#300: emoji take a colour face before the symbol fonts, which drew them in one colour on Windows

crates/text/src/color_tests.rs

@@ -183,6 +183,17 @@ fn colour_emoji_carry_their_own_pixels() {
     }
 }
 
+#[test]
+fn emoji_in_plain_text_draw_from_a_colour_face() {
+    // A symbol font among the fallbacks (Windows has one) draws U+1F600 in one colour: the emoji
+    // face comes first for it.
+    if emoji_face().is_none() {
+        return;
+    }
+    let l = layout(&TextData::new("Hi \u{1F600}"), None, None);
+    assert!(l.glyphs.iter().any(|g| g.color(1.0).is_some()), "the emoji has colour ink");
+}
+
 #[test]
 fn glyphs_place_their_ink_at_a_scale() {
     let Some(face) = emoji_face() else { return };

crates/text/src/layout.rs

@@ -329,11 +329,10 @@ pub fn layout(text: &TextData, box_width: Option<f64>, box_height: Option<f64>)
         faces.push(dbw.find(&s.font_family, &s.font_style).or_else(|| dbw.default_face()));
     }
     // Colour emoji are their own, large faces (Apple Color Emoji is ~180 MB): they are read only
-    // for a text whose characters nothing above covers.
+    // for a text with emoji, or with characters nothing above covers.
     let covered = |c: char| c == '\n' || faces.iter().flatten().any(|f| f.has_char(c)) || fallbacks.iter().any(|f| f.has_char(c));
-    if chars.iter().any(|c| !covered(*c)) {
-        fallbacks.extend(dbw.emoji_fallbacks());
-    }
+    let emoji = if chars.iter().any(|c| is_emoji(*c) || !covered(*c)) { dbw.emoji_fallbacks() } else { Vec::new() };
+    fallbacks.extend(emoji.iter().cloned());
     drop(dbw);
 
     // OpenType features the user toggled (global for the node).
@@ -364,7 +363,9 @@ pub fn layout(text: &TextData, box_width: Option<f64>, box_height: Option<f64>)
                 if c == '\n' || primary.has_char(c) {
                     return primary.clone();
                 }
-                fallbacks.iter().find(|f| f.has_char(c)).cloned().unwrap_or_else(|| primary.clone())
+                // Emoji take a colour face before the symbol fonts, which draw many of them in one colour.
+                let colour = if is_emoji(c) { emoji.iter().find(|f| f.has_char(c)) } else { None };
+                colour.or_else(|| fallbacks.iter().find(|f| f.has_char(c))).cloned().unwrap_or_else(|| primary.clone())
             };
             let first = chars.get(seg_start).copied().unwrap_or(' ');
             let face = face_for(first);
@@ -988,6 +989,13 @@ fn sanitize_size(s: f64) -> f64 {
     if s.is_finite() { s.clamp(0.5, 5000.0) } else { 12.0 }
 }
 
+/// A character drawn as a colour emoji by default: flags and the pictograph blocks.
+/// shortcut: the older symbols (U+2600–U+27BF) keep their text look even before U+FE0F; read the
+/// emoji presentation data if they should turn colour too.
+fn is_emoji(c: char) -> bool {
+    matches!(c, '\u{1F1E6}'..='\u{1F1FF}' | '\u{1F300}'..='\u{1FAFF}')
+}
+
 /// One run of chars shaped with a single face and style.
 struct Segment<'a> {
     start: usize,