlobImpl;
10#[cfg(feature = "webgpu")]
11use constellation_traits::ScriptToConstellationMessage;
12use dom_struct::dom_struct;
13use euclid::default::Size2D;
14use html5ever::{LocalName, Prefix, local_name, ns};
15#[cfg(feature = "webgpu")]
16use ipc_channel::ipc::{self as ipcchan};
17use js::error::throw_type_error;
18use js::rust::{HandleObject, HandleValue};
19use layout_api::HTMLCanvasData;
20use pixels::{EncodedImageType, Snapshot};
21use rustc_hash::FxHashMap;
22use script_bindings::weakref::WeakRef;
23use servo_media::streams::MediaStreamType;
24use servo_media::streams::registry::MediaStreamId;
25use style::attr::AttrValue;
26
27use crate::canvas_context::{CanvasContext, LayoutCanvasRenderingContextHelpers, RenderingContext};
28use crate::conversions::Convert;
29use crate::dom::attr::Attr;
30use crate::dom::bindings::callback::ExceptionHandling;
31use crate::dom::bindings::cell::{DomRefCell, Ref};
32use crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding::{
33    BlobCallback, HTMLCanvasElementMethods, RenderingContext as RootedRenderingContext,
34};
35use crate::dom::bindings::codegen::Bindings::MediaStreamBinding::MediaStreamMethods;
36use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLContextAttributes;
37use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
38use crate::dom::bindings::conversions::ConversionResult;
39use crate::dom::bindings::error::{Error, Fallible};
40use crate::dom::bindings::inheritance::Castable;
41use crate::dom::bindings::num::Finite;
42use crate::dom::bindings::refcounted::Trusted;
43use crate::dom::bindings::reflector::{DomGlobal, DomObject};
44use crate::dom::bindings::root::{Dom, DomRoot, LayoutDom, ToLayout};
45use crate::dom::bindings::str::{DOMString, USVString};
46use crate::dom::blob::Blob;
47use crate::dom::canvasrenderingcontext2d::CanvasRenderingContext2D;
48use crate::dom::document::Document;
49use crate::dom::element::{AttributeMutation, Element, LayoutElementHelpers};
50#[cfg(not(feature = "webgpu"))]
51use crate::dom::gpucanvascontext::GPUCanvasContext;
52use crate::dom::html::htmlelement::HTMLElement;
53use crate::dom::imagebitmaprenderingcontext::ImageBitmapRenderingContext;
54use crate::dom::mediastream::MediaStream;
55use crate::dom::mediastreamtrack::MediaStreamTrack;
56use crate::dom::node::{Node, NodeDamage, NodeTraits};
57use crate::dom::offscreencanvas::OffscreenCanvas;
58use crate::dom::values::UNSIGNED_LONG_MAX;
59use crate::dom::virtualmethods::VirtualMethods;
60use crate::dom::webgl::webgl2renderingcontext::WebGL2RenderingContext;
61use crate::dom::webgl::webglrenderingcontext::WebGLRenderingContext;
62#[cfg(feature = "webgpu")]
63use crate::dom::webgpu::gpucanvascontext::GPUCanvasContext;
64use crate::script_runtime::{CanGc, JSContext};
65
66const DEFAULT_WIDTH: u32 = 300;
67const DEFAULT_HEIGHT: u32 = 150;
68
69/// <https://html.spec.whatwg.org/multipage/#htmlcanvaselement>
70#[dom_struct]
71pub(crate) struct HTMLCanvasElement {
72    htmlelement: HTMLElement,
73
74    /// <https://html.spec.whatwg.org/multipage/#concept-canvas-context-mode>
75    context_mode: DomRefCell<Option<RenderingContext>>,
76
77    // This id and hashmap are used to keep track of ongoing toBlob() calls.
