[test] allow only a single shared display to avoid egl errors

platform/darwin/src/headless_backend_cgl.cpp

@@ -51,7 +51,7 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
 
 bool HeadlessBackend::hasDisplay() {
     if (!display) {
-        display.reset(new HeadlessDisplay);
+        display = HeadlessDisplay::create();
     }
     return bool(display);
 }

platform/default/mbgl/gl/headless_backend.cpp

@@ -11,10 +11,6 @@ namespace mbgl {
 
 HeadlessBackend::HeadlessBackend() = default;
 
-HeadlessBackend::HeadlessBackend(std::shared_ptr<HeadlessDisplay> display_)
-        : display(std::move(display_)) {
-}
-
 HeadlessBackend::~HeadlessBackend() {
     BackendScope guard { *this, getScopeType() };
     context.reset();

platform/default/mbgl/gl/headless_backend.hpp

@@ -12,7 +12,6 @@ class HeadlessDisplay;
 class HeadlessBackend : public RendererBackend {
 public:
     HeadlessBackend();
-    HeadlessBackend(std::shared_ptr<HeadlessDisplay>);
     ~HeadlessBackend() override;
 
     void updateAssumedState() override;

platform/default/mbgl/gl/headless_display.hpp

@@ -6,13 +6,27 @@ namespace mbgl {
 
 class HeadlessDisplay {
 public:
-    HeadlessDisplay();
+    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;
 };

platform/linux/src/headless_backend_egl.cpp

@@ -67,7 +67,7 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
 
 bool HeadlessBackend::hasDisplay() {
     if (!display) {
-        display.reset(new HeadlessDisplay);
+        display = HeadlessDisplay::create();
     }
     return bool(display);
 };

platform/linux/src/headless_backend_glx.cpp

@@ -50,7 +50,7 @@ gl::ProcAddress HeadlessBackend::initializeExtension(const char* name) {
 
 bool HeadlessBackend::hasDisplay() {
     if (!display) {
-        display.reset(new HeadlessDisplay);
+        display = HeadlessDisplay::create();
     }
     return bool(display);
 };

platform/node/src/node_map.cpp

@@ -5,7 +5,6 @@
 #include "node_geojson.hpp"
 #include "node_renderer_frontend.hpp"
 
-#include <mbgl/gl/headless_display.hpp>
 #include <mbgl/util/exception.hpp>
 #include <mbgl/renderer/renderer.hpp>
 #include <mbgl/renderer/backend_scope.hpp>
@@ -35,17 +34,11 @@ struct NodeMap::RenderOptions {
 
 Nan::Persistent<v8::Function> NodeMap::constructor;
 
-static std::shared_ptr<mbgl::HeadlessDisplay> sharedDisplay() {
-    static auto display = std::make_shared<mbgl::HeadlessDisplay>();
-    return display;
-}
-
 static const char* releasedMessage() {
     return "Map resources have already been released";
 }
 
-NodeBackend::NodeBackend()
-    : HeadlessBackend(sharedDisplay()) {}
+NodeBackend::NodeBackend(): HeadlessBackend() {}
 
 void NodeMapObserver::onDidFailLoadingMap(std::exception_ptr error) {
     std::rethrow_exception(error);
@@ -81,9 +74,6 @@ void NodeMap::Init(v8::Local<v8::Object> target) {
 
     constructor.Reset(tpl->GetFunction());
     Nan::Set(target, Nan::New("Map").ToLocalChecked(), tpl->GetFunction());
-
-    // Initialize display connection on module load.
-    sharedDisplay();
 }
 
 /**

test/api/annotations.test.cpp

@@ -30,7 +30,7 @@ std::unique_ptr<style::Image> namedMarker(const std::string& name) {
 class AnnotationTest {
 public:
     util::RunLoop loop;
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext() };
     StubFileSource fileSource;

test/api/api_misuse.test.cpp

@@ -24,7 +24,7 @@ TEST(API, RenderWithoutCallback) {
 
     util::RunLoop loop;
 
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext(), { 128, 512 } };
     StubFileSource fileSource;

test/api/custom_layer.test.cpp

@@ -89,7 +89,7 @@ public:
 TEST(CustomLayer, Basic) {
     util::RunLoop loop;
 
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext() };
     DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");

test/api/query.test.cpp

@@ -30,7 +30,7 @@ public:
     }
 
     util::RunLoop loop;
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext() };
     StubFileSource fileSource;

test/api/render_missing.test.cpp

@@ -30,7 +30,7 @@ TEST(API, TEST_REQUIRES_SERVER(RenderMissingTile)) {
 
     const auto style = util::read_file("test/fixtures/api/water_missing_tiles.json");
 
