[core] Introduce Renderer::clearData() instead of keepRenderData map options

`Renderer::clearData()` is a better API than the removed `MapOptions::keepRenderData()`:
- gives more flexibility to the client
- similar to the existing `Renderer::reduceMemoryUse()`
- the `MapOptions::keepRenderData()` API implementation could not handle the raise condition, which
happened if the new still image request had come before all tiles from the previous requests were loaded.

Co-authored-by: Dane Springmeyer <dane@mapbox.com>

include/mbgl/map/map_options.hpp

@@ -88,28 +88,6 @@ public:
      */
     bool crossSourceCollisions() const;
 
-    /**
-     * @brief Specify whether render data for layers, sources and images should be kept between renderStill() calls.
-     *
-     * This flag is ignored in Continuous mode. In Static mode and Tile mode, if this flag is set to false, all the data
-     * are created from scratch for every renderStill() call, which guaranties that no extra memory is used, however it
-     * might cause higher CPU load and network traffic.
-     *
-     * By default, it is set to true.
-     *
-     * @param keepRenderData true to enable, false to disable
-     * @return MapOptions for chaining options together.
-     */
-    MapOptions& withKeepRenderData(bool keepRenderData);
-
-    /**
-     * @brief Gets the previously set (or default) keepRenderData value.
-     *
-     * @return true if render data is kept between renderStill() calls,
-     * false otherwise.
-     */
-    bool keepRenderData() const;
-
     /**
      * @brief Sets the orientation of the Map. By default, it is set to
      * Upwards.

include/mbgl/renderer/renderer.hpp

@@ -63,6 +63,7 @@ public:
 
     // Memory
     void reduceMemoryUse();
+    void clearData();
 
 private:
     class Impl;

render-test/runner.cpp

@@ -641,6 +641,7 @@ TestOperations getAfterOperations(const Manifest& manifest) {
 }
 
 void resetContext(const TestMetadata& metadata, TestContext& ctx) {
+    ctx.getFrontend().getRenderer()->clearData();
     ctx.getFrontend().setSize(metadata.size);
     auto& map = ctx.getMap();
     map.setSize(metadata.size);
@@ -683,8 +684,7 @@ TestRunner::Impl::Impl(const TestMetadata& metadata, const mbgl::ResourceOptions
               .withMapMode(metadata.mapMode)
               .withSize(metadata.size)
               .withPixelRatio(metadata.pixelRatio)
-              .withCrossSourceCollisions(metadata.crossSourceCollisions)
-              .withKeepRenderData(metadata.mapMode != MapMode::Tile),
+              .withCrossSourceCollisions(metadata.crossSourceCollisions),
           resourceOptions) {}
 
 TestRunner::Impl::~Impl() {}

src/mbgl/map/map_impl.cpp

@@ -17,7 +17,6 @@ Map::Impl::Impl(RendererFrontend& frontend_,
       mode(mapOptions.mapMode()),
       pixelRatio(mapOptions.pixelRatio()),
       crossSourceCollisions(mapOptions.crossSourceCollisions()),
-      keepRenderData(mapOptions.keepRenderData()),
       fileSource(std::move(fileSource_)),
       style(std::make_unique<style::Style>(fileSource, pixelRatio)),
       annotationManager(*style) {
@@ -65,9 +64,8 @@ void Map::Impl::onUpdate() {
                                annotationManager.makeWeakPtr(),
                                fileSource,
                                prefetchZoomDelta,
-                               stillImageRequest.get(),
-                               crossSourceCollisions,
-                               keepRenderData};
+                               bool(stillImageRequest),
+                               crossSourceCollisions};
 
     rendererFrontend.update(std::make_shared<UpdateParameters>(std::move(params)));
 }

src/mbgl/map/map_impl.hpp

@@ -59,7 +59,6 @@ public:
     const MapMode mode;
     const float pixelRatio;
     const bool crossSourceCollisions;
-    const bool keepRenderData;
 
     MapDebugOptions debugOptions { MapDebugOptions::NoDebug };
 

src/mbgl/map/map_options.cpp

@@ -9,7 +9,6 @@ public:
     ViewportMode viewportMode = ViewportMode::Default;
     NorthOrientation orientation = NorthOrientation::Upwards;
     bool crossSourceCollisions = true;
-    bool keepRenderData = true;
     Size size = { 64, 64 };
     float pixelRatio = 1.0;
 };
@@ -55,15 +54,6 @@ bool MapOptions::crossSourceCollisions() const {
     return impl_->crossSourceCollisions;
 }
 
