1 files changed, 99 insertions, 56 deletions

diff --git a/platform/linux/src/headless_backend_egl.cpp b/platform/linux/src/headless_backend_egl.cpp
index d98b2edc03..089e344987 100644
--- a/platform/linux/src/headless_backend_egl.cpp
+++ b/platform/linux/src/headless_backend_egl.cpp
@@ -1,5 +1,4 @@
 #include <mbgl/gl/headless_backend.hpp>
-#include <mbgl/gl/headless_display.hpp>
 
 #include <mbgl/util/logging.hpp>
 
@@ -9,11 +8,83 @@
 
 namespace mbgl {
 
-struct EGLImpl : public HeadlessBackend::Impl {
-    EGLImpl(EGLContext glContext_, EGLDisplay display_, EGLConfig config_)
-            : glContext(glContext_),
-              display(display_),
-              config(config_) {
+// This class provides a singleton that contains information about the configuration used for
+// instantiating new headless rendering contexts.
+class EGLDisplayConfig {
+private:
+    // Key for singleton construction.
+    struct Key { explicit Key() = default; };
+
+public:
+    EGLDisplayConfig(Key) {
+        display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+        if (display == EGL_NO_DISPLAY) {
+            throw std::runtime_error("Failed to obtain a valid EGL display.\n");
+        }
+
+        EGLint major, minor, numConfigs;
+        if (!eglInitialize(display, &major, &minor)) {
+            throw std::runtime_error("eglInitialize() failed.\n");
+        }
+
+        if (!eglBindAPI(EGL_OPENGL_ES_API)) {
+            mbgl::Log::Error(mbgl::Event::OpenGL, "eglBindAPI(EGL_OPENGL_ES_API) returned error %d",
+                             eglGetError());
+            throw std::runtime_error("eglBindAPI() failed");
+        }
+
+        const EGLint attribs[] = {
+#if MBGL_USE_GLES2
+            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+#endif
+            EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
+            EGL_NONE
+        };
+
+        // Note: we're choosing an arbitrary pixel format, since we're not using the default surface
+        // anyway; all rendering will be directed to framebuffers which have their own configuration.
+        if (!eglChooseConfig(display, attribs, &config, 1, &numConfigs) || numConfigs != 1) {
+            throw std::runtime_error("Failed to choose ARGB config.\n");
+        }
+    }
+
+    ~EGLDisplayConfig() {
+        eglTerminate(display);
+    }
+
+    static std::shared_ptr<const EGLDisplayConfig> create() {
+        static std::weak_ptr<const EGLDisplayConfig> instance;
+        auto shared = instance.lock();
+        if (!shared) {
+            instance = shared = std::make_shared<EGLDisplayConfig>(Key{});
+        }
+        return shared;
+    }
+
+public:
+    EGLDisplay display = EGL_NO_DISPLAY;
+    EGLConfig config = 0;
+};
+
+class EGLBackendImpl : public HeadlessBackend::Impl {
+public:
+    EGLBackendImpl() {
+        // EGL initializes the context client version to 1 by default. We want to
+        // use OpenGL ES 2.0 which has the ability to create shader and program
+        // objects and also to write vertex and fragment shaders in the OpenGL ES
+        // Shading Language.
+        const EGLint attribs[] = {
+            EGL_CONTEXT_CLIENT_VERSION, 2,
+            EGL_NONE
+        };
+
+        eglContext = eglCreateContext(eglDisplay->display, eglDisplay->config, EGL_NO_CONTEXT, attribs);
+        if (eglContext == EGL_NO_CONTEXT) {
+            mbgl::Log::Error(mbgl::Event::OpenGL, "eglCreateContext() returned error 0x%04x",
+                             eglGetError());
+            throw std::runtime_error("Error creating the EGL context object.\n");
+        }
+
         // Create a dummy pbuffer. We will render to framebuffers anyway, but we need a pbuffer to
         // activate the context.
         // Note that to be able to create pbuffer surfaces, we need to choose a config that
@@ -25,77 +96,49 @@ struct EGLImpl : public HeadlessBackend::Impl {
             EGL_NONE
         };
 
