simplify transform usage where possible (#494)

crates/bevy_transform/src/components/transform.rs

@@ -1,4 +1,4 @@
-use bevy_math::{Mat3, Mat4, Quat, Vec3};
+use bevy_math::{Mat3, Mat4, Quat, Vec3, Vec4};
 use bevy_property::Properties;
 use std::fmt;
 
@@ -60,6 +60,10 @@ impl Transform {
         Vec3::from(self.value.w_axis().truncate())
     }
 
+    pub fn translation_mut(&mut self) -> &mut Vec4 {
+        self.value.w_axis_mut()
+    }
+
     pub fn rotation(&self) -> Quat {
         let scale = self.scale();
 

crates/bevy_ui/src/flex/mod.rs

@@ -193,7 +193,7 @@ pub fn flex_node_system(
     for (entity, mut node, mut transform, parent) in &mut node_transform_query.iter() {
         let layout = flex_surface.get_layout(entity).unwrap();
         node.size = Vec2::new(layout.size.width, layout.size.height);
-        let mut position = transform.translation();
+        let position = transform.translation_mut();
         position.set_x(layout.location.x + layout.size.width / 2.0);
         position.set_y(layout.location.y + layout.size.height / 2.0);
         if let Some(parent) = parent {
@@ -202,7 +202,5 @@ pub fn flex_node_system(
                 *position.y_mut() -= parent_layout.size.height / 2.0;
             }
         }
-
-        transform.set_translation(position);
     }
 }

crates/bevy_ui/src/update.rs

@@ -39,7 +39,6 @@ fn update_node_entity(
     parent_result: Option<f32>,
     previous_result: Option<f32>,
 ) -> Option<f32> {
-    let mut transform = node_query.get_mut::<Transform>(entity).ok()?;
     let mut z = UI_Z_STEP;
     let parent_global_z = parent_result.unwrap();
     if let Some(previous_global_z) = previous_result {
@@ -47,9 +46,8 @@ fn update_node_entity(
     };
     let global_z = z + parent_global_z;
 
-    let mut position = transform.translation();
+    let mut transform = node_query.get_mut::<Transform>(entity).ok()?;
-    position.set_z(z);
+    transform.translation_mut().set_z(z);
-    transform.set_translation(position);
 
     Some(global_z)
 }

crates/bevy_ui/src/widget/text.rs

@@ -1,7 +1,7 @@
 use crate::{CalculatedSize, Node};
 use bevy_asset::{Assets, Handle};
 use bevy_ecs::{Changed, Query, Res, ResMut};
-use bevy_math::{Size, Vec3};
+use bevy_math::Size;
 use bevy_render::{
     draw::{Draw, DrawContext, Drawable},
     prelude::Msaa,
@@ -61,9 +61,7 @@ pub fn draw_text_system(
     mut query: Query<(&mut Draw, &Text, &Node, &GlobalTransform)>,
 ) {
     for (mut draw, text, node, global_transform) in &mut query.iter() {
-        let position = Vec3::from(global_transform.value().w_axis().truncate())
+        let position = global_transform.translation() - (node.size / 2.0).extend(0.0);
-            - (node.size / 2.0).extend(0.0);
-
         let mut drawable_text = DrawableText {
             font: fonts.get(&text.font).unwrap(),
             font_atlas_set: font_atlas_sets

examples/game/breakout.rs

@@ -170,15 +170,11 @@ fn paddle_movement_system(
             direction += 1.0;
         }
 
-        transform.translate(Vec3::unit_x() * time.delta_seconds * direction * paddle.speed);
+        let translation = transform.translation_mut();
-
+        // move the paddle horizontally
+        *translation.x_mut() += time.delta_seconds * direction * paddle.speed;
         // bound the paddle within the walls
-        let translation = transform.translation();
+        *translation.x_mut() = translation.x().min(380.0).max(-380.0);
-        transform.set_translation(Vec3::new(
-            f32::max(-380.0, f32::min(380.0, translation.x())),
-            translation.y(),
-            translation.z(),
-        ));
     }
 }