[PATCH 0/1] MR8448: bcp47langs: Add GetFontFallbackLanguageList() stub.

[Zhiyi Zhang (＠zhiyi)]

For React Native.

[Alexandre Julliard (＠julliard)]

Alexandre Julliard (@julliard) commented about dlls/bcp47langs/tests/bcp47langs.c:
> +#include <windows.h>
> +#include "wine/test.h"
> -
>
> +static HRESULT (WINAPI *pGetFontFallbackLanguageList)(const WCHAR *, size_t, WCHAR *, size_t *);
> -
>
> +static void init_function_pointers(void)
> +{
> - HMODULE bcp47langs = LoadLibraryA("bcp47langs.dll");
> -
> - if (!bcp47langs)
> - {
> -
>    win_skip("bcp47langs.dll is unavailable.\n");
> -
>    return;
> - }
> -
> - pGetFontFallbackLanguageList = (void*)GetProcAddress(bcp47langs, "GetFontFallbackLanguageList");

Checking for the dll itself is not very useful, the tests won't be run if it's unavailable.

Also are there platforms where `GetFontFallbackLanguageList` is missing?

[PATCH 1/1] bcp47langs: Add GetFontFallbackLanguageList() stub.

[Zhiyi Zhang]

From: Zhiyi Zhang

---
 configure.ac                       |  1 +
 dlls/bcp47langs/Makefile.in        |  3 +
 dlls/bcp47langs/bcp47langs.spec    |  2 +-
 dlls/bcp47langs/main.c             | 55 ++++++++++++++++++
 dlls/bcp47langs/tests/Makefile.in  |  5 ++
 dlls/bcp47langs/tests/bcp47langs.c | 90 ++++++++++++++++++++++++++++++
 6 files changed, 155 insertions(+), 1 deletion(-)
 create mode 100644 dlls/bcp47langs/main.c
 create mode 100644 dlls/bcp47langs/tests/Makefile.in
 create mode 100644 dlls/bcp47langs/tests/bcp47langs.c

