script/dom/canvas/
offscreencanvas.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;
6use std::rc::Rc;
7
8use dom_struct::dom_struct;
9use euclid::default::Size2D;
10use js::error::throw_type_error;
11use js::rust::{HandleObject, HandleValue};
12use pixels::{EncodedImageType, Snapshot};
13use rustc_hash::FxHashMap;
14use script_bindings::inheritance::Castable;
15use script_bindings::weakref::WeakRef;
16use servo_base::id::{OffscreenCanvasId, OffscreenCanvasIndex};
17use servo_canvas_traits::webgl::{GLContextAttributes, WebGLVersion};
18use servo_constellation_traits::{BlobImpl, TransferableOffscreenCanvas};
19
20use crate::canvas_context::{CanvasContext, OffscreenRenderingContext};
21use crate::conversions::Convert;
22use crate::dom::bindings::cell::{DomRefCell, Ref};
23use crate::dom::bindings::codegen::Bindings::OffscreenCanvasBinding::{
24    ImageEncodeOptions, OffscreenCanvasMethods,
25    OffscreenRenderingContext as RootedOffscreenRenderingContext, OffscreenRenderingContextId,
26};
27use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLContextAttributes;
28use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
29use crate::dom::bindings::conversions::ConversionResult;
30use crate::dom::bindings::error::{Error, Fallible};
31use crate::dom::bindings::refcounted::{Trusted, TrustedPromise};
32use crate::dom::bindings::reflector::{DomGlobal, DomObject, reflect_dom_object_with_proto};
33use crate::dom::bindings::root::{Dom, DomRoot};
34use crate::dom::bindings::structuredclone::StructuredData;
35use crate::dom::bindings::transferable::Transferable;
36use crate::dom::blob::Blob;
37use crate::dom::eventtarget::EventTarget;
38use crate::dom::globalscope::GlobalScope;
39use crate::dom::html::htmlcanvaselement::HTMLCanvasElement;
40use crate::dom::imagebitmap::ImageBitmap;
41use crate::dom::imagebitmaprenderingcontext::ImageBitmapRenderingContext;
42use crate::dom::offscreencanvasrenderingcontext2d::OffscreenCanvasRenderingContext2D;
43use crate::dom::promise::Promise;
44use crate::dom::types::{WebGLRenderingContext, Window};
45use crate::dom::webgl::webgl2renderingcontext::WebGL2RenderingContext;
46use crate::realms::{AlreadyInRealm, InRealm};
47use crate::script_runtime::{CanGc, JSContext};
48
49/// <https://html.spec.whatwg.org/multipage/#offscreencanvas>
50#[dom_struct]
51pub(crate) struct OffscreenCanvas {
52    eventtarget: EventTarget,
53    width: Cell<u64>,
54    height: Cell<u64>,
55
56    /// Represents both the [bitmap] and the [context mode] of the canvas.
