Support texture atlases in CustomCursor::Image (#17121)

# Objective

- Bevy 0.15 added support for custom cursor images in
https://github.com/bevyengine/bevy/pull/14284.
- However, to do animated cursors using the initial support shipped in
0.15 means you'd have to animate the `Handle<Image>`: You can't use a
`TextureAtlas` like you can with sprites and UI images.
- For my use case, my cursors are spritesheets. To animate them, I'd
have to break them down into multiple `Image` assets, but that seems
less than ideal.


## Solution

- Allow users to specify a `TextureAtlas` field when creating a custom
cursor image.
- To create parity with Bevy's `TextureAtlas` support on `Sprite`s and
`ImageNode`s, this also allows users to specify `rect`, `flip_x` and
`flip_y`. In fact, for my own use case, I need to `flip_y`.

## Testing

- I added unit tests for `calculate_effective_rect` and
`extract_and_transform_rgba_pixels`.
- I added a brand new example for custom cursor images. It has controls
to toggle fields on and off. I opted to add a new example because the
existing cursor example (`window_settings`) would be far too messy for
showcasing these custom cursor features (I did start down that path but
decided to stop and make a brand new example).
- The new example uses a [Kenny cursor icon] sprite sheet. I included
the licence even though it's not required (and it's CC0).
- I decided to make the example just loop through all cursor icons for
its animation even though it's not a _realistic_ in-game animation
sequence.
- I ran the PNG through https://tinypng.com. Looks like it's about 35KB.
- I'm open to adjusting the example spritesheet if required, but if it's
fine as is, great.

[Kenny cursor icon]: https://kenney-assets.itch.io/crosshair-pack

---

## Showcase


https://github.com/user-attachments/assets/8f6be8d7-d1d4-42f9-b769-ef8532367749

## Migration Guide

The `CustomCursor::Image` enum variant has some new fields. Update your
code to set them.

Before:

```rust
CustomCursor::Image {
    handle: asset_server.load("branding/icon.png"),
    hotspot: (128, 128),
}
```

After:

```rust
CustomCursor::Image {
    handle: asset_server.load("branding/icon.png"),
    texture_atlas: None,
    flip_x: false,
    flip_y: false,
    rect: None,
    hotspot: (128, 128),
}
```

## References

- Feature request [originally raised in Discord].

[originally raised in Discord]:
https://discord.com/channels/691052431525675048/692572690833473578/1319836362219847681

Cargo.toml

@@ -3311,6 +3311,18 @@ description = "Creates a solid color window"
 category = "Window"
 wasm = true
 
+[[example]]
+name = "custom_cursor_image"
+path = "examples/window/custom_cursor_image.rs"
+doc-scrape-examples = true
+required-features = ["custom_cursor"]
+
+[package.metadata.example.custom_cursor_image]
+name = "Custom Cursor Image"
+description = "Demonstrates creating an animated custom cursor from an image"
+category = "Window"
+wasm = true
+
 [[example]]
 name = "custom_user_event"
 path = "examples/window/custom_user_event.rs"

assets/cursors/kenney_crosshairPack/License.txt

@@ -0,0 +1,19 @@
+
+
+	Crosshair Pack
+
+	by Kenney Vleugels (Kenney.nl)
+
+			------------------------------
+
+	License (Creative Commons Zero, CC0)
+	http://creativecommons.org/publicdomain/zero/1.0/
+
+	You may use these assets in personal and commercial projects.
+	Credit (Kenney or www.kenney.nl) would be nice but is not mandatory.
+
+			------------------------------
+
+	Donate:   http://support.kenney.nl
+
+	Follow on Twitter for updates: @KenneyNL (www.twitter.com/kenneynl)

crates/bevy_image/src/texture_atlas.rs

@@ -182,8 +182,12 @@ impl TextureAtlasLayout {
 /// - [`animated sprite sheet example`](https://github.com/bevyengine/bevy/blob/latest/examples/2d/sprite_sheet.rs)
 /// - [`sprite animation event example`](https://github.com/bevyengine/bevy/blob/latest/examples/2d/sprite_animation.rs)
 /// - [`texture atlas example`](https://github.com/bevyengine/bevy/blob/latest/examples/2d/texture_atlas.rs)
-#[derive(Default, Debug, Clone)]
+#[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]
-#[cfg_attr(feature = "bevy_reflect", derive(Reflect), reflect(Default, Debug))]
+#[cfg_attr(
+    feature = "bevy_reflect",
+    derive(Reflect),
+    reflect(Default, Debug, PartialEq, Hash)
+)]
 pub struct TextureAtlas {
     /// Texture atlas layout handle
     pub layout: Handle<TextureAtlasLayout>,