diff --git a/configure.ac b/configure.ac
index 6d093b52526..534ce5cb092 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2467,6 +2467,7 @@ WINE_CONFIG_MAKEFILE(dlls/avifil32/tests)
 WINE_CONFIG_MAKEFILE(dlls/avifile.dll16)
 WINE_CONFIG_MAKEFILE(dlls/avrt)
 WINE_CONFIG_MAKEFILE(dlls/bcp47langs)
+WINE_CONFIG_MAKEFILE(dlls/bcp47langs/tests)
 WINE_CONFIG_MAKEFILE(dlls/bcrypt)
 WINE_CONFIG_MAKEFILE(dlls/bcrypt/tests)
 WINE_CONFIG_MAKEFILE(dlls/bcryptprimitives)
diff --git a/dlls/bcp47langs/Makefile.in b/dlls/bcp47langs/Makefile.in
index 5eb4caaf0e7..ee013421c3b 100644
--- a/dlls/bcp47langs/Makefile.in
+++ b/dlls/bcp47langs/Makefile.in
@@ -1,2 +1,5 @@
 MODULE    = bcp47langs.dll
 IMPORTLIB = bcp47langs
+
+SOURCES = \
+	main.c
diff --git a/dlls/bcp47langs/bcp47langs.spec b/dlls/bcp47langs/bcp47langs.spec
index a054c1486a9..c90a2b59d49 100644
--- a/dlls/bcp47langs/bcp47langs.spec
+++ b/dlls/bcp47langs/bcp47langs.spec
@@ -37,7 +37,7 @@
 @ stub GetAppropriateUserPreferredAndDisplayLanguagesForUser
 @ stub GetClosestMatchingUserLanguage
 @ stub GetDisplayLanguagesForAllUsers
-@ stub GetFontFallbackLanguageList
+@ stdcall GetFontFallbackLanguageList(wstr long ptr ptr)
 @ stub GetHttpAcceptLanguageOptOut
 @ stub GetInputMethodOverrideForUser
 @ stub GetPendingUserDisplayLanguage
diff --git a/dlls/bcp47langs/main.c b/dlls/bcp47langs/main.c
new file mode 100644
index 00000000000..7ec9ebef697
--- /dev/null
+++ b/dlls/bcp47langs/main.c
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2025 Zhiyi Zhang for CodeWeavers
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#include <stdarg.h>
+#include <windef.h>
+#include <winbase.h>
+#include <winnls.h>
+#include "wine/debug.h"
+
+WINE_DEFAULT_DEBUG_CHANNEL(bcp47langs);
+
+HRESULT WINAPI GetFontFallbackLanguageList(const WCHAR *lang, size_t buffer_length, WCHAR *buffer,
+                                           size_t *required_buffer_length)
+{
+    WCHAR locale[LOCALE_NAME_MAX_LENGTH];
+    size_t lang_length;
+
+    FIXME("lang %s, buffer_length %Iu, buffer %p, required_buffer_length %p stub!\n",
+          wine_dbgstr_w(lang), buffer_length, buffer, required_buffer_length);
+
+    if (!buffer_length || !buffer)
+        return E_INVALIDARG;
+
+    if (!lang)
+    {
+        if (!GetUserDefaultLocaleName(locale, LOCALE_NAME_MAX_LENGTH))
+            return E_FAIL;
+
+        lang = locale;
+    }
+
+    /* Return the original language as the fallback language list */
+    lang_length = wcslen(lang) + 1;
+    *required_buffer_length = lang_length;
+    if (buffer_length < lang_length)
+        return E_NOT_SUFFICIENT_BUFFER;
+
+    memcpy(buffer, lang, lang_length * sizeof(WCHAR));
+    return S_OK;
+}
diff --git a/dlls/bcp47langs/tests/Makefile.in b/dlls/bcp47langs/tests/Makefile.in
new file mode 100644
index 00000000000..3c2cee465cf
--- /dev/null
+++ b/dlls/bcp47langs/tests/Makefile.in
@@ -0,0 +1,5 @@
+TESTDLL = bcp47langs.dll
+IMPORTS = bcp47langs
+
+SOURCES = \
+	bcp47langs.c
diff --git a/dlls/bcp47langs/tests/bcp47langs.c b/dlls/bcp47langs/tests/bcp47langs.c
new file mode 100644
index 00000000000..812445b21e8
--- /dev/null
+++ b/dlls/bcp47langs/tests/bcp47langs.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2025 Zhiyi Zhang for CodeWeavers
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include "wine/test.h"
+
+static HRESULT (WINAPI *pGetFontFallbackLanguageList)(const WCHAR *, size_t, WCHAR *, size_t *);
+
+static void init_function_pointers(void)
+{
+    HMODULE bcp47langs = LoadLibraryA("bcp47langs.dll");
+
+    if (!bcp47langs)
+    {
+        win_skip("bcp47langs.dll is unavailable.\n");
+        return;
+    }
+
+    pGetFontFallbackLanguageList = (void*)GetProcAddress(bcp47langs, "GetFontFallbackLanguageList");
+}
+
+static void test_GetFontFallbackLanguageList(void)
+{
+    size_t required_size;
+    WCHAR buffer[128];
+    HRESULT hr;
+
+    if (!pGetFontFallbackLanguageList)
+    {
+        win_skip("GetFontFallbackLanguageList() is unavailable.\n");
+        return;
+    }
+
+    /* Parameter checks */
+    required_size = 0xdeadbeef;
+    hr = pGetFontFallbackLanguageList(NULL, ARRAY_SIZE(buffer), buffer, &required_size);
+    ok(hr == S_OK, "Got unexpected hr %#lx.\n", hr);
+    ok(required_size != 0xdeadbeef, "Got unexpected size %Iu.\n", required_size);
+
+    hr = pGetFontFallbackLanguageList(L"en-US", 0, buffer, &required_size);
+    ok(hr == E_INVALIDARG, "Got unexpected hr %#lx.\n", hr);
+
+    required_size = 0;
+    hr = pGetFontFallbackLanguageList(L"en-US", 1, buffer, &required_size);
+    ok(hr == E_NOT_SUFFICIENT_BUFFER, "Got unexpected hr %#lx.\n", hr);
+    ok(required_size > 0, "Got unexpected size %Iu.\n", required_size);
+
+    hr = pGetFontFallbackLanguageList(L"en-US", ARRAY_SIZE(buffer), NULL, &required_size);
+    ok(hr == E_INVALIDARG, "Got unexpected hr %#lx.\n", hr);
+
+    if (0) /* Crashes on Windows */
+    {
+    hr = pGetFontFallbackLanguageList(L"en-US", ARRAY_SIZE(buffer), buffer, NULL);
+    ok(hr == E_INVALIDARG, "Got unexpected hr %#lx.\n", hr);
+    }
+
+    hr = pGetFontFallbackLanguageList(L"deadbeef", ARRAY_SIZE(buffer), buffer, &required_size);
+    todo_wine
+    ok(hr == E_INVALIDARG, "Got unexpected hr %#lx.\n", hr);
+
+    /* Normal call */
+    required_size = 0;
+    hr = pGetFontFallbackLanguageList(L"en-US", ARRAY_SIZE(buffer), buffer, &required_size);
+    ok(hr == S_OK, "Got unexpected hr %#lx.\n", hr);
+    ok(!wcsncmp(buffer, L"en-US", wcslen(L"en-US")), "Got unexpected %s.\n", wine_dbgstr_w(buffer));
+    ok(required_size >= (wcslen(L"en-US") + 1), "Got unexpected size %Iu.\n", required_size);
+}
+
+START_TEST(bcp47langs)
+{
+    init_function_pointers();
+
+    test_GetFontFallbackLanguageList();
+}