57    ///
58    /// [bitmap]: https://html.spec.whatwg.org/multipage/#offscreencanvas-bitmap
59    /// [context mode]: https://html.spec.whatwg.org/multipage/#offscreencanvas-context-mode
60    context: DomRefCell<Option<OffscreenRenderingContext>>,
61
62    /// <https://html.spec.whatwg.org/multipage/#offscreencanvas-placeholder>
63    placeholder: Option<WeakRef<HTMLCanvasElement>>,
64}
65
66impl OffscreenCanvas {
67    pub(crate) fn new_inherited(
68        width: u64,
69        height: u64,
70        placeholder: Option<WeakRef<HTMLCanvasElement>>,
71    ) -> OffscreenCanvas {
72        OffscreenCanvas {
73            eventtarget: EventTarget::new_inherited(),
74            width: Cell::new(width),
75            height: Cell::new(height),
76            context: DomRefCell::new(None),
77            placeholder,
78        }
79    }
80
81    pub(crate) fn new(
82        global: &GlobalScope,
83        proto: Option<HandleObject>,
84        width: u64,
85        height: u64,
86        placeholder: Option<WeakRef<HTMLCanvasElement>>,
87        can_gc: CanGc,
88    ) -> DomRoot<OffscreenCanvas> {
89        reflect_dom_object_with_proto(
90            Box::new(OffscreenCanvas::new_inherited(width, height, placeholder)),
91            global,
92            proto,
93            can_gc,
94        )
95    }
96
97    pub(crate) fn get_size(&self) -> Size2D<u32> {
98        Size2D::new(
99            self.Width().try_into().unwrap_or(u32::MAX),
100            self.Height().try_into().unwrap_or(u32::MAX),
101        )
102    }
103
104    #[expect(unsafe_code)]
105    fn get_gl_attributes(
106        cx: JSContext,
107        options: HandleValue,
108        can_gc: CanGc,
109    ) -> Option<GLContextAttributes> {
110        unsafe {
111            match WebGLContextAttributes::new(cx, options, can_gc) {
112                Ok(ConversionResult::Success(attrs)) => Some(attrs.convert()),
113                Ok(ConversionResult::Failure(error)) => {
114                    throw_type_error(*cx, &error);
115                    None
116                },
117                _ => {
118                    debug!("Unexpected error on conversion of WebGLContextAttributes");
119                    None
120                },
121            }
122        }
123    }
124
125    pub(crate) fn origin_is_clean(&self) -> bool {
126        match *self.context.borrow() {
127            Some(ref context) => context.origin_is_clean(),
128            _ => true,
129        }
130    }
131
132    pub(crate) fn context(&self) -> Option<Ref<'_, OffscreenRenderingContext>> {
133        Ref::filter_map(self.context.borrow(), |ctx| ctx.as_ref()).ok()
134    }
135
136    pub(crate) fn get_image_data(&self) -> Option<Snapshot> {
137        match self.context.borrow().as_ref() {
138            Some(context) => context.get_image_data(),
139            None => {
140                let size = self.get_size();
141                if size.is_empty() ||
142                    pixels::compute_rgba8_byte_length_if_within_limit(
143                        size.width as usize,
144                        size.height as usize,
145                    )
146                    .is_none()
147                {
148                    None
149                } else {
150                    Some(Snapshot::cleared(size))
151                }
152            },
153        }
154    }
155
156    pub(crate) fn get_or_init_2d_context(
157        &self,
158        can_gc: CanGc,
159    ) -> Option<DomRoot<OffscreenCanvasRenderingContext2D>> {
160        if let Some(ctx) = self.context() {
161            return match *ctx {
162                OffscreenRenderingContext::Context2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
163                _ => None,
164            };
165        }
166        let context =
167            OffscreenCanvasRenderingContext2D::new(&self.global(), self, self.get_size(), can_gc)?;
168        *self.context.borrow_mut() = Some(OffscreenRenderingContext::Context2d(Dom::from_ref(
169            &*context,
170        )));
171        Some(context)
172    }
173
174    /// <https://html.spec.whatwg.org/multipage/#offscreen-context-type-bitmaprenderer>
175    pub(crate) fn get_or_init_bitmaprenderer_context(
176        &self,
177        can_gc: CanGc,
178    ) -> Option<DomRoot<ImageBitmapRenderingContext>> {
179        // Return the same object as was returned the last time the method was
180        // invoked with this same first argument.
181        if let Some(ctx) = self.context() {
182            return match *ctx {
183                OffscreenRenderingContext::BitmapRenderer(ref ctx) => Some(DomRoot::from_ref(ctx)),
184                _ => None,
185            };
186        }
187
188        // Step 1. Let context be the result of running the
189        // ImageBitmapRenderingContext creation algorithm given this and
190        // options.
191        let canvas =
192            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(self));
193
194        let context = ImageBitmapRenderingContext::new(&self.global(), &canvas, can_gc);
195
196        // Step 2. Set this's context mode to bitmaprenderer.