78    callback_id: Cell<u32>,
79    #[ignore_malloc_size_of = "not implemented for webidl callbacks"]
80    blob_callbacks: RefCell<FxHashMap<u32, Rc<BlobCallback>>>,
81}
82
83impl HTMLCanvasElement {
84    fn new_inherited(
85        local_name: LocalName,
86        prefix: Option<Prefix>,
87        document: &Document,
88    ) -> HTMLCanvasElement {
89        HTMLCanvasElement {
90            htmlelement: HTMLElement::new_inherited(local_name, prefix, document),
91            context_mode: DomRefCell::new(None),
92            callback_id: Cell::new(0),
93            blob_callbacks: RefCell::new(FxHashMap::default()),
94        }
95    }
96
97    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
98    pub(crate) fn new(
99        local_name: LocalName,
100        prefix: Option<Prefix>,
101        document: &Document,
102        proto: Option<HandleObject>,
103        can_gc: CanGc,
104    ) -> DomRoot<HTMLCanvasElement> {
105        Node::reflect_node_with_proto(
106            Box::new(HTMLCanvasElement::new_inherited(
107                local_name, prefix, document,
108            )),
109            document,
110            proto,
111            can_gc,
112        )
113    }
114
115    fn recreate_contexts_after_resize(&self) {
116        if let Some(ref context) = *self.context_mode.borrow() {
117            context.resize()
118        }
119    }
120
121    pub(crate) fn get_size(&self) -> Size2D<u32> {
122        Size2D::new(self.Width(), self.Height())
123    }
124
125    pub(crate) fn origin_is_clean(&self) -> bool {
126        match *self.context_mode.borrow() {
127            Some(ref context) => context.origin_is_clean(),
128            _ => true,
129        }
130    }
131
132    pub(crate) fn mark_as_dirty(&self) {
133        if let Some(ref context) = *self.context_mode.borrow() {
134            context.mark_as_dirty()
135        }
136    }
137
138    pub(crate) fn set_natural_width(&self, value: u32, can_gc: CanGc) {
139        let value = if value > UNSIGNED_LONG_MAX {
140            DEFAULT_WIDTH
141        } else {
142            value
143        };
144        let element = self.upcast::<Element>();
145        element.set_uint_attribute(&html5ever::local_name!("width"), value, can_gc);
146    }
147
148    pub(crate) fn set_natural_height(&self, value: u32, can_gc: CanGc) {
149        let value = if value > UNSIGNED_LONG_MAX {
150            DEFAULT_HEIGHT
151        } else {
152            value
153        };
154        let element = self.upcast::<Element>();
155        element.set_uint_attribute(&html5ever::local_name!("height"), value, can_gc);
156    }
157}
158
159pub(crate) trait LayoutHTMLCanvasElementHelpers {
160    fn data(self) -> HTMLCanvasData;
161}
162
163impl LayoutHTMLCanvasElementHelpers for LayoutDom<'_, HTMLCanvasElement> {
164    #[allow(unsafe_code)]
165    fn data(self) -> HTMLCanvasData {
166        let source = unsafe {
167            match self.unsafe_get().context_mode.borrow_for_layout().as_ref() {
168                Some(RenderingContext::Context2d(context)) => {
169                    context.to_layout().canvas_data_source()
170                },
171                Some(RenderingContext::BitmapRenderer(context)) => {
172                    context.to_layout().canvas_data_source()
173                },
174                Some(RenderingContext::WebGL(context)) => context.to_layout().canvas_data_source(),
175                Some(RenderingContext::WebGL2(context)) => context.to_layout().canvas_data_source(),
176                #[cfg(feature = "webgpu")]
177                Some(RenderingContext::WebGPU(context)) => context.to_layout().canvas_data_source(),
178                Some(RenderingContext::Placeholder(_)) | None => None,
179            }
180        };
181
182        let width_attr = self
183            .upcast::<Element>()
184            .get_attr_for_layout(&ns!(), &local_name!("width"));
185        let height_attr = self
186            .upcast::<Element>()
187            .get_attr_for_layout(&ns!(), &local_name!("height"));
188        HTMLCanvasData {
189            source,
190            width: width_attr.map_or(DEFAULT_WIDTH, |val| val.as_uint()),
191            height: height_attr.map_or(DEFAULT_HEIGHT, |val| val.as_uint()),
192        }
193    }
194}
195
196impl HTMLCanvasElement {
197    pub(crate) fn context(&self) -> Option<Ref<'_, RenderingContext>> {
198        Ref::filter_map(self.context_mode.borrow(), |ctx| ctx.as_ref()).ok()
199    }
200
201    fn get_or_init_2d_context(&self, can_gc: CanGc) -> Option<DomRoot<CanvasRenderingContext2D>> {
202        if let Some(ctx) = self.context() {
203            return match *ctx {
204                RenderingContext::Context2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
205                _ => None,
206            };
207        }
208
209        let window = self.owner_window();
210        let size = self.get_size();
211        let context = CanvasRenderingContext2D::new(window.as_global_scope(), self, size, can_gc)?;
212        *self.context_mode.borrow_mut() =
213            Some(RenderingContext::Context2d(Dom::from_ref(&*context)));
214        Some(context)
215    }
216
217    /// <https://html.spec.whatwg.org/multipage/#canvas-context-bitmaprenderer>
218    fn get_or_init_bitmaprenderer_context(
219        &self,
220        can_gc: CanGc,
221    ) -> Option<DomRoot<ImageBitmapRenderingContext>> {
222        // Return the same object as was returned the last time the method was
223        // invoked with this same first argument.
