[core] Make the BackgroundScheduler a singleton

- Do not carry it over everywhere as parameter, it is a shared
  instance anyway and the lifecycle is pretty much the app lifecycle
  from the moment we instantiate a map.
- Rename to BackgroundScheduler because it is a Scheduler that will
  do tasks in the background, we don't make assumptions if it is a
  thread pool or a single thread.
- Most importantly, remove the dependency from `core` on `platform`.

6 files changed, 4 insertions, 17 deletions

diff --git a/platform/qt/qt.cmake b/platform/qt/qt.cmake
index 911af25bc4..fb572b807b 100644
--- a/platform/qt/qt.cmake
+++ b/platform/qt/qt.cmake
@@ -17,12 +17,6 @@ set(MBGL_QT_CORE_FILES
     PRIVATE platform/default/include/mbgl/gl/headless_backend.hpp
     PRIVATE platform/qt/src/headless_backend_qt.cpp
 
-    # Thread pool
-    PRIVATE platform/default/src/mbgl/util/shared_thread_pool.cpp
-    PRIVATE platform/default/include/mbgl/util/shared_thread_pool.hpp
-    PRIVATE platform/default/src/mbgl/util/default_thread_pool.cpp
-    PRIVATE platform/default/include/mbgl/util/default_thread_pool.hpp
-
     # Thread
     PRIVATE platform/qt/src/thread_local.cpp
 
diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index e54733aba7..329bf23085 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -43,7 +43,6 @@
 #include <mbgl/util/projection.hpp>
 #include <mbgl/util/rapidjson.hpp>
 #include <mbgl/util/run_loop.hpp>
-#include <mbgl/util/shared_thread_pool.hpp>
 #include <mbgl/util/traits.hpp>
 #include <mbgl/actor/scheduler.hpp>
 
@@ -1724,7 +1723,6 @@ mbgl::ResourceOptions resourceOptionsFromQMapboxGLSettings(const QMapboxGLSettin
 
 QMapboxGLPrivate::QMapboxGLPrivate(QMapboxGL *q, const QMapboxGLSettings &settings, const QSize &size, qreal pixelRatio_)
     : QObject(q)
-    , m_threadPool(mbgl::sharedThreadPool())
     , m_mode(settings.contextMode())
     , m_pixelRatio(pixelRatio_)
     , m_localFontFamily(settings.localFontFamily())
@@ -1741,7 +1739,7 @@ QMapboxGLPrivate::QMapboxGLPrivate(QMapboxGL *q, const QMapboxGLSettings &settin
     auto resourceOptions = resourceOptionsFromQMapboxGLSettings(settings);
 
     // Setup the Map object.
-    mapObj = std::make_unique<mbgl::Map>(*this, *m_mapObserver, *m_threadPool,
+    mapObj = std::make_unique<mbgl::Map>(*this, *m_mapObserver,
                                          mapOptionsFromQMapboxGLSettings(settings, size, m_pixelRatio),
                                          resourceOptions);
 
@@ -1799,7 +1797,6 @@ void QMapboxGLPrivate::createRenderer()
 
     m_mapRenderer = std::make_unique<QMapboxGLMapRenderer>(
         m_pixelRatio,
-        *m_threadPool,
         m_mode,
         m_localFontFamily
     );
diff --git a/platform/qt/src/qmapboxgl_map_renderer.cpp b/platform/qt/src/qmapboxgl_map_renderer.cpp
index d72b5d0f2c..eba50af6bf 100644
--- a/platform/qt/src/qmapboxgl_map_renderer.cpp
+++ b/platform/qt/src/qmapboxgl_map_renderer.cpp
@@ -26,9 +26,9 @@ static auto *getScheduler() {
     return scheduler.localData().get();
 };
 
-QMapboxGLMapRenderer::QMapboxGLMapRenderer(qreal pixelRatio, mbgl::ThreadPool &tp, QMapboxGLSettings::GLContextMode mode, const QString &localFontFamily)
+QMapboxGLMapRenderer::QMapboxGLMapRenderer(qreal pixelRatio, QMapboxGLSettings::GLContextMode mode, const QString &localFontFamily)
     : m_backend(static_cast<mbgl::gfx::ContextMode>(mode)),
-      m_renderer(std::make_unique<mbgl::Renderer>(m_backend, pixelRatio, tp, mbgl::optional<std::string> {},
+      m_renderer(std::make_unique<mbgl::Renderer>(m_backend, pixelRatio, mbgl::optional<std::string> {},
                  localFontFamily.isEmpty() ? mbgl::nullopt : mbgl::optional<std::string> { localFontFamily.toStdString() }))
     , m_forceScheduler(needsToForceScheduler())
 {
diff --git a/platform/qt/src/qmapboxgl_map_renderer.hpp b/platform/qt/src/qmapboxgl_map_renderer.hpp
index 7db0da99fa..2769b2b874 100644
--- a/platform/qt/src/qmapboxgl_map_renderer.hpp
+++ b/platform/qt/src/qmapboxgl_map_renderer.hpp
@@ -5,7 +5,6 @@
 
 #include <mbgl/renderer/renderer.hpp>
 #include <mbgl/renderer/renderer_observer.hpp>
-#include <mbgl/util/shared_thread_pool.hpp>
 #include <mbgl/util/util.hpp>
 
 #include <QtGlobal>
@@ -25,7 +24,7 @@ class QMapboxGLMapRenderer : public QObject
     Q_OBJECT
 
 public:
-    QMapboxGLMapRenderer(qreal pixelRatio, mbgl::ThreadPool &, QMapboxGLSettings::GLContextMode, const QString &localFontFamily);
+    QMapboxGLMapRenderer(qreal pixelRatio, QMapboxGLSettings::GLContextMode, const QString &localFontFamily);
     virtual ~QMapboxGLMapRenderer();
 
     void render();
diff --git a/platform/qt/src/qmapboxgl_p.hpp b/platform/qt/src/qmapboxgl_p.hpp
index 6a5b5ce04f..7f7040d7ac 100644
--- a/platform/qt/src/qmapboxgl_p.hpp
+++ b/platform/qt/src/qmapboxgl_p.hpp
@@ -8,7 +8,6 @@
 #include <mbgl/map/map.hpp>
 #include <mbgl/renderer/renderer_frontend.hpp>
 #include <mbgl/storage/resource_transform.hpp>
-#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/util/geo.hpp>
 
 #include <QObject>
@@ -56,7 +55,6 @@ private:
     std::shared_ptr<mbgl::UpdateParameters> m_updateParameters;
 
     std::unique_ptr<QMapboxGLMapObserver> m_mapObserver;
-    std::shared_ptr<mbgl::ThreadPool> m_threadPool;
     std::unique_ptr<QMapboxGLMapRenderer> m_mapRenderer;
     std::unique_ptr<mbgl::Actor<mbgl::ResourceTransform>> m_resourceTransform;
 
diff --git a/platform/qt/src/qmapboxgl_renderer_backend.hpp b/platform/qt/src/qmapboxgl_renderer_backend.hpp
index aba8003323..f821eda969 100644
--- a/platform/qt/src/qmapboxgl_renderer_backend.hpp
+++ b/platform/qt/src/qmapboxgl_renderer_backend.hpp
@@ -4,7 +4,6 @@
 
 #include <mbgl/gfx/renderable.hpp>
 #include <mbgl/gl/renderer_backend.hpp>
-#include <mbgl/util/shared_thread_pool.hpp>
 
 class QMapboxGLRendererBackend final : public mbgl::gl::RendererBackend,
                                        public mbgl::gfx::Renderable {