webgpu/
canvas_context.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
5//! Main process implementation of [GPUCanvasContext](https://www.w3.org/TR/webgpu/#canvas-context)
6
7use std::ptr::NonNull;
8use std::sync::{Arc, Mutex};
9
10use arrayvec::ArrayVec;
11use base::Epoch;
12use compositing_traits::{
13    CrossProcessCompositorApi, ExternalImageSource, SerializableImageData,
14    WebRenderExternalImageApi,
15};
16use euclid::default::Size2D;
17use ipc_channel::ipc::IpcSender;
18use log::warn;
19use pixels::{SharedSnapshot, Snapshot, SnapshotAlphaMode, SnapshotPixelFormat};
20use rustc_hash::FxHashMap;
21use webgpu_traits::{
22    ContextConfiguration, PRESENTATION_BUFFER_COUNT, PendingTexture, WebGPUContextId, WebGPUMsg,
23};
24use webrender_api::units::DeviceIntSize;
25use webrender_api::{
26    ExternalImageData, ExternalImageId, ExternalImageType, ImageDescriptor, ImageDescriptorFlags,
27    ImageFormat, ImageKey,
28};
29use wgpu_core::device::HostMap;
30use wgpu_core::global::Global;
31use wgpu_core::id::{
32    self, BufferId, CommandBufferId, CommandEncoderId, DeviceId, QueueId, TextureId,
33};
34use wgpu_core::resource::{
35    BufferAccessError, BufferDescriptor, BufferMapOperation, CreateBufferError,
36};
37use wgpu_types::{
38    BufferUsages, COPY_BYTES_PER_ROW_ALIGNMENT, CommandBufferDescriptor, CommandEncoderDescriptor,
39    Extent3d, Origin3d, TexelCopyBufferInfo, TexelCopyBufferLayout, TexelCopyTextureInfo,
40    TextureAspect,
41};
42
43pub type WebGpuExternalImageMap = Arc<Mutex<FxHashMap<WebGPUContextId, ContextData>>>;
44
45const fn image_data(context_id: WebGPUContextId) -> ExternalImageData {
46    ExternalImageData {
47        id: ExternalImageId(context_id.0),
48        channel_index: 0,
49        image_type: ExternalImageType::Buffer,
50        normalized_uvs: false,
51    }
52}
53
54/// Allocated buffer on GPU device
55#[derive(Clone, Copy, Debug)]
56struct Buffer {
57    device_id: DeviceId,
58    queue_id: QueueId,
59    size: u64,
60}
61
62impl Buffer {
63    /// Returns true if buffer is compatible with provided configuration
64    fn has_compatible_config(&self, config: &ContextConfiguration) -> bool {
65        config.device_id == self.device_id && self.size == config.buffer_size()
66    }
67}
68
69/// Mapped GPUBuffer
70#[derive(Debug)]
71struct MappedBuffer {
72    buffer: Buffer,
73    data: NonNull<u8>,
74    len: u64,
75    image_size: Size2D<u32>,
76    image_format: ImageFormat,
77    is_opaque: bool,
78}
79
80// Mapped buffer can be shared between safely (it's read-only)
81unsafe impl Send for MappedBuffer {}
82
83impl MappedBuffer {
84    const fn slice(&'_ self) -> &'_ [u8] {
85        // Safety: Pointer is from wgpu, and we only use it here
86        unsafe { std::slice::from_raw_parts(self.data.as_ptr(), self.len as usize) }
87    }
88
89    fn stride(&self) -> u32 {
90        (self.image_size.width * self.image_format.bytes_per_pixel() as u32)
91            .next_multiple_of(COPY_BYTES_PER_ROW_ALIGNMENT)
92    }
93}
94
95#[derive(Debug)]
96enum StagingBufferState {
97    /// The Initial state: the buffer has yet to be created with only an
98    /// id reserved for it.
99    Unassigned,
100    /// The buffer is allocated in the WGPU Device and is ready to be used.
101    Available(Buffer),
102    /// `mapAsync` is currently running on the buffer.
103    Mapping(Buffer),
104    /// The buffer is currently mapped.
