config: union type formatters

src/config/Config.zig

@@ -3065,6 +3065,20 @@ pub const FontStyle = union(enum) {
         };
     }
 
+    /// Used by Formatter
+    pub fn formatEntry(self: Self, formatter: anytype) !void {
+        switch (self) {
+            .default, .false => try formatter.formatEntry(
+                []const u8,
+                @tagName(self),
+            ),
+
+            .name => |name| {
+                try formatter.formatEntry([:0]const u8, name);
+            },
+        }
+    }
+
     test "parseCLI" {
         const testing = std.testing;
         var arena = ArenaAllocator.init(testing.allocator);
@@ -3081,6 +3095,51 @@ pub const FontStyle = union(enum) {
         try p.parseCLI(alloc, "bold");
         try testing.expectEqualStrings("bold", p.name);
     }
+
+    test "formatConfig default" {
+        const testing = std.testing;
+        var buf = std.ArrayList(u8).init(testing.allocator);
+        defer buf.deinit();
+
+        var arena = ArenaAllocator.init(testing.allocator);
+        defer arena.deinit();
+        const alloc = arena.allocator();
+
+        var p: Self = .{ .default = {} };
+        try p.parseCLI(alloc, "default");
+        try p.formatEntry(formatterpkg.entryFormatter("a", buf.writer()));
+        try std.testing.expectEqualSlices(u8, "a = default\n", buf.items);
+    }
+
+    test "formatConfig false" {
+        const testing = std.testing;
+        var buf = std.ArrayList(u8).init(testing.allocator);
+        defer buf.deinit();
+
+        var arena = ArenaAllocator.init(testing.allocator);
+        defer arena.deinit();
+        const alloc = arena.allocator();
+
+        var p: Self = .{ .default = {} };
+        try p.parseCLI(alloc, "false");
+        try p.formatEntry(formatterpkg.entryFormatter("a", buf.writer()));
+        try std.testing.expectEqualSlices(u8, "a = false\n", buf.items);
+    }
+
+    test "formatConfig named" {
+        const testing = std.testing;
+        var buf = std.ArrayList(u8).init(testing.allocator);
+        defer buf.deinit();
+
+        var arena = ArenaAllocator.init(testing.allocator);
+        defer arena.deinit();
+        const alloc = arena.allocator();
+
+        var p: Self = .{ .default = {} };
+        try p.parseCLI(alloc, "bold");
+        try p.formatEntry(formatterpkg.entryFormatter("a", buf.writer()));
+        try std.testing.expectEqualSlices(u8, "a = bold\n", buf.items);
+    }
 };
 
 /// See "link" for documentation.

src/config/formatter.zig

@@ -113,8 +113,10 @@ pub fn formatEntry(
             else => {},
         },
 
-        // TODO
-        .Union => return,
+        .Union => if (@hasDecl(T, "formatEntry")) {
+            try value.formatEntry(entryFormatter(name, writer));
+            return;
+        },
 
         else => {},
     }

src/font/face/Metrics.zig

@@ -119,6 +119,34 @@ pub const Modifier = union(enum) {
         return try parse(input orelse return error.ValueRequired);
     }
 
+    /// Used by config formatter
+    pub fn formatEntry(self: Modifier, formatter: anytype) !void {
+        var buf: [1024]u8 = undefined;
+        switch (self) {
+            .percent => |v| {
+                try formatter.formatEntry(
+                    []const u8,
+                    std.fmt.bufPrint(
+                        &buf,
+                        "{d}%",
+                        .{(v - 1) * 100},
+                    ) catch return error.OutOfMemory,
+                );
+            },
+
+            .absolute => |v| {
+                try formatter.formatEntry(
+                    []const u8,
+                    std.fmt.bufPrint(
+                        &buf,
+                        "{d}",
+                        .{v},
+                    ) catch return error.OutOfMemory,
+                );
+            },
+        }
+    }
+
     /// Apply a modifier to a numeric value.
     pub fn apply(self: Modifier, v: u32) u32 {
         return switch (self) {
@@ -140,6 +168,28 @@ pub const Modifier = union(enum) {
             },
         };
     }
+
+    test "formatConfig percent" {
+        const configpkg = @import("../../config.zig");
+        const testing = std.testing;
+        var buf = std.ArrayList(u8).init(testing.allocator);
+        defer buf.deinit();
+
+        const p = try parseCLI("24%");
+        try p.formatEntry(configpkg.entryFormatter("a", buf.writer()));
+        try std.testing.expectEqualSlices(u8, "a = 24%\n", buf.items);
+    }
+
+    test "formatConfig absolute" {
+        const configpkg = @import("../../config.zig");
+        const testing = std.testing;
+        var buf = std.ArrayList(u8).init(testing.allocator);
+        defer buf.deinit();
+
+        const p = try parseCLI("-30");
+        try p.formatEntry(configpkg.entryFormatter("a", buf.writer()));
+        try std.testing.expectEqualSlices(u8, "a = -30\n", buf.items);
+    }
 };
 
 /// Key is an enum of all the available metrics keys.