一、概述

最近准备使用 Flutter 的 3.24 版本打包上架 APP，结果前天看到有人提了一个 issue: https://github.com/flutter/flutter/issues/158423 (opens new window) ，说分别使用 3.24.3 和 3.24.4 提交苹果审核时，都惨遭被拒~

苹果反馈的信息如下：

Guideline 2.5.1 - Performance - Software Requirements

The app uses or references the following non-public or deprecated APIs:

Frameworks/Flutter.framework/Flutter

Symbols:

• _kCTFontPaletteAttribute
• _kCTFontPaletteColorsAttribute

The use of non-public or deprecated APIs is not permitted, as they can lead to a poor user experience should these APIs change and are otherwise not supported on Apple platforms.

可以看到，是说 Flutter 使用了未公开的 API，并且他使用 strings 命令也验证了这一点。

3.24.x

strings Runner.app/Frameworks/Flutter.framework/Flutter | grep kCT
SkCTMShader
kCTFontVariationAxisHiddenKey
kCTFontPaletteAttribute
kCTFontPaletteColorsAttribute

3.22.3

strings Runner.app/Frameworks/Flutter.framework/Flutter | grep kCT
SkCTMShader
kCTFontVariationAxisHiddenKey

我先在 Flutter 引擎源码中搜索，结果压根就搜索不到，随后打开了前几日编译好的引擎调试项目，结果一搜一个准，在 third_party 依赖下的 Skia 代码中，很快就定位到了引入未公开 API 的相关提交记录 https://skia-review.googlesource.com/c/skia/+/867836 (opens new window) 。

我一看完就啪的一声敲起来了，很快啊！上来就是一个 Revert https://skia-review.googlesource.com/c/skia/+/918416 (opens new window) 。

目前此次受影响的 Flutter 版本范围暂时是 3.24.0 ~ 3.24.4，得等待新版本的发布才可以解决。建议还没用上 3.24 的小伙伴先不要升级，那如果已经是 3.24 或者是一定要用 3.24.4 及以下版本的小伙伴要怎么办呢？那就跟我一起来自编译引擎吧~

二、编译引擎

环境

注意：全程需要科学上网环境，请自行查找和配置

首先拉取最新的 depot_tools，放到一个合适的位置，比如我放在 ~/development 目录下

cd ~/development
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

将 depot_tools 添加至环境变量，在你的终端配置文件里补充如下内容

终端配置文件因人而异，如：~/.bash_profile、~/.zshrc、~/.zprofile，请自行判断

export PATH = "$HOME/development/depot_tools":$PATH

然后 source ~/.zshrc（这里请根据自身情况修改终端配置文件路径）

拉源码

找个合适的目录，创建 engine 目录并进入

mkdir engine
cd engine

开始拉取源码

fetch flutter

它会在当前目录下创建 .gclient 文件，写好配置，并执行 gclient sync

solutions = [
  {
    "custom_deps": {},
    "deps_file": "DEPS",
    "managed": False,
    "name": "src/flutter",
    "safesync_url": "",
    "url": "https://github.com/flutter/engine.git",
  },
]

如果在拉取代码的过程中遇到如下问题

remote: Enumerating objects: 835563, done.
remote: Counting objects: 100% (1612/1612), done.
remote: Compressing objects: 100% (1011/1011), done.
error: RPC failed; curl 92 HTTP/2 stream 5 was not closed cleanly: CANCEL (err 8)
error: 1481 bytes of body are still expected
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output

src/flutter (ERROR)
----------------------------------------
[0:00:00] Started.

别慌，执行下方命令让其接着拉，直至完成

gclient sync

拉取完成后，去查看我们使用的 Flutter 版本对应的引擎版本，这里以 3.24.4 为例，打开链接：https://github.com/flutter/flutter/blob/3.24.4/bin/internal/engine.version ，拿到 db49896cf25ceabc44096d5f088d86414e05a7aa

执行如下命令进行切换

cd src/flutter
git checkout db49896cf25ceabc44096d5f088d86414e05a7aa

执行完成会输出如下内容

Previous HEAD position was b0a4ca92c4 Add FlPointerManager to process pointer events from GTK in a form suitable for Flutter. (#56443)
HEAD is now at db49896cf2 [CP-stable]Add xcprivacy privacy manifest to macOS framework (#55366)
post-checkout: The engine source tree has been updated.

You may need to run "gclient sync -D"

按照提示执行

gclient sync -D

调整源码

按路径 engine/src/flutter/third_party/skia/src/ports/SkTypeface_mac_ct.cpp 打开文件，按下方内容进行修改（红：删除，绿：新增）

static CFStringRef getCTFontPaletteAttribute() {
-    static CFStringRef* kCTFontPaletteAttributePtr =
-        static_cast<CFStringRef*>(dlsym(RTLD_DEFAULT, "kCTFontPaletteAttribute"));
-    return *kCTFontPaletteAttributePtr;
+    return nullptr;
+    //static CFStringRef* kCTFontPaletteAttributePtr =
+    //    static_cast<CFStringRef*>(dlsym(RTLD_DEFAULT, "kCTFontPaletteAttribute"));
+    //return *kCTFontPaletteAttributePtr;
}
static CFStringRef getCTFontPaletteColorsAttribute() {
-    static CFStringRef* kCTFontPaletteColorsAttributePtr =
-        static_cast<CFStringRef*>(dlsym(RTLD_DEFAULT, "kCTFontPaletteColorsAttribute"));
-    return *kCTFontPaletteColorsAttributePtr;
+    return nullptr;
+    //static CFStringRef* kCTFontPaletteColorsAttributePtr =
+    //    static_cast<CFStringRef*>(dlsym(RTLD_DEFAULT, "kCTFontPaletteColorsAttribute"));
+    //return *kCTFontPaletteColorsAttributePtr;
}