197        *self.context.borrow_mut() = Some(OffscreenRenderingContext::BitmapRenderer(
198            Dom::from_ref(&*context),
199        ));
200
201        // Step 3. Return context.
202        Some(context)
203    }
204
205    // <https://html.spec.whatwg.org/multipage/#offscreen-context-type-webgl>
206    pub(crate) fn get_or_init_webgl_context(
207        &self,
208        cx: JSContext,
209        options: HandleValue,
210        can_gc: CanGc,
211    ) -> Option<DomRoot<WebGLRenderingContext>> {
212        if let Some(ctx) = self.context() {
213            return match *ctx {
214                OffscreenRenderingContext::WebGL(ref ctx) => Some(DomRoot::from_ref(ctx)),
215                _ => None,
216            };
217        }
218
219        // 1. Let context be the result of following the instructions given in the
220        // WebGL specifications' Context Creation sections.
221        let canvas =
222            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(self));
223        let size = self.get_size();
224        let attrs = Self::get_gl_attributes(cx, options, can_gc)?;
225        self.global()
226            .downcast::<Window>()
227            .and_then(|window| {
228                WebGLRenderingContext::new(
229                    window,
230                    &canvas,
231                    WebGLVersion::WebGL1,
232                    size,
233                    attrs,
234                    can_gc,
235                )
236            })
237            .map(|context| {
238                // Step 2. If context is null, then return null;
239                // otherwise set this's context mode to webgl or webgl2.
240                *self.context.borrow_mut() =
241                    Some(OffscreenRenderingContext::WebGL(Dom::from_ref(&*context)));
242
243                // Step 3. Return context.
244                context
245            })
246    }
247
248    // <https://html.spec.whatwg.org/multipage/#offscreen-context-type-webgl>
249    fn get_or_init_webgl2_context(
250        &self,
251        cx: JSContext,
252        options: HandleValue,
253        can_gc: CanGc,
254    ) -> Option<DomRoot<WebGL2RenderingContext>> {
255        if !WebGL2RenderingContext::is_webgl2_enabled(cx, self.global().reflector().get_jsobject())
256        {
257            return None;
258        }
259        if let Some(ctx) = self.context() {
260            return match *ctx {
261                OffscreenRenderingContext::WebGL2(ref ctx) => Some(DomRoot::from_ref(ctx)),
262                _ => None,
263            };
264        }
265
266        // 1. Let context be the result of following the instructions given in the
267        // WebGL specifications' Context Creation sections.
268        let canvas =
269            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(self));
270        let size = self.get_size();
271        let attrs = Self::get_gl_attributes(cx, options, can_gc)?;
272        self.global()
273            .downcast::<Window>()
274            .and_then(|window| WebGL2RenderingContext::new(window, &canvas, size, attrs, can_gc))
275            .map(|context| {
276                // Step 2. If context is null, then return null;
277                // otherwise set this's context mode to webgl or webgl2.
278                *self.context.borrow_mut() =
279                    Some(OffscreenRenderingContext::WebGL2(Dom::from_ref(&*context)));
280
281                // Step 3. Return context.
282                context
283            })
284    }
285
286    pub(crate) fn placeholder(&self) -> Option<DomRoot<HTMLCanvasElement>> {
287        self.placeholder
288            .as_ref()
289            .and_then(|placeholder| placeholder.root())
290    }
291}
292
293impl Transferable for OffscreenCanvas {
294    type Index = OffscreenCanvasIndex;
295    type Data = TransferableOffscreenCanvas;
296
297    /// <https://html.spec.whatwg.org/multipage/#the-offscreencanvas-interface:transfer-steps>
298    fn transfer(
299        &self,
300        _cx: &mut js::context::JSContext,
301    ) -> Fallible<(OffscreenCanvasId, TransferableOffscreenCanvas)> {
302        // <https://html.spec.whatwg.org/multipage/#structuredserializewithtransfer>
303        // Step 5.2. If transferable has a [[Detached]] internal slot and
304        // transferable.[[Detached]] is true, then throw a "DataCloneError"
305        // DOMException.
