Skip to content

android: Make the backend zero-copy #331

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
MarijnS95 wants to merge 1 commit into
base: master
Choose a base branch
from
+19 −21
Draft

android: Make the backend zero-copy #331

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 19 additions & 21 deletions src/backends/android.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use raw_window_handle::AndroidNdkWindowHandle;
use raw_window_handle::{HasDisplayHandle, HasWindowHandle, RawWindowHandle};

use crate::error::InitError;
use crate::{util, BufferInterface, Pixel, Rect, SoftBufferError, SurfaceInterface};
use crate::{BufferInterface, Pixel, Rect, SoftBufferError, SurfaceInterface};

/// The handle to a window for software buffering.
#[derive(Debug)]
Expand Down Expand Up @@ -52,7 +52,7 @@ impl<D: HasDisplayHandle, W: HasWindowHandle> SurfaceInterface<D, W> for Android
&self.window
}

/// Also changes the pixel format to [`HardwareBufferFormat::R8G8B8A8_UNORM`].
/// Also changes the pixel format to [`HardwareBufferFormat::R8G8B8X8_UNORM`].
fn resize(&mut self, width: NonZeroU32, height: NonZeroU32) -> Result<(), SoftBufferError> {
let (width, height) = (|| {
let width = NonZeroI32::try_from(width).ok()?;
Expand Down Expand Up @@ -99,12 +99,8 @@ impl<D: HasDisplayHandle, W: HasWindowHandle> SurfaceInterface<D, W> for Android
));
}

let buffer =
vec![Pixel::default(); native_window_buffer.stride() * native_window_buffer.height()];

Ok(BufferImpl {
native_window_buffer,
buffer: util::PixelBuffer(buffer),
})
}

Expand All @@ -117,7 +113,6 @@ impl<D: HasDisplayHandle, W: HasWindowHandle> SurfaceInterface<D, W> for Android
#[derive(Debug)]
pub struct BufferImpl<'surface> {
native_window_buffer: NativeWindowBufferLockGuard<'surface>,
buffer: util::PixelBuffer,
}

// TODO: Move to NativeWindowBufferLockGuard?
Expand All @@ -138,7 +133,20 @@ impl BufferInterface for BufferImpl<'_> {

#[inline]
fn pixels_mut(&mut self) -> &mut [Pixel] {
&mut self.buffer
let native_buffer = self.native_window_buffer.bytes().unwrap();
// assert_eq!(
// native_buffer.len(),
// self.native_window_buffer.stride() * self.native_window_buffer.height()
// );
// TODO: Validate that Android actually initializes (possibly with garbage) the buffer, or
// let softbuffer initialize it, or return MaybeUninit<Pixel>?
// i.e. consider age().
Comment on lines +141 to +143
Copy link
Member

@ids1024 ids1024 Feb 2, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

As long as android is using a swap chain of two or three buffers and we can get the buffer age, it probably makes the most sense for softbuffer to zero-initialize the buffers, if Android doesn't already do that.

It shouldn't really add any meaningful cost to zero each buffer once.

unsafe {
std::slice::from_raw_parts_mut(
native_buffer.as_mut_ptr().cast(),
native_buffer.len() / 4,
)
}
}

#[inline]
Expand All @@ -147,7 +155,7 @@ impl BufferInterface for BufferImpl<'_> {
}

// TODO: This function is pretty slow this way
fn present_with_damage(mut self, damage: &[Rect]) -> Result<(), SoftBufferError> {
fn present_with_damage(self, damage: &[Rect]) -> Result<(), SoftBufferError> {
// TODO: Android requires the damage rect _at lock time_
// Since we're faking the backing buffer _anyway_, we could even fake the surface lock
// and lock it here (if it doesn't influence timings).
Expand All @@ -158,18 +166,8 @@ impl BufferInterface for BufferImpl<'_> {
// when the enlarged damage region is not re-rendered?
let _ = damage;

// Unreachable as we checked before that this is a valid, mappable format
let native_buffer = self.native_window_buffer.bytes().unwrap();

// Write RGB(A) to the output.
// TODO: Use `slice::write_copy_of_slice` once stable and in MSRV.
// TODO(madsmtm): Verify that this compiles down to an efficient copy.
for (pixel, output) in self.buffer.iter().zip(native_buffer.chunks_mut(4)) {
output[0].write(pixel.r);
output[1].write(pixel.g);
output[2].write(pixel.b);
output[3].write(pixel.a);
}
// The surface will be presented when it is unlocked, which happens when the owned guard
// is dropped.

Ok(())
}
Expand Down