224        if let Some(ctx) = self.context() {
225            return match *ctx {
226                RenderingContext::BitmapRenderer(ref ctx) => Some(DomRoot::from_ref(ctx)),
227                _ => None,
228            };
229        }
230
231        // Step 1. Let context be the result of running the
232        // ImageBitmapRenderingContext creation algorithm given this and
233        // options.
234        let canvas =
235            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
236
237        let context = ImageBitmapRenderingContext::new(&self.owner_global(), &canvas, can_gc);
238
239        // Step 2. Set this's context mode to bitmaprenderer.
240        *self.context_mode.borrow_mut() =
241            Some(RenderingContext::BitmapRenderer(Dom::from_ref(&*context)));
242
243        // Step 3. Return context.
244        Some(context)
245    }
246
247    fn get_or_init_webgl_context(
248        &self,
249        cx: JSContext,
250        options: HandleValue,
251        can_gc: CanGc,
252    ) -> Option<DomRoot<WebGLRenderingContext>> {
253        if let Some(ctx) = self.context() {
254            return match *ctx {
255                RenderingContext::WebGL(ref ctx) => Some(DomRoot::from_ref(ctx)),
256                _ => None,
257            };
258        }
259        let window = self.owner_window();
260        let canvas =
261            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
262        let size = self.get_size();
263        let attrs = Self::get_gl_attributes(cx, options, can_gc)?;
264        let context = WebGLRenderingContext::new(
265            &window,
266            &canvas,
267            WebGLVersion::WebGL1,
268            size,
269            attrs,
270            can_gc,
271        )?;
272        *self.context_mode.borrow_mut() = Some(RenderingContext::WebGL(Dom::from_ref(&*context)));
273        Some(context)
274    }
275
276    fn get_or_init_webgl2_context(
277        &self,
278        cx: JSContext,
279        options: HandleValue,
280        can_gc: CanGc,
281    ) -> Option<DomRoot<WebGL2RenderingContext>> {
282        if !WebGL2RenderingContext::is_webgl2_enabled(cx, self.global().reflector().get_jsobject())
283        {
284            return None;
285        }
286        if let Some(ctx) = self.context() {
287            return match *ctx {
288                RenderingContext::WebGL2(ref ctx) => Some(DomRoot::from_ref(ctx)),
289                _ => None,
290            };
291        }
292        let window = self.owner_window();
293        let canvas =
294            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
295        let size = self.get_size();
296        let attrs = Self::get_gl_attributes(cx, options, can_gc)?;
297        let context = WebGL2RenderingContext::new(&window, &canvas, size, attrs, can_gc)?;
298        *self.context_mode.borrow_mut() = Some(RenderingContext::WebGL2(Dom::from_ref(&*context)));
299        Some(context)
300    }
301
302    #[cfg(not(feature = "webgpu"))]
303    fn get_or_init_webgpu_context(&self) -> Option<DomRoot<GPUCanvasContext>> {
304        None
305    }
306
307    #[cfg(feature = "webgpu")]
308    fn get_or_init_webgpu_context(&self, can_gc: CanGc) -> Option<DomRoot<GPUCanvasContext>> {
309        if let Some(ctx) = self.context() {
310            return match *ctx {
311                RenderingContext::WebGPU(ref ctx) => Some(DomRoot::from_ref(ctx)),
312                _ => None,
313            };
314        }
315        let (sender, receiver) = ipcchan::channel().unwrap();
316        let global_scope = self.owner_global();
317        let _ = global_scope
318            .script_to_constellation_chan()
319            .send(ScriptToConstellationMessage::GetWebGPUChan(sender));
320        receiver
321            .recv()
322            .expect("Failed to get WebGPU channel")
323            .map(|channel| {
324                let context = GPUCanvasContext::new(&global_scope, self, channel, can_gc);
325                *self.context_mode.borrow_mut() =
326                    Some(RenderingContext::WebGPU(Dom::from_ref(&*context)));
327                context
328            })
329    }
330
331    /// Gets the base WebGLRenderingContext for WebGL or WebGL 2, if exists.
