Feature request: split PixmapMut into ranges of scan lines

[Pr0methean]

I have a task that creates a vertical stack of animation frames, where each frame is rendered separately. If I had a separate PixmapMut for each frame, then I'd be able to render the frames in parallel without needing any synchronization. And since a range of scan lines is a contiguous range of bytes, this should be feasible with the existing PixmapMut type.

[RazrFalcon]

Can you illustrate what you want with some code?

[Pr0methean]

I'd like to turn this:

    let out = Arc::new(Mutex::new(out));
    let mut join_set = JoinSet::new();
    for (index, frame) in frames.into_vec().into_iter().enumerate() {
        let out = out.clone();
        join_set.spawn(frame.map(async move |frame_pixmap: SimpleArcow<MaybeFromPool<Pixmap>>| {
            out.lock().draw_pixmap(
                0,
                (index as i32) * (frame_height as i32),
                frame_pixmap.as_ref(),
                &PixmapPaint::default(),
                Transform::default(),
                None,
            );
        }));
    }

into this:

    let mut remainder = out;
    for (index, frame) in frames.into_vec().into_iter().enumerate() {
        let (frame_out, remainder) = remainder.split_at_scan_line(frame_height);
        join_set.spawn(frame.map(async move |frame_pixmap: SimpleArcow<MaybeFromPool<Pixmap>>| {
            frame_out.draw_pixmap(
                0,
                0,
                frame_pixmap.as_ref(),
                &PixmapPaint::default(),
                Transform::default(),
                None,
            );
        }));
    }

[RazrFalcon]

So you basically want a wrapper for slice::split_at_mut? It might be doable, but would take a while to implement.
For now you can do it on your side.

[Pr0methean]

Yeah, that's the idea.

…

On Tue, Apr 2, 2024, 05:04 Yevhenii Reizner ***@***.***> wrote: So you basically want a wrapper for slice::split_at_mut? It might be doable, but would take a while to implement. For now you can do it on your side. — Reply to this email directly, view it on GitHub <#118 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABF3NBNYLWVJVERPB2IT2JTY3KNDDAVCNFSM6AAAAABFSAW7B2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMZRHA3DAOJXHA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[Pr0methean]

I've managed to do it on my end, but it's an ugly solution because variables used from inside a JoinSet have to be &'static.

    let out = Box::leak(Box::new(if clear_output {
        allocate_pixmap_empty(width, total_height)
    } else {
        allocate_pixmap_for_overwrite(background.width(), total_height)
    })) as *mut MaybeFromPool<Pixmap>;
    let background = (*background).as_ref();
    let out_data = unsafe { out.as_mut() }.unwrap().data_mut();
    let mut frame_chunks = out_data.chunks_mut(
        frame_height as usize * width as usize * size_of::<PremultipliedColorU8>()
    );
    let mut join_set = JoinSet::new();
    for frame in frames.into_vec().into_iter() {
        let frame_pixels = frame_chunks.next().unwrap();
        let mut frame_buffer = PixmapMut::from_bytes(frame_pixels, width, frame_height).unwrap();
        frame_buffer.draw_pixmap(
            0,
            0,
            background,
            &PixmapPaint::default(),
            Transform::default(),
            None,
        );
        let frame_buffer = Box::new(frame_buffer);
        join_set.spawn(frame.map(async move |frame_pixmap: SimpleArcow<MaybeFromPool<Pixmap>>| {
            Box::leak(frame_buffer).draw_pixmap(
                0,
                0,
                frame_pixmap.as_ref(),
                &PixmapPaint::default(),
                Transform::default(),
                None,
            );
        }));
    }
    let out = unsafe { Box::from_raw(out) };
    join_all(join_set).await;