From 43837843ff1b53af1b7745870c8493f984a06be9 Mon Sep 17 00:00:00 2001
From: "Thiago Marcos P. Santos" <tmpsantos@gmail.com>
Date: Tue, 19 Mar 2019 15:55:06 +0200
Subject: [core] Expose a way of flushing the graphics pipeline

Useful for apps before going to background that are
restricted by the OS of performing any operation.
---
 include/mbgl/renderer/renderer.hpp  | 2 ++
 src/mbgl/gl/context.cpp             | 4 ++++
 src/mbgl/gl/context.hpp             | 5 +++++
 src/mbgl/renderer/renderer.cpp      | 4 ++++
 src/mbgl/renderer/renderer_impl.cpp | 6 ++++++
 src/mbgl/renderer/renderer_impl.hpp | 2 ++
 6 files changed, 23 insertions(+)

diff --git a/include/mbgl/renderer/renderer.hpp b/include/mbgl/renderer/renderer.hpp
index 1d92f9c0cb..0bed4cdaa8 100644
--- a/include/mbgl/renderer/renderer.hpp
+++ b/include/mbgl/renderer/renderer.hpp
@@ -34,6 +34,8 @@ public:
 
     void render(const UpdateParameters&);
 
+    void flush();
+
     // Feature queries
     std::vector<Feature> queryRenderedFeatures(const ScreenLineString&, const RenderedQueryOptions& options = {}) const;
     std::vector<Feature> queryRenderedFeatures(const ScreenCoordinate& point, const RenderedQueryOptions& options = {}) const;
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 5193381251..c5b9422351 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -775,5 +775,9 @@ void Context::performCleanup() {
     }
 }
 
+void Context::flush() {
+    MBGL_CHECK_ERROR(glFinish());
+}
+
 } // namespace gl
 } // namespace mbgl
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index fe09390cc6..d40f6e0bca 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -116,6 +116,11 @@ public:
     // Only call this while the OpenGL context is exclusive to this thread.
     void reset();
 
+    // Flush pending graphics commands. Will block until the pipeline
+    // is empty. Should be used only with a very good reason because
+    // it will have a performance impact.
+    void flush();
+
     bool empty() const {
         return pooledTextures.empty()
             && abandonedPrograms.empty()
diff --git a/src/mbgl/renderer/renderer.cpp b/src/mbgl/renderer/renderer.cpp
index fbd9049207..4da7b78374 100644
--- a/src/mbgl/renderer/renderer.cpp
+++ b/src/mbgl/renderer/renderer.cpp
@@ -34,6 +34,10 @@ void Renderer::render(const UpdateParameters& updateParameters) {
     impl->render(updateParameters);
 }
 
+void Renderer::flush() {
+    impl->flush();
+}
+
 std::vector<Feature> Renderer::queryRenderedFeatures(const ScreenLineString& geometry, const RenderedQueryOptions& options) const {
     return impl->queryRenderedFeatures(geometry, options);
 }
diff --git a/src/mbgl/renderer/renderer_impl.cpp b/src/mbgl/renderer/renderer_impl.cpp
index 471536cf40..987e241c4a 100644
--- a/src/mbgl/renderer/renderer_impl.cpp
+++ b/src/mbgl/renderer/renderer_impl.cpp
@@ -614,6 +614,12 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
     parameters.context.performCleanup();
 }
 
+void  Renderer::Impl::flush() {
+    assert(BackendScope::exists());
+
+    backend.getContext().flush();
+}
+
 std::vector<Feature> Renderer::Impl::queryRenderedFeatures(const ScreenLineString& geometry, const RenderedQueryOptions& options) const {
     std::vector<const RenderLayer*> layers;
     if (options.layerIDs) {
diff --git a/src/mbgl/renderer/renderer_impl.hpp b/src/mbgl/renderer/renderer_impl.hpp
index 05bf2e9b2b..a036bfc7ff 100644
--- a/src/mbgl/renderer/renderer_impl.hpp
+++ b/src/mbgl/renderer/renderer_impl.hpp
@@ -48,6 +48,8 @@ public:
 
     void render(const UpdateParameters&);
 
+    void flush();
+
     std::vector<Feature> queryRenderedFeatures(const ScreenLineString&, const RenderedQueryOptions&) const;
     std::vector<Feature> querySourceFeatures(const std::string& sourceID, const SourceQueryOptions&) const;
     std::vector<Feature> queryShapeAnnotations(const ScreenLineString&) const;
-- 
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