Window icons (#497)

src/icon.rs

@@ -0,0 +1,160 @@
+use std::{fmt, mem};
+use std::error::Error;
+#[cfg(feature = "icon_loading")]
+use std::io::{BufRead, Seek};
+#[cfg(feature = "icon_loading")]
+use std::path::Path;
+
+#[cfg(feature = "icon_loading")]
+use image;
+
+#[repr(C)]
+#[derive(Debug)]
+pub(crate) struct Pixel {
+    pub(crate) r: u8,
+    pub(crate) g: u8,
+    pub(crate) b: u8,
+    pub(crate) a: u8,
+}
+
+pub(crate) const PIXEL_SIZE: usize = mem::size_of::<Pixel>();
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// An error produced when using `Icon::from_rgba` with invalid arguments.
+pub enum BadIcon {
+    /// Produced when the length of the `rgba` argument isn't divisible by 4, thus `rgba` can't be
+    /// safely interpreted as 32bpp RGBA pixels.
+    ByteCountNotDivisibleBy4 {
+        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.
+    DimensionsVsPixelCount {
+        width: u32,
+        height: u32,
+        width_x_height: usize,
+        pixel_count: usize,
+    },
+}
+
+impl fmt::Display for BadIcon {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let msg = match self {
+            &BadIcon::ByteCountNotDivisibleBy4 { byte_count } => format!(
+                "The length of the `rgba` argument ({:?}) isn't divisible by 4, making it impossible to interpret as 32bpp RGBA pixels.",
+                byte_count,
+            ),
+            &BadIcon::DimensionsVsPixelCount {
+                width,
+                height,
+                width_x_height,
+                pixel_count,
+            } => format!(
+                "The specified dimensions ({:?}x{:?}) don't match the number of pixels supplied by the `rgba` argument ({:?}). For those dimensions, the expected pixel count is {:?}.",
+                width, height, pixel_count, width_x_height,
+            ),
+        };
+        write!(formatter, "{}", msg)
+    }
+}
+
+impl Error for BadIcon {
+    fn description(&self) -> &str {
+        "A valid icon cannot be created from these arguments"
+    }
+
+    fn cause(&self) -> Option<&Error> {
+        Some(self)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+/// An icon used for the window titlebar, taskbar, etc.
+///
+/// Enabling the `icon_loading` feature provides you with several convenience methods for creating
+/// an `Icon` from any format supported by the [image](https://github.com/PistonDevelopers/image)
+/// crate.
+pub struct Icon {
+    pub(crate) rgba: Vec<u8>,
+    pub(crate) width: u32,
+    pub(crate) height: u32,
+}
+
+impl Icon {
+    /// Creates an `Icon` from 32bpp RGBA data.
+    ///
+    /// The length of `rgba` must be divisible by 4, and `width * height` must equal
+    /// `rgba.len() / 4`. Otherwise, this will return a `BadIcon` error.
+    pub fn from_rgba(rgba: Vec<u8>, width: u32, height: u32) -> Result<Self, BadIcon> {
+        if rgba.len() % PIXEL_SIZE != 0 {
+            return Err(BadIcon::ByteCountNotDivisibleBy4 { byte_count: rgba.len() });
+        }
+        let pixel_count = rgba.len() / PIXEL_SIZE;
+        if pixel_count != (width * height) as usize {
+            Err(BadIcon::DimensionsVsPixelCount {
+                width,
+                height,
+                width_x_height: (width * height) as usize,
+                pixel_count,
+            })
+        } else {
+            Ok(Icon { rgba, width, height })
+        }
+    }
+
+    #[cfg(feature = "icon_loading")]
+    /// Loads an `Icon` from the path of an image on the filesystem.
+    pub fn from_path<P: AsRef<Path>>(path: P) -> image::ImageResult<Self> {
+        image::open(path).map(Into::into)
+    }
+
+    #[cfg(feature = "icon_loading")]
+    /// Loads an `Icon` from anything implementing `BufRead` and `Seek`.
+    pub fn from_reader<R: BufRead + Seek>(
+        reader: R,
+        format: image::ImageFormat,
+    ) -> image::ImageResult<Self> {
+        image::load(reader, format).map(Into::into)
+    }
+
+    #[cfg(feature = "icon_loading")]
+    /// Loads an `Icon` from the unprocessed bytes of an image file.
+    /// Uses heuristics to determine format.
+    pub fn from_bytes(bytes: &[u8]) -> image::ImageResult<Self> {
+        image::load_from_memory(bytes).map(Into::into)
+    }
+
+    #[cfg(feature = "icon_loading")]
+    /// Loads an `Icon` from the unprocessed bytes of an image.
+    pub fn from_bytes_with_format(
+        bytes: &[u8],
+        format: image::ImageFormat,
+    ) -> image::ImageResult<Self> {
+        image::load_from_memory_with_format(bytes, format).map(Into::into)
+    }
+}
+
+#[cfg(feature = "icon_loading")]
+impl From<image::DynamicImage> for Icon {
+    fn from(image: image::DynamicImage) -> Self {
+        use image::{GenericImage, Pixel};
+        let (width, height) = image.dimensions();
+        let mut rgba = Vec::with_capacity((width * height) as usize * PIXEL_SIZE);
+        for (_, _, pixel) in image.pixels() {
+            rgba.extend_from_slice(&pixel.to_rgba().data);
+        }
+        Icon { rgba, width, height }
+    }
+}
+
+#[cfg(feature = "icon_loading")]
+impl From<image::RgbaImage> for Icon {
+    fn from(buf: image::RgbaImage) -> Self {
+        let (width, height) = buf.dimensions();
+        let mut rgba = Vec::with_capacity((width * height) as usize * PIXEL_SIZE);
+        for (_, _, pixel) in buf.enumerate_pixels() {
+            rgba.extend_from_slice(&pixel.data);
+        }
+        Icon { rgba, width, height }
+    }
+}