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#include <mbgl/gl/headless_backend.hpp>
#include <mbgl/util/logging.hpp>
#include <OpenGL/OpenGL.h>
#include <CoreFoundation/CoreFoundation.h>
#include <string>
#include <stdexcept>
namespace mbgl {
namespace gl {
// This class provides a singleton that contains information about the pixel format used for
// instantiating new headless rendering contexts.
class CGLDisplayConfig {
private:
// Key for singleton construction.
struct Key { explicit Key() = default; };
public:
CGLDisplayConfig(Key) {
// TODO: test if OpenGL 4.1 with GL_ARB_ES2_compatibility is supported
// If it is, use kCGLOGLPVersion_3_2_Core and enable that extension.
CGLPixelFormatAttribute attributes[] = {
kCGLPFAOpenGLProfile, static_cast<CGLPixelFormatAttribute>(kCGLOGLPVersion_Legacy),
// Not adding kCGLPFAAccelerated, as this will make headless rendering impossible when running in VMs.
kCGLPFAClosestPolicy,
kCGLPFAAccumSize, static_cast<CGLPixelFormatAttribute>(32),
kCGLPFAColorSize, static_cast<CGLPixelFormatAttribute>(24),
kCGLPFAAlphaSize, static_cast<CGLPixelFormatAttribute>(8),
kCGLPFADepthSize, static_cast<CGLPixelFormatAttribute>(16),
kCGLPFAStencilSize, static_cast<CGLPixelFormatAttribute>(8),
kCGLPFASupportsAutomaticGraphicsSwitching,
kCGLPFAAllowOfflineRenderers, // Allows using the integrated GPU
static_cast<CGLPixelFormatAttribute>(0)
};
GLint num;
// TODO: obtain all configurations and choose the best one.
const CGLError error = CGLChoosePixelFormat(attributes, &pixelFormat, &num);
if (error != kCGLNoError) {
throw std::runtime_error(std::string("Error choosing pixel format:") + CGLErrorString(error) + "\n");
}
if (num <= 0) {
throw std::runtime_error("No pixel formats found.");
}
}
~CGLDisplayConfig() {
const CGLError error = CGLDestroyPixelFormat(pixelFormat);
if (error != kCGLNoError) {
Log::Error(Event::OpenGL, std::string("Error destroying pixel format:") + CGLErrorString(error));
}
}
static std::shared_ptr<const CGLDisplayConfig> create() {
static std::weak_ptr<const CGLDisplayConfig> instance;
auto shared = instance.lock();
if (!shared) {
instance = shared = std::make_shared<CGLDisplayConfig>(Key{});
}
return shared;
}
public:
CGLPixelFormatObj pixelFormat = nullptr;
};
class CGLBackendImpl : public HeadlessBackend::Impl {
public:
CGLBackendImpl() {
CGLError error = CGLCreateContext(cglDisplay->pixelFormat, nullptr, &glContext);
if (error != kCGLNoError) {
throw std::runtime_error(std::string("Error creating GL context object:") +
CGLErrorString(error) + "\n");
}
error = CGLEnable(glContext, kCGLCEMPEngine);
if (error != kCGLNoError) {
throw std::runtime_error(std::string("Error enabling OpenGL multithreading:") +
CGLErrorString(error) + "\n");
}
}
~CGLBackendImpl() final {
CGLDestroyContext(glContext);
}
gl::ProcAddress getExtensionFunctionPointer(const char* name) final {
static CFBundleRef framework = CFBundleGetBundleWithIdentifier(CFSTR("com.apple.opengl"));
if (!framework) {
throw std::runtime_error("Failed to load OpenGL framework.");
}
CFStringRef str =
CFStringCreateWithCString(kCFAllocatorDefault, name, kCFStringEncodingASCII);
void* symbol = CFBundleGetFunctionPointerForName(framework, str);
CFRelease(str);
return reinterpret_cast<gl::ProcAddress>(symbol);
}
void activateContext() final {
CGLError error = CGLSetCurrentContext(glContext);
if (error != kCGLNoError) {
throw std::runtime_error(std::string("Switching OpenGL context failed:") +
CGLErrorString(error) + "\n");
}
}
void deactivateContext() final {
CGLError error = CGLSetCurrentContext(nullptr);
if (error != kCGLNoError) {
throw std::runtime_error(std::string("Removing OpenGL context failed:") +
CGLErrorString(error) + "\n");
}
}
private:
const std::shared_ptr<const CGLDisplayConfig> cglDisplay = CGLDisplayConfig::create();
CGLContextObj glContext = nullptr;
};
void HeadlessBackend::createImpl() {
assert(!impl);
impl = std::make_unique<CGLBackendImpl>();
}
} // namespace gl
} // namespace mbgl
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