win32: Copy icon pixels to BGRA instead of mutating the shared buffer

winit-win32/src/icon.rs

@@ -20,7 +20,7 @@ use winit_core::icon::*;
 use super::util;
 use crate::WinIcon;
 
-pub(crate) const PIXEL_SIZE: usize = mem::size_of::<Pixel>();
+pub(crate) const PIXEL_SIZE: usize = mem::size_of::<u32>();
 
 unsafe impl Send for WinIcon {}
 
@@ -96,14 +96,11 @@ impl WinIcon {
     pub(crate) fn from_rgba(rgba: &RgbaIcon) -> Result<Self, BadIcon> {
         let pixel_count = rgba.buffer().len() / PIXEL_SIZE;
         let mut and_mask = Vec::with_capacity(pixel_count);
-        let pixels = unsafe {
-            std::slice::from_raw_parts_mut(rgba.buffer().as_ptr() as *mut Pixel, pixel_count)
-        };
-        for pixel in pixels {
-            and_mask.push(pixel.a.wrapping_sub(u8::MAX)); // invert alpha channel
-            pixel.convert_to_bgra();
+        let mut bgra = Vec::with_capacity(rgba.buffer().len());
+        for pixel in rgba.buffer().chunks_exact(PIXEL_SIZE) {
+            and_mask.push(pixel[3].wrapping_sub(u8::MAX)); // invert alpha channel
+            bgra.extend_from_slice(&[pixel[2], pixel[1], pixel[0], pixel[3]]);
         }
-        assert_eq!(and_mask.len(), pixel_count);
         let handle = unsafe {
             CreateIcon(
                 ptr::null_mut(),
@@ -112,7 +109,7 @@ impl WinIcon {
                 1,
                 (PIXEL_SIZE * 8) as u8,
                 and_mask.as_ptr(),
-                rgba.buffer().as_ptr(),
+                bgra.as_ptr(),
             )
         };
         if !handle.is_null() {
@@ -135,12 +132,6 @@ impl fmt::Debug for WinIcon {
     }
 }
 
-impl Pixel {
-    fn convert_to_bgra(&mut self) {
-        mem::swap(&mut self.r, &mut self.b);
-    }
-}
-
 #[derive(Debug, Clone, Copy)]
 pub enum IconType {
     Small = ICON_SMALL as isize,
@@ -252,12 +243,3 @@ impl RaiiCursor {
         self.handle
     }
 }
-
-#[repr(C)]
-#[derive(Debug)]
-pub(crate) struct Pixel {
-    pub(crate) r: u8,
-    pub(crate) g: u8,
-    pub(crate) b: u8,
-    pub(crate) a: u8,
-}

winit/src/changelog/unreleased.md

@@ -117,6 +117,9 @@ changelog entry.
   `DefWindowProc` for normal propagation.
 - On Windows, fix getting the window's DPI internally leaks `HDC` handles.
   Also only call `GetDC` when on < Windows 8.1 which improves its performance.
+- On Windows, fix window icons rendering with red and blue swapped when the same `Icon` is
+  applied more than once (e.g. sharing one icon between the window and the taskbar). The RGBA
+  to BGRA conversion no longer mutates the shared pixel buffer.
 - On Redox, handle `EINTR` when reading from `event_socket` instead of panicking.
 - On X11, fix all pointer input being dropped for absolute pointing devices
   without pressure or tilt axes, such as the emulated tablets of