105    Mapped(MappedBuffer),
106}
107
108/// A staging buffer used for texture to buffer to CPU copy operations.
109#[derive(Debug)]
110struct StagingBuffer {
111    global: Arc<Global>,
112    buffer_id: BufferId,
113    state: StagingBufferState,
114}
115
116// [`StagingBuffer`] only used for reading (never for writing)
117// so it is safe to share between threads.
118unsafe impl Sync for StagingBuffer {}
119
120impl StagingBuffer {
121    fn new(global: Arc<Global>, buffer_id: BufferId) -> Self {
122        Self {
123            global,
124            buffer_id,
125            state: StagingBufferState::Unassigned,
126        }
127    }
128
129    const fn is_mapped(&self) -> bool {
130        matches!(self.state, StagingBufferState::Mapped(..))
131    }
132
133    /// Return true if buffer can be used directly with provided config
134    /// without any additional work
135    fn is_available_and_has_compatible_config(&self, config: &ContextConfiguration) -> bool {
136        let StagingBufferState::Available(buffer) = &self.state else {
137            return false;
138        };
139        buffer.has_compatible_config(config)
140    }
141
142    /// Return true if buffer is not mapping or being mapped
143    const fn needs_assignment(&self) -> bool {
144        matches!(
145            self.state,
146            StagingBufferState::Unassigned | StagingBufferState::Available(_)
147        )
148    }
149
150    /// Make buffer available by unmapping / destroying it and then recreating it if needed.
151    fn ensure_available(&mut self, config: &ContextConfiguration) -> Result<(), CreateBufferError> {
152        let recreate = match &self.state {
153            StagingBufferState::Unassigned => true,
154            StagingBufferState::Available(buffer) |
155            StagingBufferState::Mapping(buffer) |
156            StagingBufferState::Mapped(MappedBuffer { buffer, .. }) => {
157                if buffer.has_compatible_config(config) {
158                    let _ = self.global.buffer_unmap(self.buffer_id);
159                    false
160                } else {
161                    self.global.buffer_drop(self.buffer_id);
162                    true
163                }
164            },
165        };
166        if recreate {
167            let buffer_size = config.buffer_size();
168            let (_, error) = self.global.device_create_buffer(
169                config.device_id,
170                &BufferDescriptor {
171                    label: None,
172                    size: buffer_size,
173                    usage: BufferUsages::MAP_READ | BufferUsages::COPY_DST,
174                    mapped_at_creation: false,
175                },
176                Some(self.buffer_id),
177            );
178            if let Some(error) = error {
179                return Err(error);
180            };
181            self.state = StagingBufferState::Available(Buffer {
182                device_id: config.device_id,
183                queue_id: config.queue_id,
184                size: buffer_size,
185            });
186        }
187        Ok(())
188    }
189
190    /// Makes buffer available and prepares command encoder
191    /// that will copy texture to this staging buffer.
192    ///
193    /// Caller must submit command buffer to queue.
194    fn prepare_load_texture_command_buffer(
195        &mut self,
196        texture_id: TextureId,
197        encoder_id: CommandEncoderId,
198        config: &ContextConfiguration,
199    ) -> Result<CommandBufferId, Box<dyn std::error::Error>> {
200        self.ensure_available(config)?;
201        let StagingBufferState::Available(buffer) = &self.state else {
202            unreachable!("Should be made available by `ensure_available`")
203        };
204        let device_id = buffer.device_id;
205        let command_descriptor = CommandEncoderDescriptor { label: None };
206        let (encoder_id, error) = self.global.device_create_command_encoder(
207            device_id,
208            &command_descriptor,
209            Some(encoder_id),
210        );
211        if let Some(error) = error {
212            return Err(error.into());
213        };
214        let buffer_info = TexelCopyBufferInfo {
215            buffer: self.buffer_id,
216            layout: TexelCopyBufferLayout {
217                offset: 0,
218                bytes_per_row: Some(config.stride()),
219                rows_per_image: None,
220            },
221        };
222        let texture_info = TexelCopyTextureInfo {
223            texture: texture_id,
224            mip_level: 0,
225            origin: Origin3d::ZERO,
226            aspect: TextureAspect::All,
227        };
228        let copy_size = Extent3d {
229            width: config.size.width,
230            height: config.size.height,
231            depth_or_array_layers: 1,
232        };
233        self.global.command_encoder_copy_texture_to_buffer(
234            encoder_id,
235            &texture_info,
236            &buffer_info,
237            &copy_size,
238        )?;
239        let (command_buffer_id, error) = self
240            .global
241            .command_encoder_finish(encoder_id, &CommandBufferDescriptor::default());
242        if let Some(error) = error {
243            return Err(error.into());
244        };
245        Ok(command_buffer_id)
246    }
247
248    /// Unmaps the buffer or cancels a mapping operation if one is in progress.
