Fix image measure function to apply inherent aspect ratio to style sizes (#13555)

# Objective

- Fixes https://github.com/bevyengine/bevy/issues/13155
- fixes https://github.com/bevyengine/bevy/issues/13517
- Supercedes https://github.com/bevyengine/bevy/pull/13381
- Requires https://github.com/DioxusLabs/taffy/pull/661

## Solution

- Taffy has been updated to:
    - Apply size styles to absolutely positioned children
    - Pass the node's `Style` through to the measure function
- Bevy's image measure function has been updated to make use of this
style information

## Notes

- This is currently using a git version of Taffy. If this is tested as
fixing the issue then we can turn that into a Taffy 0.5 release (this
would be the only change between Taffy 0.4 and Taffy 0.5 so upgrading is
not expected to be an issue)
- This implementation may not be completely correct. I would have
preferred to extend Taffy's gentest infrastructure to handle images and
used that to nail down the correct behaviour. But I don't have time for
that atm so we'll have to iterate on this in future. This PR at least
puts that under Bevy's control.

## Testing

- I manually tested the game_menu_example (from
https://github.com/bevyengine/bevy/issues/13155)
- More testing is probably merited

---

## Changelog

No changelog should be required as it fixes a regression on `main` that
was not present in bevy 0.13. The changelog for "Taffy upgrade" may want
to be changed from 0.4 to 0.5 if this change gets merged.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>

crates/bevy_ui/Cargo.toml

@@ -31,7 +31,7 @@ bevy_window = { path = "../bevy_window", version = "0.14.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.14.0-dev" }
 
 # other
-taffy = { version = "0.4" }
+taffy = { version = "0.5" }
 serde = { version = "1", features = ["derive"], optional = true }
 bytemuck = { version = "1.5", features = ["derive"] }
 thiserror = "1.0.0"

crates/bevy_ui/src/layout/ui_surface.rs

@@ -213,7 +213,8 @@ without UI components as a child of an entity with UI components, results may be
                     |known_dimensions: taffy::Size<Option<f32>>,
                      available_space: taffy::Size<taffy::AvailableSpace>,
                      _node_id: taffy::NodeId,
-                     context: Option<&mut NodeMeasure>|
+                     context: Option<&mut NodeMeasure>,
+                     style: &taffy::Style|
                      -> taffy::Size<f32> {
                         context
                             .map(|ctx| {
@@ -222,6 +223,7 @@ without UI components as a child of an entity with UI components, results may be
                                     known_dimensions.height,
                                     available_space.width,
                                     available_space.height,
+                                    style,
                                 );
                                 taffy::Size {
                                     width: size.x,

crates/bevy_ui/src/measurement.rs

@@ -26,6 +26,7 @@ pub trait Measure: Send + Sync + 'static {
         height: Option<f32>,
         available_width: AvailableSpace,
         available_height: AvailableSpace,
+        style: &taffy::Style,
     ) -> Vec2;
 }
 
@@ -48,20 +49,21 @@ impl Measure for NodeMeasure {
         height: Option<f32>,
         available_width: AvailableSpace,
         available_height: AvailableSpace,
+        style: &taffy::Style,
     ) -> Vec2 {
         match self {
             NodeMeasure::Fixed(fixed) => {
-                fixed.measure(width, height, available_width, available_height)
+                fixed.measure(width, height, available_width, available_height, style)
             }
             #[cfg(feature = "bevy_text")]
             NodeMeasure::Text(text) => {
-                text.measure(width, height, available_width, available_height)
+                text.measure(width, height, available_width, available_height, style)
             }
             NodeMeasure::Image(image) => {
-                image.measure(width, height, available_width, available_height)
+                image.measure(width, height, available_width, available_height, style)
             }
             NodeMeasure::Custom(custom) => {
-                custom.measure(width, height, available_width, available_height)
+                custom.measure(width, height, available_width, available_height, style)
             }
         }
     }
@@ -81,6 +83,7 @@ impl Measure for FixedMeasure {
         _: Option<f32>,
         _: AvailableSpace,
         _: AvailableSpace,
+        _: &taffy::Style,
     ) -> Vec2 {
         self.size
     }

crates/bevy_ui/src/widget/image.rs

@@ -8,6 +8,7 @@ use bevy_reflect::{std_traits::ReflectDefault, Reflect};
 use bevy_render::texture::Image;
 use bevy_sprite::{TextureAtlas, TextureAtlasLayout};
 use bevy_window::{PrimaryWindow, Window};
+use taffy::{MaybeMath, MaybeResolve};
 
 /// The size of the image's texture
 ///
@@ -40,26 +41,50 @@ impl Measure for ImageMeasure {
         &self,
         width: Option<f32>,
         height: Option<f32>,
-        _: AvailableSpace,
-        _: AvailableSpace,
+        available_width: AvailableSpace,
+        available_height: AvailableSpace,
+        style: &taffy::Style,
     ) -> Vec2 {
-        let mut size = self.size;
-        match (width, height) {
-            (None, None) => {}
-            (Some(width), None) => {
-                size.y = width * size.y / size.x;
-                size.x = width;
-            }
-            (None, Some(height)) => {
-                size.x = height * size.x / size.y;
-                size.y = height;
-            }
-            (Some(width), Some(height)) => {
-                size.x = width;
-                size.y = height;
-            }
+        // Convert available width/height into an option
+        let parent_width = available_width.into_option();
+        let parent_height = available_height.into_option();
+
+        // Resolve styles
+        let s_aspect_ratio = style.aspect_ratio;
+        let s_width = style.size.width.maybe_resolve(parent_width);
+        let s_min_width = style.min_size.width.maybe_resolve(parent_width);
+        let s_max_width = style.max_size.width.maybe_resolve(parent_width);
+        let s_height = style.size.height.maybe_resolve(parent_height);
+        let s_min_height = style.min_size.height.maybe_resolve(parent_height);
+        let s_max_height = style.max_size.height.maybe_resolve(parent_height);
+
+        // Determine width and height from styles and known_sizes (if a size is available
+        // from any of these sources)
+        let width = width.or(s_width
+            .or(s_min_width)
+            .maybe_clamp(s_min_width, s_max_width));
+        let height = height.or(s_height
+            .or(s_min_height)
+            .maybe_clamp(s_min_height, s_max_height));
+
+        // Use aspect_ratio from style, fall back to inherent aspect ratio
+        let aspect_ratio = s_aspect_ratio.unwrap_or_else(|| self.size.x / self.size.y);
+
+        // Apply aspect ratio
+        // If only one of width or height was determined at this point, then the other is set beyond this point using the aspect ratio.
+        let taffy_size = taffy::Size { width, height }.maybe_apply_aspect_ratio(Some(aspect_ratio));
+
+        // Use computed sizes or fall back to image's inherent size
+        Vec2 {
+            x: taffy_size
+                .width
+                .unwrap_or(self.size.x)
+                .maybe_clamp(s_min_width, s_max_width),
+            y: taffy_size
+                .height
+                .unwrap_or(self.size.y)
+                .maybe_clamp(s_min_height, s_max_height),
         }
-        size
     }
 }
 

crates/bevy_ui/src/widget/text.rs

@@ -51,6 +51,7 @@ impl Measure for TextMeasure {
         height: Option<f32>,
         available_width: AvailableSpace,
         _available_height: AvailableSpace,
+        _style: &taffy::Style,
     ) -> Vec2 {
         let x = width.unwrap_or_else(|| match available_width {
             AvailableSpace::Definite(x) => {