feat: add line height to TextFont

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: Option<f32> = None;
         let mut spans: Vec<(usize, &str, &TextFont, FontFaceInfo, Color)> =
             core::mem::take(&mut self.spans_buffer)
                 .into_iter()
@@ -130,6 +131,12 @@ impl TextPipeline {
 
             // Get max font size for use in cosmic Metrics.
             font_size = font_size.max(text_font.font_size);
+            line_height = match (line_height, text_font.line_height) {
+                (None, None) => None,
+                (Some(x), None) => Some(x),
+                (None, Some(y)) => Some(y),
+                (Some(x), Some(y)) => Some(x.max(y)),
+            };
 
             // Load Bevy fonts into cosmic-text's font system.
             let face_info = load_font_to_fontdb(
@@ -146,7 +153,7 @@ impl TextPipeline {
             spans.push((span_index, span, text_font, face_info, color));
         }
 
-        let line_height = font_size * 1.2;
+        let line_height = line_height.unwrap_or(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 +493,13 @@ 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.unwrap_or(text_font.font_size * 1.2),
+            }
+            .scale(scale_factor as f32),
+        )
         .color(cosmic_text::Color(color.to_linear().as_u32()));
     attrs
 }

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 in pixels, from the top of one line to the top of the
+    /// next.
+    ///
+    /// If not set, the line height will be 1.2 * `font_size`.
+    pub line_height: Option<f32>,
     /// The antialiasing method to use when rendering text.
     pub font_smoothing: FontSmoothing,
 }
@@ -323,6 +328,7 @@ impl Default for TextFont {
         Self {
             font: Default::default(),
             font_size: 20.0,
+            line_height: None,
             font_smoothing: Default::default(),
         }
     }