332    pub(crate) fn get_base_webgl_context(&self) -> Option<DomRoot<WebGLRenderingContext>> {
333        match *self.context_mode.borrow() {
334            Some(RenderingContext::WebGL(ref context)) => Some(DomRoot::from_ref(context)),
335            Some(RenderingContext::WebGL2(ref context)) => Some(context.base_context()),
336            _ => None,
337        }
338    }
339
340    #[allow(unsafe_code)]
341    fn get_gl_attributes(
342        cx: JSContext,
343        options: HandleValue,
344        can_gc: CanGc,
345    ) -> Option<GLContextAttributes> {
346        unsafe {
347            match WebGLContextAttributes::new(cx, options, can_gc) {
348                Ok(ConversionResult::Success(attrs)) => Some(attrs.convert()),
349                Ok(ConversionResult::Failure(error)) => {
350                    throw_type_error(*cx, &error);
351                    None
352                },
353                _ => {
354                    debug!("Unexpected error on conversion of WebGLContextAttributes");
355                    None
356                },
357            }
358        }
359    }
360
361    pub(crate) fn is_valid(&self) -> bool {
362        self.Height() != 0 && self.Width() != 0
363    }
364
365    pub(crate) fn get_image_data(&self) -> Option<Snapshot> {
366        match self.context_mode.borrow().as_ref() {
367            Some(context) => context.get_image_data(),
368            None => {
369                let size = self.get_size();
370                if size.is_empty() ||
371                    pixels::compute_rgba8_byte_length_if_within_limit(
372                        size.width as usize,
373                        size.height as usize,
374                    )
375                    .is_none()
376                {
377                    None
378                } else {
379                    Some(Snapshot::cleared(size.cast()))
380                }
381            },
382        }
383    }
384
385    fn maybe_quality(quality: HandleValue) -> Option<f64> {
386        if quality.is_number() {
387            Some(quality.to_number())
388        } else {
389            None
390        }
391    }
392}
393
394impl HTMLCanvasElementMethods<crate::DomTypeHolder> for HTMLCanvasElement {
395    // https://html.spec.whatwg.org/multipage/#dom-canvas-width
396    make_uint_getter!(Width, "width", DEFAULT_WIDTH);
397
398    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-width>
399    fn SetWidth(&self, value: u32, can_gc: CanGc) -> Fallible<()> {
400        // > When setting the value of the width or height attribute, if the context mode of the canvas element
401        // > is set to placeholder, the user agent must throw an "InvalidStateError" DOMException and leave the
402        // > attribute's value unchanged.
403        if let Some(RenderingContext::Placeholder(_)) = *self.context_mode.borrow() {
404            return Err(Error::InvalidState);
405        }
406
407        let value = if value > UNSIGNED_LONG_MAX {
408            DEFAULT_WIDTH
409        } else {
410            value
411        };
412        let element = self.upcast::<Element>();
413        element.set_uint_attribute(&html5ever::local_name!("width"), value, can_gc);
414        Ok(())
415    }
416
417    // https://html.spec.whatwg.org/multipage/#dom-canvas-height
418    make_uint_getter!(Height, "height", DEFAULT_HEIGHT);
419
420    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-height>
421    fn SetHeight(&self, value: u32, can_gc: CanGc) -> Fallible<()> {
422        // > When setting the value of the width or height attribute, if the context mode of the canvas element
423        // > is set to placeholder, the user agent must throw an "InvalidStateError" DOMException and leave the
424        // > attribute's value unchanged.
425        if let Some(RenderingContext::Placeholder(_)) = *self.context_mode.borrow() {
426            return Err(Error::InvalidState);
427        }
428
429        let value = if value > UNSIGNED_LONG_MAX {
430            DEFAULT_HEIGHT
431        } else {
432            value
433        };
434        let element = self.upcast::<Element>();
435        element.set_uint_attribute(&html5ever::local_name!("height"), value, can_gc);
436        Ok(())
437    }
438
439    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-getcontext>
440    fn GetContext(
441        &self,
442        cx: JSContext,
443        id: DOMString,
444        options: HandleValue,
445        can_gc: CanGc,
446    ) -> Fallible<Option<RootedRenderingContext>> {
447        // Always throw an InvalidState exception when the canvas is in Placeholder mode (See table in the spec).