306        if let Some(OffscreenRenderingContext::Detached) = *self.context.borrow() {
307            return Err(Error::DataClone(None));
308        }
309
310        // Step 1. If value's context mode is not equal to none, then throw an
311        // "InvalidStateError" DOMException.
312        if !self.context.borrow().is_none() {
313            return Err(Error::InvalidState(None));
314        }
315
316        // TODO(#37882): Allow to transfer with a placeholder canvas element.
317        if self.placeholder.is_some() {
318            return Err(Error::InvalidState(None));
319        }
320
321        // Step 2. Set value's context mode to detached.
322        *self.context.borrow_mut() = Some(OffscreenRenderingContext::Detached);
323
324        // Step 3. Let width and height be the dimensions of value's bitmap.
325        // Step 5. Unset value's bitmap.
326        let width = self.width.replace(0);
327        let height = self.height.replace(0);
328
329        // TODO(#37918) Step 4. Let language and direction be the values of
330        // value's inherited language and inherited direction.
331
332        // Step 6. Set dataHolder.[[Width]] to width and dataHolder.[[Height]]
333        // to height.
334
335        // TODO(#37918) Step 7. Set dataHolder.[[Language]] to language and
336        // dataHolder.[[Direction]] to direction.
337
338        // TODO(#37882) Step 8. Set dataHolder.[[PlaceholderCanvas]] to be a
339        // weak reference to value's placeholder canvas element, if value has
340        // one, or null if it does not.
341        let transferred = TransferableOffscreenCanvas { width, height };
342
343        Ok((OffscreenCanvasId::new(), transferred))
344    }
345
346    /// <https://html.spec.whatwg.org/multipage/#the-offscreencanvas-interface:transfer-receiving-steps>
347    fn transfer_receive(
348        cx: &mut js::context::JSContext,
349        owner: &GlobalScope,
350        _: OffscreenCanvasId,
351        transferred: TransferableOffscreenCanvas,
352    ) -> Result<DomRoot<Self>, ()> {
353        // Step 1. Initialize value's bitmap to a rectangular array of
354        // transparent black pixels with width given by dataHolder.[[Width]] and
355        // height given by dataHolder.[[Height]].
356
357        // TODO(#37918) Step 2. Set value's inherited language to
358        // dataHolder.[[Language]] and its inherited direction to
359        // dataHolder.[[Direction]].
360
361        // TODO(#37882) Step 3. If dataHolder.[[PlaceholderCanvas]] is not null,
362        // set value's placeholder canvas element to
363        // dataHolder.[[PlaceholderCanvas]] (while maintaining the weak
364        // reference semantics).
365        Ok(OffscreenCanvas::new(
366            owner,
367            None,
368            transferred.width,
369            transferred.height,
370            None,
371            CanGc::from_cx(cx),
372        ))
373    }
374
375    fn serialized_storage<'a>(
376        data: StructuredData<'a, '_>,
377    ) -> &'a mut Option<FxHashMap<OffscreenCanvasId, Self::Data>> {
378        match data {
379            StructuredData::Reader(r) => &mut r.offscreen_canvases,
380            StructuredData::Writer(w) => &mut w.offscreen_canvases,
381        }
382    }
383}
384
385impl OffscreenCanvasMethods<crate::DomTypeHolder> for OffscreenCanvas {
386    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas>
387    fn Constructor(
388        global: &GlobalScope,
389        proto: Option<HandleObject>,
390        can_gc: CanGc,
391        width: u64,
392        height: u64,
393    ) -> Fallible<DomRoot<OffscreenCanvas>> {
394        Ok(OffscreenCanvas::new(
395            global, proto, width, height, None, can_gc,
396        ))
397    }
398
399    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-getcontext>
400    fn GetContext(
401        &self,
402        cx: JSContext,
403        id: OffscreenRenderingContextId,
404        options: HandleValue,
405        can_gc: CanGc,
406    ) -> Fallible<Option<RootedOffscreenRenderingContext>> {
407        // Step 3. Throw an "InvalidStateError" DOMException if the
408        // OffscreenCanvas object's context mode is detached.
