Replace the f32 font_size value of TextStyle with an enum value

crates/bevy_text/src/lib.rs

@@ -22,7 +22,7 @@ pub use text2d::*;
 
 pub mod prelude {
     #[doc(hidden)]
-    pub use crate::{Font, Text, Text2dBundle, TextAlignment, TextError, TextSection, TextStyle};
+    pub use crate::{Font, Text, Text2dBundle, TextAlignment, TextError, TextSection, TextStyle, DefaultFontSize, FontSize};
 }
 
 use bevy_app::prelude::*;
@@ -88,6 +88,7 @@ impl Plugin for TextPlugin {
             .init_asset_loader::<FontLoader>()
             .init_resource::<TextSettings>()
             .init_resource::<FontAtlasWarning>()
+            .init_resource::<DefaultFontSize>()
             .insert_resource(TextPipeline::default())
             .add_systems(
                 PostUpdate,

crates/bevy_text/src/pipeline.rs

@@ -10,9 +10,9 @@ use bevy_utils::HashMap;
 use glyph_brush_layout::{FontId, GlyphPositioner, SectionGeometry, SectionText};
 
 use crate::{
-    compute_text_bounds, error::TextError, glyph_brush::GlyphBrush, scale_value, BreakLineOn, Font,
+    compute_text_bounds, error::TextError, glyph_brush::GlyphBrush, BreakLineOn, Font,
     FontAtlasSet, FontAtlasWarning, PositionedGlyph, TextAlignment, TextSection, TextSettings,
-    YAxisOrientation,
+    YAxisOrientation, DefaultFontSize,
 };
 
 #[derive(Default, Resource)]
@@ -54,6 +54,8 @@ impl TextPipeline {
         text_settings: &TextSettings,
         font_atlas_warning: &mut FontAtlasWarning,
         y_axis_orientation: YAxisOrientation,
+        viewport_height: f32,
+        default_font_size: DefaultFontSize,
     ) -> Result<TextLayoutInfo, TextError> {
         let mut scaled_fonts = Vec::with_capacity(sections.len());
         let sections = sections
@@ -63,7 +65,9 @@ impl TextPipeline {
                     .get(&section.style.font)
                     .ok_or(TextError::NoSuchFont)?;
                 let font_id = self.get_or_insert_font_id(&section.style.font, font);
-                let font_size = scale_value(section.style.font_size, scale_factor);
+                // let resolved_font_size = section.style.font_size.resolve(default_font_size, viewport_height);
+                // let font_size = scale_value(resolved_font_size, scale_factor);
+                let font_size = section.style.font_size.resolve(default_font_size, viewport_height, scale_factor);
 
                 scaled_fonts.push(ab_glyph::Font::as_scaled(&font.font, font_size));
 
@@ -109,6 +113,8 @@ impl TextPipeline {
         scale_factor: f64,
         text_alignment: TextAlignment,
         linebreak_behaviour: BreakLineOn,
+        viewport_height: f32,
+        default_font_size: DefaultFontSize,
     ) -> Result<TextMeasureInfo, TextError> {
         let mut auto_fonts = Vec::with_capacity(sections.len());
         let mut scaled_fonts = Vec::with_capacity(sections.len());
@@ -119,7 +125,7 @@ impl TextPipeline {
                 let font = fonts
                     .get(&section.style.font)
                     .ok_or(TextError::NoSuchFont)?;
-                let font_size = scale_value(section.style.font_size, scale_factor);
+                let font_size = section.style.font_size.resolve(default_font_size, viewport_height, scale_factor);
                 auto_fonts.push(font.font.clone());
                 let px_scale_font = ab_glyph::Font::into_scaled(font.font.clone(), font_size);
                 scaled_fonts.push(px_scale_font);

crates/bevy_text/src/text.rs

@@ -1,5 +1,5 @@
 use bevy_asset::Handle;
-use bevy_ecs::{prelude::Component, reflect::ReflectComponent};
+use bevy_ecs::{prelude::Component, reflect::ReflectComponent, system::Resource};
 use bevy_reflect::prelude::*;
 use bevy_render::color::Color;
 use bevy_utils::default;
@@ -174,20 +174,69 @@ pub struct TextStyle {
     ///
     /// A new font atlas is generated for every combination of font handle and scaled font size
     /// which can have a strong performance impact.
-    pub font_size: f32,
+    pub font_size: FontSize,
     pub color: Color,
 }
 
 impl Default for TextStyle {
     fn default() -> Self {
         Self {
             font: DEFAULT_FONT_HANDLE.typed(),
-            font_size: 12.0,
+            font_size: FontSize::Default,
             color: Color::WHITE,
         }
     }
 }
 