249    fn unmap(&mut self) {
250        match self.state {
251            StagingBufferState::Unassigned | StagingBufferState::Available(_) => {},
252            StagingBufferState::Mapping(buffer) |
253            StagingBufferState::Mapped(MappedBuffer { buffer, .. }) => {
254                let _ = self.global.buffer_unmap(self.buffer_id);
255                self.state = StagingBufferState::Available(buffer)
256            },
257        }
258    }
259
260    /// Obtain a snapshot from this buffer if is mapped or return `None` if it is not mapped.
261    fn snapshot(&self) -> Option<Snapshot> {
262        let StagingBufferState::Mapped(mapped) = &self.state else {
263            return None;
264        };
265        let format = match mapped.image_format {
266            ImageFormat::RGBA8 => SnapshotPixelFormat::RGBA,
267            ImageFormat::BGRA8 => SnapshotPixelFormat::BGRA,
268            _ => unreachable!("GPUCanvasContext does not support other formats per spec"),
269        };
270        let alpha_mode = if mapped.is_opaque {
271            SnapshotAlphaMode::AsOpaque {
272                premultiplied: false,
273            }
274        } else {
275            SnapshotAlphaMode::Transparent {
276                premultiplied: true,
277            }
278        };
279        let padded_byte_width = mapped.stride();
280        let data = mapped.slice();
281        let bytes_per_pixel = mapped.image_format.bytes_per_pixel() as usize;
282        let mut result_unpadded =
283            Vec::<u8>::with_capacity(mapped.image_size.area() as usize * bytes_per_pixel);
284        for row in 0..mapped.image_size.height {
285            let start = (row * padded_byte_width).try_into().ok()?;
286            result_unpadded
287                .extend(&data[start..start + mapped.image_size.width as usize * bytes_per_pixel]);
288        }
289        let mut snapshot =
290            Snapshot::from_vec(mapped.image_size, format, alpha_mode, result_unpadded);
291        if mapped.is_opaque {
292            snapshot.transform(SnapshotAlphaMode::Opaque, snapshot.format())
293        }
294        Some(snapshot)
295    }
296}
297
298impl Drop for StagingBuffer {
299    fn drop(&mut self) {
300        match self.state {
301            StagingBufferState::Unassigned => {},
302            StagingBufferState::Available(_) |
303            StagingBufferState::Mapping(_) |
304            StagingBufferState::Mapped(_) => {
305                self.global.buffer_drop(self.buffer_id);
306            },
307        }
308    }
309}
310
311pub struct WebGpuExternalImages {
312    pub image_map: WebGpuExternalImageMap,
313    pub locked_ids: FxHashMap<WebGPUContextId, PresentationStagingBuffer>,
314}
315
316impl WebGpuExternalImages {
317    pub fn new(image_map: WebGpuExternalImageMap) -> Self {
318        Self {
319            image_map,
320            locked_ids: Default::default(),
321        }
322    }
323}
324
325impl WebRenderExternalImageApi for WebGpuExternalImages {
326    fn lock(&mut self, id: u64) -> (ExternalImageSource<'_>, Size2D<i32>) {
327        let id = WebGPUContextId(id);
328        let presentation = {
329            let mut webgpu_contexts = self.image_map.lock().unwrap();
330            webgpu_contexts
331                .get_mut(&id)
332                .and_then(|context_data| context_data.presentation.clone())
333        };
334        let Some(presentation) = presentation else {
335            return (ExternalImageSource::Invalid, Size2D::zero());
336        };
337        self.locked_ids.insert(id, presentation);
338        let presentation = self.locked_ids.get(&id).unwrap();
339        let StagingBufferState::Mapped(mapped_buffer) = &presentation.staging_buffer.state else {
340            unreachable!("Presentation staging buffer should be mapped")
341        };
342        let size = mapped_buffer.image_size;
343        (
344            ExternalImageSource::RawData(mapped_buffer.slice()),
345            size.cast().cast_unit(),
346        )
347    }
348
349    fn unlock(&mut self, id: u64) {
350        let id = WebGPUContextId(id);
351        let Some(presentation) = self.locked_ids.remove(&id) else {
352            return;
353        };
354        let mut webgpu_contexts = self.image_map.lock().unwrap();
355        if let Some(context_data) = webgpu_contexts.get_mut(&id) {
356            // We use this to return staging buffer if a newer one exists.
