Merge pull request #670 from mitchellh/font-fallbakc

font: fallback search should search full discovery chain

pkg/macos/text/font.zig

@@ -7,7 +7,7 @@ const text = @import("../text.zig");
 const c = @import("c.zig");
 
 pub const Font = opaque {
-    pub fn createWithFontDescriptor(desc: *text.FontDescriptor, size: f32) Allocator.Error!*Font {
+    pub fn createWithFontDescriptor(desc: *const text.FontDescriptor, size: f32) Allocator.Error!*Font {
         return @as(
             ?*Font,
             @ptrFromInt(@intFromPtr(c.CTFontCreateWithFontDescriptor(

src/font/Group.zig

@@ -327,6 +327,7 @@ pub fn indexForCodepoint(
 
     // If we are regular, try looking for a fallback using discovery.
     if (style == .regular and font.Discover != void) {
+        log.debug("searching for a fallback font for cp={x}", .{cp});
         if (self.discover) |disco| discover: {
             var disco_it = disco.discover(self.alloc, .{
                 .codepoint = cp,
@@ -337,19 +338,27 @@ pub fn indexForCodepoint(
             }) catch break :discover;
             defer disco_it.deinit();
 
-            if (disco_it.next() catch break :discover) |face| {
+            while (true) {
+                const face_ = disco_it.next() catch |err| {
+                    log.warn("fallback search failed with error err={}", .{err});
+                    break;
+                };
+                const face = face_ orelse break;
+
                 // Discovery is supposed to only return faces that have our
                 // codepoint but we can't search presentation in discovery so
                 // we have to check it here.
-                if (face.hasCodepoint(cp, p)) {
+                if (!face.hasCodepoint(cp, p)) continue;
-                    var buf: [256]u8 = undefined;
+
-                    log.info("found codepoint 0x{x} in fallback face={s}", .{
+                var buf: [256]u8 = undefined;
-                        cp,
+                log.info("found codepoint 0x{x} in fallback face={s}", .{
-                        face.name(&buf) catch "<error>",
+                    cp,
-                    });
+                    face.name(&buf) catch "<error>",
-                    return self.addFace(style, .{ .deferred = face }) catch break :discover;
+                });
-                }
+                return self.addFace(style, .{ .deferred = face }) catch break :discover;
             }
+
+            log.debug("no fallback face found for cp={x}", .{cp});
         }
     }
 

src/font/discovery.zig

@@ -399,6 +399,7 @@ pub const CoreText = struct {
 
         style: Style = .unmatched,
         monospace: bool = false,
+        codepoint: bool = false,
 
         const Style = enum(u8) { unmatched = 0, match = 0xFF, _ };
 
@@ -410,6 +411,26 @@ pub const CoreText = struct {
     fn score(desc: *const Descriptor, ct_desc: *const macos.text.FontDescriptor) Score {
         var score_acc: Score = .{};
 
+        // If we're searching for a codepoint, prioritize fonts that
+        // have that codepoint.
+        if (desc.codepoint > 0) codepoint: {
+            const font = macos.text.Font.createWithFontDescriptor(ct_desc, 12) catch
+                break :codepoint;
+            defer font.release();
+
+            // Turn UTF-32 into UTF-16 for CT API
+            var unichars: [2]u16 = undefined;
+            const pair = macos.foundation.stringGetSurrogatePairForLongCharacter(
+                desc.codepoint,
+                &unichars,
+            );
+            const len: usize = if (pair) 2 else 1;
+
+            // Get our glyphs
+            var glyphs = [2]macos.graphics.Glyph{ 0, 0 };
+            score_acc.codepoint = font.getGlyphsForCharacters(unichars[0..len], glyphs[0..len]);
+        }
+
         // Get our symbolic traits for the descriptor so we can compare
         // boolean attributes like bold, monospace, etc.
         const symbolic_traits: macos.text.FontSymbolicTraits = traits: {