+/// The default font size.
+/// Used when the size field of TextStyle is set to Default.
+#[derive(Resource, Clone, Copy, Debug)]
+pub enum DefaultFontSize {
+    /// Default font size in logical pixels
+    Px(f32),
+    /// Default font size expressed as a percentage of the height of the viewport.
+    Vh(f32),
+}
+
+impl Default for DefaultFontSize {
+    fn default() -> Self {
+        DefaultFontSize::Px(12.)
+    }
+}
+
+/// The size of a font
+#[derive(Default, Copy, Clone, Debug, Reflect)]
+pub enum FontSize {
+    /// The size of the font in logical pixels
+    Px(f32),
+    /// The size of the font expressed as a percentage of the height of the viewport.
+    Vh(f32),
+    /// Use the size from the `DefaultFontSize` resource
+    #[default]
+    Default,
+}
+
+impl From<DefaultFontSize> for FontSize {
+    fn from(value: DefaultFontSize) -> Self {
+        match value {
+            DefaultFontSize::Px(px) => FontSize::Px(px),
+            DefaultFontSize::Vh(vh) => FontSize::Vh(vh),
+        }
+    }
+}
+
+
+impl FontSize {
+    /// Resolve the `FontSize` to a numeric value in logical pixels.
+    pub fn resolve(self, default_font_size: DefaultFontSize, viewport_height: f32, scale_factor: f64) -> f32 {
+        match self {
+            FontSize::Px(px) => (px as f64 * scale_factor) as f32,
+            FontSize::Vh(vh) => viewport_height * vh / 100.,
+            FontSize::Default => Self::from(default_font_size).resolve(default_font_size, viewport_height, scale_factor),
+        }
+    }
+}
+
 /// Determines how lines will be broken when preventing text from running out of bounds.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Reflect, Serialize, Deserialize)]
 #[reflect(Serialize, Deserialize)]

crates/bevy_text/src/text2d.rs

@@ -24,7 +24,7 @@ use bevy_window::{PrimaryWindow, Window, WindowScaleFactorChanged};
 
 use crate::{
     BreakLineOn, Font, FontAtlasSet, FontAtlasWarning, PositionedGlyph, Text, TextError,
-    TextLayoutInfo, TextPipeline, TextSettings, YAxisOrientation,
+    TextLayoutInfo, TextPipeline, TextSettings, YAxisOrientation, DefaultFontSize,
 };
 
 /// The maximum width and height of text. The text will wrap according to the specified size.
@@ -161,15 +161,16 @@ pub fn update_text2d_layout(
     mut font_atlas_set_storage: ResMut<Assets<FontAtlasSet>>,
     mut text_pipeline: ResMut<TextPipeline>,
     mut text_query: Query<(Entity, Ref<Text>, Ref<Text2dBounds>, &mut TextLayoutInfo)>,
+    default_font_size: Res<DefaultFontSize>,
 ) {
     // We need to consume the entire iterator, hence `last`
     let factor_changed = scale_factor_changed.iter().last().is_some();
 
     // TODO: Support window-independent scaling: https://github.com/bevyengine/bevy/issues/5621
-    let scale_factor = windows
+    let (scale_factor, view_height) = windows
         .get_single()
-        .map(|window| window.resolution.scale_factor())
-        .unwrap_or(1.0);
+        .map(|window| (window.resolution.scale_factor(), window.resolution.height()))
+        .unwrap_or((1.0, 600.));
 
     for (entity, text, bounds, mut text_layout_info) in &mut text_query {
         if factor_changed || text.is_changed() || bounds.is_changed() || queue.remove(&entity) {
@@ -195,6 +196,8 @@ pub fn update_text2d_layout(
                 text_settings.as_ref(),
                 &mut font_atlas_warning,
                 YAxisOrientation::BottomToTop,
+                view_height,
+                *default_font_size,
             ) {
                 Err(TextError::NoSuchFont) => {
                     // There was an error processing the text layout, let's add this entity to the