crates/bevy_winit/src/cursor.rs

@@ -6,6 +6,10 @@ use crate::{
 };
 #[cfg(feature = "custom_cursor")]
 use crate::{
+    custom_cursor::{
+        calculate_effective_rect, extract_and_transform_rgba_pixels, extract_rgba_pixels,
+        CustomCursorPlugin,
+    },
     state::{CustomCursorCache, CustomCursorCacheKey},
     WinitCustomCursor,
 };
@@ -25,21 +29,21 @@ use bevy_ecs::{
     world::{OnRemove, Ref},
 };
 #[cfg(feature = "custom_cursor")]
-use bevy_image::Image;
+use bevy_image::{Image, TextureAtlas, TextureAtlasLayout};
+#[cfg(feature = "custom_cursor")]
+use bevy_math::URect;
 use bevy_reflect::{std_traits::ReflectDefault, Reflect};
 use bevy_utils::HashSet;
 use bevy_window::{SystemCursorIcon, Window};
 #[cfg(feature = "custom_cursor")]
 use tracing::warn;
-#[cfg(feature = "custom_cursor")]
-use wgpu_types::TextureFormat;
 
 pub(crate) struct CursorPlugin;
 
 impl Plugin for CursorPlugin {
     fn build(&self, app: &mut App) {
         #[cfg(feature = "custom_cursor")]
-        app.init_resource::<CustomCursorCache>();
+        app.add_plugins(CustomCursorPlugin);
 
         app.register_type::<CursorIcon>()
             .add_systems(Last, update_cursors);
@@ -87,6 +91,19 @@ pub enum CustomCursor {
         /// The image must be in 8 bit int or 32 bit float rgba. PNG images
         /// work well for this.
         handle: Handle<Image>,
+        /// The (optional) texture atlas used to render the image.
+        texture_atlas: Option<TextureAtlas>,
+        /// Whether the image should be flipped along its x-axis.
+        flip_x: bool,
+        /// Whether the image should be flipped along its y-axis.
+        flip_y: bool,
+        /// An optional rectangle representing the region of the image to
+        /// render, instead of rendering the full image. This is an easy one-off
+        /// alternative to using a [`TextureAtlas`].
+        ///
+        /// When used with a [`TextureAtlas`], the rect is offset by the atlas's
+        /// minimal (top-left) corner position.
+        rect: Option<URect>,
         /// X and Y coordinates of the hotspot in pixels. The hotspot must be
         /// within the image bounds.
         hotspot: (u16, u16),
@@ -108,6 +125,7 @@ fn update_cursors(
     windows: Query<(Entity, Ref<CursorIcon>), With<Window>>,
     #[cfg(feature = "custom_cursor")] cursor_cache: Res<CustomCursorCache>,
     #[cfg(feature = "custom_cursor")] images: Res<Assets<Image>>,
+    #[cfg(feature = "custom_cursor")] texture_atlases: Res<Assets<TextureAtlasLayout>>,
     mut queue: Local<HashSet<Entity>>,
 ) {
     for (entity, cursor) in windows.iter() {
@@ -117,8 +135,22 @@ fn update_cursors(
 
         let cursor_source = match cursor.as_ref() {
             #[cfg(feature = "custom_cursor")]
-            CursorIcon::Custom(CustomCursor::Image { handle, hotspot }) => {
+            CursorIcon::Custom(CustomCursor::Image {
-                let cache_key = CustomCursorCacheKey::Asset(handle.id());
+                handle,
+                texture_atlas,
+                flip_x,
+                flip_y,
+                rect,
+                hotspot,
+            }) => {
+                let cache_key = CustomCursorCacheKey::Image {
+                    id: handle.id(),
+                    texture_atlas_layout_id: texture_atlas.as_ref().map(|a| a.layout.id()),
+                    texture_atlas_index: texture_atlas.as_ref().map(|a| a.index),
+                    flip_x: *flip_x,
+                    flip_y: *flip_y,
+                    rect: *rect,
+                };
 
                 if cursor_cache.0.contains_key(&cache_key) {
                     CursorSource::CustomCached(cache_key)
@@ -130,17 +162,25 @@ fn update_cursors(
                         queue.insert(entity);
                         continue;
                     };
-                    let Some(rgba) = image_to_rgba_pixels(image) else {
+
+                    let (rect, needs_sub_image) =
+                        calculate_effective_rect(&texture_atlases, image, texture_atlas, rect);
+
+                    let maybe_rgba = if *flip_x || *flip_y || needs_sub_image {
+                        extract_and_transform_rgba_pixels(image, *flip_x, *flip_y, rect)
+                    } else {
+                        extract_rgba_pixels(image)
+                    };
+
+                    let Some(rgba) = maybe_rgba else {
                         warn!("Cursor image {handle:?} not accepted because it's not rgba8 or rgba32float format");
                         continue;
                     };
 