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext(), { 256, 512 } };
     float pixelRatio { 1 };

test/api/repeated_render.test.cpp

@@ -27,7 +27,7 @@ TEST(API, RepeatedRender) {
 
     const auto style = util::read_file("test/fixtures/api/water.json");
 
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext(), { 512, 512 } };
     float pixelRatio { 1 };
@@ -84,7 +84,7 @@ TEST(API, ZoomHistory) {
 
     const auto style = util::read_file("test/fixtures/api/empty.json");
 
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext(), { 512, 512 } };
     DefaultFileSource fileSource(":memory:", ".");

test/gl/object.test.cpp

@@ -47,7 +47,7 @@ TEST(GLObject, Value) {
 }
 
 TEST(GLObject, Store) {
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view(backend.getContext());
 

test/map/map.test.cpp

@@ -6,6 +6,7 @@
 #include <mbgl/map/map.hpp>
 #include <mbgl/renderer/backend_scope.hpp>
 #include <mbgl/gl/headless_backend.hpp>
+#include <mbgl/gl/headless_display.hpp>
 #include <mbgl/gl/offscreen_view.hpp>
 #include <mbgl/gl/context.hpp>
 #include <mbgl/util/default_thread_pool.hpp>
@@ -539,8 +540,8 @@ TEST(Map, DontLoadUnneededTiles) {
 
 TEST(Map, TEST_DISABLED_ON_CI(ContinuousRendering)) {
     util::RunLoop runLoop;
-    HeadlessBackend backend { test::sharedDisplay() };
-    BackendScope scope(backend);
+    HeadlessBackend backend;
+    BackendScope scope { backend };
     OffscreenView view { backend.getContext() };
     ThreadPool threadPool { 4 };
     DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");

test/map/prefetch.test.cpp

@@ -24,7 +24,7 @@ using namespace std::literals::string_literals;
 
 TEST(Map, PrefetchTiles) {
     util::RunLoop runLoop;
-    HeadlessBackend backend(test::sharedDisplay());
+    HeadlessBackend backend;
     BackendScope scope(backend);
     OffscreenView view(backend.getContext(), { 512, 512 });
     ThreadPool threadPool(4);

test/src/mbgl/test/util.cpp

@@ -2,7 +2,6 @@
 
 #include <mbgl/map/map.hpp>
 #include <mbgl/gl/offscreen_view.hpp>
-#include <mbgl/gl/headless_display.hpp>
 #include <mbgl/util/logging.hpp>
 #include <mbgl/util/image.hpp>
 #include <mbgl/util/io.hpp>
@@ -99,11 +98,6 @@ Server::~Server() {
     }
 }
 
-std::shared_ptr<HeadlessDisplay> sharedDisplay() {
-    static auto display = std::make_shared<HeadlessDisplay>();
-    return display;
-}
-
 PremultipliedImage render(Map& map, OffscreenView& view) {
     PremultipliedImage result;
     map.renderStill([&](std::exception_ptr) {

test/src/mbgl/test/util.hpp

@@ -70,8 +70,6 @@ private:
     int fd = -1;
 };
 
-std::shared_ptr<HeadlessDisplay> sharedDisplay();
-
 PremultipliedImage render(Map&, OffscreenView&);
 
 void checkImage(const std::string& base,

test/tile/annotation_tile.test.cpp

@@ -29,7 +29,7 @@ public:
     ThreadPool threadPool { 1 };
     style::Style style { loop, fileSource, 1 };
     AnnotationManager annotationManager { style };
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     RenderStyle renderStyle { threadPool, fileSource };
     ImageManager imageManager;

test/util/memory.test.cpp

@@ -38,7 +38,7 @@ public:
     }
 
     util::RunLoop runLoop;
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view { backend.getContext(), { 512, 512 } };
     StubFileSource fileSource;

test/util/offscreen_texture.test.cpp

@@ -11,7 +11,7 @@
 using namespace mbgl;
 
 TEST(OffscreenTexture, EmptyRed) {
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     OffscreenView view(backend.getContext(), { 512, 256 });
 
@@ -74,7 +74,7 @@ struct Buffer {
 
 
 TEST(OffscreenTexture, RenderToTexture) {
-    HeadlessBackend backend { test::sharedDisplay() };
+    HeadlessBackend backend;
     BackendScope scope { backend };
     auto& context = backend.getContext();