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MobileGL/MobileGL/MG_Impl/DyldInterpose/DyldInterpose.cpp
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// MobileGL - MobileGL/MG_Impl/DyldInterpose/DyldInterpose.cpp
// Copyright (c) 2025-2026 MobileGL-Dev
// Licensed under the GNU Lesser General Public License v3.0:
// https://www.gnu.org/licenses/gpl-3.0.txt
// https://www.gnu.org/licenses/lgpl-3.0.txt
// SPDX-License-Identifier: LGPL-3.0-only
// End of Source File Header
#include <Includes.h>
#if defined(__APPLE__)
#include "MG_Impl/CGLImpl/CGLImpl.h"
#include "MG_Impl/GetProcAddress.h"
#include <CoreGraphics/CoreGraphics.h>
#include <CoreVideo/CVDisplayLink.h>
#include <cstdint>
#include <dlfcn.h>
namespace {
struct DyldInterposeEntry {
const void* Replacement;
const void* Replacee;
};
bool IsGLProcName(const char* name) {
if (name == nullptr) {
return false;
}
if (strncmp(name, "CGL", 3) == 0) {
return true;
}
if (strncmp(name, "gl", 2) != 0) {
return false;
}
// Avoid stealing glfw*/glib*/glX*/global application symbols.
return name[2] >= 'A' && name[2] <= 'Z' && name[2] != 'X';
}
void* MobileGLDlsym(void* handle, const char* symbol) {
if (IsGLProcName(symbol)) {
if (void* proc = MobileGL::MG_Impl::GetProcAddress(symbol)) {
return proc;
}
}
return dlsym(handle, symbol);
}
CGDirectDisplayID DisplayForMask(GLint displayMask) {
constexpr std::uint32_t MaxDisplays = sizeof(CGOpenGLDisplayMask) * 8;
CGDirectDisplayID displays[MaxDisplays] = {};
std::uint32_t displayCount = 0;
if (displayMask != 0 &&
CGGetActiveDisplayList(MaxDisplays, displays, &displayCount) == kCGErrorSuccess) {
const auto mask = static_cast<CGOpenGLDisplayMask>(displayMask);
for (std::uint32_t i = 0; i < displayCount; ++i) {
if ((CGDisplayIDToOpenGLDisplayMask(displays[i]) & mask) != 0) {
return displays[i];
}
}
}
return CGMainDisplayID();
}
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
CVReturn MobileGLCVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(
CVDisplayLinkRef displayLink,
CGLContextObj context,
CGLPixelFormatObj pixelFormat) {
GLint virtualScreen = 0;
if (MobileGL::MG_Impl::CGLImpl::GetVirtualScreen(context, &virtualScreen) == kCGLNoError) {
GLint displayMask = 0;
if (!displayLink ||
MobileGL::MG_Impl::CGLImpl::DescribePixelFormat(
pixelFormat, virtualScreen, kCGLPFADisplayMask, &displayMask) != kCGLNoError) {
return kCVReturnInvalidArgument;
}
return CVDisplayLinkSetCurrentCGDisplay(displayLink, DisplayForMask(displayMask));
}
using OriginalFunction = CVReturn (*)(CVDisplayLinkRef, CGLContextObj, CGLPixelFormatObj);
static const auto original = reinterpret_cast<OriginalFunction>(
dlsym(RTLD_NEXT, "CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext"));
return original ? original(displayLink, context, pixelFormat) : kCVReturnError;
}
__attribute__((used)) static const DyldInterposeEntry kMobileGLDyldInterpose[]
__attribute__((section("__DATA,__interpose"))) = {
{reinterpret_cast<const void*>(MobileGLDlsym), reinterpret_cast<const void*>(dlsym)},
{reinterpret_cast<const void*>(MobileGLCVDisplayLinkSetCurrentCGDisplayFromOpenGLContext),
reinterpret_cast<const void*>(CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext)},
};
#pragma clang diagnostic pop
} // namespace
#endif