-                    let width = image.texture_descriptor.size.width;
-                    let height = image.texture_descriptor.size.height;
                     let source = match WinitCustomCursor::from_rgba(
                         rgba,
-                        width as u16,
+                        rect.width() as u16,
-                        height as u16,
+                        rect.height() as u16,
                         hotspot.0,
                         hotspot.1,
                     ) {
@@ -190,28 +230,3 @@ fn on_remove_cursor_icon(trigger: Trigger<OnRemove, CursorIcon>, mut commands: C
             convert_system_cursor_icon(SystemCursorIcon::Default),
         ))));
 }
-
-#[cfg(feature = "custom_cursor")]
-/// Returns the image data as a `Vec<u8>`.
-/// Only supports rgba8 and rgba32float formats.
-fn image_to_rgba_pixels(image: &Image) -> Option<Vec<u8>> {
-    match image.texture_descriptor.format {
-        TextureFormat::Rgba8Unorm
-        | TextureFormat::Rgba8UnormSrgb
-        | TextureFormat::Rgba8Snorm
-        | TextureFormat::Rgba8Uint
-        | TextureFormat::Rgba8Sint => Some(image.data.clone()),
-        TextureFormat::Rgba32Float => Some(
-            image
-                .data
-                .chunks(4)
-                .map(|chunk| {
-                    let chunk = chunk.try_into().unwrap();
-                    let num = bytemuck::cast_ref::<[u8; 4], f32>(chunk);
-                    (num * 255.0) as u8
-                })
-                .collect(),
-        ),
-        _ => None,
-    }
-}