-        glSurface = eglCreatePbufferSurface(display, config, surfAttribs);
-        if (glSurface == EGL_NO_SURFACE) {
+        eglSurface = eglCreatePbufferSurface(eglDisplay->display, eglDisplay->config, surfAttribs);
+        if (eglSurface == EGL_NO_SURFACE) {
             throw std::runtime_error("Could not create surface: " + std::to_string(eglGetError()));
         }
     }
 
-    ~EGLImpl() {
-        if (glSurface != EGL_NO_SURFACE) {
-            if (!eglDestroySurface(display, glSurface)) {
-                throw std::runtime_error("Failed to destroy EGL surface.\n");
+    ~EGLBackendImpl() final {
+        if (eglSurface != EGL_NO_SURFACE) {
+            if (!eglDestroySurface(eglDisplay->display, eglSurface)) {
+                Log::Error(Event::OpenGL, "Failed to destroy EGL surface.");
             }
-            glSurface = EGL_NO_SURFACE;
+            eglSurface = EGL_NO_SURFACE;
         }
-        if (!eglDestroyContext(display, glContext)) {
-            throw std::runtime_error("Failed to destroy EGL context.\n");
+        if (!eglDestroyContext(eglDisplay->display, eglContext)) {
+            Log::Error(Event::OpenGL, "Failed to destroy EGL context.");
         }
     }
 
+    gl::ProcAddress getExtensionFunctionPointer(const char* name) final {
+        return eglGetProcAddress(name);
+    }
+
     void activateContext() final {
-        if (!eglMakeCurrent(display, glSurface, glSurface, glContext)) {
+        if (!eglMakeCurrent(eglDisplay->display, eglSurface, eglSurface, eglContext)) {
             throw std::runtime_error("Switching OpenGL context failed.\n");
         }
     }
 
     void deactivateContext() final {
-        if (!eglMakeCurrent(display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT)) {
+        if (!eglMakeCurrent(eglDisplay->display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT)) {
             throw std::runtime_error("Removing OpenGL context failed.\n");
         }
     }
 
-    EGLContext glContext = EGL_NO_CONTEXT;
-    EGLDisplay display = EGL_NO_DISPLAY;
-    EGLConfig config = 0;
-    EGLSurface glSurface = EGL_NO_SURFACE;
+private:
+    const std::shared_ptr<const EGLDisplayConfig> eglDisplay = EGLDisplayConfig::create();
+    EGLContext eglContext = EGL_NO_CONTEXT;
+    EGLSurface eglSurface = EGL_NO_SURFACE;
 };
 
-gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
-    return eglGetProcAddress(name);
-}
-
-bool HeadlessBackend::hasDisplay() {
-    if (!display) {
-        display.reset(new HeadlessDisplay);
-    }
-    return bool(display);
-};
-
-void HeadlessBackend::createContext() {
-    assert(!hasContext());
-    assert(hasDisplay());
-
-    EGLDisplay display_ = display->attribute<EGLDisplay>();
-    EGLConfig& config = display->attribute<EGLConfig&>();
-
-    // EGL initializes the context client version to 1 by default. We want to
-    // use OpenGL ES 2.0 which has the ability to create shader and program
-    // objects and also to write vertex and fragment shaders in the OpenGL ES
-    // Shading Language.
-    const EGLint attribs[] = {
-        EGL_CONTEXT_CLIENT_VERSION, 2,
-        EGL_NONE
-    };
-
-    EGLContext glContext = eglCreateContext(display_, config, EGL_NO_CONTEXT, attribs);
-    if (glContext == EGL_NO_CONTEXT) {
-        mbgl::Log::Error(mbgl::Event::OpenGL, "eglCreateContext() returned error 0x%04x",
-                         eglGetError());
-        throw std::runtime_error("Error creating the EGL context object.\n");
-    }
-
-    impl.reset(new EGLImpl(glContext, display_, config));
+void HeadlessBackend::createImpl() {
+    assert(!impl);
+    impl = std::make_unique<EGLBackendImpl>();
 }
 
 } // namespace mbgl