[core] fold HeadlessDisplay into the headless RenderBackend implementation

17 files changed, 285 insertions, 442 deletions

diff --git a/platform/darwin/src/headless_backend_cgl.cpp b/platform/darwin/src/headless_backend_cgl.cpp
index 3b0c3aaf35..6e19213f52 100644
--- a/platform/darwin/src/headless_backend_cgl.cpp
+++ b/platform/darwin/src/headless_backend_cgl.cpp
@@ -1,5 +1,5 @@
 #include <mbgl/gl/headless_backend.hpp>
-#include <mbgl/gl/headless_display.hpp>
+#include <mbgl/util/logging.hpp>
 
 #include <OpenGL/OpenGL.h>
 #include <CoreFoundation/CoreFoundation.h>
@@ -9,11 +9,78 @@
 
 namespace mbgl {
 
+// 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;
+};
+
 struct CGLImpl : public HeadlessBackend::Impl {
-    CGLImpl(CGLContextObj glContext_) : glContext(glContext_) {
+    CGLImpl() {
+        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");
+        }
     }
 
-    ~CGLImpl() {
+    ~CGLImpl() final {
         CGLDestroyContext(glContext);
     }
 
@@ -33,10 +100,13 @@ struct CGLImpl : public HeadlessBackend::Impl {
         }
     }
 
+private:
+    const std::shared_ptr<const CGLDisplayConfig> cglDisplay = CGLDisplayConfig::create();
     CGLContextObj glContext = nullptr;
 };
 
 gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
+    assert(hasContext());
     static CFBundleRef framework = CFBundleGetBundleWithIdentifier(CFSTR("com.apple.opengl"));
     if (!framework) {
         throw std::runtime_error("Failed to load OpenGL framework.");
@@ -49,30 +119,9 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
     return reinterpret_cast<gl::ProcAddress>(symbol);
 }
 
-bool HeadlessBackend::hasDisplay() {
-    if (!display) {
-        display = HeadlessDisplay::create();
-    }
-    return bool(display);
-}
-
 void HeadlessBackend::createContext() {
     assert(!hasContext());
-
-    CGLContextObj glContext = nullptr;
-    CGLError error = CGLCreateContext(display->attribute<CGLPixelFormatObj>(), 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");
-    }
-
-    impl.reset(new CGLImpl(glContext));
+    impl = std::make_unique<CGLImpl>();
 }
 
 } // namespace mbgl
diff --git a/platform/darwin/src/headless_backend_eagl.mm b/platform/darwin/src/headless_backend_eagl.mm
index 1daaeaf54c..6bf5787f60 100644
--- a/platform/darwin/src/headless_backend_eagl.mm
+++ b/platform/darwin/src/headless_backend_eagl.mm
@@ -7,23 +7,26 @@
 namespace mbgl {
 
 struct EAGLImpl : public HeadlessBackend::Impl {
-    EAGLImpl(EAGLContext* glContext_) : glContext(glContext_) {
-        [reinterpret_cast<EAGLContext*>(glContext) retain];
-        reinterpret_cast<EAGLContext*>(glContext).multiThreaded = YES;
+    EAGLImpl() {
+        glContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
+        if (glContext == nil) {
+            throw std::runtime_error("Error creating GL context object");
+        }
+        glContext.multiThreaded = YES;
     }
 
-    ~EAGLImpl() {
-        [glContext release];
-    }
+    // Required for ARC to deallocate correctly.
+    ~EAGLImpl() final = default;
 
-    void activateContext() {
+    void activateContext() final {
         [EAGLContext setCurrentContext:glContext];
     }
 
-    void deactivateContext() {
+    void deactivateContext() final {
         [EAGLContext setCurrentContext:nil];
     }
 
+private:
     EAGLContext* glContext = nullptr;
 };
 
@@ -40,17 +43,9 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
     return reinterpret_cast<gl::ProcAddress>(symbol);
 }
 
-bool HeadlessBackend::hasDisplay() {
-    return true;
-}
-
 void HeadlessBackend::createContext() {
-    EAGLContext* glContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
-    if (glContext == nil) {
-        throw std::runtime_error("Error creating GL context object");
-    }
-
-    impl.reset(new EAGLImpl(glContext));
+    assert(!hasContext());
+    impl = std::make_unique<EAGLImpl>();
 }
 
