Flip UI image (bevyengine#6292)

# Objective
Fixes  bevyengine#3225, Allow for flippable UI Images

## Solution
Add flip_x and flip_y fields to UiImage, and swap the UV coordinates accordingly in ui_prepare_nodes.

## Changelog
* Changes UiImage to a struct with texture, flip_x, and flip_y fields.
* Adds flip_x and flip_y fields to ExtractedUiNode.
* Changes extract_uinodes to extract the flip_x and flip_y values from UiImage.
* Changes prepare_uinodes to swap the UV coordinates as required.
* Changes UiImage derefs to texture field accesses.

crates/bevy_ui/src/render/mod.rs

@@ -192,6 +192,8 @@ pub struct ExtractedUiNode {
     pub image: Handle<Image>,
     pub atlas_size: Option<Vec2>,
     pub clip: Option<Rect>,
+    pub flip_x: bool,
+    pub flip_y: bool,
     pub scale_factor: f32,
 }
 
@@ -225,13 +227,11 @@ pub fn extract_uinodes(
             if !visibility.is_visible() {
                 continue;
             }
-
-            let image = if let Some(image) = maybe_image {
-                image.0.clone_weak()
+            let (image, flip_x, flip_y) = if let Some(image) = maybe_image {
+                (image.texture.clone_weak(), image.flip_x, image.flip_y)
             } else {
-                DEFAULT_IMAGE_HANDLE.typed().clone_weak()
+                (DEFAULT_IMAGE_HANDLE.typed().clone_weak(), false, false)
             };
-
             // Skip loading images
             if !images.contains(&image) {
                 continue;
@@ -252,6 +252,8 @@ pub fn extract_uinodes(
                 image,
                 atlas_size: None,
                 clip: clip.map(|clip| clip.clip),
+                flip_x,
+                flip_y,
                 scale_factor,
             });
         }
@@ -378,6 +380,8 @@ pub fn extract_text_uinodes(
                     image: texture,
                     atlas_size,
                     clip: clip.map(|clip| clip.clip),
+                    flip_x: false,
+                    flip_y: false,
                     scale_factor,
                 });
             }
@@ -512,7 +516,7 @@ pub fn prepare_uinodes(
         }
 
         let atlas_extent = extracted_uinode.atlas_size.unwrap_or(uinode_rect.max);
-        let uvs = [
+        let mut uvs = [
             Vec2::new(
                 uinode_rect.min.x + positions_diff[0].x * extracted_uinode.scale_factor,
                 uinode_rect.min.y + positions_diff[0].y * extracted_uinode.scale_factor,
@@ -532,6 +536,13 @@ pub fn prepare_uinodes(
         ]
         .map(|pos| pos / atlas_extent);
 
+        if extracted_uinode.flip_x {
+            uvs = [uvs[1], uvs[0], uvs[3], uvs[2]];
+        }
+        if extracted_uinode.flip_y {
+            uvs = [uvs[3], uvs[2], uvs[1], uvs[0]];
+        }
+
         for i in QUAD_INDICES {
             ui_meta.vertices.push(UiVertex {
                 position: positions_clipped[i].into(),

crates/bevy_ui/src/ui_node.rs

@@ -1,6 +1,5 @@
 use crate::{Size, UiRect};
 use bevy_asset::Handle;
-use bevy_derive::{Deref, DerefMut};
 use bevy_ecs::{prelude::Component, reflect::ReflectComponent};
 use bevy_math::{Rect, Vec2};
 use bevy_reflect::prelude::*;
@@ -452,19 +451,39 @@ impl From<Color> for BackgroundColor {
 }
 
 /// The 2D texture displayed for this UI node
-#[derive(Component, Clone, Debug, Reflect, Deref, DerefMut)]
+#[derive(Component, Clone, Debug, Reflect)]
 #[reflect(Component, Default)]
-pub struct UiImage(pub Handle<Image>);
+pub struct UiImage {
+    /// Handle to the texture
+    pub texture: Handle<Image>,
+    /// Whether the image should be flipped along its x-axis
+    pub flip_x: bool,
+    /// Whether the image should be flipped along its y-axis
+    pub flip_y: bool,
+}
 
 impl Default for UiImage {
-    fn default() -> Self {
-        Self(DEFAULT_IMAGE_HANDLE.typed())
+    fn default() -> UiImage {
+        UiImage {
+            texture: DEFAULT_IMAGE_HANDLE.typed(),
+            flip_x: false,
+            flip_y: false,
+        }
+    }
+}
+
+impl UiImage {
+    pub fn new(texture: Handle<Image>) -> Self {
+        Self {
+            texture,
+            ..Default::default()
+        }
     }
 }
 
 impl From<Handle<Image>> for UiImage {
-    fn from(handle: Handle<Image>) -> Self {
-        Self(handle)
+    fn from(texture: Handle<Image>) -> Self {
+        Self::new(texture)
     }
 }
 

crates/bevy_ui/src/widget/image.rs

@@ -26,7 +26,7 @@ pub fn image_node_system(
     mut query: Query<(&mut CalculatedSize, &UiImage), (With<ImageMode>, Without<Text>)>,
 ) {
     for (mut calculated_size, image) in &mut query {
-        if let Some(texture) = textures.get(image) {
+        if let Some(texture) = textures.get(&image.texture) {
             let size = Size {
                 width: Val::Px(texture.texture_descriptor.size.width as f32),
                 height: Val::Px(texture.texture_descriptor.size.height as f32),

examples/games/game_menu.rs

@@ -90,7 +90,7 @@ mod splash {
                     size: Size::new(Val::Px(200.0), Val::Auto),
                     ..default()
                 },
-                image: UiImage(icon),
+                image: UiImage::new(icon),
                 ..default()
             },
             OnSplashScreen,
@@ -462,7 +462,7 @@ mod menu {
                         let icon = asset_server.load("textures/Game Icons/right.png");
                         parent.spawn(ImageBundle {
                             style: button_icon_style.clone(),
-                            image: UiImage(icon),
+                            image: UiImage::new(icon),
                             ..default()
                         });
                         parent.spawn(TextBundle::from_section(
@@ -483,7 +483,7 @@ mod menu {
                         let icon = asset_server.load("textures/Game Icons/wrench.png");
                         parent.spawn(ImageBundle {
                             style: button_icon_style.clone(),
-                            image: UiImage(icon),
+                            image: UiImage::new(icon),
                             ..default()
                         });
                         parent.spawn(TextBundle::from_section(
@@ -504,7 +504,7 @@ mod menu {
                         let icon = asset_server.load("textures/Game Icons/exitRight.png");
                         parent.spawn(ImageBundle {
                             style: button_icon_style,
-                            image: UiImage(icon),
+                            image: UiImage::new(icon),
                             ..default()
                         });
                         parent.spawn(TextBundle::from_section("Quit", button_text_style));