From 21ffb118afc9d3efd2149b00c3326a3682afad64 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Tue, 6 Feb 2024 21:41:22 -0500
Subject: [PATCH] LibGfx/OpenType: Support cmaps with format Unicode

Some fonts only contain unicode tables. This makes them work.
---
 Userland/Libraries/LibGfx/Font/OpenType/Cmap.h   | 10 ++++++++++
 Userland/Libraries/LibGfx/Font/OpenType/Font.cpp | 13 ++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Cmap.h b/Userland/Libraries/LibGfx/Font/OpenType/Cmap.h
index d5e4deeb1e..f7701916cd 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Cmap.h
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Cmap.h
@@ -34,6 +34,16 @@ public:
             ManyToOneRange = 13,
             UnicodeVariationSequences = 14,
         };
+        enum class UnicodeEncoding {
+            DeprecatedUnicode1_0 = 0,
+            DeprecatedUnicode1_1 = 1,
+            DeprecatedISO10646 = 2,
+            Unicode2_0_BMP_Only = 3,
+            Unicode2_0_FullRepertoire = 4,
+            UnicodeVariationSequences = 5, // "for use with subtable format 14"
+            UnicodeFullRepertoire = 6,     // "for use with subtable format 13"
+        };
+
         enum class WindowsEncoding {
             UnicodeBMP = 1,
             UnicodeFullRepertoire = 10,
diff --git a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
index 9280a796d3..0ef0cf038d 100644
--- a/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
+++ b/Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
@@ -236,7 +236,18 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
         /* NOTE: The encoding records are sorted first by platform ID, then by encoding ID.
            This means that the Windows platform will take precedence over Macintosh, which is
            usually what we want here. */
-        if (platform.value() == Cmap::Subtable::Platform::Windows) {
+        if (platform.value() == Cmap::Subtable::Platform::Unicode) {
+            if (subtable.encoding_id() == (u16)Cmap::Subtable::UnicodeEncoding::Unicode2_0_FullRepertoire) {
+                // "Encoding ID 3 should be used in conjunction with 'cmap' subtable formats 4 or 6."
+                cmap.set_active_index(i);
+                break;
+            }
+            if (subtable.encoding_id() == (u16)Cmap::Subtable::UnicodeEncoding::Unicode2_0_BMP_Only) {
+                // "Encoding ID 4 should be used in conjunction with subtable formats 10 or 12."
+                cmap.set_active_index(i);
+                break;
+            }
+        } else if (platform.value() == Cmap::Subtable::Platform::Windows) {
             if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) {
                 cmap.set_active_index(i);
                 break;