 } // namespace mbgl
diff --git a/platform/darwin/src/headless_display_cgl.cpp b/platform/darwin/src/headless_display_cgl.cpp
deleted file mode 100644
index 5b7a1f2bac..0000000000
--- a/platform/darwin/src/headless_display_cgl.cpp
+++ /dev/null
@@ -1,60 +0,0 @@
-#include <mbgl/gl/headless_display.hpp>
-
-#include <OpenGL/OpenGL.h>
-
-#include <stdexcept>
-#include <string>
-
-namespace mbgl {
-
-class HeadlessDisplay::Impl {
-public:
-    Impl();
-    ~Impl();
-    CGLPixelFormatObj pixelFormat = nullptr;
-};
-
-HeadlessDisplay::Impl::Impl() {
-    // 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;
-    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.");
-    }
-}
-
-HeadlessDisplay::Impl::~Impl() {
-    CGLDestroyPixelFormat(pixelFormat);
-}
-
-template <>
-CGLPixelFormatObj HeadlessDisplay::attribute() const {
-    return impl->pixelFormat;
-}
-
-HeadlessDisplay::HeadlessDisplay()
-    : impl(std::make_unique<Impl>()) {
-}
-
-HeadlessDisplay::~HeadlessDisplay() {
-}
-
-} // namespace mbgl
diff --git a/platform/default/headless_backend_osmesa.cpp b/platform/default/headless_backend_osmesa.cpp
index 5042f5ed10..4cb0bfc5c4 100644
--- a/platform/default/headless_backend_osmesa.cpp
+++ b/platform/default/headless_backend_osmesa.cpp
@@ -8,10 +8,18 @@
 namespace mbgl {
 
 struct OSMesaImpl : public HeadlessBackend::Impl {
-    OSMesaImpl(OSMesaContext glContext_) : glContext(glContext_) {
+    OSMesaImpl() {
+#if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
+        glContext = OSMesaCreateContextExt(OSMESA_RGBA, 16, 0, 0, nullptr);
+#else
+        glContext = OSMesaCreateContext(OSMESA_RGBA, nullptr);
+#endif
+        if (glContext == nullptr) {
+            throw std::runtime_error("Error creating GL context object.");
+        }
     }
 
-    ~OSMesaImpl() {
+    ~OSMesaImpl() final {
         OSMesaDestroyContext(glContext);
     }
 
@@ -21,6 +29,7 @@ struct OSMesaImpl : public HeadlessBackend::Impl {
         }
     }
 
+private:
     OSMesaContext glContext = nullptr;
     GLubyte fakeBuffer = 0;
 };
@@ -29,23 +38,9 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
     return OSMesaGetProcAddress(name);
 }
 
-bool HeadlessBackend::hasDisplay() {
-    return true;
-};
-
 void HeadlessBackend::createContext() {
     assert(!hasContext());
-
-#if OSMESA_MAJOR_VERSION * 100 + OSMESA_MINOR_VERSION >= 305
-    OSMesaContext glContext = OSMesaCreateContextExt(OSMESA_RGBA, 16, 0, 0, nullptr);
-#else
-    OSMesaContext glContext = OSMesaCreateContext(OSMESA_RGBA, nullptr);
-#endif
-    if (glContext == nullptr) {
-        throw std::runtime_error("Error creating GL context object.");
-    }
-
-    impl.reset(new OSMesaImpl(glContext));
+    impl = std::make_unique<OSMesaImpl>();
 }
 
 } // namespace mbgl
diff --git a/platform/default/mbgl/gl/headless_backend.cpp b/platform/default/mbgl/gl/headless_backend.cpp
index edf637a560..2c81005686 100644
--- a/platform/default/mbgl/gl/headless_backend.cpp
+++ b/platform/default/mbgl/gl/headless_backend.cpp
@@ -1,5 +1,4 @@
 #include <mbgl/gl/headless_backend.hpp>
-#include <mbgl/gl/headless_display.hpp>
 #include <mbgl/gl/context.hpp>
 #include <mbgl/renderer/backend_scope.hpp>
 