...

static bool apply_palette(CFMutableDictionaryRef attributes,
                          const SkFontArguments::Palette& palette) {
    bool changedAttributes = false;
-    if (palette.index != 0 || palette.overrideCount) {
+    if ((palette.index != 0 || palette.overrideCount) && getCTFontPaletteAttribute()) {
        SkUniqueCFRef<CFNumberRef> paletteIndex(
                CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &palette.index));
        CFDictionarySetValue(attributes, getCTFontPaletteAttribute(), paletteIndex.get());
        changedAttributes = true;
    }

-    if (palette.overrideCount) {
+    if (palette.overrideCount && getCTFontPaletteColorsAttribute()) {
        SkUniqueCFRef<CFMutableDictionaryRef> overrides(

...

相应修改来自: https://skia-review.googlesource.com/c/skia/+/918518 (opens new window)

编译

来到 engine/src 目录，使用 gn 编译生成 ninja 构建文件

./flutter/tools/gn --runtime-mode release --mac-cpu arm64
./flutter/tools/gn --ios --runtime-mode release

使用 ninja 编译引擎的最终产物

ninja -C out/host_release_arm64
ninja -C out/ios_release

如果你当前是 MacOS 15 的 Sequoia 系统，在执行 ninja -C out/host_release_arm64 时会遇到如下错误

COPY '/System/Library/Fonts/A...arty/txt/assets/Apple Color Emoji.ttc'
FAILED: gen/flutter/third_party/txt/assets/Apple Color Emoji.ttc
ln -f '/System/Library/Fonts/Apple Color Emoji.ttc' 'gen/flutter/third_party/txt/assets/Apple Color Emoji.ttc' 2>/dev/null || (rm -rf 'gen/flutter/third_party/txt/assets/Apple Color Emoji.ttc' && cp -af '/System/Library/Fonts/Apple Color Emoji.ttc' 'gen/flutter/third_party/txt/assets/Apple Color Emoji.ttc')
cp: chflags: gen/flutter/third_party/txt/assets/Apple Color Emoji.ttc: Operation not permitted
[18/4139] SOLINK libvk_swiftshader.dylib libvk_swiftshader.dylib.TOC
ninja: build stopped: subcommand failed.

别急，打开 engine/src/build/toolchain/mac/BUILD.gn，做如下修改，修改完再执行 gn 和 ninja

    tool("copy") {
-      command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
+      command = "ln -f {{source}} {{output}} 2>/dev/null || (rsync -a --delete {{source}} {{output}})"
      description = "COPY {{source}} {{output}}"
    }

相应的 issue: #152978 (opens new window)

好了，静静等待编译完成。

请注意，这将是个十分漫长且全程 CPU 占用率为 100% 的过程~

建议使用一台空闲的 Mac 电脑去做这个事！否则你将啥活也干不了~

验证

进入 engine/src/out/ios_release

strings Flutter.framework/Flutter | grep kCT

SkCTMShader
kCTFontVariationAxisHiddenKey

可以看到，没有 kCTFontPaletteAttribute 和 kCTFontPaletteColorsAttribute。

使用本地引擎

执行如下命令对项目进行编译

flutter build ipa \
--local-engine-src-path=/Users/lxf/engine/src \
--local-engine=ios_release \
--local-engine-host=host_release_arm64

如果你有使用 realm 的话，可能会遇到如下错误

Installing realm (1.0.3)
[!] /bin/bash -c
set -e
source "/Users/lxf/app/ios/Flutter/flutter_export_environment.sh" && cd "$FLUTTER_APPLICATION_PATH" && "$FLUTTER_ROOT/bin/flutter" pub run realm install --target-os-type ios --flavor flutter

You must specify --local-engine or --local-web-sdk if you are using a locally built engine or web sdk.

你需要对该文件 /Users/lxf/app/ios/.symlinks/plugins/realm/ios/realm.podspec 进行修改，在 \"$FLUTTER_ROOT/bin/flutter\" 和 pub 中间加上引擎相关参数。如下所示

s.prepare_command           = "source \"#{project_dir}/Flutter/flutter_export_environment.sh\" && cd \"$FLUTTER_APPLICATION_PATH\" && \"$FLUTTER_ROOT/bin/flutter\" --local-engine-src-path /Users/lxf/engine/src --local-engine ios_release --local-engine-host host_release_arm64 pub run realm install --target-os-type ios --flavor flutter"

:script => 'source "$PROJECT_DIR/../Flutter/flutter_export_environment.sh" && cd "$FLUTTER_APPLICATION_PATH" && "$FLUTTER_ROOT/bin/flutter" --local-engine-src-path /Users/lxf/engine/src --local-engine ios_release --local-engine-host host_release_arm64 pub run realm install --target-os-type ios --flavor flutter',

如果你只是想对项目进行配置，则将 ipa 改为 ios，并加上 --config-only 参数即可。

flutter build ios \
--local-engine-src-path=/Users/lxf/engine/src \
--local-engine=ios_release \
--local-engine-host=host_release_arm64 \
--config-only

以前使用本地引擎只需要 --local-engine 参数，现在要求结合 --local-engine-host 一块使用，这里附上相关 issue：https://github.com/flutter/flutter/issues/132245 (opens new window) ，想了解的可以点开看看

三、最后

过程不难，麻烦的是拉源码和编译真的好慢，而且空间占用还大~

好了，本篇到此结束，感谢大家的支持，我们下次再见！ 👋