From bb381747711866c8f9da089c2d5b9498d9c4b076 Mon Sep 17 00:00:00 2001
From: Cyborus <cyborus@cyborus.xyz>
Date: Mon, 2 Dec 2024 14:00:29 -0500
Subject: [PATCH] feat: add line height to `TextFont`

---
 crates/bevy_text/src/lib.rs       |  1 +
 crates/bevy_text/src/pipeline.rs  | 11 +++++++++--
 crates/bevy_text/src/text.rs      | 33 +++++++++++++++++++++++++++++++
 examples/dev_tools/fps_overlay.rs |  1 +
 4 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_text/src/lib.rs b/crates/bevy_text/src/lib.rs
index ad9feb7fdcf0f..d039d9941123e 100644
--- a/crates/bevy_text/src/lib.rs
+++ b/crates/bevy_text/src/lib.rs
@@ -113,6 +113,7 @@ impl Plugin for TextPlugin {
         app.init_asset::<Font>()
             .register_type::<Text2d>()
             .register_type::<TextFont>()
+            .register_type::<LineHeight>()
             .register_type::<TextColor>()
             .register_type::<TextSpan>()
             .register_type::<TextBounds>()
diff --git a/crates/bevy_text/src/pipeline.rs b/crates/bevy_text/src/pipeline.rs
index f8e7274ef31f2..6ff1e306dbdb8 100644
--- a/crates/bevy_text/src/pipeline.rs
+++ b/crates/bevy_text/src/pipeline.rs
@@ -98,6 +98,7 @@ impl TextPipeline {
         // Collect span information into a vec. This is necessary because font loading requires mut access
         // to FontSystem, which the cosmic-text Buffer also needs.
         let mut font_size: f32 = 0.;
+        let mut line_height: f32 = 0.0;
         let mut spans: Vec<(usize, &str, &TextFont, FontFaceInfo, Color)> =
             core::mem::take(&mut self.spans_buffer)
                 .into_iter()
@@ -130,6 +131,7 @@ impl TextPipeline {
 
             // Get max font size for use in cosmic Metrics.
             font_size = font_size.max(text_font.font_size);
+            line_height = line_height.max(text_font.line_height.eval(text_font.font_size));
 
             // Load Bevy fonts into cosmic-text's font system.
             let face_info = load_font_to_fontdb(
@@ -146,7 +148,6 @@ impl TextPipeline {
             spans.push((span_index, span, text_font, face_info, color));
         }
 
-        let line_height = font_size * 1.2;
         let mut metrics = Metrics::new(font_size, line_height).scale(scale_factor as f32);
         // Metrics of 0.0 cause `Buffer::set_metrics` to panic. We hack around this by 'falling
         // through' to call `Buffer::set_rich_text` with zero spans so any cached text will be cleared without
@@ -486,7 +487,13 @@ fn get_attrs<'a>(
         .stretch(face_info.stretch)
         .style(face_info.style)
         .weight(face_info.weight)
-        .metrics(Metrics::relative(text_font.font_size, 1.2).scale(scale_factor as f32))
+        .metrics(
+            Metrics {
+                font_size: text_font.font_size,
+                line_height: text_font.line_height.eval(text_font.font_size),
+            }
+            .scale(scale_factor as f32),
+        )
         .color(cosmic_text::Color(color.to_linear().as_u32()));
     attrs
 }
diff --git a/crates/bevy_text/src/text.rs b/crates/bevy_text/src/text.rs
index 0effb361aa302..7b9d5bfd10924 100644
--- a/crates/bevy_text/src/text.rs
+++ b/crates/bevy_text/src/text.rs
@@ -284,6 +284,11 @@ pub struct TextFont {
     /// 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,
+    /// The vertical height of a line of text, from the top of one line to the top of the
+    /// next.
+    ///
+    /// Defaults to `LineHeight::Scalar(1.2)`
+    pub line_height: LineHeight,
     /// The antialiasing method to use when rendering text.
     pub font_smoothing: FontSmoothing,
 }
@@ -323,11 +328,39 @@ impl Default for TextFont {
         Self {
             font: Default::default(),
             font_size: 20.0,
+            line_height: LineHeight::default(),
             font_smoothing: Default::default(),
         }
     }
 }
 
+/// Specifies the height of each line of text for `Text` and `Text2d`
+///
+/// Default is 1.2x the font size
+#[derive(Debug, Clone, Copy, Reflect)]
+#[reflect(Debug)]
+pub enum LineHeight {
+    /// Set line height to a specific number of pixels
+    Px(f32),
+    /// Set line height to a multiple of the font size
+    Scalar(f32),
+}
+
+impl LineHeight {
+    pub(crate) fn eval(self, font_size: f32) -> f32 {
+        match self {
+            LineHeight::Px(px) => px,
+            LineHeight::Scalar(scale) => scale * font_size,
+        }
+    }
+}
+
+impl Default for LineHeight {
+    fn default() -> Self {
+        LineHeight::Scalar(1.2)
+    }
+}
+
 /// The color of the text for this section.
 #[derive(Component, Copy, Clone, Debug, Deref, DerefMut, Reflect)]
 #[reflect(Component, Default, Debug)]
diff --git a/examples/dev_tools/fps_overlay.rs b/examples/dev_tools/fps_overlay.rs
index 0dcc5e5218be5..a1c11bb3ce026 100644
--- a/examples/dev_tools/fps_overlay.rs
+++ b/examples/dev_tools/fps_overlay.rs
@@ -26,6 +26,7 @@ fn main() {
                         font: default(),
                         // We could also disable font smoothing,
                         font_smoothing: FontSmoothing::default(),
+                        ..default()
                     },
                     // We can also change color of the overlay
                     text_color: OverlayColor::GREEN,