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Introduce snapshot concept of canvas (#36119)

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Each canvas context returns snapshot instead of just raw bytes. This
allows as to hold off conversions (BGRA <-> RGBA, (un)premultiply) to
when/if they are actually needed. For example when loading snapshot into
webgl we can load both RGBA and BGRA so no conversion is really needed.

Currently whole thing is designed to be able to be extend on
https://github.com/servo/ipc-channel/pull/356, to make less copies.
Hence some commented out code.


Fixes #35759
There are tests for these changes in WPT

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
This commit is contained in:
sagudev 2025-04-23 09:32:47 +02:00 • committed by GitHub
parent b6967fc4c8
commit 73b778e67f
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37 changed files with 724 additions and 251 deletions
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36
components/script/dom/webglrenderingcontext.rs
View file

@ -34,6 +34,7 @@ use pixels::{self, PixelFormat};
use script_layout_interface::HTMLCanvasDataSource;
use serde::{Deserialize, Serialize};
use servo_config::pref;
use snapshot::Snapshot;
use webrender_api::ImageKey;
use crate::canvas_context::CanvasContext;
@ -628,11 +629,15 @@ impl WebGLRenderingContext {
if !canvas.origin_is_clean() {
return Err(Error::Security);
}
if let Some((data, size)) = canvas.fetch_all_data() {
let data = data.unwrap_or_else(|| {
IpcSharedMemory::from_bytes(&vec![0; size.area() as usize * 4])
});
TexPixels::new(data, size, PixelFormat::BGRA8, true)
if let Some(snapshot) = canvas.get_image_data() {
let snapshot = snapshot.as_ipc();
let size = snapshot.size().cast();
let format = match snapshot.format() {
snapshot::PixelFormat::RGBA => PixelFormat::RGBA8,
snapshot::PixelFormat::BGRA => PixelFormat::BGRA8,
};
let premultiply = snapshot.alpha_mode().is_premultiplied();
TexPixels::new(snapshot.to_ipc_shared_memory(), size, format, premultiply)
} else {
return Ok(None);
}
@ -1922,18 +1927,13 @@ impl CanvasContext for WebGLRenderingContext {
}
}
fn get_image_data_as_shared_memory(&self) -> Option<IpcSharedMemory> {
// TODO: add a method in WebGLRenderingContext to get the pixels.
None
}
// Used by HTMLCanvasElement.toDataURL
//
// This emits errors quite liberally, but the spec says that this operation
// can fail and that it is UB what happens in that case.
//
// https://www.khronos.org/registry/webgl/specs/latest/1.0/#2.2
fn get_image_data(&self) -> Option<Vec<u8>> {
fn get_image_data(&self) -> Option<Snapshot> {
handle_potential_webgl_error!(self, self.validate_framebuffer(), return None);
let mut size = self.size().cast();
@ -1945,14 +1945,20 @@ impl CanvasContext for WebGLRenderingContext {
size.width = cmp::min(size.width, fb_width as u32);
size.height = cmp::min(size.height, fb_height as u32);
let (sender, receiver) = ipc::bytes_channel().unwrap();
let (sender, receiver) = ipc::channel().unwrap();
self.send_command(WebGLCommand::ReadPixels(
Rect::from_size(size),
constants::RGBA,
constants::UNSIGNED_BYTE,
sender,
));
Some(receiver.recv().unwrap())
let (data, alpha_mode) = receiver.recv().unwrap();
Some(Snapshot::from_vec(
size.cast(),
snapshot::PixelFormat::RGBA,
alpha_mode,
data.to_vec(),
))
}
fn mark_as_dirty(&self) {
@ -3826,11 +3832,11 @@ impl WebGLRenderingContextMethods<crate::DomTypeHolder> for WebGLRenderingContex
dest_offset += -y * row_len;
}
let (sender, receiver) = ipc::bytes_channel().unwrap();
let (sender, receiver) = ipc::channel().unwrap();
self.send_command(WebGLCommand::ReadPixels(
src_rect, format, pixel_type, sender,
));
let src = receiver.recv().unwrap();
let (src, _) = receiver.recv().unwrap();
let src_row_len = src_rect.size.width as usize * bytes_per_pixel as usize;
for i in 0..src_rect.size.height {