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

script/dom/canvas/
offscreencanvas.rs
