deferred face hasCodepoint

src/font/DeferredFace.zig

@@ -11,6 +11,7 @@ const assert = std.debug.assert;
 const fontconfig = @import("fontconfig");
 const options = @import("main.zig").options;
 const Face = @import("main.zig").Face;
+const Presentation = @import("main.zig").Presentation;
 
 /// The loaded face (once loaded).
 face: ?Face = null,
@@ -35,3 +36,42 @@ pub fn deinit(self: *DeferredFace) void {
 pub inline fn loaded(self: DeferredFace) bool {
     return self.face != null;
 }
+
+/// Returns true if this face can satisfy the given codepoint and
+/// presentation. If presentation is null, then it just checks if the
+/// codepoint is present at all.
+///
+/// This should not require the face to be loaded IF we're using a
+/// discovery mechanism (i.e. fontconfig). If no discovery is used,
+/// the face is always expected to be loaded.
+pub fn hasCodepoint(self: DeferredFace, cp: u32, p: ?Presentation) bool {
+    // If we have the face, use the face.
+    if (self.face) |face| {
+        if (p) |desired| if (face.presentation != desired) return false;
+        return face.glyphIndex(cp) != null;
+    }
+
+    // If we are using fontconfig, use the fontconfig metadata to
+    // avoid loading the face.
+    if (options.fontconfig) {
+        // Check if char exists
+        if (!self.fc.charset.hasChar(cp)) return false;
+
+        // If we have a presentation, check it matches
+        if (p) |desired| {
+            const emoji_lang = "und-zsye";
+            const actual: Presentation = if (self.fc.langset.hasLang(emoji_lang))
+                .emoji
+            else
+                .text;
+
+            return desired == actual;
+        }
+
+        return true;
+    }
+
+    // This is unreachable because discovery mechanisms terminate, and
+    // if we're not using a discovery mechanism, the face MUST be loaded.
+    unreachable;
+}

src/font/Group.zig

@@ -112,13 +112,7 @@ pub fn indexForCodepoint(
 
 fn indexForCodepointExact(self: Group, cp: u32, style: Style, p: ?Presentation) ?FontIndex {
     for (self.faces.get(style).items) |deferred, i| {
-        const face = deferred.face.?;
-
-        // If the presentation is null, we allow the first presentation we
-        // can find. Otherwise, we check for the specific one requested.
-        if (p != null and face.presentation != p.?) continue;
-
-        if (face.glyphIndex(cp) != null) {
+        if (deferred.hasCodepoint(cp, p)) {
             return FontIndex{
                 .style = style,
                 .idx = @intCast(FontIndex.IndexInt, i),