357            presentation.maybe_destroy(context_data);
358        } else {
359            // This will not free this buffer id in script,
360            // but that's okay because we still have many free ids.
361            drop(presentation);
362        }
363    }
364}
365
366/// Staging buffer currently used for presenting the epoch.
367///
368/// Users should [`ContextData::replace_presentation`] when done.
369#[derive(Clone)]
370pub struct PresentationStagingBuffer {
371    epoch: Epoch,
372    staging_buffer: Arc<StagingBuffer>,
373}
374
375impl PresentationStagingBuffer {
376    fn new(epoch: Epoch, staging_buffer: StagingBuffer) -> Self {
377        Self {
378            epoch,
379            staging_buffer: Arc::new(staging_buffer),
380        }
381    }
382
383    /// If the internal staging buffer is not shared,
384    /// unmap it and call [`ContextData::return_staging_buffer`] with it.
385    fn maybe_destroy(self, context_data: &mut ContextData) {
386        if let Some(mut staging_buffer) = Arc::into_inner(self.staging_buffer) {
387            staging_buffer.unmap();
388            context_data.return_staging_buffer(staging_buffer);
389        }
390    }
391}
392
393/// The embedder process-side representation of what is the `GPUCanvasContext` in script.
394pub struct ContextData {
395    /// The [`ImageKey`] of the WebRender image associated with this context.
396    image_key: Option<ImageKey>,
397    /// The current size of this context.
398    size: DeviceIntSize,
399    /// Staging buffers that are not actively used.
400    ///
401    /// Staging buffer here are either [`StagingBufferState::Unassigned`] or [`StagingBufferState::Available`].
402    /// They are removed from here when they are in process of being mapped or are already mapped.
403    inactive_staging_buffers: ArrayVec<StagingBuffer, PRESENTATION_BUFFER_COUNT>,
404    /// The [`PresentationStagingBuffer`] of the most recent presentation. This will
405    /// be `None` directly after initialization, as clearing is handled completely in
406    /// the `ScriptThread`.
407    presentation: Option<PresentationStagingBuffer>,
408    /// Next epoch to be used
409    next_epoch: Epoch,
410}
411
412impl ContextData {
413    fn new(
414        global: &Arc<Global>,
415        buffer_ids: ArrayVec<id::BufferId, PRESENTATION_BUFFER_COUNT>,
416        size: DeviceIntSize,
417    ) -> Self {
418        Self {
419            image_key: None,
420            size,
421            inactive_staging_buffers: buffer_ids
422                .iter()
423                .map(|buffer_id| StagingBuffer::new(global.clone(), *buffer_id))
424                .collect(),
425            presentation: None,
426            next_epoch: Epoch(1),
427        }
428    }
429
430    /// Returns `None` if no staging buffer is unused or failure when making it available
431    fn get_or_make_available_buffer(
432        &'_ mut self,
433        config: &ContextConfiguration,
434    ) -> Option<StagingBuffer> {
435        self.inactive_staging_buffers
436            .iter()
437            // Try to get first preallocated GPUBuffer.
438            .position(|staging_buffer| {
439                staging_buffer.is_available_and_has_compatible_config(config)
440            })
441            // Fall back to the first inactive staging buffer.
