ui: feed computed text position into bevy_ui flex

and remove TextAlign because it is now redundant

crates/bevy_math/src/geometry.rs

@@ -2,7 +2,7 @@ use std::ops::{Add, AddAssign};
 use glam::Vec2;
 
 #[derive(Copy, Clone, PartialEq, Debug)]
-pub struct Size<T> {
+pub struct Size<T=f32> {
     pub width: T,
     pub height: T,
 }

crates/bevy_text/src/draw.rs

@@ -1,5 +1,5 @@
 use crate::{Font, FontAtlasSet};
-use ab_glyph::{FontVec, Glyph, PxScale, PxScaleFont, ScaleFont};
+use ab_glyph::{Glyph, PxScale, ScaleFont};
 use bevy_asset::Assets;
 use bevy_math::{Mat4, Vec2, Vec3};
 use bevy_render::{
@@ -17,7 +17,6 @@ use bevy_sprite::{TextureAtlas, TextureAtlasSprite};
 pub struct TextStyle {
     pub font_size: f32,
     pub color: Color,
-    pub align: TextAlign,
 }
 
 impl Default for TextStyle {
@@ -25,23 +24,10 @@ impl Default for TextStyle {
         Self {
             color: Color::WHITE,
             font_size: 12.0,
-            align: TextAlign::default(),
         }
     }
 }
 
-pub enum TextAlign {
-    Left,
-    Center,
-    Right,
-}
-
-impl Default for TextAlign {
-    fn default() -> Self {
-        TextAlign::Left
-    }
-}
-
 pub struct DrawableText<'a> {
     pub font: &'a Font,
     pub font_atlas_set: &'a FontAtlasSet,
@@ -54,26 +40,6 @@ pub struct DrawableText<'a> {
     pub text: &'a str,
 }
 
-fn get_text_width(text: &str, scaled_font: &PxScaleFont<&&FontVec>) -> f32 {
-    let mut last_glyph: Option<Glyph> = None;
-    let mut position = 0.0;
-    for character in text.chars() {
-        if character.is_control() {
-            continue;
-        }
-
-        let glyph = scaled_font.scaled_glyph(character);
-        if let Some(last_glyph) = last_glyph.take() {
-            position += scaled_font.kern(last_glyph.id, glyph.id);
-        }
-
-        position += scaled_font.h_advance(glyph.id);
-        last_glyph = Some(glyph);
-    }
-
-    position
-}
-
 impl<'a> Drawable for DrawableText<'a> {
     fn draw(&mut self, draw: &mut Draw, context: &mut DrawContext) -> Result<(), DrawError> {
         context.set_pipeline(
@@ -109,17 +75,6 @@ impl<'a> Drawable for DrawableText<'a> {
         let scale = PxScale::from(self.style.font_size);
         let scaled_font = ab_glyph::Font::as_scaled(&font, scale);
         let mut caret = self.position;
-        match self.style.align {
-            TextAlign::Left => { /* already aligned left by default */ }
-            TextAlign::Center => {
-                *caret.x_mut() +=
-                    self.container_size.x() / 2.0 - get_text_width(&self.text, &scaled_font) / 2.0
-            }
-            TextAlign::Right => {
-                *caret.x_mut() += self.container_size.x() - get_text_width(&self.text, &scaled_font)
-            }
-        }
-
         let mut last_glyph: Option<Glyph> = None;
 
         // set local per-character bindings

crates/bevy_text/src/font_atlas_set.rs

@@ -1,5 +1,5 @@
 use crate::{Font, FontAtlas};
-use ab_glyph::ScaleFont;
+use ab_glyph::{Glyph, ScaleFont};
 use bevy_asset::{Assets, Handle};
 use bevy_core::FloatOrd;
 use bevy_math::Vec2;
@@ -49,24 +49,35 @@ impl FontAtlasSet {
         textures: &mut Assets<Texture>,
         font_size: f32,
         text: &str,
-    ) {
+    ) -> f32 {
         let font = fonts.get(&self.font).unwrap();
         let scaled_font = ab_glyph::Font::as_scaled(&font.font, font_size);
         let font_atlas = self
             .font_atlases
             .entry(FloatOrd(font_size))
             .or_insert_with(|| FontAtlas::new(textures, texture_atlases, Vec2::new(512.0, 512.0)));
+
+        let mut last_glyph: Option<Glyph> = None;
+        let mut width = 0.0;
         for character in text.chars() {
-            if character.is_control() || font_atlas.get_char_index(character).is_some() {
+            if character.is_control() {
                 continue;
             }
-
             let glyph = scaled_font.scaled_glyph(character);
-            if let Some(outlined_glyph) = scaled_font.outline_glyph(glyph) {
+            if let Some(last_glyph) = last_glyph.take() {
-                let glyph_texture = Font::get_outlined_glyph_texture(outlined_glyph);
+                width += scaled_font.kern(last_glyph.id, glyph.id);
-                font_atlas.add_char(textures, texture_atlases, character, &glyph_texture);
             }
+            if font_atlas.get_char_index(character).is_none() {
+                if let Some(outlined_glyph) = scaled_font.outline_glyph(glyph.clone()) {
+                    let glyph_texture = Font::get_outlined_glyph_texture(outlined_glyph);
+                    font_atlas.add_char(textures, texture_atlases, character, &glyph_texture);
+                }
+            }
+            width += scaled_font.h_advance(glyph.id);
+            last_glyph = Some(glyph);
         }
+
+        width
     }
 