409        if let Some(OffscreenRenderingContext::Detached) = *self.context.borrow() {
410            return Err(Error::InvalidState(None));
411        }
412
413        match id {
414            OffscreenRenderingContextId::_2d => Ok(self
415                .get_or_init_2d_context(can_gc)
416                .map(RootedOffscreenRenderingContext::OffscreenCanvasRenderingContext2D)),
417            OffscreenRenderingContextId::Bitmaprenderer => Ok(self
418                .get_or_init_bitmaprenderer_context(can_gc)
419                .map(RootedOffscreenRenderingContext::ImageBitmapRenderingContext)),
420            OffscreenRenderingContextId::Webgl => Ok(self
421                .get_or_init_webgl_context(cx, options, can_gc)
422                .map(RootedOffscreenRenderingContext::WebGLRenderingContext)),
423            OffscreenRenderingContextId::Experimental_webgl => Ok(self
424                .get_or_init_webgl_context(cx, options, can_gc)
425                .map(RootedOffscreenRenderingContext::WebGLRenderingContext)),
426            OffscreenRenderingContextId::Webgl2 => Ok(self
427                .get_or_init_webgl2_context(cx, options, can_gc)
428                .map(RootedOffscreenRenderingContext::WebGL2RenderingContext)),
429            OffscreenRenderingContextId::Experimental_webgl2 => Ok(self
430                .get_or_init_webgl2_context(cx, options, can_gc)
431                .map(RootedOffscreenRenderingContext::WebGL2RenderingContext)),
432        }
433    }
434
435    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-width>
436    fn Width(&self) -> u64 {
437        self.width.get()
438    }
439
440    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-width>
441    fn SetWidth(&self, value: u64, can_gc: CanGc) {
442        self.width.set(value);
443
444        if let Some(canvas_context) = self.context() {
445            canvas_context.resize();
446        }
447
448        if let Some(canvas) = self.placeholder() {
449            canvas.set_natural_width(value as _, can_gc)
450        }
451    }
452
453    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-height>
454    fn Height(&self) -> u64 {
455        self.height.get()
456    }
457
458    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-height>
459    fn SetHeight(&self, value: u64, can_gc: CanGc) {
460        self.height.set(value);
461
462        if let Some(canvas_context) = self.context() {
463            canvas_context.resize();
464        }
465
466        if let Some(canvas) = self.placeholder() {
467            canvas.set_natural_height(value as _, can_gc)
468        }
469    }
470
471    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-transfertoimagebitmap>
472    fn TransferToImageBitmap(&self, can_gc: CanGc) -> Fallible<DomRoot<ImageBitmap>> {
473        // Step 1. If the value of this OffscreenCanvas object's [[Detached]]
474        // internal slot is set to true, then throw an "InvalidStateError"
475        // DOMException.
476        if let Some(OffscreenRenderingContext::Detached) = *self.context.borrow() {
477            return Err(Error::InvalidState(None));
478        }
479
480        // Step 2. If this OffscreenCanvas object's context mode is set to none,
481        // then throw an "InvalidStateError" DOMException.
482        if self.context.borrow().is_none() {
483            return Err(Error::InvalidState(None));
484        }
485
486        // Step 3. Let image be a newly created ImageBitmap object that
487        // references the same underlying bitmap data as this OffscreenCanvas
488        // object's bitmap.