442            .or_else(|| {
443                self.inactive_staging_buffers
444                    .iter()
445                    .position(|staging_buffer| staging_buffer.needs_assignment())
446            })
447            // Or just the use first one.
448            .or_else(|| {
449                if self.inactive_staging_buffers.is_empty() {
450                    None
451                } else {
452                    Some(0)
453                }
454            })
455            .and_then(|index| {
456                let mut staging_buffer = self.inactive_staging_buffers.remove(index);
457                if staging_buffer.ensure_available(config).is_ok() {
458                    Some(staging_buffer)
459                } else {
460                    // If we fail to make it available, return it to the list of inactive staging buffers.
461                    self.inactive_staging_buffers.push(staging_buffer);
462                    None
463                }
464            })
465    }
466
467    /// Destroy the context that this [`ContextData`] represents,
468    /// freeing all of its buffers, and deleting the associated WebRender image.
469    fn destroy(
470        mut self,
471        script_sender: &IpcSender<WebGPUMsg>,
472        compositor_api: &CrossProcessCompositorApi,
473    ) {
474        // This frees the id in the `ScriptThread`.
475        for staging_buffer in self.inactive_staging_buffers {
476            if let Err(error) = script_sender.send(WebGPUMsg::FreeBuffer(staging_buffer.buffer_id))
477            {
478                warn!(
479                    "Unable to send FreeBuffer({:?}) ({error})",
480                    staging_buffer.buffer_id
481                );
482            };
483        }
484        if let Some(image_key) = self.image_key.take() {
485            compositor_api.delete_image(image_key);
486        }
487    }
488
489    /// Advance the [`Epoch`] and return the new one.
490    fn next_epoch(&mut self) -> Epoch {
491        let epoch = self.next_epoch;
492        self.next_epoch.next();
493        epoch
494    }
495
496    /// If the given [`PresentationStagingBuffer`] is for a newer presentation, replace the existing
497    /// one. Deallocate the older one by calling [`Self::return_staging_buffer`] on it.
498    fn replace_presentation(&mut self, presentation: PresentationStagingBuffer) {
499        let stale_presentation = if presentation.epoch >=
500            self.presentation
501                .as_ref()
502                .map(|p| p.epoch)
503                .unwrap_or_default()
504        {
505            self.presentation.replace(presentation)
506        } else {
507            Some(presentation)
508        };
509        if let Some(stale_presentation) = stale_presentation {
510            stale_presentation.maybe_destroy(self);
511        }
512    }
513
514    fn clear_presentation(&mut self) {
515        if let Some(stale_presentation) = self.presentation.take() {
516            stale_presentation.maybe_destroy(self);
517        }
518    }
519
520    fn return_staging_buffer(&mut self, staging_buffer: StagingBuffer) {
521        self.inactive_staging_buffers.push(staging_buffer)
522    }
523}
524
525impl crate::WGPU {
526    pub(crate) fn create_context(
527        &self,
528        context_id: WebGPUContextId,
529        size: DeviceIntSize,
530        buffer_ids: ArrayVec<id::BufferId, PRESENTATION_BUFFER_COUNT>,
531    ) {
532        let context_data = ContextData::new(&self.global, buffer_ids, size);
533        assert!(
534            self.wgpu_image_map
535                .lock()
536                .unwrap()
537                .insert(context_id, context_data)
538                .is_none(),
539            "Context should be created only once!"