@@ -36,9 +35,6 @@ void HeadlessBackend::activate() {
     active = true;
 
     if (!hasContext()) {
-        if (!hasDisplay()) {
-            throw std::runtime_error("Display is not set");
-        }
         createContext();
     }
 
diff --git a/platform/default/mbgl/gl/headless_backend.hpp b/platform/default/mbgl/gl/headless_backend.hpp
index 66f861e213..f96b01300b 100644
--- a/platform/default/mbgl/gl/headless_backend.hpp
+++ b/platform/default/mbgl/gl/headless_backend.hpp
@@ -7,8 +7,6 @@
 
 namespace mbgl {
 
-class HeadlessDisplay;
-
 class HeadlessBackend : public RendererBackend {
 public:
     HeadlessBackend(Size = { 256, 256 });
@@ -35,11 +33,9 @@ private:
     void deactivate() override;
 
     bool hasContext() const { return bool(impl); }
-    bool hasDisplay();
 
     void createContext();
 
-    std::shared_ptr<HeadlessDisplay> display;
     std::unique_ptr<Impl> impl;
 
     Size size;
diff --git a/platform/default/mbgl/gl/headless_display.cpp b/platform/default/mbgl/gl/headless_display.cpp
deleted file mode 100644
index 6247046c29..0000000000
--- a/platform/default/mbgl/gl/headless_display.cpp
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <mbgl/gl/headless_display.hpp>
-
-namespace mbgl {
-
-class HeadlessDisplay::Impl {};
-
-HeadlessDisplay::HeadlessDisplay() {
-    // no-op
-}
-
-HeadlessDisplay::~HeadlessDisplay() {
-    // no-op
-}
-
-} // namespace mbgl
diff --git a/platform/default/mbgl/gl/headless_display.hpp b/platform/default/mbgl/gl/headless_display.hpp
deleted file mode 100644
index 8c294655e5..0000000000
--- a/platform/default/mbgl/gl/headless_display.hpp
+++ /dev/null
@@ -1,34 +0,0 @@
-#pragma once
-
-#include <memory>
-
-namespace mbgl {
-
-class HeadlessDisplay {
-public:
-    static std::shared_ptr<HeadlessDisplay> create() {
-        static std::weak_ptr<HeadlessDisplay> instance;
-        
-        auto shared = instance.lock();
-        
-        if (!shared) {
-            instance = shared = std::shared_ptr<HeadlessDisplay>(new HeadlessDisplay());
-        }
-        
-        return shared;
-    }
-
-    
-    ~HeadlessDisplay();
-
-    template <typename DisplayAttribute>
-    DisplayAttribute attribute() const;
-
-private:
-    HeadlessDisplay();
-    
-    class Impl;
-    std::unique_ptr<Impl>  impl;
-};
-
-} // namespace mbgl
diff --git a/platform/ios/config.cmake b/platform/ios/config.cmake
index c3db194988..e9b3f4b218 100644
--- a/platform/ios/config.cmake
+++ b/platform/ios/config.cmake
@@ -46,8 +46,6 @@ macro(mbgl_platform_core)
         PRIVATE platform/default/mbgl/gl/headless_backend.cpp
         PRIVATE platform/default/mbgl/gl/headless_backend.hpp
         PRIVATE platform/darwin/src/headless_backend_eagl.mm
-        PRIVATE platform/default/mbgl/gl/headless_display.cpp
-        PRIVATE platform/default/mbgl/gl/headless_display.hpp
 
         # Snapshotting
         PRIVATE platform/default/mbgl/map/map_snapshotter.cpp
@@ -68,13 +66,6 @@ macro(mbgl_platform_core)
         PRIVATE -fvisibility=hidden
     )
 
