1 files changed, 80 insertions, 0 deletions
diff --git a/core/src/window/icon.rs b/core/src/window/icon.rs
new file mode 100644
index 00000000..31868ecf
--- /dev/null
+++ b/core/src/window/icon.rs
@@ -0,0 +1,80 @@
+//! Change the icon of a window.
+use crate::Size;
+
+use std::mem;
+
+/// Builds an  [`Icon`] from its RGBA pixels in the sRGB color space.
+pub fn from_rgba(
+    rgba: Vec<u8>,
+    width: u32,
+    height: u32,
+) -> Result<Icon, Error> {
+    const PIXEL_SIZE: usize = mem::size_of::<u8>() * 4;
+
+    if rgba.len() % PIXEL_SIZE != 0 {
+        return Err(Error::ByteCountNotDivisibleBy4 {
+            byte_count: rgba.len(),
+        });
+    }
+
+    let pixel_count = rgba.len() / PIXEL_SIZE;
+
+    if pixel_count != (width * height) as usize {
+        return Err(Error::DimensionsVsPixelCount {
+            width,
+            height,
+            width_x_height: (width * height) as usize,
+            pixel_count,
+        });
+    }
+
+    Ok(Icon {
+        rgba,
+        size: Size::new(width, height),
+    })
+}
+
+/// An window icon normally used for the titlebar or taskbar.
+#[derive(Debug, Clone)]
+pub struct Icon {
+    rgba: Vec<u8>,
+    size: Size<u32>,
+}
+
+impl Icon {
+    /// Returns the raw data of the [`Icon`].
+    pub fn into_raw(self) -> (Vec<u8>, Size<u32>) {
+        (self.rgba, self.size)
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+/// An error produced when using [`Icon::from_rgba`] with invalid arguments.
+pub enum Error {
+    /// Produced when the length of the `rgba` argument isn't divisible by 4, thus `rgba` can't be
+    /// safely interpreted as 32bpp RGBA pixels.
+    #[error(
+        "The provided RGBA data (with length {byte_count}) isn't divisible \
+        by 4. Therefore, it cannot be safely interpreted as 32bpp RGBA pixels"
+    )]
+    ByteCountNotDivisibleBy4 {
+        /// The length of the provided RGBA data.
+        byte_count: usize,
+    },
+    /// Produced when the number of pixels (`rgba.len() / 4`) isn't equal to `width * height`.
+    /// At least one of your arguments is incorrect.
+    #[error(
+        "The number of RGBA pixels ({pixel_count}) does not match the \
+        provided dimensions ({width}x{height})."
+    )]
+    DimensionsVsPixelCount {
+        /// The provided width.
+        width: u32,
+        /// The provided height.
+        height: u32,
+        /// The product of `width` and `height`.
+        width_x_height: usize,
+        /// The amount of pixels of the provided RGBA data.
+        pixel_count: usize,
+    },
+}