crates/bevy_winit/src/custom_cursor.rs

@@ -0,0 +1,490 @@
+use bevy_app::{App, Plugin};
+use bevy_asset::Assets;
+use bevy_image::{Image, TextureAtlas, TextureAtlasLayout, TextureAtlasPlugin};
+use bevy_math::{ops, Rect, URect, UVec2, Vec2};
+use wgpu_types::TextureFormat;
+
+use crate::state::CustomCursorCache;
+
+/// Adds support for custom cursors.
+pub(crate) struct CustomCursorPlugin;
+
+impl Plugin for CustomCursorPlugin {
+    fn build(&self, app: &mut App) {
+        if !app.is_plugin_added::<TextureAtlasPlugin>() {
+            app.add_plugins(TextureAtlasPlugin);
+        }
+
+        app.init_resource::<CustomCursorCache>();
+    }
+}
+
+/// Determines the effective rect and returns it along with a flag to indicate
+/// whether a sub-image operation is needed. The flag allows the caller to
+/// determine whether the image data needs a sub-image extracted from it. Note:
+/// To avoid lossy comparisons between [`Rect`] and [`URect`], the flag is
+/// always set to `true` when a [`TextureAtlas`] is used.
+#[inline(always)]
+pub(crate) fn calculate_effective_rect(
+    texture_atlas_layouts: &Assets<TextureAtlasLayout>,
+    image: &Image,
+    texture_atlas: &Option<TextureAtlas>,
+    rect: &Option<URect>,
+) -> (Rect, bool) {
+    let atlas_rect = texture_atlas
+        .as_ref()
+        .and_then(|s| s.texture_rect(texture_atlas_layouts))
+        .map(|r| r.as_rect());
+
+    match (atlas_rect, rect) {
+        (None, None) => (
+            Rect {
+                min: Vec2::ZERO,
+                max: Vec2::new(
+                    image.texture_descriptor.size.width as f32,
+                    image.texture_descriptor.size.height as f32,
+                ),
+            },
+            false,
+        ),
+        (None, Some(image_rect)) => (
+            image_rect.as_rect(),
+            image_rect
+                != &URect {
+                    min: UVec2::ZERO,
+                    max: UVec2::new(
+                        image.texture_descriptor.size.width,
+                        image.texture_descriptor.size.height,
+                    ),
+                },
+        ),
+        (Some(atlas_rect), None) => (atlas_rect, true),
+        (Some(atlas_rect), Some(image_rect)) => (
+            {
+                let mut image_rect = image_rect.as_rect();
+                image_rect.min += atlas_rect.min;
+                image_rect.max += atlas_rect.min;
+                image_rect
+            },
+            true,
+        ),
+    }
+}
+
+/// Extracts the RGBA pixel data from `image`, converting it if necessary.
+///
+/// Only supports rgba8 and rgba32float formats.
+pub(crate) fn extract_rgba_pixels(image: &Image) -> Option<Vec<u8>> {
+    match image.texture_descriptor.format {
+        TextureFormat::Rgba8Unorm
+        | TextureFormat::Rgba8UnormSrgb
+        | TextureFormat::Rgba8Snorm
+        | TextureFormat::Rgba8Uint
+        | TextureFormat::Rgba8Sint => Some(image.data.clone()),
+        TextureFormat::Rgba32Float => Some(
+            image
+                .data
+                .chunks(4)
+                .map(|chunk| {
+                    let chunk = chunk.try_into().unwrap();
+                    let num = bytemuck::cast_ref::<[u8; 4], f32>(chunk);
+                    ops::round(num.clamp(0.0, 1.0) * 255.0) as u8
+                })
+                .collect(),
+        ),
+        _ => None,
+    }
+}
+
+/// Returns the `image` data as a `Vec<u8>` for the specified sub-region.
+///
+/// The image is flipped along the x and y axes if `flip_x` and `flip_y` are
+/// `true`, respectively.
+///
+/// Only supports rgba8 and rgba32float formats.
+pub(crate) fn extract_and_transform_rgba_pixels(
+    image: &Image,
+    flip_x: bool,
+    flip_y: bool,
+    rect: Rect,
+) -> Option<Vec<u8>> {
+    let image_data = extract_rgba_pixels(image)?;
+
+    let width = rect.width() as usize;
+    let height = rect.height() as usize;
+    let mut sub_image_data = Vec::with_capacity(width * height * 4); // assuming 4 bytes per pixel (RGBA8)
+
+    for y in 0..height {
+        for x in 0..width {
+            let src_x = if flip_x { width - 1 - x } else { x };
+            let src_y = if flip_y { height - 1 - y } else { y };
+            let index = ((rect.min.y as usize + src_y)
+                * image.texture_descriptor.size.width as usize
+                + (rect.min.x as usize + src_x))
+                * 4;
+            sub_image_data.extend_from_slice(&image_data[index..index + 4]);
+        }
+    }
+
+    Some(sub_image_data)
+}
+
+#[cfg(test)]
+mod tests {
+    use bevy_app::App;
+    use bevy_asset::RenderAssetUsages;
+    use bevy_image::Image;
+    use bevy_math::Rect;
+    use bevy_math::Vec2;
+    use wgpu_types::{Extent3d, TextureDimension};
+
+    use super::*;
+
+    fn create_image_rgba8(data: &[u8]) -> Image {
+        Image::new(
+            Extent3d {
+                width: 3,
+                height: 3,
+                depth_or_array_layers: 1,
