Add Buffer::byte_stride

Author: madsmtm

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Added `Buffer::pixels()` for accessing the buffer's pixel data.
 - Added `Buffer::pixel_rows()` for iterating over rows of the buffer data.
 - Added `Buffer::pixels_iter()` for iterating over each pixel with its associated `x`/`y` coordinate.
+- Added `Buffer::byte_stride()` for pixel buffers whose rows are aligned and may contain padding bytes at the end. Prefer to use the above helpers instead of accessing pixel data directly.
 - **Breaking:** Removed generic type parameters `D` and `W` from `Buffer<'_>` struct.
 - **Breaking:** Removed `Deref[Mut]` implementation on `Buffer<'_>`. Use `Buffer::pixels()` instead.
 

examples/animation.rs

@@ -22,7 +22,7 @@ fn main() {
             let window = util::make_window(event_loop, |w| w);
 
             let old_size = (0, 0);
-            let frames = pre_render_frames(0, 0);
+            let frames = pre_render_frames(0, 0, 0);
 
             (window, old_size, frames)
         },
@@ -65,7 +65,7 @@ fn main() {
                 let size = (buffer.width().get(), buffer.height().get());
                 if size != *old_size {
                     *old_size = size;
-                    *frames = pre_render_frames(size.0, size.1);
+                    *frames = pre_render_frames(buffer.byte_stride().get() / 4, size.0, size.1);
                 }
 
                 let frame = &frames[((elapsed * 60.0).round() as usize).clamp(0, 59)];
@@ -95,11 +95,11 @@ fn main() {
     util::run_app(event_loop, app);
 }
 
-fn pre_render_frames(width: u32, height: u32) -> Vec<Vec<u32>> {
+fn pre_render_frames(stride: u32, width: u32, height: u32) -> Vec<Vec<u32>> {
     let render = |frame_id| {
         let elapsed = ((frame_id as f64) / (60.0)) * 2.0 * PI;
 
-        let coords = (0..height).flat_map(|x| (0..width).map(move |y| (x, y)));
+        let coords = (0..height).flat_map(|x| (0..stride).map(move |y| (x, y)));
         coords
             .map(|(x, y)| {
                 let y = (y as f64) / (height as f64);

examples/fruit.rs

@@ -51,14 +51,14 @@ fn main() {
                 };
 
                 let mut buffer = surface.buffer_mut().unwrap();
-                let width = fruit.width();
+                let stride = buffer.byte_stride().get() / 4;
                 for (x, y, pixel) in fruit.pixels() {
                     let red = pixel.0[0] as u32;
                     let green = pixel.0[1] as u32;
                     let blue = pixel.0[2] as u32;
 
                     let color = blue | (green << 8) | (red << 16);
-                    buffer.pixels()[(y * width + x) as usize] = color;
+                    buffer.pixels()[(y * stride + x) as usize] = color;
                 }
 
                 buffer.present().unwrap();

src/backend_dispatch.rs

@@ -146,6 +146,16 @@ macro_rules! make_dispatch {
         }
 
         impl BufferInterface for BufferDispatch<'_> {
+            #[inline]
+            fn byte_stride(&self) -> NonZeroU32 {
+                match self {
+                    $(
+                        $(#[$attr])*
+                        Self::$name(inner) => inner.byte_stride(),
+                    )*
+                }
+            }
+
             #[inline]
             fn width(&self) -> NonZeroU32 {
                 match self {

src/backend_interface.rs

@@ -35,6 +35,7 @@ pub(crate) trait SurfaceInterface<D: HasDisplayHandle + ?Sized, W: HasWindowHand
 }
 
 pub(crate) trait BufferInterface {
+    fn byte_stride(&self) -> NonZeroU32;
     fn width(&self) -> NonZeroU32;
     fn height(&self) -> NonZeroU32;
     fn pixels_mut(&mut self) -> &mut [u32];

src/backends/android.rs

@@ -123,6 +123,10 @@ pub struct BufferImpl<'a> {
 unsafe impl Send for BufferImpl<'_> {}
 
 impl BufferInterface for BufferImpl<'_> {
+    fn byte_stride(&self) -> NonZeroU32 {
+        NonZeroU32::new(self.width().get() * 4).unwrap()
+    }
+
     fn width(&self) -> NonZeroU32 {
         NonZeroU32::new(self.native_window_buffer.width() as u32).unwrap()
     }

src/backends/cg.rs

@@ -279,6 +279,10 @@ pub struct BufferImpl<'a> {
 }
 
 impl BufferInterface for BufferImpl<'_> {
+    fn byte_stride(&self) -> NonZeroU32 {
+        NonZeroU32::new(self.width().get() * 4).unwrap()
+    }
+
     fn width(&self) -> NonZeroU32 {
         NonZeroU32::new(self.width as u32).unwrap()
     }

src/backends/kms.rs

@@ -305,6 +305,10 @@ impl<D: ?Sized, W: ?Sized> Drop for KmsImpl<D, W> {
 }
 
 impl BufferInterface for BufferImpl<'_> {
+    fn byte_stride(&self) -> NonZeroU32 {
+        NonZeroU32::new(self.width().get() * 4).unwrap()
+    }
+
     fn width(&self) -> NonZeroU32 {
         self.size.0
     }

src/backends/orbital.rs

@@ -153,6 +153,10 @@ pub struct BufferImpl<'a> {
 }
 
 impl BufferInterface for BufferImpl<'_> {
+    fn byte_stride(&self) -> NonZeroU32 {
+        NonZeroU32::new(self.width().get() * 4).unwrap()
+    }
+
     fn width(&self) -> NonZeroU32 {
         NonZeroU32::new(self.width as u32).unwrap()
     }

src/backends/wayland/mod.rs

@@ -219,6 +219,10 @@ pub struct BufferImpl<'a> {
 }
 
 impl BufferInterface for BufferImpl<'_> {
+    fn byte_stride(&self) -> NonZeroU32 {
+        NonZeroU32::new(self.width as u32 * 4).unwrap()
+    }
+
     fn width(&self) -> NonZeroU32 {
         NonZeroU32::new(self.width as u32).unwrap()
     }