     pub fn get_glyph_atlas_info(&self, font_size: f32, character: char) -> Option<GlyphAtlasInfo> {

crates/bevy_text/src/lib.rs

@@ -11,7 +11,7 @@ pub use font_atlas_set::*;
 pub use font_loader::*;
 
 pub mod prelude {
-    pub use crate::{Font, TextAlign, TextStyle};
+    pub use crate::{Font, TextStyle};
 }
 
 use bevy_app::prelude::*;

crates/bevy_ui/src/entity.rs

@@ -2,7 +2,7 @@ use super::Node;
 use crate::{
     render::UI_PIPELINE_HANDLE,
     widget::{Button, Text},
-    Click, FocusPolicy, Hover, Style,
+    Click, FocusPolicy, Hover, Style, CalculatedSize,
 };
 use bevy_asset::Handle;
 use bevy_ecs::Bundle;
@@ -68,6 +68,7 @@ pub struct TextComponents {
     pub style: Style,
     pub draw: Draw,
     pub text: Text,
+    pub calculated_size: CalculatedSize,
     pub focus_policy: FocusPolicy,
     pub transform: Transform,
     pub local_transform: LocalTransform,
@@ -83,6 +84,7 @@ impl Default for TextComponents {
             },
             text: Default::default(),
             node: Default::default(),
+            calculated_size: Default::default(),
             style: Default::default(),
             transform: Default::default(),
             local_transform: Default::default(),

crates/bevy_ui/src/flex/mod.rs

@@ -1,6 +1,6 @@
 mod convert;
 
-use crate::{Style, Node};
+use crate::{CalculatedSize, Node, Style};
 use bevy_ecs::{Changed, Entity, Query, Res, ResMut, With, Without};
 use bevy_math::Vec2;
 use bevy_transform::prelude::{Children, LocalTransform, Parent};
@@ -10,7 +10,6 @@ use stretch::Stretch;
 
 pub struct FlexSurface {
     entity_to_stretch: HashMap<Entity, stretch::node::Node>,
-    stretch_to_entity: HashMap<stretch::node::Node, Entity>,
     window_nodes: HashMap<WindowId, stretch::node::Node>,
     stretch: Stretch,
 }
@@ -19,7 +18,6 @@ impl Default for FlexSurface {
     fn default() -> Self {
         Self {
             entity_to_stretch: Default::default(),
-            stretch_to_entity: Default::default(),
             window_nodes: Default::default(),
             stretch: Stretch::new(),
         }
@@ -30,12 +28,10 @@ impl FlexSurface {
     pub fn upsert_node(&mut self, entity: Entity, style: &Style) {
         let mut added = false;
         let stretch = &mut self.stretch;
-        let stretch_to_entity = &mut self.stretch_to_entity;
         let stretch_style = style.into();
         let stretch_node = self.entity_to_stretch.entry(entity).or_insert_with(|| {
             added = true;
             let stretch_node = stretch.new_node(stretch_style, Vec::new()).unwrap();
-            stretch_to_entity.insert(stretch_node, entity);
             stretch_node
         });
 