448        if let Some(RenderingContext::Placeholder(_)) = *self.context_mode.borrow() {
449            return Err(Error::InvalidState);
450        }
451
452        Ok(match &*id {
453            "2d" => self
454                .get_or_init_2d_context(can_gc)
455                .map(RootedRenderingContext::CanvasRenderingContext2D),
456            "bitmaprenderer" => self
457                .get_or_init_bitmaprenderer_context(can_gc)
458                .map(RootedRenderingContext::ImageBitmapRenderingContext),
459            "webgl" | "experimental-webgl" => self
460                .get_or_init_webgl_context(cx, options, can_gc)
461                .map(RootedRenderingContext::WebGLRenderingContext),
462            "webgl2" | "experimental-webgl2" => self
463                .get_or_init_webgl2_context(cx, options, can_gc)
464                .map(RootedRenderingContext::WebGL2RenderingContext),
465            #[cfg(feature = "webgpu")]
466            "webgpu" => self
467                .get_or_init_webgpu_context(can_gc)
468                .map(RootedRenderingContext::GPUCanvasContext),
469            _ => None,
470        })
471    }
472
473    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-todataurl>
474    fn ToDataURL(
475        &self,
476        _context: JSContext,
477        mime_type: DOMString,
478        quality: HandleValue,
479    ) -> Fallible<USVString> {
480        // Step 1: If this canvas element's bitmap's origin-clean flag is set to false,
481        // then throw a "SecurityError" DOMException.
482        if !self.origin_is_clean() {
483            return Err(Error::Security);
484        }
485
486        // Step 2: If this canvas element's bitmap has no pixels (i.e. either its
487        // horizontal dimension or its vertical dimension is zero), then return the string
488        // "data:,". (This is the shortest data: URL; it represents the empty string in a
489        // text/plain resource.)
490        if self.Width() == 0 || self.Height() == 0 {
491            return Ok(USVString("data:,".into()));
492        }
493
494        // Step 3: Let file be a serialization of this canvas element's bitmap as a file,
495        // passing type and quality if given.
496        let Some(mut snapshot) = self.get_image_data() else {
497            return Ok(USVString("data:,".into()));
498        };
499
500        let image_type = EncodedImageType::from(mime_type.to_string());
501
502        let mut url = format!("data:{};base64,", image_type.as_mime_type());
503
504        let mut encoder = base64::write::EncoderStringWriter::from_consumer(
505            &mut url,
506            &base64::engine::general_purpose::STANDARD,
507        );
508
509        if snapshot
510            .encode_for_mime_type(&image_type, Self::maybe_quality(quality), &mut encoder)
511            .is_err()
512        {
513            // Step 4. If file is null, then return "data:,".
514            return Ok(USVString("data:,".into()));
515        }
516
517        // Step 5. Return a data: URL representing file. [RFC2397]
518        encoder.into_inner();
519        Ok(USVString(url))
520    }
521
522    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-toblob>
523    fn ToBlob(
524        &self,
525        _cx: JSContext,
526        callback: Rc<BlobCallback>,
527        mime_type: DOMString,
528        quality: HandleValue,
529    ) -> Fallible<()> {
530        // Step 1.
531        // If this canvas element's bitmap's origin-clean flag is set to false, then throw a
532        // "SecurityError" DOMException.
533        if !self.origin_is_clean() {
534            return Err(Error::Security);
535        }
536
537        // Step 2. Let result be null.
538        // Step 3. If this canvas element's bitmap has pixels (i.e., neither its horizontal dimension
539        // nor its vertical dimension is zero),
540        // then set result to a copy of this canvas element's bitmap.
541        let result = if self.Width() == 0 || self.Height() == 0 {
542            None
543        } else {
544            self.get_image_data()
545        };
546
547        let this = Trusted::new(self);
548        let callback_id = self.callback_id.get().wrapping_add(1);
549        self.callback_id.set(callback_id);
550
551        self.blob_callbacks
552            .borrow_mut()
553            .insert(callback_id, callback);
554        let quality = Self::maybe_quality(quality);
555        let image_type = EncodedImageType::from(mime_type.to_string());
556
557        self.global()
558            .task_manager()
559            .canvas_blob_task_source()
560            .queue(task!(to_blob: move || {
561                let this = this.root();
562                let Some(callback) = &this.blob_callbacks.borrow_mut().remove(&callback_id) else {
563                    return error!("Expected blob callback, but found none!");
564                };
565
566                let Some(mut snapshot) = result else {
567                    let _ = callback.Call__(None, ExceptionHandling::Report, CanGc::note());
568                    return;
569                };
570
571                // Step 4.1: If result is non-null, then set result to a serialization of
572                // result as a file with type and quality if given.
