No Displays from CGGetOnlineDisplayList when using NAPI

[kusti8]

Version: 13.6.0
Platform: Darwin kusti8s-iMac.local 19.0.0 Darwin Kernel Version 19.0.0: Wed Sep 25 20:18:50 PDT 2019; root:xnu-6153.11.26~2/RELEASE_X86_64 x86_64
Subsystem: NAPI

I have a really interesting issue that first came up when I tried to port my wxWidgets bindings with NAPI to Mac. It kept on reporting that 0 displays were detected. Running it through lldb shows the CGGetOnlineDisplayList function returns 0 displays.

I created a very minimal test example here:

make.sh

c++ -fno-exceptions '-DNAPI_DISABLE_CPP_EXCEPTIONS' '-DNODE_GYP_MODULE_NAME=test' '-DUSING_UV_SHARED=1' '-DUSING_V8_SHARED=1' '-DV8_DEPRECATION_WARNINGS=1' '-DV8_DEPRECATION_WARNINGS' '-DV8_IMMINENT_DEPRECATION_WARNINGS' '-D_DARWIN_USE_64_BIT_INODE=1' '-D_LARGEFILE_SOURCE' '-D_FILE_OFFSET_BITS=64' '-DOPENSSL_NO_PINSHARED' '-DOPENSSL_THREADS' '-DNAPI_VERSION=4' '-D_UNICODE' '-DUNICODE' '-DBUILDING_NODE_EXTENSION' -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/include/node -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/src -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/deps/openssl/config -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/deps/openssl/openssl/include -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/deps/uv/include -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/deps/zlib -I/Users/kusti8/Library/Caches/node-gyp/13.6.0/deps/v8/include -I/Users/kusti8/Documents/GitHub/node-wx-napi/node_modules/node-addon-api  -Os -gdwarf-2 -mmacosx-version-min=10.9 -arch x86_64 -Wall -Wendif-labels -W -Wno-unused-parameter -std=gnu++1y -stdlib=libc++ -fno-rtti -fno-strict-aliasing -D_FILE_OFFSET_BITS=64 -fno-common -fvisibility-inlines-hidden -MMD -MF main.o.d.raw   -c -o main.o main.cpp
c++ -bundle -undefined dynamic_lookup -Wl,-no_pie -Wl,-search_paths_first -mmacosx-version-min=10.9 -arch x86_64 -L. -stdlib=libc++  -o out.node main.o -framework IOKit -framework Carbon -framework Cocoa -framework AudioToolbox -framework System -framework OpenGL -framework Security -framework ApplicationServices -framework WebKit -framework QuartzCore -framework CoreGraphics

And then main.cpp

#include <ApplicationServices/ApplicationServices.h>
#include <napi.h>

Napi::Value desktopSize(const Napi::CallbackInfo &info)
{

    uint32_t numDisplays = 0;
    CGGetOnlineDisplayList(0, NULL, &numDisplays);
    printf("Displays %d\n", numDisplays);
    printf("Displays %d\n", numDisplays);

    return Napi::Value();
}

Napi::Object Init(Napi::Env env, Napi::Object exports)
{
    exports.Set("desktopSize", Napi::Function::New(env, desktopSize));
    return exports;
}

NODE_API_MODULE(NODE_GYP_MODULE_NAME, Init)

int main(int argc, char **argv)
{
    uint32_t numDisplays = 0;
    CGGetOnlineDisplayList(0, NULL, &numDisplays);
    printf("Displays %d\n", numDisplays);
    return 0;
}

When calling this through node, displays is printed as 0. However, when I remove -bundle in the linking phase, comment out everything above int main(int argc, char **argv) and run it as an executable, it prints out the correct number of displays: 1.

I don't know anything about how Node works on the inside, but to me it looks like some sort of sandboxing thing, but I really have no idea. Or maybe I'm forgetting a compiler flag.

Thanks,
Gustav

[richardlau]

Suspect this is related to libuv/libuv#2566, libuv/libuv#2568 and libuv/libuv#2593.

cc @nodejs/platform-macos

[shayneoneill]

Is there an eta on this one? Its a showstopper of a bug

[addaleax]

/cc @cjihrig @nodejs/libuv

[cjihrig]

I can cut a libuv 1.34.2 release. It would still take two days to land and then however long after that to make it into a Node release.

[cjihrig]

libuv update in #31477. The rest is in the Node team's hands.

[zcbenz]

@bnoordhuis @cjihrig Can the fix be backported to Node v12? Currently all GUI bindings fail to work on macOS due to this bug.

[richardlau]

@zcbenz a libuv update is included in the next proposed 12.x release: #32313