Optimize Android backend a bit using buffer stride

Author: madsmtm

src/backends/android.rs

@@ -99,7 +99,7 @@ impl<D: HasDisplayHandle, W: HasWindowHandle> SurfaceInterface<D, W> for Android
             ));
         }
 
-        let buffer = vec![0; native_window_buffer.width() * native_window_buffer.height()];
+        let buffer = vec![0; native_window_buffer.stride() * native_window_buffer.height()];
 
         Ok(BufferImpl {
             native_window_buffer,
@@ -124,7 +124,7 @@ unsafe impl Send for BufferImpl<'_> {}
 
 impl BufferInterface for BufferImpl<'_> {
     fn byte_stride(&self) -> NonZeroU32 {
-        NonZeroU32::new(self.width().get() * 4).unwrap()
+        NonZeroU32::new(self.native_window_buffer.stride() as u32 * 4).unwrap()
     }
 
     fn width(&self) -> NonZeroU32 {
@@ -147,26 +147,18 @@ impl BufferInterface for BufferImpl<'_> {
 
     // TODO: This function is pretty slow this way
     fn present(mut self) -> Result<(), SoftBufferError> {
-        let input_lines = self.buffer.chunks(self.native_window_buffer.width());
-        for (output, input) in self
-            .native_window_buffer
-            .lines()
-            // Unreachable as we checked before that this is a valid, mappable format
-            .unwrap()
-            .zip(input_lines)
-        {
-            // .lines() removed the stride
-            assert_eq!(output.len(), input.len() * 4);
-
-            for (i, pixel) in input.iter().enumerate() {
-                // Swizzle colors from BGR(A) to RGB(A)
-                let [b, g, r, a] = pixel.to_le_bytes();
-                output[i * 4].write(r);
-                output[i * 4 + 1].write(g);
-                output[i * 4 + 2].write(b);
-                output[i * 4 + 3].write(a);
-            }
+        // Unreachable as we checked before that this is a valid, mappable format
+        let native_buffer = self.native_window_buffer.bytes().unwrap();
+
+        for (pixel, output) in self.buffer.iter().zip(native_buffer.chunks_mut(4)) {
+            // Swizzle colors from BGR(A) to RGB(A)
+            let [b, g, r, a] = pixel.to_le_bytes();
+            output[0].write(r);
+            output[1].write(g);
+            output[2].write(b);
+            output[3].write(a);
         }
+
         Ok(())
     }
 

src/lib.rs

@@ -241,18 +241,19 @@ impl<D: HasDisplayHandle, W: HasWindowHandle> HasWindowHandle for Surface<D, W>
 /// B: Blue channel
 ///
 /// # Platform dependent behavior
+///
 /// No-copy presentation is currently supported on:
 /// - Wayland
 /// - X, when XShm is available
 /// - Win32
 /// - Orbital, when buffer size matches window size
 ///
 /// Currently [`Buffer::present`] must block copying image data on:
-/// - Web
 /// - AppKit
 /// - UIKit
 ///
-/// Buffer copies an channel swizzling happen on:
+/// Buffer copies and channel swizzling happen on:
+/// - Web
 /// - Android
 #[derive(Debug)]
 pub struct Buffer<'a> {