573                // Step 4.2: Queue an element task on the canvas blob serialization task
574                // source given the canvas element to run these steps:
575                let mut encoded: Vec<u8> = vec![];
576                let blob_impl;
577                let blob;
578                let result = match snapshot.encode_for_mime_type(&image_type, quality, &mut encoded) {
579                   Ok(..) => {
580                       // Step 4.2.1: If result is non-null, then set result to a new Blob
581                       // object, created in the relevant realm of this canvas element,
582                       // representing result. [FILEAPI]
583                       blob_impl = BlobImpl::new_from_bytes(encoded, image_type.as_mime_type());
584                       blob = Blob::new(&this.global(), blob_impl, CanGc::note());
585                       Some(&*blob)
586                   }
587                   Err(..) => None,
588                };
589
590                // Step 4.2.2: Invoke callback with « result » and "report".
591                let _ = callback.Call__(result, ExceptionHandling::Report, CanGc::note());
592            }));
593
594        Ok(())
595    }
596
597    /// <https://html.spec.whatwg.org/multipage/#dom-canvas-transfercontroltooffscreen>
598    fn TransferControlToOffscreen(&self, can_gc: CanGc) -> Fallible<DomRoot<OffscreenCanvas>> {
599        if self.context_mode.borrow().is_some() {
600            // Step 1.
601            // If this canvas element's context mode is not set to none, throw an "InvalidStateError" DOMException.
602            return Err(Error::InvalidState);
603        };
604
605        // Step 2.
606        // Let offscreenCanvas be a new OffscreenCanvas object with its width and height equal to the values of
607        // the width and height content attributes of this canvas element.
608        // Step 3.
609        // Set the placeholder canvas element of offscreenCanvas to a weak reference to this canvas element.
610        let offscreen_canvas = OffscreenCanvas::new(
611            &self.global(),
612            None,
613            self.Width().into(),
614            self.Height().into(),
615            Some(WeakRef::new(self)),
616            can_gc,
617        );
618
619        // Step 4. Set this canvas element's context mode to placeholder.
620        *self.context_mode.borrow_mut() =
621            Some(RenderingContext::Placeholder(offscreen_canvas.as_traced()));
622
623        // Step 5. Return offscreenCanvas.
624        Ok(offscreen_canvas)
625    }
626
627    /// <https://w3c.github.io/mediacapture-fromelement/#dom-htmlcanvaselement-capturestream>
628    fn CaptureStream(
629        &self,
630        _frame_request_rate: Option<Finite<f64>>,
631        can_gc: CanGc,
632    ) -> DomRoot<MediaStream> {
633        let global = self.global();
634        let stream = MediaStream::new(&global, can_gc);
635        let track = MediaStreamTrack::new(
636            &global,
637            MediaStreamId::new(),
638            MediaStreamType::Video,
639            can_gc,
640        );
641        stream.AddTrack(&track);
642        stream
643    }
644}
645
646impl VirtualMethods for HTMLCanvasElement {
647    fn super_type(&self) -> Option<&dyn VirtualMethods> {
648        Some(self.upcast::<HTMLElement>() as &dyn VirtualMethods)
649    }
650
651    fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation, can_gc: CanGc) {
652        self.super_type()
653            .unwrap()
654            .attribute_mutated(attr, mutation, can_gc);
655        match attr.local_name() {
656            &local_name!("width") | &local_name!("height") => {
657                self.recreate_contexts_after_resize();
658                self.upcast::<Node>().dirty(NodeDamage::Other);
659            },
660            _ => {},
661        };
662    }
663
664    fn parse_plain_attribute(&self, name: &LocalName, value: DOMString) -> AttrValue {
665        match *name {
666            local_name!("width") => AttrValue::from_u32(value.into(), DEFAULT_WIDTH),
667            local_name!("height") => AttrValue::from_u32(value.into(), DEFAULT_HEIGHT),
668            _ => self
669                .super_type()
670                .unwrap()
671                .parse_plain_attribute(name, value),
672        }
673    }
674}
675
676impl Convert<GLContextAttributes> for WebGLContextAttributes {
677    fn convert(self) -> GLContextAttributes {
678        GLContextAttributes {
679            alpha: self.alpha,
680            depth: self.depth,
681            stencil: self.stencil,
682            antialias: self.antialias,
683            premultiplied_alpha: self.premultipliedAlpha,
684            preserve_drawing_buffer: self.preserveDrawingBuffer,
685        }
686    }
687}
script/dom/html/htmlcanvaselement.rs

script/dom/html/
htmlcanvaselement.rs