+            },
+            TextureDimension::D2,
+            data.to_vec(),
+            TextureFormat::Rgba8UnormSrgb,
+            RenderAssetUsages::default(),
+        )
+    }
+
+    macro_rules! test_calculate_effective_rect {
+        ($name:ident, $use_texture_atlas:expr, $rect:expr, $expected_rect:expr, $expected_needs_sub_image:expr) => {
+            #[test]
+            fn $name() {
+                let mut app = App::new();
+                let mut texture_atlas_layout_assets = Assets::<TextureAtlasLayout>::default();
+
+                // Create a simple 3x3 texture atlas layout for the test cases
+                // that use a texture atlas. In the future we could adjust the
+                // test cases to use different texture atlas layouts.
+                let layout = TextureAtlasLayout::from_grid(UVec2::new(3, 3), 1, 1, None, None);
+                let layout_handle = texture_atlas_layout_assets.add(layout);
+
+                app.insert_resource(texture_atlas_layout_assets);
+
+                let texture_atlases = app
+                    .world()
+                    .get_resource::<Assets<TextureAtlasLayout>>()
+                    .unwrap();
+
+                let image = create_image_rgba8(&[0; 3 * 3 * 4]); // 3x3 image
+
+                let texture_atlas = if $use_texture_atlas {
+                    Some(TextureAtlas::from(layout_handle))
+                } else {
+                    None
+                };
+
+                let rect = $rect;
+
+                let (result_rect, needs_sub_image) =
+                    calculate_effective_rect(&texture_atlases, &image, &texture_atlas, &rect);
+
+                assert_eq!(result_rect, $expected_rect);
+                assert_eq!(needs_sub_image, $expected_needs_sub_image);
+            }
+        };
+    }
+
+    test_calculate_effective_rect!(
+        no_texture_atlas_no_rect,
+        false,
+        None,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        false
+    );
+
+    test_calculate_effective_rect!(
+        no_texture_atlas_with_partial_rect,
+        false,
+        Some(URect {
+            min: UVec2::new(1, 1),
+            max: UVec2::new(3, 3)
+        }),
+        Rect {
+            min: Vec2::new(1.0, 1.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        true
+    );
+
+    test_calculate_effective_rect!(
+        no_texture_atlas_with_full_rect,
+        false,
+        Some(URect {
+            min: UVec2::ZERO,
+            max: UVec2::new(3, 3)
+        }),
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        false
+    );
+
+    test_calculate_effective_rect!(
+        texture_atlas_no_rect,
+        true,
+        None,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        true // always needs sub-image to avoid comparing Rect against URect
+    );
+
+    test_calculate_effective_rect!(
+        texture_atlas_rect,
+        true,
+        Some(URect {
+            min: UVec2::ZERO,
+            max: UVec2::new(3, 3)
+        }),
+        Rect {
+            min: Vec2::new(0.0, 0.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        true // always needs sub-image to avoid comparing Rect against URect
+    );
+
+    fn create_image_rgba32float(data: &[u8]) -> Image {
+        let float_data: Vec<f32> = data
+            .chunks(4)
+            .flat_map(|chunk| {
+                chunk
+                    .iter()
+                    .map(|&x| x as f32 / 255.0) // convert each channel to f32
+                    .collect::<Vec<f32>>()
+            })
+            .collect();
+
+        Image::new(
+            Extent3d {
+                width: 3,
+                height: 3,
+                depth_or_array_layers: 1,
+            },
+            TextureDimension::D2,
+            bytemuck::cast_slice(&float_data).to_vec(),
+            TextureFormat::Rgba32Float,
+            RenderAssetUsages::default(),
+        )
+    }
+
+    macro_rules! test_extract_and_transform_rgba_pixels {
+        ($name:ident, $flip_x:expr, $flip_y:expr, $rect:expr, $expected:expr) => {
+            #[test]
+            fn $name() {
+                let image_data: &[u8] = &[
+                    // Row 1: Red, Green, Blue
+                    255, 0, 0, 255, // Red
+                    0, 255, 0, 255, // Green
+                    0, 0, 255, 255, // Blue
+                    // Row 2: Yellow, Cyan, Magenta
+                    255, 255, 0, 255, // Yellow
+                    0, 255, 255, 255, // Cyan
+                    255, 0, 255, 255, // Magenta
+                    // Row 3: White, Gray, Black
+                    255, 255, 255, 255, // White
+                    128, 128, 128, 255, // Gray
+                    0, 0, 0, 255, // Black
+                ];
+
+                // RGBA8 test
+                {
+                    let image = create_image_rgba8(image_data);
+                    let rect = $rect;