@@ -46,6 +42,44 @@ impl FlexSurface {
         }
     }
 
+    pub fn upsert_leaf(&mut self, entity: Entity, style: &Style, calculated_size: CalculatedSize) {
+        let mut added = false;
+        let stretch = &mut self.stretch;
+        let stretch_style = style.into();
+        let stretch_node = self.entity_to_stretch.entry(entity).or_insert_with(|| {
+            added = true;
+            let stretch_node = stretch
+                .new_leaf(
+                    stretch_style,
+                    Box::new(move |_| {
+                        Ok(stretch::geometry::Size {
+                            width: calculated_size.size.width,
+                            height: calculated_size.size.height,
+                        })
+                    }),
+                )
+                .unwrap();
+            stretch_node
+        });
+
+        if !added {
+            self.stretch
+                .set_style(*stretch_node, stretch_style)
+                .unwrap();
+            self.stretch
+                .set_measure(
+                    *stretch_node,
+                    Some(Box::new(move |_| {
+                        Ok(stretch::geometry::Size {
+                            width: calculated_size.size.width,
+                            height: calculated_size.size.height,
+                        })
+                    })),
+                )
+                .unwrap();
+        }
+    }
+
     pub fn update_children(&mut self, entity: Entity, children: &Children) {
         let mut stretch_children = Vec::with_capacity(children.len());
         for child in children.iter() {
@@ -63,10 +97,7 @@ impl FlexSurface {
         let stretch = &mut self.stretch;
         let node = self.window_nodes.entry(window.id).or_insert_with(|| {
             stretch
-                .new_node(
+                .new_node(stretch::style::Style::default(), Vec::new())
-                    stretch::style::Style::default(),
-                    Vec::new(),
-                )
                 .unwrap()
         });
 
@@ -120,7 +151,8 @@ pub fn flex_node_system(
     windows: Res<Windows>,
     mut flex_surface: ResMut<FlexSurface>,
     mut root_node_query: Query<With<Node, Without<Parent, Entity>>>,
-    mut node_query: Query<With<Node, (Entity, Changed<Style>)>>,
+    mut node_query: Query<With<Node, (Entity, Changed<Style>, Option<&CalculatedSize>)>>,
+    mut changed_size_query: Query<With<Node, (Entity, &Style, Changed<CalculatedSize>)>>,
     mut children_query: Query<With<Node, (Entity, Changed<Children>)>>,
     mut node_transform_query: Query<(Entity, &mut Node, &mut LocalTransform, Option<&Parent>)>,
 ) {
@@ -130,9 +162,17 @@ pub fn flex_node_system(
     }
 
     // update changed nodes
-    for (entity, style) in &mut node_query.iter() {
+    for (entity, style, calculated_size) in &mut node_query.iter() {
         // TODO: remove node from old hierarchy if its root has changed
-        flex_surface.upsert_node(entity, &style);
+        if let Some(calculated_size) = calculated_size {
+            flex_surface.upsert_leaf(entity, &style, *calculated_size);
+        } else {
+            flex_surface.upsert_node(entity, &style);
+        }
+    }
+
+    for (entity, style, calculated_size) in &mut changed_size_query.iter() {
+        flex_surface.upsert_leaf(entity, &style, *calculated_size);
     }
 
     // TODO: handle removed nodes

crates/bevy_ui/src/lib.rs

@@ -39,7 +39,7 @@ impl AppPlugin for UiPlugin {
             // add these stages to front because these must run before transform update systems
             .add_system_to_stage_front(stage::POST_UPDATE, flex_node_system.system())
             .add_system_to_stage_front(stage::POST_UPDATE, ui_z_system.system())
-            .add_system_to_stage(stage::POST_UPDATE, widget::text_system.system())
+            .add_system_to_stage_front(stage::POST_UPDATE, widget::text_system.system())
             .add_system_to_stage(bevy_render::stage::DRAW, widget::draw_text_system.system());
 
         let resources = app.resources();

crates/bevy_ui/src/node.rs

@@ -41,7 +41,11 @@ impl AddAssign<f32> for Val {
             Val::Percent(value) => *value += rhs,
         }
     }
+}
 
+#[derive(Default, Copy, Clone)]
+pub struct CalculatedSize {
+    pub size: Size,
 }
 
 #[derive(Clone, PartialEq, Debug)]

crates/bevy_ui/src/widget/text.rs

@@ -1,6 +1,7 @@
-use crate::Node;
+use crate::{CalculatedSize, Node};
 use bevy_asset::{Assets, Handle};
-use bevy_ecs::{Query, Res, ResMut};
+use bevy_ecs::{Changed, Query, Res, ResMut};
+use bevy_math::Size;
 use bevy_render::{
     draw::{Draw, DrawContext, Drawable},
     renderer::{AssetRenderResourceBindings, RenderResourceBindings},
@@ -22,9 +23,9 @@ pub fn text_system(
     fonts: Res<Assets<Font>>,
     mut font_atlas_sets: ResMut<Assets<FontAtlasSet>>,
     mut texture_atlases: ResMut<Assets<TextureAtlas>>,
-    mut query: Query<&Text>,
+    mut query: Query<(Changed<Text>, &mut CalculatedSize)>,
 ) {
-    for text in &mut query.iter() {
+    for (text, mut calculated_size) in &mut query.iter() {
         let font_atlases = font_atlas_sets
             .get_or_insert_with(Handle::from_id(text.font.id), || {
                 FontAtlasSet::new(text.font)
@@ -35,13 +36,15 @@ pub fn text_system(
         // resource generation needs to happen AFTER the render graph systems. maybe draw systems should execute within the
         // render graph so ordering like this can be taken into account? Maybe the RENDER_GRAPH_SYSTEMS stage should be removed entirely
         // in favor of node.update()? Regardless, in the immediate short term the current approach is fine.
-        font_atlases.add_glyphs_to_atlas(
+        let width = font_atlases.add_glyphs_to_atlas(
             &fonts,
             &mut texture_atlases,
             &mut textures,
             text.style.font_size,
             &text.value,
         );
+
+        calculated_size.size = Size::new(width, text.style.font_size);
     }
 }
 

