Handle default metrics in shift.rs

crates/typst-library/src/text/font/mod.rs

@@ -215,10 +215,10 @@ pub struct FontMetrics {
     pub underline: LineMetrics,
     /// Recommended metrics for an overline.
     pub overline: LineMetrics,
-    /// Metrics for subscripts.
+    /// Metrics for subscripts, if provided by the font.
-    pub subscript: ScriptMetrics,
+    pub subscript: Option<ScriptMetrics>,
-    /// Metrics for superscripts.
+    /// Metrics for superscripts, if provided by the font.
-    pub superscript: ScriptMetrics,
+    pub superscript: Option<ScriptMetrics>,
 }
 
 impl FontMetrics {
@@ -254,25 +254,19 @@ impl FontMetrics {
             thickness: underline.thickness,
         };
 
-        let subscript = match ttf.subscript_metrics() {
+        let subscript = ttf.subscript_metrics().map(|metrics| ScriptMetrics {
-            None => ScriptMetrics::default_subscript(),
-            Some(metrics) => ScriptMetrics {
             width: to_em(metrics.x_size),
             height: to_em(metrics.y_size),
             horizontal_offset: to_em(metrics.x_offset),
             vertical_offset: -to_em(metrics.y_offset),
-            },
+        });
-        };
 
-        let superscript = match ttf.superscript_metrics() {
+        let superscript = ttf.superscript_metrics().map(|metrics| ScriptMetrics {
-            None => ScriptMetrics::default_superscript(),
-            Some(metrics) => ScriptMetrics {
             width: to_em(metrics.x_size),
             height: to_em(metrics.y_size),
             horizontal_offset: to_em(metrics.x_offset),
             vertical_offset: to_em(metrics.y_offset),
-            },
+        });
-        };
 
         Self {
             units_per_em,
@@ -328,34 +322,6 @@ pub struct ScriptMetrics {
     pub vertical_offset: Em,
 }
 
-impl ScriptMetrics {
-    /// Creates default script metrics with the specified vertical offset.
-    pub const fn default_with_vertical_offset(offset: Em) -> Self {
-        Self {
-            width: Em::new(0.6),
-            height: Em::new(0.6),
-            horizontal_offset: Em::zero(),
-            vertical_offset: offset,
-        }
-    }
-
-    /// Returns the default metrics for subscripts.
-    ///
-    /// This can be used as a last resort if neither the user nor the font
-    /// provided those metrics.
-    pub const fn default_subscript() -> Self {
-        Self::default_with_vertical_offset(Em::new(-0.2))
-    }
-
-    /// Returns the default metrics for superscripts.
-    ///
-    /// This can be used as a last resort if neither the user nor the font
-    /// provided those metrics.
-    pub const fn default_superscript() -> Self {
-        Self::default_with_vertical_offset(Em::new(0.5))
-    }
-}
-
 /// Identifies a vertical metric of a font.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
 pub enum VerticalFontMetric {

crates/typst-library/src/text/shift.rs

@@ -197,17 +197,28 @@ impl ScriptKind {
     /// provided those metrics.
     pub const fn default_metrics(self) -> ScriptMetrics {
         match self {
-            Self::Sub => ScriptMetrics::default_subscript(),
+            Self::Sub => ScriptMetrics {
-            Self::Super => ScriptMetrics::default_superscript(),
+                width: Em::new(0.6),
+                height: Em::new(0.6),
+                horizontal_offset: Em::zero(),
+                vertical_offset: Em::new(-0.2),
+            },
+            Self::Super => ScriptMetrics {
+                width: Em::new(0.6),
+                height: Em::new(0.6),
+                horizontal_offset: Em::zero(),
+                vertical_offset: Em::new(0.5),
+            },
         }
     }
 
     /// Reads the script metrics from the font table for to this script kind.
-    pub const fn read_metrics(self, font_metrics: &FontMetrics) -> ScriptMetrics {
+    pub fn read_metrics(self, font_metrics: &FontMetrics) -> ScriptMetrics {
         match self {
             Self::Sub => font_metrics.subscript,
             Self::Super => font_metrics.superscript,
         }
+        .unwrap_or(self.default_metrics())
     }
 
     /// The corresponding OpenType feature.