fontique: Move creation of attributes from fontconfig (#212)

This exposes `from_fontconfig` functions on `FontStretch`, `FontStyle`,
and `FontWeight` rather than only defining them locally within the
fontconfig code.

This is in preparation for a change similar to #209 where these types
and others get pulled into a shared vocabulary crate and this sort of
constructor helper would be useful to others.

---------

Co-authored-by: Daniel McNab <[email protected]>

Author: waywardmonkeys

CHANGELOG.md

@@ -17,6 +17,10 @@ This release has an [MSRV] of 1.75.
 
 ### Added
 
+#### Fontique
+
+- `FontStretch`, `FontStyle`, and `FontWeight` get helper functions `from_fontconfig` ([#212] by [@waywardmonkeys][])
+
 #### Parley
 
 - `Generation` on `PlainEditor` to help implement lazy drawing. ([#143] by [@xorgy])

fontique/src/attributes.rs

@@ -191,6 +191,28 @@ impl FontStretch {
     }
 }
 
+impl FontStretch {
+    /// Creates a new stretch attribute with the given value from Fontconfig.
+    ///
+    /// The values are determined based on the [fonts.conf documentation].
+    ///
+    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
+    pub fn from_fontconfig(width: i32) -> Self {
+        match width {
+            50 => Self::ULTRA_CONDENSED,
+            63 => Self::EXTRA_CONDENSED,
+            75 => Self::CONDENSED,
+            87 => Self::SEMI_CONDENSED,
+            100 => Self::NORMAL,
+            113 => Self::SEMI_EXPANDED,
+            125 => Self::EXPANDED,
+            150 => Self::EXTRA_EXPANDED,
+            200 => Self::ULTRA_EXPANDED,
+            _ => Self::from_ratio(width as f32 / 100.0),
+        }
+    }
+}
+
 impl fmt::Display for FontStretch {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let value = self.0 * 1000.0;
@@ -304,6 +326,49 @@ impl FontWeight {
     }
 }
 
+impl FontWeight {
+    /// Creates a new weight attribute with the given value from Fontconfig.
+    ///
+    /// The values are determined based on the [fonts.conf documentation].
+    ///
+    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
+    pub fn from_fontconfig(weight: i32) -> Self {
+        // A selection of OpenType weights (first) and their corresponding fontconfig value (second)
+        // Invariant: The fontconfig values are sorted
+        const MAP: &[(i32, i32)] = &[
+            (0, 0),
+            (100, 0),
+            (200, 40),
+            (300, 50),
+            (350, 55),
+            (380, 75),
+            (400, 80),
+            (500, 100),
+            (600, 180),
+            (700, 200),
+            (800, 205),
+            (900, 210),
+            (950, 215),
+        ];
+        for (i, (ot, fc)) in MAP.iter().skip(1).enumerate() {
+            if weight == *fc {
+                return Self::new(*ot as f32);
+            }
+            // Linear interpolation if not an exact match
+            if weight < *fc {
+                let weight = weight as f32;
+                let fc_a = MAP[i - 1].1 as f32;
+                let fc_b = *fc as f32;
+                let ot_a = MAP[i - 1].1 as f32;
+                let ot_b = *ot as f32;
+                let t = (fc_a - fc_b) / (weight - fc_a);
+                return Self::new(ot_a + (ot_b - ot_a) * t);
+            }
+        }
+        Self::EXTRA_BLACK
+    }
+}
+
 impl Default for FontWeight {
     fn default() -> Self {
         Self::NORMAL
@@ -399,6 +464,21 @@ impl FontStyle {
     }
 }
 