crates/bevy_ui/src/widget/text.rs

@@ -13,7 +13,7 @@ use bevy_render::texture::Image;
 use bevy_sprite::TextureAtlas;
 use bevy_text::{
     BreakLineOn, Font, FontAtlasSet, FontAtlasWarning, Text, TextError, TextLayoutInfo,
-    TextMeasureInfo, TextPipeline, TextSettings, YAxisOrientation,
+    TextMeasureInfo, TextPipeline, TextSettings, YAxisOrientation, DefaultFontSize,
 };
 use bevy_window::{PrimaryWindow, Window};
 use taffy::style::AvailableSpace;
@@ -82,13 +82,17 @@ fn create_text_measure(
     text: Ref<Text>,
     mut content_size: Mut<ContentSize>,
     mut text_flags: Mut<TextFlags>,
+    view_height: f32,
+    default_font_size: DefaultFontSize,
 ) {
     match text_pipeline.create_text_measure(
         fonts,
         &text.sections,
         scale_factor,
         text.alignment,
         text.linebreak_behavior,
+        view_height,
+        default_font_size
     ) {
         Ok(measure) => {
             if text.linebreak_behavior == BreakLineOn::NoWrap {
@@ -129,11 +133,12 @@ pub fn measure_text_system(
     ui_scale: Res<UiScale>,
     mut text_pipeline: ResMut<TextPipeline>,
     mut text_query: Query<(Ref<Text>, &mut ContentSize, &mut TextFlags), With<Node>>,
+    default_font_size: Res<DefaultFontSize>,
 ) {
-    let window_scale_factor = windows
+    let (window_scale_factor, view_height) = windows
         .get_single()
-        .map(|window| window.resolution.scale_factor())
-        .unwrap_or(1.);
+        .map(|window| (window.resolution.scale_factor(), window.resolution.height()))
+        .unwrap_or((1., 600.));
 
     let scale_factor = ui_scale.0 * window_scale_factor;
 
@@ -149,6 +154,8 @@ pub fn measure_text_system(
                     text,
                     content_size,
                     text_flags,
+                    view_height,
+                    *default_font_size
                 );
             }
         }
@@ -164,6 +171,8 @@ pub fn measure_text_system(
                 text,
                 content_size,
                 text_flags,
+                view_height,
+                *default_font_size
             );
         }
     }
@@ -184,6 +193,8 @@ fn queue_text(
     node: Ref<Node>,
     mut text_flags: Mut<TextFlags>,
     mut text_layout_info: Mut<TextLayoutInfo>,
+    view_height: f32,
+    default_font_size: DefaultFontSize,
 ) {
     // Skip the text node if it is waiting for a new measure func
     if !text_flags.needs_new_measure_func {
@@ -208,6 +219,8 @@ fn queue_text(
             text_settings,
             font_atlas_warning,
             YAxisOrientation::TopToBottom,
+            view_height,
+            default_font_size,
         ) {
             Err(TextError::NoSuchFont) => {
                 // There was an error processing the text layout, try again next frame
@@ -245,12 +258,13 @@ pub fn text_system(
     mut font_atlas_set_storage: ResMut<Assets<FontAtlasSet>>,
     mut text_pipeline: ResMut<TextPipeline>,
     mut text_query: Query<(Ref<Node>, &Text, &mut TextLayoutInfo, &mut TextFlags)>,
+    default_font_size: Res<DefaultFontSize>,
 ) {
     // TODO: Support window-independent scaling: https://github.com/bevyengine/bevy/issues/5621
-    let window_scale_factor = windows
+    let (window_scale_factor, view_height) = windows
         .get_single()
-        .map(|window| window.resolution.scale_factor())
-        .unwrap_or(1.);
+        .map(|window| (window.resolution.scale_factor(), window.height()))
+        .unwrap_or((1., 600.));
 
     let scale_factor = ui_scale.0 * window_scale_factor;
 
@@ -271,6 +285,8 @@ pub fn text_system(
                     node,
                     text_flags,
                     text_layout_info,
+                    view_height,
+                    *default_font_size,
                 );
             }
         }
@@ -292,6 +308,8 @@ pub fn text_system(
                 node,
                 text_flags,
                 text_layout_info,
+                view_height,
+                *default_font_size,
             );
         }
     }

examples/ui/text.rs

@@ -36,7 +36,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
             TextStyle {
                 // This font is loaded and will be used instead of the default font.
                 font: asset_server.load("fonts/FiraSans-Bold.ttf"),
-                font_size: 100.0,
+                font_size: FontSize::Vh(50.0),
                 color: Color::WHITE,
             },
         ) // Set the alignment of the Text
@@ -59,12 +59,12 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
                 TextStyle {
                     // This font is loaded and will be used instead of the default font.
                     font: asset_server.load("fonts/FiraSans-Bold.ttf"),
-                    font_size: 60.0,
+                    font_size: FontSize::Px(60.0),
                     color: Color::WHITE,
                 },
             ),
             TextSection::from_style(TextStyle {
-                font_size: 60.0,
+                font_size: FontSize::Px(60.0),
                 color: Color::GOLD,
                 // If no font is specified, it will use the default font.
                 ..default()