[core] separate Backend from View for headless rendering

1 files changed, 58 insertions, 0 deletions

diff --git a/platform/darwin/src/headless_backend_cgl.cpp b/platform/darwin/src/headless_backend_cgl.cpp
new file mode 100644
index 0000000000..4ca567f55c
--- /dev/null
+++ b/platform/darwin/src/headless_backend_cgl.cpp
@@ -0,0 +1,58 @@
+#include <mbgl/platform/default/headless_backend.hpp>
+#include <mbgl/platform/default/headless_display.hpp>
+
+#include <CoreFoundation/CoreFoundation.h>
+
+#include <string>
+#include <stdexcept>
+
+namespace mbgl {
+
+gl::glProc HeadlessBackend::initializeExtension(const char* name) {
+    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::glProc>(symbol);
+}
+
+void HeadlessBackend::createContext() {
+    CGLError error = CGLCreateContext(display->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");
+    }
+}
+
+void HeadlessBackend::destroyContext() {
+    CGLDestroyContext(glContext);
+}
+
+void HeadlessBackend::activateContext() {
+    CGLError error = CGLSetCurrentContext(glContext);
+    if (error != kCGLNoError) {
+        throw std::runtime_error(std::string("Switching OpenGL context failed:") +
+                                 CGLErrorString(error) + "\n");
+    }
+}
+
+void HeadlessBackend::deactivateContext() {
+    CGLError error = CGLSetCurrentContext(nullptr);
+    if (error != kCGLNoError) {
+        throw std::runtime_error(std::string("Removing OpenGL context failed:") +
+                                 CGLErrorString(error) + "\n");
+    }
+}
+
+} // namespace mbgl