[qt] Render asynchronously

platform/qt/src/qmapboxgl_map_renderer.cpp

@@ -0,0 +1,43 @@
+#include "qmapboxgl_map_renderer.hpp"
+
+#include <QtGlobal>
+
+QMapboxGLMapRenderer::QMapboxGLMapRenderer(qreal pixelRatio,
+        mbgl::DefaultFileSource &fs, mbgl::ThreadPool &tp, QMapboxGLSettings::GLContextMode mode)
+    : m_renderer(std::make_unique<mbgl::Renderer>(m_backend, pixelRatio, fs, tp, static_cast<mbgl::GLContextMode>(mode)))
+{
+}
+
+QMapboxGLMapRenderer::~QMapboxGLMapRenderer()
+{
+}
+
+void QMapboxGLMapRenderer::updateParameters(std::shared_ptr<mbgl::UpdateParameters> newParameters)
+{
+    std::lock_guard<std::mutex> lock(m_updateMutex);
+    m_updateParameters = std::move(newParameters);
+}
+
+void QMapboxGLMapRenderer::updateFramebufferSize(const mbgl::Size &size)
+{
+    std::lock_guard<std::mutex> lock(m_updateMutex);
+    m_backend.setFramebufferSize(size);
+}
+
+void QMapboxGLMapRenderer::render()
+{
+    std::shared_ptr<mbgl::UpdateParameters> params;
+    {
+        // Lock on the parameters
+        std::unique_lock<std::mutex> lock(m_updateMutex);
+        if (!m_updateParameters) return;
+
+        // Hold on to the update parameters during render
+        params = m_updateParameters;
+    }
+
+    // The OpenGL implementation automatically enables the OpenGL context for us.
+    mbgl::BackendScope scope(m_backend, mbgl::BackendScope::ScopeType::Implicit);
+
+    m_renderer->render(*params);
+}