examples/game/breakout.rs

@@ -71,7 +71,6 @@ fn setup(
                 style: TextStyle {
                     color: Color::rgb(0.2, 0.2, 0.8).into(),
                     font_size: 40.0,
-                    ..Default::default()
                 },
             },
             style: Style {

examples/ui/button.rs

@@ -95,13 +95,13 @@ fn setup(
         .spawn(UiCameraComponents::default())
         .spawn(ButtonComponents {
             style: Style {
-                size: Size::new(Val::Px(150.0), Val::Px(70.0)),
+                size: Size::new(Val::Px(150.0), Val::Px(65.0)),
-                align_self: AlignSelf::Center,
+                // center button
-                margin: Rect {
+                margin: Rect::all(Val::Auto),
-                    left: Val::Auto,
+                // horizontally center child text
-                    right: Val::Auto,
+                justify_content: JustifyContent::Center,
-                    ..Default::default()
+                // vertically center child text
-                },
+                align_items: AlignItems::Center,
                 ..Default::default()
             },
             material: button_materials.normal,
@@ -109,21 +109,12 @@ fn setup(
         })
         .with_children(|parent| {
             parent.spawn(TextComponents {
-                style: Style {
-                    size: Size::new(Val::Percent(100.0), Val::Percent(100.0)),
-                    margin: Rect {
-                        bottom: Val::Px(10.0),
-                        ..Default::default()
-                    },
-                    ..Default::default()
-                },
                 text: Text {
                     value: "Button".to_string(),
                     font: asset_server.load("assets/fonts/FiraSans-Bold.ttf").unwrap(),
                     style: TextStyle {
                         font_size: 40.0,
                         color: Color::rgb(0.8, 0.8, 0.8),
-                        align: TextAlign::Center,
                     },
                 },
                 ..Default::default()

examples/ui/font_atlas_debug.rs

@@ -81,7 +81,6 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>, mut state: ResM
                 style: TextStyle {
                     font_size: 60.0,
                     color: Color::WHITE,
-                    ..Default::default()
                 },
             },
             ..Default::default()

examples/ui/text.rs

@@ -26,17 +26,19 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     let font_handle = asset_server.load("assets/fonts/FiraSans-Bold.ttf").unwrap();
     commands
         // 2d camera
-        .spawn(Camera2dComponents::default())
+        .spawn(UiCameraComponents::default())
         // texture
         .spawn(TextComponents {
-            node: Node::default(),
+            style: Style {
+                align_self: AlignSelf::FlexEnd,
+                ..Default::default()
+            },
             text: Text {
                 value: "FPS:".to_string(),
                 font: font_handle,
                 style: TextStyle {
                     font_size: 60.0,
                     color: Color::WHITE,
-                    align: TextAlign::Left,
                 },
             },
             ..Default::default()

examples/ui/ui.rs

@@ -61,12 +61,7 @@ fn setup(
                             // text
                             parent.spawn(TextComponents {
                                 style: Style {
-                                    size: Size::new(Val::Px(100.0), Val::Px(30.0)),
+                                    margin: Rect::all(Val::Px(5.0)),
-                                    margin: Rect {
-                                        left: Val::Px(5.0),
-                                        top: Val::Px(5.0),
-                                        ..Default::default()
-                                    },
                                     ..Default::default()
                                 },
                                 text: Text {
@@ -77,7 +72,6 @@ fn setup(
                                     style: TextStyle {
                                         font_size: 30.0,
                                         color: Color::WHITE,
-                                        ..Default::default()
                                     },
                                 },
                                 ..Default::default()
@@ -103,7 +97,7 @@ fn setup(
                             bottom: Val::Px(10.0),
                             ..Default::default()
                         },
-                        border: Rect::all(Val::Px(10.0)),
+                        border: Rect::all(Val::Px(20.0)),
                         ..Default::default()
                     },
                     material: materials.add(Color::rgb(0.1, 0.1, 1.0).into()),