-    # TODO: Remove this by converting to ARC
-    set_source_files_properties(
-        platform/darwin/src/headless_backend_eagl.mm
-            PROPERTIES
-        COMPILE_FLAGS -fno-objc-arc
-    )
-
     target_include_directories(mbgl-core
         PUBLIC platform/darwin
         PUBLIC platform/default
diff --git a/platform/linux/config.cmake b/platform/linux/config.cmake
index edac8e59ac..c64e20eddf 100644
--- a/platform/linux/config.cmake
+++ b/platform/linux/config.cmake
@@ -19,7 +19,6 @@ macro(mbgl_platform_core)
     if(WITH_OSMESA)
         target_sources(mbgl-core
             PRIVATE platform/default/headless_backend_osmesa.cpp
-            PRIVATE platform/default/mbgl/gl/headless_display.cpp
         )
         target_link_libraries(mbgl-core
             PUBLIC -lOSMesa
@@ -27,7 +26,6 @@ macro(mbgl_platform_core)
     elseif(WITH_EGL)
         target_sources(mbgl-core
             PRIVATE platform/linux/src/headless_backend_egl.cpp
-            PRIVATE platform/linux/src/headless_display_egl.cpp
         )
         target_link_libraries(mbgl-core
             PUBLIC -lGLESv2
@@ -37,7 +35,6 @@ macro(mbgl_platform_core)
     else()
         target_sources(mbgl-core
             PRIVATE platform/linux/src/headless_backend_glx.cpp
-            PRIVATE platform/linux/src/headless_display_glx.cpp
         )
         target_link_libraries(mbgl-core
             PUBLIC -lGL
@@ -66,7 +63,6 @@ macro(mbgl_platform_core)
         PRIVATE platform/default/mbgl/gl/headless_frontend.hpp
         PRIVATE platform/default/mbgl/gl/headless_backend.cpp
         PRIVATE platform/default/mbgl/gl/headless_backend.hpp
-        PRIVATE platform/default/mbgl/gl/headless_display.hpp
 
         # Thread pool
         PRIVATE platform/default/mbgl/util/default_thread_pool.cpp
diff --git a/platform/linux/src/headless_backend_egl.cpp b/platform/linux/src/headless_backend_egl.cpp
index 0784173af7..7d3a3d1ec1 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 +8,82 @@
 
 namespace mbgl {
 
+// 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;
+};
+
 struct EGLImpl : public HeadlessBackend::Impl {
-    EGLImpl(EGLContext glContext_, EGLDisplay display_, EGLConfig config_)
-            : glContext(glContext_),
-              display(display_),
-              config(config_) {
+    EGLImpl() {
+        // 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 +95,49 @@ 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");
+    ~EGLImpl() 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.");
         }
     }
 
     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 = HeadlessDisplay::create();
-    }
-    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));
+    impl = std::make_unique<EGLImpl>();
 }
 
 } // namespace mbgl
diff --git a/platform/linux/src/headless_backend_glx.cpp b/platform/linux/src/headless_backend_glx.cpp
index 0ba7f08630..6d2939da0f 100644
--- a/platform/linux/src/headless_backend_glx.cpp
+++ b/platform/linux/src/headless_backend_glx.cpp
@@ -1,5 +1,4 @@
 #include <mbgl/gl/headless_backend.hpp>
-#include <mbgl/gl/headless_display.hpp>
 