489        let Some(snapshot) = self.get_image_data() else {
490            return Err(Error::InvalidState(None));
491        };
492
493        let image_bitmap = ImageBitmap::new(&self.global(), snapshot, can_gc);
494        image_bitmap.set_origin_clean(self.origin_is_clean());
495
496        // Step 4. Set this OffscreenCanvas object's bitmap to reference a newly
497        // created bitmap of the same dimensions and color space as the previous
498        // bitmap, and with its pixels initialized to transparent black, or
499        // opaque black if the rendering context's alpha is false.
500        if let Some(canvas_context) = self.context() {
501            canvas_context.reset_bitmap();
502        }
503
504        // Step 5. Return image.
505        Ok(image_bitmap)
506    }
507
508    /// <https://html.spec.whatwg.org/multipage/#dom-offscreencanvas-converttoblob>
509    fn ConvertToBlob(&self, options: &ImageEncodeOptions, can_gc: CanGc) -> Rc<Promise> {
510        // Step 5. Let result be a new promise object.
511        let in_realm_proof = AlreadyInRealm::assert::<crate::DomTypeHolder>();
512        let promise = Promise::new_in_current_realm(InRealm::Already(&in_realm_proof), can_gc);
513
514        // Step 1. If the value of this's [[Detached]] internal slot is true,
515        // then return a promise rejected with an "InvalidStateError"
516        // DOMException.
517        if let Some(OffscreenRenderingContext::Detached) = *self.context.borrow() {
518            promise.reject_error(Error::InvalidState(None), can_gc);
519            return promise;
520        }
521
522        // Step 2. If this's context mode is 2d and the rendering context's
523        // output bitmap's origin-clean flag is set to false, then return a
524        // promise rejected with a "SecurityError" DOMException.
525        if !self.origin_is_clean() {
526            promise.reject_error(Error::Security(None), can_gc);
527            return promise;
528        }
529
530        // Step 3. If this's bitmap has no pixels (i.e., either its horizontal
531        // dimension or its vertical dimension is zero), then return a promise
532        // rejected with an "IndexSizeError" DOMException.
533        if self.Width() == 0 || self.Height() == 0 {
534            promise.reject_error(Error::IndexSize(None), can_gc);
535            return promise;
536        }
537
538        // Step 4. Let bitmap be a copy of this's bitmap.
539        let Some(mut snapshot) = self.get_image_data() else {
540            promise.reject_error(Error::InvalidState(None), can_gc);
541            return promise;
542        };
543
544        // Step 7. Run these steps in parallel:
545        // Step 7.1. Let file be a serialization of bitmap as a file, with
546        // options's type and quality if present.
547        // Step 7.2. Queue a global task on the canvas blob serialization task
548        // source given global to run these steps:
549        let trusted_this = Trusted::new(self);
550        let trusted_promise = TrustedPromise::new(promise.clone());
551
552        let image_type = EncodedImageType::from(options.type_.to_string());
553        let quality = options.quality;
554
555        self.global()
556            .task_manager()
557            .canvas_blob_task_source()
558            .queue(task!(convert_to_blob: move |cx| {
559                let this = trusted_this.root();
560                let promise = trusted_promise.root();
561
562                let mut encoded: Vec<u8> = vec![];
563
564                if snapshot.encode_for_mime_type(&image_type, quality, &mut encoded).is_err() {
565                    // Step 7.2.1. If file is null, then reject result with an
566                    // "EncodingError" DOMException.
567                    promise.reject_error(Error::Encoding(None), CanGc::from_cx(cx));
568                    return;
569                };
570
571                // Step 7.2.2. Otherwise, resolve result with a new Blob object,
572                // created in global's relevant realm, representing file.
573                let blob_impl = BlobImpl::new_from_bytes(encoded, image_type.as_mime_type());
574                let blob = Blob::new(&this.global(), blob_impl, CanGc::from_cx(cx));
575
576                promise.resolve_native(&blob, CanGc::from_cx(cx));
577            }));
578
579        // Step 8. Return result.
580        promise
581    }
582}
script/dom/canvas/offscreencanvas.rs

script/dom/canvas/
offscreencanvas.rs
