[core] add continuous rendering test that terminates once it settles down

This is to test that continuous mode stops rerendering once no further changes are needed, i.e. to test the absence of "busy rendering".

1 files changed, 59 insertions, 0 deletions

diff --git a/test/map/map.test.cpp b/test/map/map.test.cpp
index a62bd10b57..71267e9a60 100644
--- a/test/map/map.test.cpp
+++ b/test/map/map.test.cpp
@@ -13,6 +13,7 @@
 #include <mbgl/util/image.hpp>
 #include <mbgl/util/io.hpp>
 #include <mbgl/util/run_loop.hpp>
+#include <mbgl/util/async_task.hpp>
 #include <mbgl/style/layers/background_layer.hpp>
 #include <mbgl/util/color.hpp>
 
@@ -442,3 +443,61 @@ TEST(Map, DontLoadUnneededTiles) {
         EXPECT_EQ(referenceTiles[z], tiles) << "zoom level " << z;
     }
 }
+
+
+class MockBackend : public HeadlessBackend {
+public:
+    std::function<void()> callback;
+    void invalidate() override {
+        if (callback) {
+            callback();
+        }
+    }
+};
+
+TEST(Map, ContinuousRendering) {
+    util::RunLoop runLoop;
+    MockBackend backend;
+    OffscreenView view { backend.getContext() };
+    ThreadPool threadPool { 4 };
+
+#ifdef MBGL_ASSET_ZIP
+    // Regenerate with `cd test/fixtures/api/ && zip -r assets.zip assets/`
+    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets.zip");
+#else
+    DefaultFileSource fileSource(":memory:", "test/fixtures/api/assets");
+#endif
+
+    Map map(backend, view.size, 1, fileSource, threadPool, MapMode::Continuous);
+
+    using namespace std::chrono_literals;
+
+    util::Timer emergencyShutoff;
+    emergencyShutoff.start(10s, 0s, [&] {
+        util::RunLoop::Get()->stop();
+        FAIL() << "Did not stop rendering";
+    });
+
+    util::Timer timer;
+    util::AsyncTask render{[&] {
+        if (map.isFullyLoaded()) {
+            // Abort the test after 1 second after the map loading fully. Note that a "fully loaded
+            // map" doesn't mean that we won't render anymore: we could still render fade in/fade
+            // out or other animations.
+            // If we are continuing to render indefinitely, the emergency shutoff above will trigger
+            // and the test will fail since the regular time will be constantly reset.
+            timer.start(1s, 0s, [&] {
+                util::RunLoop::Get()->stop();
+            });
+        }
+
+        map.render(view);
+    }};
+
+    backend.callback = [&] {
+        render.send();
+    };
+
+    map.setStyleJSON(util::read_file("test/fixtures/api/water.json"));
+    util::RunLoop::Get()->run();
+}