 #include <mbgl/util/logging.hpp>
 
@@ -9,79 +8,122 @@
 
 namespace mbgl {
 
+// This class provides a singleton that contains information about the configuration used for
+// instantiating new headless rendering contexts.
+class GLXDisplayConfig {
+private:
+    // Key for singleton construction.
+    struct Key { explicit Key() = default; };
+
+public:
+    GLXDisplayConfig(Key) {
+        if (!XInitThreads()) {
+            throw std::runtime_error("Failed to XInitThreads.");
+        }
+
+        xDisplay = XOpenDisplay(nullptr);
+        if (xDisplay == nullptr) {
+            throw std::runtime_error("Failed to open X display.");
+        }
+
+        const auto* extensions = reinterpret_cast<const char*>(
+            glXQueryServerString(xDisplay, DefaultScreen(xDisplay), GLX_EXTENSIONS));
+        if (!extensions) {
+            throw std::runtime_error("Cannot read GLX extensions.");
+        }
+        if (!strstr(extensions, "GLX_SGIX_fbconfig")) {
+            throw std::runtime_error("Extension GLX_SGIX_fbconfig was not found.");
+        }
+        if (!strstr(extensions, "GLX_SGIX_pbuffer")) {
+            throw std::runtime_error("Cannot find glXCreateContextAttribsARB.");
+        }
+
+        // We're creating a dummy pbuffer anyway that we're not using.
+        static int pixelFormat[] = { GLX_DRAWABLE_TYPE, GLX_PBUFFER_BIT, None };
+
+        int configs = 0;
+        fbConfigs = glXChooseFBConfig(xDisplay, DefaultScreen(xDisplay), pixelFormat, &configs);
+        if (fbConfigs == nullptr) {
+            throw std::runtime_error("Failed to glXChooseFBConfig.");
+        }
+        if (configs <= 0) {
+            throw std::runtime_error("No Framebuffer configurations.");
+        }
+    }
+
+    ~GLXDisplayConfig() {
+        XFree(fbConfigs);
+        XCloseDisplay(xDisplay);
+    }
+
+    static std::shared_ptr<const GLXDisplayConfig> create() {
+        static std::weak_ptr<const GLXDisplayConfig> instance;
+        auto shared = instance.lock();
+        if (!shared) {
+            instance = shared = std::make_shared<GLXDisplayConfig>(Key{});
+        }
+        return shared;
+    }
+
+public:
+    Display* xDisplay = nullptr;
+    GLXFBConfig* fbConfigs = nullptr;
+};
+
 struct GLXImpl : public HeadlessBackend::Impl {
-    GLXImpl(GLXContext glContext_, GLXPbuffer glxPbuffer_, Display* xDisplay_, GLXFBConfig* fbConfigs_)
-            : glContext(glContext_),
-              glxPbuffer(glxPbuffer_),
-              xDisplay(xDisplay_),
-              fbConfigs(fbConfigs_) {
+    GLXImpl() {
+        // Try to create a legacy context.
+        glContext = glXCreateNewContext(glxDisplay->xDisplay, glxDisplay->fbConfigs[0],
+                                        GLX_RGBA_TYPE, None, True);
+        if (glContext && !glXIsDirect(glxDisplay->xDisplay, glContext)) {
+            Log::Error(Event::OpenGL, "failed to create direct OpenGL Legacy context");
+            glXDestroyContext(glxDisplay->xDisplay, glContext);
+            glContext = nullptr;
+        }
+        if (glContext == nullptr) {
+            throw std::runtime_error("Error creating GL context object.");
+        }
+
+        // Create a dummy pbuffer. We will render to framebuffers anyway, but we need a pbuffer to
+        // activate the context.
+        int pbufferAttributes[] = { GLX_PBUFFER_WIDTH, 8, GLX_PBUFFER_HEIGHT, 8, None };
+        glxPbuffer =
+            glXCreatePbuffer(glxDisplay->xDisplay, glxDisplay->fbConfigs[0], pbufferAttributes);
     }
 
-    ~GLXImpl() override {
+    ~GLXImpl() final {
         if (glxPbuffer) {
-            glXDestroyPbuffer(xDisplay, glxPbuffer);
+            glXDestroyPbuffer(glxDisplay->xDisplay, glxPbuffer);
         }
-        glXDestroyContext(xDisplay, glContext);
+        glXDestroyContext(glxDisplay->xDisplay, glContext);
     }
 
     void activateContext() final {
-        if (!glXMakeContextCurrent(xDisplay, glxPbuffer, glxPbuffer, glContext)) {
+        if (!glXMakeContextCurrent(glxDisplay->xDisplay, glxPbuffer, glxPbuffer, glContext)) {
             throw std::runtime_error("Switching OpenGL context failed.\n");
         }
     }
 
     void deactivateContext() final {
-        if (!glXMakeContextCurrent(xDisplay, 0, 0, nullptr)) {
+        if (!glXMakeContextCurrent(glxDisplay->xDisplay, 0, 0, nullptr)) {
             throw std::runtime_error("Removing OpenGL context failed.\n");
         }
     }
 
+private:
+    const std::shared_ptr<const GLXDisplayConfig> glxDisplay = GLXDisplayConfig::create();
+
     GLXContext glContext = nullptr;
     GLXPbuffer glxPbuffer = 0;
-
-    // Needed for ImplDeleter.
-    Display* xDisplay = nullptr;
-    GLXFBConfig* fbConfigs = nullptr;
 };
 
 gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
     return glXGetProcAddress(reinterpret_cast<const GLubyte*>(name));
 }
 