+                    let result = extract_and_transform_rgba_pixels(&image, $flip_x, $flip_y, rect);
+                    assert_eq!(result, Some($expected.to_vec()));
+                }
+
+                // RGBA32Float test
+                {
+                    let image = create_image_rgba32float(image_data);
+                    let rect = $rect;
+                    let result = extract_and_transform_rgba_pixels(&image, $flip_x, $flip_y, rect);
+                    assert_eq!(result, Some($expected.to_vec()));
+                }
+            }
+        };
+    }
+
+    test_extract_and_transform_rgba_pixels!(
+        no_flip_full_image,
+        false,
+        false,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 1: Red, Green, Blue
+            255, 0, 0, 255, // Red
+            0, 255, 0, 255, // Green
+            0, 0, 255, 255, // Blue
+            // Row 2: Yellow, Cyan, Magenta
+            255, 255, 0, 255, // Yellow
+            0, 255, 255, 255, // Cyan
+            255, 0, 255, 255, // Magenta
+            // Row 3: White, Gray, Black
+            255, 255, 255, 255, // White
+            128, 128, 128, 255, // Gray
+            0, 0, 0, 255, // Black
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_x_full_image,
+        true,
+        false,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 1 flipped: Blue, Green, Red
+            0, 0, 255, 255, // Blue
+            0, 255, 0, 255, // Green
+            255, 0, 0, 255, // Red
+            // Row 2 flipped: Magenta, Cyan, Yellow
+            255, 0, 255, 255, // Magenta
+            0, 255, 255, 255, // Cyan
+            255, 255, 0, 255, // Yellow
+            // Row 3 flipped: Black, Gray, White
+            0, 0, 0, 255, // Black
+            128, 128, 128, 255, // Gray
+            255, 255, 255, 255, // White
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_y_full_image,
+        false,
+        true,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 3: White, Gray, Black
+            255, 255, 255, 255, // White
+            128, 128, 128, 255, // Gray
+            0, 0, 0, 255, // Black
+            // Row 2: Yellow, Cyan, Magenta
+            255, 255, 0, 255, // Yellow
+            0, 255, 255, 255, // Cyan
+            255, 0, 255, 255, // Magenta
+            // Row 1: Red, Green, Blue
+            255, 0, 0, 255, // Red
+            0, 255, 0, 255, // Green
+            0, 0, 255, 255, // Blue
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_both_full_image,
+        true,
+        true,
+        Rect {
+            min: Vec2::ZERO,
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 3 flipped: Black, Gray, White
+            0, 0, 0, 255, // Black
+            128, 128, 128, 255, // Gray
+            255, 255, 255, 255, // White
+            // Row 2 flipped: Magenta, Cyan, Yellow
+            255, 0, 255, 255, // Magenta
+            0, 255, 255, 255, // Cyan
+            255, 255, 0, 255, // Yellow
+            // Row 1 flipped: Blue, Green, Red
+            0, 0, 255, 255, // Blue
+            0, 255, 0, 255, // Green
+            255, 0, 0, 255, // Red
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        no_flip_rect,
+        false,
+        false,
+        Rect {
+            min: Vec2::new(1.0, 1.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Only includes part of the original image (sub-rectangle)
+            // Row 2, columns 2-3: Cyan, Magenta
+            0, 255, 255, 255, // Cyan
+            255, 0, 255, 255, // Magenta
+            // Row 3, columns 2-3: Gray, Black
+            128, 128, 128, 255, // Gray
+            0, 0, 0, 255, // Black
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_x_rect,
+        true,
+        false,
+        Rect {
+            min: Vec2::new(1.0, 1.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 2 flipped: Magenta, Cyan
+            255, 0, 255, 255, // Magenta
+            0, 255, 255, 255, // Cyan
+            // Row 3 flipped: Black, Gray
+            0, 0, 0, 255, // Black
+            128, 128, 128, 255, // Gray
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_y_rect,
+        false,
+        true,
+        Rect {
+            min: Vec2::new(1.0, 1.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 3 first: Gray, Black
+            128, 128, 128, 255, // Gray
+            0, 0, 0, 255, // Black
+            // Row 2 second: Cyan, Magenta
+            0, 255, 255, 255, // Cyan
+            255, 0, 255, 255, // Magenta
+        ]
+    );
+
+    test_extract_and_transform_rgba_pixels!(
+        flip_both_rect,
+        true,
+        true,
+        Rect {
+            min: Vec2::new(1.0, 1.0),
+            max: Vec2::new(3.0, 3.0)
+        },
+        [
+            // Row 3 flipped: Black, Gray
+            0, 0, 0, 255, // Black
+            128, 128, 128, 255, // Gray
+            // Row 2 flipped: Magenta, Cyan
+            255, 0, 255, 255, // Magenta
+            0, 255, 255, 255, // Cyan
+        ]
+    );
+}