+impl FontStyle {
+    /// Creates a new style attribute with the given value from Fontconfig.
+    ///
+    /// The values are determined based on the [fonts.conf documentation].
+    ///
+    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
+    pub fn from_fontconfig(slant: i32) -> Self {
+        match slant {
+            100 => Self::Italic,
+            110 => Self::Oblique(None),
+            _ => Self::Normal,
+        }
+    }
+}
+
 impl fmt::Display for FontStyle {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let value = match self {

fontique/src/backend/fontconfig/cache.rs

@@ -6,83 +6,6 @@ use fontconfig_cache_parser::{Cache, CharSetLeaf, Object, Pattern, Value};
 use std::io::Read;
 use std::path::PathBuf;
 
-impl FontStretch {
-    /// Creates a new stretch attribute with the given value from Fontconfig.
-    ///
-    /// The values are determined based on the [fonts.conf documentation].
-    ///
-    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
-    pub fn from_fc(width: i32) -> Self {
-        match width {
-            50 => Self::ULTRA_CONDENSED,
-            63 => Self::EXTRA_CONDENSED,
-            75 => Self::CONDENSED,
-            87 => Self::SEMI_CONDENSED,
-            100 => Self::NORMAL,
-            113 => Self::SEMI_EXPANDED,
-            125 => Self::EXPANDED,
-            150 => Self::EXTRA_EXPANDED,
-            200 => Self::ULTRA_EXPANDED,
-            _ => Self::from_ratio(width as f32 / 100.0),
-        }
-    }
-}
-
-impl FontStyle {
-    /// Creates a new style attribute with the given value from Fontconfig.
-    ///
-    /// The values are determined based on the [fonts.conf documentation].
-    ///
-    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
-    fn from_fc(slant: i32) -> Self {
-        match slant {
-            100 => Self::Italic,
-            110 => Self::Oblique(None),
-            _ => Self::Normal,
-        }
-    }
-}
-
-impl FontWeight {
-    /// Creates a new weight attribute with the given value from Fontconfig.
-    ///
-    /// The values are determined based on the [fonts.conf documentation].
-    ///
-    /// [fonts.conf documentation]: https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
-    fn from_fc(weight: i32) -> Self {
-        const MAP: &[(i32, i32)] = &[
-            (0, 0),
-            (100, 0),
-            (200, 40),
-            (300, 50),
-            (350, 55),
-            (380, 75),
-            (400, 80),
-            (500, 100),
-            (600, 180),
-            (700, 200),
-            (800, 205),
-            (900, 210),
-            (950, 215),
-        ];
-        for (i, (ot, fc)) in MAP.iter().skip(1).enumerate() {
-            if weight == *fc {
-                return Self::new(*ot as f32);
-            }
-            if weight < *fc {
-                let weight = weight as f32;
-                let fc_a = MAP[i - 1].1 as f32;
-                let fc_b = *fc as f32;
-                let ot_a = MAP[i - 1].1 as f32;
-                let ot_b = *ot as f32;
-                let t = (fc_a - fc_b) / (weight - fc_a);
-                return Self::new(ot_a + (ot_b - ot_a) * t);
-            }
-        }
-        Self::EXTRA_BLACK
-    }
-}
-
 #[derive(Default)]
 pub struct CachedFont {
     pub family: Vec<String>,
@@ -177,21 +100,21 @@ fn parse_font(
             Object::Slant => {
                 for val in elt.values().ok()? {
                     if let Value::Int(i) = val.ok()? {
-                        font.style = FontStyle::from_fc(i as _);
+                        font.style = FontStyle::from_fontconfig(i as _);
                     }
                 }
             }
             Object::Weight => {
                 for val in elt.values().ok()? {
                     if let Value::Int(i) = val.ok()? {
-                        font.weight = FontWeight::from_fc(i as _);
+                        font.weight = FontWeight::from_fontconfig(i as _);
                     }
                 }
             }
             Object::Width => {
                 for val in elt.values().ok()? {
                     if let Value::Int(i) = val.ok()? {
-                        font.stretch = FontStretch::from_fc(i as _);
+                        font.stretch = FontStretch::from_fontconfig(i as _);
                     }
                 }
             }