Remove RwLock around Font::characters

egui_demo_lib/src/apps/demo/font_book.rs

@@ -73,7 +73,7 @@ impl super::View for FontBook {
         let named_chars = self.named_chars.entry(text_style).or_insert_with(|| {
             ui.fonts()
                 .lock()
-                .font(text_style)
+                .font_mut(text_style)
                 .characters()
                 .iter()
                 .filter(|chr| !chr.is_whitespace() && !chr.is_ascii_control())

epaint/src/text/font.rs

@@ -205,7 +205,7 @@ pub struct Font {
     text_style: TextStyle,
     fonts: Vec<Arc<FontImpl>>,
     /// Lazily calculated.
-    characters: RwLock<Option<std::collections::BTreeSet<char>>>,
+    characters: Option<std::collections::BTreeSet<char>>,
     replacement_glyph: (FontIndex, GlyphInfo),
     pixels_per_point: f32,
     row_height: f32,
@@ -218,7 +218,7 @@ impl Font {
             return Self {
                 text_style,
                 fonts,
-                characters: RwLock::new(None),
+                characters: None,
                 replacement_glyph: Default::default(),
                 pixels_per_point: 1.0,
                 row_height: 0.0,
@@ -232,7 +232,7 @@ impl Font {
         let mut slf = Self {
             text_style,
             fonts,
-            characters: RwLock::new(None),
+            characters: None,
             replacement_glyph: Default::default(),
             pixels_per_point,
             row_height,
@@ -266,15 +266,14 @@ impl Font {
     }
 
     /// All supported characters
-    pub fn characters(&self) -> BTreeSet<char> {
-        if self.characters.read().is_none() {
+    pub fn characters(&mut self) -> &BTreeSet<char> {
+        self.characters.get_or_insert_with(|| {
             let mut characters = BTreeSet::new();
             for font in &self.fonts {
                 characters.extend(font.characters());
             }
-            self.characters.write().replace(characters);
-        }
-        self.characters.read().clone().unwrap()
+            characters
+        })
     }
 
     #[inline(always)]

epaint/src/text/fonts.rs

@@ -416,11 +416,6 @@ impl FontsImpl {
         &self.definitions
     }
 
-    #[inline]
-    pub fn font(&self, text_style: TextStyle) -> &Font {
-        &self.fonts[&text_style]
-    }
-
     #[inline]
     pub fn font_mut(&mut self, text_style: TextStyle) -> &mut Font {
         self.fonts.get_mut(&text_style).unwrap()