crates/bevy_winit/src/lib.rs

@@ -50,6 +50,8 @@ use crate::{
 pub mod accessibility;
 mod converters;
 pub mod cursor;
+#[cfg(feature = "custom_cursor")]
+mod custom_cursor;
 mod state;
 mod system;
 mod winit_config;

crates/bevy_winit/src/state.rs

@@ -11,12 +11,14 @@ use bevy_ecs::{
     world::FromWorld,
 };
 #[cfg(feature = "custom_cursor")]
-use bevy_image::Image;
+use bevy_image::{Image, TextureAtlasLayout};
 use bevy_input::{
     gestures::*,
     mouse::{MouseButtonInput, MouseMotion, MouseScrollUnit, MouseWheel},
 };
 use bevy_log::{error, trace, warn};
+#[cfg(feature = "custom_cursor")]
+use bevy_math::URect;
 use bevy_math::{ivec2, DVec2, Vec2};
 #[cfg(not(target_arch = "wasm32"))]
 use bevy_tasks::tick_global_task_pools_on_main_thread;
@@ -150,10 +152,17 @@ impl<T: Event> WinitAppRunnerState<T> {
 /// Identifiers for custom cursors used in caching.
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub enum CustomCursorCacheKey {
-    /// An `AssetId` to a cursor.
+    /// A custom cursor with an image.
-    Asset(AssetId<Image>),
+    Image {
+        id: AssetId<Image>,
+        texture_atlas_layout_id: Option<AssetId<TextureAtlasLayout>>,
+        texture_atlas_index: Option<usize>,
+        flip_x: bool,
+        flip_y: bool,
+        rect: Option<URect>,
+    },
     #[cfg(all(target_family = "wasm", target_os = "unknown"))]
-    /// An URL to a cursor.
+    /// A custom cursor with a URL.
     Url(String),
 }
 