-bool HeadlessBackend::hasDisplay() {
-    if (!display) {
-        display = HeadlessDisplay::create();
-    }
-    return bool(display);
-};
-
 void HeadlessBackend::createContext() {
     assert(!hasContext());
-
-    auto* xDisplay = display->attribute<Display*>();
-    auto* fbConfigs = display->attribute<GLXFBConfig*>();
-
-    // Try to create a legacy context.
-    GLXContext glContext = glXCreateNewContext(xDisplay, fbConfigs[0], GLX_RGBA_TYPE, None, True);
-    if (glContext && !glXIsDirect(xDisplay, glContext)) {
-        Log::Error(Event::OpenGL, "failed to create direct OpenGL Legacy context");
-        glXDestroyContext(xDisplay, glContext);
-        glContext = nullptr;
-    }
-    if (glContext == nullptr) {
-        throw std::runtime_error("Error creating GL context object.");
-    }
-
-    // Create a dummy pbuffer. We will render to framebuffers anyway, but we need a pbuffer to
-    // activate the context.
-    int pbufferAttributes[] = {
-        GLX_PBUFFER_WIDTH, 8,
-        GLX_PBUFFER_HEIGHT, 8,
-        None
-    };
-    GLXPbuffer glxPbuffer = glXCreatePbuffer(xDisplay, fbConfigs[0], pbufferAttributes);
-
-    impl = std::make_unique<mbgl::GLXImpl>(glContext, glxPbuffer, xDisplay, fbConfigs);
+    impl = std::make_unique<GLXImpl>();
 }
 
 } // namespace mbgl
diff --git a/platform/linux/src/headless_display_egl.cpp b/platform/linux/src/headless_display_egl.cpp
deleted file mode 100644
index b746211924..0000000000
--- a/platform/linux/src/headless_display_egl.cpp
+++ /dev/null
@@ -1,68 +0,0 @@
-#include <mbgl/gl/headless_display.hpp>
-#include <mbgl/util/logging.hpp>
-#include <mbgl/util/string.hpp>
-
-#include <EGL/egl.h>
-
-namespace mbgl {
-
-class HeadlessDisplay::Impl {
-public:
-    Impl();
-    ~Impl();
-
-    EGLDisplay display = EGL_NO_DISPLAY;
-    EGLConfig config = 0;
-};
-
-HeadlessDisplay::Impl::Impl() {
-    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
-    };
-
-    if (!eglChooseConfig(display, attribs, &config, 1, &numConfigs) || numConfigs != 1) {
-        throw std::runtime_error("Failed to choose ARGB config.\n");
-    }
-}
-
-HeadlessDisplay::Impl::~Impl() {
-    eglTerminate(display);
-}
-
-template <>
-EGLDisplay HeadlessDisplay::attribute() const {
-    return impl->display;
-}
-
-template <>
-EGLConfig& HeadlessDisplay::attribute() const {
-    return impl->config;
-}
-
-HeadlessDisplay::HeadlessDisplay()
-    : impl(std::make_unique<Impl>()) {
-}
-
-HeadlessDisplay::~HeadlessDisplay() {
-}
-
-} // namespace mbgl
diff --git a/platform/linux/src/headless_display_glx.cpp b/platform/linux/src/headless_display_glx.cpp
deleted file mode 100644
index 5dc342154d..0000000000
--- a/platform/linux/src/headless_display_glx.cpp
+++ /dev/null
@@ -1,78 +0,0 @@
-#include <mbgl/gl/headless_display.hpp>
-
-#include <GL/glx.h>
-
-#include <cstring>
-#include <stdexcept>
-#include <string>
-
-namespace mbgl {
-
-class HeadlessDisplay::Impl {
-public:
-    Impl();
-    ~Impl();
-
-    Display* xDisplay = nullptr;
-    GLXFBConfig* fbConfigs = nullptr;
-};
-
-HeadlessDisplay::Impl::Impl() {
-    if (!XInitThreads()) {
-        throw std::runtime_error("Failed to XInitThreads.");
-    }
-
-    xDisplay = XOpenDisplay(nullptr);
-    if (xDisplay == nullptr) {
-        throw std::runtime_error("Failed to open X display.");
-    }
-
-    const auto *extensions = reinterpret_cast<const char *>(glXQueryServerString(xDisplay, DefaultScreen(xDisplay), GLX_EXTENSIONS));
-    if (!extensions) {
-        throw std::runtime_error("Cannot read GLX extensions.");
-    }
-    if (!strstr(extensions,"GLX_SGIX_fbconfig")) {
-        throw std::runtime_error("Extension GLX_SGIX_fbconfig was not found.");
-    }
-    if (!strstr(extensions, "GLX_SGIX_pbuffer")) {
-        throw std::runtime_error("Cannot find glXCreateContextAttribsARB.");
-    }
-
-    // We're creating a dummy pbuffer anyway that we're not using.
-    static int pixelFormat[] = {
-        GLX_DRAWABLE_TYPE, GLX_PBUFFER_BIT,
-        None
-    };
-
-    int configs = 0;
-    fbConfigs = glXChooseFBConfig(xDisplay, DefaultScreen(xDisplay), pixelFormat, &configs);
-    if (fbConfigs == nullptr) {
-        throw std::runtime_error("Failed to glXChooseFBConfig.");
-    }
-    if (configs <= 0) {
-        throw std::runtime_error("No Framebuffer configurations.");
-    }
-}
-
-HeadlessDisplay::Impl::~Impl() {
-    XFree(fbConfigs);
-    XCloseDisplay(xDisplay);
-}
-
-template <>
-Display* HeadlessDisplay::attribute() const {
-    return impl->xDisplay;
-}
-
-template <>
-GLXFBConfig* HeadlessDisplay::attribute() const {
-    return impl->fbConfigs;
-}
-
-HeadlessDisplay::HeadlessDisplay()
-    : impl(std::make_unique<Impl>()) {
-}
-
-HeadlessDisplay::~HeadlessDisplay() = default;
-
-} // namespace mbgl
diff --git a/platform/macos/config.cmake b/platform/macos/config.cmake
index 2716f7c84d..b7312216c0 100644
--- a/platform/macos/config.cmake
+++ b/platform/macos/config.cmake
@@ -32,8 +32,6 @@ macro(mbgl_platform_core)
         PRIVATE platform/default/mbgl/gl/headless_backend.cpp
         PRIVATE platform/default/mbgl/gl/headless_backend.hpp
         PRIVATE platform/darwin/src/headless_backend_cgl.cpp
-        PRIVATE platform/default/mbgl/gl/headless_display.hpp
-        PRIVATE platform/darwin/src/headless_display_cgl.cpp
 