540        );
541    }
542
543    pub(crate) fn set_image_key(&self, context_id: WebGPUContextId, image_key: ImageKey) {
544        let mut webgpu_contexts = self.wgpu_image_map.lock().unwrap();
545        let context_data = webgpu_contexts.get_mut(&context_id).unwrap();
546
547        if let Some(old_image_key) = context_data.image_key.replace(image_key) {
548            self.compositor_api.delete_image(old_image_key);
549        }
550
551        self.compositor_api.add_image(
552            image_key,
553            ImageDescriptor {
554                format: ImageFormat::BGRA8,
555                size: context_data.size,
556                stride: None,
557                offset: 0,
558                flags: ImageDescriptorFlags::empty(),
559            },
560            SerializableImageData::External(image_data(context_id)),
561        );
562    }
563
564    pub(crate) fn get_image(
565        &self,
566        context_id: WebGPUContextId,
567        pending_texture: Option<PendingTexture>,
568        sender: IpcSender<SharedSnapshot>,
569    ) {
570        let mut webgpu_contexts = self.wgpu_image_map.lock().unwrap();
571        let context_data = webgpu_contexts.get_mut(&context_id).unwrap();
572        if let Some(PendingTexture {
573            texture_id,
574            encoder_id,
575            configuration,
576        }) = pending_texture
577        {
578            let Some(staging_buffer) = context_data.get_or_make_available_buffer(&configuration)
579            else {
580                warn!("Failure obtaining available staging buffer");
581                sender
582                    .send(SharedSnapshot::cleared(configuration.size))
583                    .unwrap();
584                return;
585            };
586
587            let epoch = context_data.next_epoch();
588            let wgpu_image_map = self.wgpu_image_map.clone();
589            let sender = sender.clone();
590            drop(webgpu_contexts);
591            self.texture_download(
592                texture_id,
593                encoder_id,
594                staging_buffer,
595                configuration,
596                move |staging_buffer| {
597                    let mut webgpu_contexts = wgpu_image_map.lock().unwrap();
598                    let context_data = webgpu_contexts.get_mut(&context_id).unwrap();
599                    sender
600                        .send(
601                            staging_buffer
602                                .snapshot()
603                                .as_ref()
604                                .map(Snapshot::to_shared)
605                                .unwrap_or_else(|| SharedSnapshot::cleared(configuration.size)),
606                        )
607                        .unwrap();
608                    if staging_buffer.is_mapped() {
609                        context_data.replace_presentation(PresentationStagingBuffer::new(
610                            epoch,
611                            staging_buffer,
612                        ));
613                    } else {
614                        // failure
615                        context_data.return_staging_buffer(staging_buffer);
616                    }
617                },
618            );
619        } else {
620            sender
621                .send(
622                    context_data
623                        .presentation
624                        .as_ref()
625                        .and_then(|presentation_staging_buffer| {
626                            presentation_staging_buffer.staging_buffer.snapshot()
627                        })
628                        .unwrap_or_else(Snapshot::empty)
629                        .to_shared(),
630                )
631                .unwrap();
632        }
633    }
634
635    /// Read the texture to the staging buffer, map it to CPU memory, and update the
636    /// image in WebRender when complete.
637    pub(crate) fn present(
638        &self,
639        context_id: WebGPUContextId,
640        pending_texture: Option<PendingTexture>,
641        size: Size2D<u32>,
642        canvas_epoch: Epoch,
643    ) {
644        let mut webgpu_contexts = self.wgpu_image_map.lock().unwrap();
645        let context_data = webgpu_contexts.get_mut(&context_id).unwrap();
646
647        let Some(image_key) = context_data.image_key else {
648            return;
649        };
650
651        let Some(PendingTexture {
652            texture_id,
653            encoder_id,
654            configuration,
655        }) = pending_texture
656        else {
657            context_data.clear_presentation();
658            self.compositor_api.update_image(
659                image_key,
660                ImageDescriptor {
661                    format: ImageFormat::BGRA8,
662                    size: size.cast_unit().cast(),
663                    stride: None,
664                    offset: 0,
665                    flags: ImageDescriptorFlags::empty(),
666                },
667                SerializableImageData::External(image_data(context_id)),
668                Some(canvas_epoch),
669            );
670            return;
671        };
672        let Some(staging_buffer) = context_data.get_or_make_available_buffer(&configuration) else {
673            warn!("Failure obtaining available staging buffer");
674            context_data.clear_presentation();
675            self.compositor_api.update_image(
676                image_key,
677                configuration.into(),
678                SerializableImageData::External(image_data(context_id)),
679                Some(canvas_epoch),
680            );
681            return;
682        };
683        let epoch = context_data.next_epoch();
684        let wgpu_image_map = self.wgpu_image_map.clone();
685        let compositor_api = self.compositor_api.clone();
686        drop(webgpu_contexts);
687        self.texture_download(
688            texture_id,
689            encoder_id,
690            staging_buffer,
691            configuration,
692            move |staging_buffer| {
693                let mut webgpu_contexts = wgpu_image_map.lock().unwrap();
694                let context_data = webgpu_contexts.get_mut(&context_id).unwrap();
695                if staging_buffer.is_mapped() {
696                    context_data.replace_presentation(PresentationStagingBuffer::new(
697                        epoch,
698                        staging_buffer,
699                    ));
700                } else {
701                    context_data.return_staging_buffer(staging_buffer);
702                    context_data.clear_presentation();
703                }
704                // update image in WR
705                compositor_api.update_image(
706                    image_key,
707                    configuration.into(),
708                    SerializableImageData::External(image_data(context_id)),
709                    Some(canvas_epoch),
710                );
711            },
712        );
713    }
714
715    /// Copies data from provided texture using `encoder_id` to the provided [`StagingBuffer`].