examples/README.md

@@ -544,6 +544,7 @@ Example | Description
 Example | Description
 --- | ---
 [Clear Color](../examples/window/clear_color.rs) | Creates a solid color window
+[Custom Cursor Image](../examples/window/custom_cursor_image.rs) | Demonstrates creating an animated custom cursor from an image
 [Custom User Event](../examples/window/custom_user_event.rs) | Handles custom user events within the event loop
 [Low Power](../examples/window/low_power.rs) | Demonstrates settings to reduce power use for bevy applications
 [Monitor info](../examples/window/monitor_info.rs) | Displays information about available monitors (displays).

examples/window/custom_cursor_image.rs

@@ -0,0 +1,228 @@
+//! Illustrates how to use a custom cursor image with a texture atlas and
+//! animation.
+
+use std::time::Duration;
+
+use bevy::winit::cursor::CustomCursor;
+use bevy::{prelude::*, winit::cursor::CursorIcon};
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_systems(
+            Startup,
+            (setup_cursor_icon, setup_camera, setup_instructions),
+        )
+        .add_systems(
+            Update,
+            (
+                execute_animation,
+                toggle_texture_atlas,
+                toggle_flip_x,
+                toggle_flip_y,
+                cycle_rect,
+            ),
+        )
+        .run();
+}
+
+fn setup_cursor_icon(
+    mut commands: Commands,
+    asset_server: Res<AssetServer>,
+    mut texture_atlas_layouts: ResMut<Assets<TextureAtlasLayout>>,
+    window: Single<Entity, With<Window>>,
+) {
+    let layout =
+        TextureAtlasLayout::from_grid(UVec2::splat(64), 20, 10, Some(UVec2::splat(5)), None);
+    let texture_atlas_layout = texture_atlas_layouts.add(layout);
+
+    let animation_config = AnimationConfig::new(0, 199, 1, 4);
+
+    commands.entity(*window).insert((
+        CursorIcon::Custom(CustomCursor::Image {
+            // Image to use as the cursor.
+            handle: asset_server
+                .load("cursors/kenney_crosshairPack/Tilesheet/crosshairs_tilesheet_white.png"),
+            // Optional texture atlas allows you to pick a section of the image
+            // and animate it.
+            texture_atlas: Some(TextureAtlas {
+                layout: texture_atlas_layout.clone(),
+                index: animation_config.first_sprite_index,
+            }),
+            flip_x: false,
+            flip_y: false,
+            // Optional section of the image to use as the cursor.
+            rect: None,
+            // The hotspot is the point in the cursor image that will be
+            // positioned at the mouse cursor's position.
+            hotspot: (0, 0),
+        }),
+        animation_config,
+    ));
+}
+
+fn setup_camera(mut commands: Commands) {
+    commands.spawn(Camera3d::default());
+}
+
+fn setup_instructions(mut commands: Commands) {
+    commands.spawn((
+        Text::new(
+            "Press T to toggle the cursor's `texture_atlas`.\n
+Press X to toggle the cursor's `flip_x` setting.\n
+Press Y to toggle the cursor's `flip_y` setting.\n
+Press C to cycle through the sections of the cursor's image using `rect`.",
+        ),
+        Node {
+            position_type: PositionType::Absolute,
+            bottom: Val::Px(12.0),
+            left: Val::Px(12.0),
+            ..default()
+        },
+    ));
+}
+
+#[derive(Component)]
+struct AnimationConfig {
+    first_sprite_index: usize,
+    last_sprite_index: usize,
+    increment: usize,
+    fps: u8,
+    frame_timer: Timer,
+}
+
+impl AnimationConfig {
+    fn new(first: usize, last: usize, increment: usize, fps: u8) -> Self {
+        Self {
+            first_sprite_index: first,
+            last_sprite_index: last,
+            increment,
+            fps,
+            frame_timer: Self::timer_from_fps(fps),
+        }
+    }
+
+    fn timer_from_fps(fps: u8) -> Timer {
+        Timer::new(Duration::from_secs_f32(1.0 / (fps as f32)), TimerMode::Once)
+    }
+}
+
+/// This system loops through all the sprites in the [`CursorIcon`]'s
+/// [`TextureAtlas`], from [`AnimationConfig`]'s `first_sprite_index` to
+/// `last_sprite_index`.
+fn execute_animation(time: Res<Time>, mut query: Query<(&mut AnimationConfig, &mut CursorIcon)>) {
+    for (mut config, mut cursor_icon) in &mut query {
+        if let CursorIcon::Custom(CustomCursor::Image {
+            ref mut texture_atlas,
+            ..
+        }) = *cursor_icon
+        {
+            config.frame_timer.tick(time.delta());
+
+            if config.frame_timer.finished() {
+                if let Some(atlas) = texture_atlas {
+                    atlas.index += config.increment;
+
+                    if atlas.index > config.last_sprite_index {
+                        atlas.index = config.first_sprite_index;
+                    }
+
+                    config.frame_timer = AnimationConfig::timer_from_fps(config.fps);
+                }
+            }
+        }
+    }
+}
+
+fn toggle_texture_atlas(
+    input: Res<ButtonInput<KeyCode>>,
+    mut query: Query<&mut CursorIcon, With<Window>>,
+    mut cached_atlas: Local<Option<TextureAtlas>>, // this lets us restore the previous value
+) {
+    if input.just_pressed(KeyCode::KeyT) {
+        for mut cursor_icon in &mut query {
+            if let CursorIcon::Custom(CustomCursor::Image {
+                ref mut texture_atlas,
+                ..
+            }) = *cursor_icon
+            {
+                *texture_atlas = match texture_atlas.take() {
+                    Some(a) => {
+                        *cached_atlas = Some(a.clone());
+                        None
+                    }
+                    None => cached_atlas.take(),
+                };
+            }
+        }
+    }
+}
+
+fn toggle_flip_x(
+    input: Res<ButtonInput<KeyCode>>,
+    mut query: Query<&mut CursorIcon, With<Window>>,
+) {
+    if input.just_pressed(KeyCode::KeyX) {
+        for mut cursor_icon in &mut query {
+            if let CursorIcon::Custom(CustomCursor::Image { ref mut flip_x, .. }) = *cursor_icon {
+                *flip_x = !*flip_x;
+            }
+        }
+    }
+}
+
+fn toggle_flip_y(
+    input: Res<ButtonInput<KeyCode>>,
+    mut query: Query<&mut CursorIcon, With<Window>>,
+) {
+    if input.just_pressed(KeyCode::KeyY) {
+        for mut cursor_icon in &mut query {
+            if let CursorIcon::Custom(CustomCursor::Image { ref mut flip_y, .. }) = *cursor_icon {
+                *flip_y = !*flip_y;
+            }
+        }
+    }
+}
+
+/// This system alternates the [`CursorIcon`]'s `rect` field between `None` and
+/// 4 sections/rectangles of the cursor's image.
+fn cycle_rect(input: Res<ButtonInput<KeyCode>>, mut query: Query<&mut CursorIcon, With<Window>>) {
+    if !input.just_pressed(KeyCode::KeyC) {
+        return;
+    }
+
+    const RECT_SIZE: u32 = 32; // half the size of a tile in the texture atlas
+
+    const SECTIONS: [Option<URect>; 5] = [
+        Some(URect {
+            min: UVec2::ZERO,
+            max: UVec2::splat(RECT_SIZE),
+        }),
+        Some(URect {
+            min: UVec2::new(RECT_SIZE, 0),
+            max: UVec2::new(2 * RECT_SIZE, RECT_SIZE),
+        }),
+        Some(URect {
+            min: UVec2::new(0, RECT_SIZE),
+            max: UVec2::new(RECT_SIZE, 2 * RECT_SIZE),
+        }),
+        Some(URect {
+            min: UVec2::new(RECT_SIZE, RECT_SIZE),
+            max: UVec2::splat(2 * RECT_SIZE),
+        }),
+        None, // reset to None
+    ];
+
+    for mut cursor_icon in &mut query {
+        if let CursorIcon::Custom(CustomCursor::Image { ref mut rect, .. }) = *cursor_icon {
+            let next_rect = SECTIONS
+                .iter()
+                .cycle()
+                .skip_while(|&&corner| corner != *rect)
+                .nth(1) // move to the next element
+                .unwrap_or(&None);
+
+            *rect = *next_rect;
+        }
+    }
+}

examples/window/window_settings.rs

@@ -165,6 +165,10 @@ fn init_cursor_icons(
         #[cfg(feature = "custom_cursor")]
         CustomCursor::Image {
             handle: asset_server.load("branding/icon.png"),
+            texture_atlas: None,
+            flip_x: false,
+            flip_y: false,
+            rect: None,
             hotspot: (128, 128),
         }
         .into(),