         # Snapshotting
         PRIVATE platform/default/mbgl/map/map_snapshotter.cpp
diff --git a/platform/qt/qt.cmake b/platform/qt/qt.cmake
index 1bcb869fc9..7b3c7fe1a2 100644
--- a/platform/qt/qt.cmake
+++ b/platform/qt/qt.cmake
@@ -17,8 +17,6 @@ set(MBGL_QT_CORE_FILES
     PRIVATE platform/default/mbgl/gl/headless_frontend.hpp
     PRIVATE platform/default/mbgl/gl/headless_backend.cpp
     PRIVATE platform/default/mbgl/gl/headless_backend.hpp
-    PRIVATE platform/default/mbgl/gl/headless_display.cpp
-    PRIVATE platform/default/mbgl/gl/headless_display.hpp
     PRIVATE platform/qt/src/headless_backend_qt.cpp
 
     # Thread pool
diff --git a/platform/qt/src/headless_backend_qt.cpp b/platform/qt/src/headless_backend_qt.cpp
index 5f95b2f96a..7985ca9f2d 100644
--- a/platform/qt/src/headless_backend_qt.cpp
+++ b/platform/qt/src/headless_backend_qt.cpp
@@ -12,7 +12,10 @@
 
 namespace mbgl {
 
-struct QtImpl : public HeadlessBackend::Impl {
+class QtImpl : public HeadlessBackend::Impl {
+public:
+    ~QtImpl() final = default;
+
     void activateContext() final {
         widget.makeCurrent();
     }
@@ -21,6 +24,7 @@ struct QtImpl : public HeadlessBackend::Impl {
         widget.doneCurrent();
     }
 
+private:
     QGLWidget widget;
 };
 
@@ -34,13 +38,9 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
 #endif
 }
 
-bool HeadlessBackend::hasDisplay() {
-    return true;
-};
-
 void HeadlessBackend::createContext() {
     assert(!hasContext());
-    impl.reset(new QtImpl);
+    impl = std::make_unique<QtImpl>();
 }
 
 } // namespace mbgl