716    ///
717    /// `callback` is guaranteed to be called.
718    ///
719    /// Returns a [`StagingBuffer`] with the [`StagingBufferState::Mapped`] state
720    /// on success or [`StagingBufferState::Available`] on failure.
721    fn texture_download(
722        &self,
723        texture_id: TextureId,
724        encoder_id: CommandEncoderId,
725        mut staging_buffer: StagingBuffer,
726        config: ContextConfiguration,
727        callback: impl FnOnce(StagingBuffer) + Send + 'static,
728    ) {
729        let Ok(command_buffer_id) =
730            staging_buffer.prepare_load_texture_command_buffer(texture_id, encoder_id, &config)
731        else {
732            return callback(staging_buffer);
733        };
734        let StagingBufferState::Available(buffer) = &staging_buffer.state else {
735            unreachable!("`prepare_load_texture_command_buffer` should make buffer available")
736        };
737        let buffer_id = staging_buffer.buffer_id;
738        let buffer_size = buffer.size;
739        {
740            let _guard = self.poller.lock();
741            let result = self
742                .global
743                .queue_submit(buffer.queue_id, &[command_buffer_id]);
744            if result.is_err() {
745                return callback(staging_buffer);
746            }
747        }
748        staging_buffer.state = match staging_buffer.state {
749            StagingBufferState::Available(buffer) => StagingBufferState::Mapping(buffer),
750            _ => unreachable!("`prepare_load_texture_command_buffer` should make buffer available"),
751        };
752        let map_callback = {
753            let token = self.poller.token();
754            Box::new(move |result: Result<(), BufferAccessError>| {
755                drop(token);
756                staging_buffer.state = match staging_buffer.state {
757                    StagingBufferState::Mapping(buffer) => {
758                        if let Ok((data, len)) = result.and_then(|_| {
759                            staging_buffer.global.buffer_get_mapped_range(
760                                staging_buffer.buffer_id,
761                                0,
762                                Some(buffer.size),
763                            )
764                        }) {
765                            StagingBufferState::Mapped(MappedBuffer {
766                                buffer,
767                                data,
768                                len,
769                                image_size: config.size,
770                                image_format: config.format,
771                                is_opaque: config.is_opaque,
772                            })
773                        } else {
774                            StagingBufferState::Available(buffer)
775                        }
776                    },
777                    _ => {
778                        unreachable!("Mapping buffer should have StagingBufferState::Mapping state")
779                    },
780                };
781                callback(staging_buffer);
782            })
783        };
784        let map_op = BufferMapOperation {
785            host: HostMap::Read,
786            callback: Some(map_callback),
787        };
788        // error is handled by map_callback
789        let _ = self
790            .global
791            .buffer_map_async(buffer_id, 0, Some(buffer_size), map_op);
792        self.poller.wake();
793    }
794
795    pub(crate) fn destroy_context(&mut self, context_id: WebGPUContextId) {
796        self.wgpu_image_map
797            .lock()
798            .unwrap()
799            .remove(&context_id)
800            .unwrap()
801            .destroy(&self.script_sender, &self.compositor_api);
802    }
803}
webgpu/canvas_context.rs

webgpu/
canvas_context.rs