-MapOptions& MapOptions::withKeepRenderData(bool keepRenderData_) {
-    impl_->keepRenderData = keepRenderData_;
-    return *this;
-}
-
-bool MapOptions::keepRenderData() const {
-    return impl_->keepRenderData;
-}
-
 MapOptions& MapOptions::withNorthOrientation(NorthOrientation orientation) {
     impl_->orientation = orientation;
     return *this;

src/mbgl/renderer/render_orchestrator.cpp

@@ -141,10 +141,6 @@ std::unique_ptr<RenderTree> RenderOrchestrator::createRenderTree(
     if (!isMapModeContinuous) {
         // Reset zoom history state.
         zoomHistory.first = true;
-        if (!updateParameters->keepRenderData && stillImageRequest != updateParameters->stillImageRequest) {
-            clearData();
-            stillImageRequest = updateParameters->stillImageRequest;
-        }
     }
 
     if (LayerManager::annotationsEnabled) {

src/mbgl/renderer/render_orchestrator.hpp

@@ -75,11 +75,11 @@ public:
 
     void reduceMemoryUse();
     void dumpDebugLogs();
+    void clearData();
 
 private:
     bool isLoaded() const;
     bool hasTransitions(TimePoint) const;
-    void clearData();
 
     RenderSource* getRenderSource(const std::string& id) const;
 
@@ -127,7 +127,6 @@ private:
 
     const bool backgroundLayerAsColor;
     bool contextLost = false;
-    const void* stillImageRequest = nullptr;
 
     // Vectors with reserved capacity of layerImpls->size() to avoid reallocation
     // on each frame.

src/mbgl/renderer/renderer.cpp

@@ -131,4 +131,8 @@ void Renderer::reduceMemoryUse() {
     impl->orchestrator.reduceMemoryUse();
 }
 
+void Renderer::clearData() {
+    impl->orchestrator.clearData();
+}
+
 } // namespace mbgl

src/mbgl/renderer/update_parameters.hpp

@@ -41,12 +41,9 @@ public:
     const uint8_t prefetchZoomDelta;
     
     // For still image requests, render requested
-    const void* stillImageRequest;
+    const bool stillImageRequest;
 
     const bool crossSourceCollisions;
-
-    // If set, the render data from the previous render calls is kept.
-    const bool keepRenderData;
 };
 
 } // namespace mbgl

test/map/map.test.cpp

@@ -10,6 +10,7 @@
 #include <mbgl/gl/context.hpp>
 #include <mbgl/map/map_options.hpp>
 #include <mbgl/math/log2.hpp>
+#include <mbgl/renderer/renderer.hpp>
 #include <mbgl/renderer/update_parameters.hpp>
 #include <mbgl/storage/file_source_manager.hpp>
 #include <mbgl/storage/main_resource_loader.hpp>
@@ -1362,7 +1363,7 @@ constexpr auto styleJSON = R"STYLE({
 }
 
 TEST(Map, KeepRenderData) {
-    MapTest<> test{std::move(MapOptions().withMapMode(MapMode::Static).withKeepRenderData(true))};
+    MapTest<> test;
     int requestsCount = 0;
     test.fileSource->tileResponse = [&](const Resource&) {
         ++requestsCount;
@@ -1371,30 +1372,19 @@ TEST(Map, KeepRenderData) {
         return res;
     };
     test.map.jumpTo(CameraOptions().withZoom(10));
-    test.map.getStyle().loadJSON(styleJSON);
-    test.frontend.render(test.map);
-    EXPECT_EQ(4, requestsCount);
-
-    test.map.getStyle().loadJSON(styleJSON);
-    test.frontend.render(test.map);
-    EXPECT_EQ(4, requestsCount);
-}
-
-TEST(Map, DontKeepRenderData) {
-    MapTest<> test{std::move(MapOptions().withMapMode(MapMode::Static).withKeepRenderData(false))};
-    int requestsCount = 0;
-    test.fileSource->tileResponse = [&](const Resource&) {
-        ++requestsCount;
-        Response res;
-        res.noContent = true;
-        return res;
-    };
-    test.map.jumpTo(CameraOptions().withZoom(10));
-    test.map.getStyle().loadJSON(styleJSON);
-    test.frontend.render(test.map);
-    EXPECT_EQ(4, requestsCount);
-
-    test.map.getStyle().loadJSON(styleJSON);
-    test.frontend.render(test.map);
-    EXPECT_EQ(8, requestsCount);
+    const int iterations = 3;
+    // Keep render data.
+    for (int i = 1; i <= iterations; ++i) {
+        test.map.getStyle().loadJSON(styleJSON);
+        test.frontend.render(test.map);
+        EXPECT_EQ(4, requestsCount);
+    }
+    requestsCount = 0;
+    // Clear render data.
+    for (int i = 1; i <= iterations; ++i) {
+        test.frontend.getRenderer()->clearData();
+        test.map.getStyle().loadJSON(styleJSON);
+        test.frontend.render(test.map);
+        EXPECT_EQ(4 * i, requestsCount);
+    }
 }