[core] use stale styles

This adds support for using cached styles that are stale. They're treated like changing styles; when the refreshed style changed compared to the one we've already had, we're swapping out the entire style, which might cause a slight flicker.

10 files changed, 105 insertions, 11 deletions

diff --git a/platform/linux/scripts/after_script.sh b/platform/linux/scripts/after_script.sh
index f8e4bc3486..b5397f1df2 100755
--- a/platform/linux/scripts/after_script.sh
+++ b/platform/linux/scripts/after_script.sh
@@ -10,6 +10,6 @@ if [ ! -z "${AWS_ACCESS_KEY_ID}" ] && [ ! -z "${AWS_SECRET_ACCESS_KEY}" ] ; then
 
     REPO_NAME=$(basename $TRAVIS_REPO_SLUG)
 
-    aws s3 cp --recursive --acl public-read test/fixtures/annotations \
-        s3://mapbox/$REPO_NAME/render-tests/$TRAVIS_JOB_NUMBER/annotations
+    aws s3 cp --recursive --acl public-read --exclude "*" --include "*/actual.png" test/fixtures \
+        s3://mapbox/$REPO_NAME/render-tests/$TRAVIS_JOB_NUMBER
 fi
diff --git a/src/mbgl/map/map_context.cpp b/src/mbgl/map/map_context.cpp
index 6f12e968bd..eb17e20aea 100644
--- a/src/mbgl/map/map_context.cpp
+++ b/src/mbgl/map/map_context.cpp
@@ -105,12 +105,6 @@ void MapContext::setStyleURL(const std::string& url) {
 
     FileSource* fs = util::ThreadContext::getFileSource();
     styleRequest = fs->request({ Resource::Kind::Style, styleURL }, [this, base](Response res) {
-        if (res.stale) {
-            // Only handle fresh responses.
-            return;
-        }
-        styleRequest = nullptr;
-
         if (res.error) {
             if (res.error->reason == Response::Error::Reason::NotFound &&
                 util::mapbox::isMapboxURL(styleURL)) {
@@ -120,9 +114,11 @@ void MapContext::setStyleURL(const std::string& url) {
                 data.loading = false;
             }
         } else {
-            loadStyleJSON(*res.data, base);
+            // We got a new stylesheet; only update when it's different from the previous one.
+            if (styleJSON != *res.data) {
+                loadStyleJSON(*res.data, base);
+            }
         }
-
     });
 }
 
@@ -132,7 +128,7 @@ void MapContext::setStyleJSON(const std::string& json, const std::string& base)
     }
 
     styleURL.clear();
-    styleJSON = json;
+    styleJSON.clear();
 
     style = std::make_unique<Style>(data);
 
@@ -144,6 +140,7 @@ void MapContext::loadStyleJSON(const std::string& json, const std::string& base)
 
     style->setJSON(json, base);
     style->setObserver(this);
+    styleJSON = json;
 
     // force style cascade, causing all pending transitions to complete.
     style->cascade();
diff --git a/src/mbgl/style/style.cpp b/src/mbgl/style/style.cpp
index fbca01311b..f64bdfc921 100644
--- a/src/mbgl/style/style.cpp
+++ b/src/mbgl/style/style.cpp
@@ -43,6 +43,9 @@ Style::Style(MapData& data_)
 }
 
 void Style::setJSON(const std::string& json, const std::string&) {
+    sources.clear();
+    layers.clear();
+
     rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> doc;
     doc.Parse<0>((const char *const)json.c_str());
     if (doc.HasParseError()) {
diff --git a/test/fixtures/stale/0-0-0.vector.pbf b/test/fixtures/stale/0-0-0.vector.pbf
new file mode 100644
index 0000000000..a0f049ad43
--- /dev/null
+++ b/test/fixtures/stale/0-0-0.vector.pbf
diff --git a/test/fixtures/stale/stale_style/expected.png b/test/fixtures/stale/stale_style/expected.png
new file mode 100644
index 0000000000..d3c6ef3cd5
--- /dev/null
+++ b/test/fixtures/stale/stale_style/expected.png
diff --git a/test/fixtures/stale/streets.json b/test/fixtures/stale/streets.json
new file mode 100644
index 0000000000..11cb5c8557
--- /dev/null
+++ b/test/fixtures/stale/streets.json
@@ -0,0 +1,14 @@
+{
+  "bounds": [ -180, -85.0511, 180, 85.0511 ],
+  "center": [ 0, 0, 0 ],
+  "description": "",
+  "format": "pbf",
+  "id": "streets",
+  "maskLevel": 8,
+  "maxzoom": 15,
+  "minzoom": 0,
+  "name": "Streets",
+  "scheme": "xyz",
+  "tilejson": "2.0.0",
+  "tiles": [ "asset://test/fixtures/stale/{z}-{x}-{y}.vector.pbf" ]
+}
diff --git a/test/fixtures/stale/style.json b/test/fixtures/stale/style.json
new file mode 100644
index 0000000000..ca86503d4f
--- /dev/null
+++ b/test/fixtures/stale/style.json
@@ -0,0 +1,25 @@
+{
+  "version": 8,
+  "name": "Water",
+  "sources": {
+    "mapbox": {
+      "type": "vector",
+      "url": "asset://test/fixtures/stale/streets.json"
+    }
+  },
+  "layers": [{
+    "id": "background",
+    "type": "background",
+    "paint": {
+      "background-color": "red"
+    }
+  }, {
+    "id": "water",
+    "type": "fill",
+    "source": "mapbox",
+    "source-layer": "water",
+    "paint": {
+      "fill-color": "blue"
+    }
+  }]
+}
diff --git a/test/storage/cache_stale.cpp b/test/storage/cache_stale.cpp
new file mode 100644
index 0000000000..cc421f7c34
--- /dev/null
+++ b/test/storage/cache_stale.cpp
@@ -0,0 +1,51 @@
+#include "storage.hpp"
+
+#include <mbgl/platform/default/headless_display.hpp>
+#include <mbgl/platform/default/headless_view.hpp>
+#include <mbgl/storage/sqlite_cache.hpp>
+#include <mbgl/storage/default_file_source.hpp>
+
+#include <mbgl/platform/log.hpp>
+#include <mbgl/util/work_request.hpp>
+#include <mbgl/util/io.hpp>
+
+using namespace mbgl;
+using namespace std::literals::chrono_literals;
+using namespace std::literals::string_literals;
+
+namespace {
+
+void checkRendering(Map& map, const char *name, std::chrono::milliseconds timeout) {
+    test::checkImage("test/fixtures/stale/"s + name, test::render(map, timeout), 0.001, 0.1);
+}
+
+Response expiredItem(const std::string& path) {
+    Response response;
+    response.data = std::make_shared<std::string>(util::read_file("test/fixtures/"s + path));
+    response.expires = 0s;
+    return response;
+}
+
+const std::string prefix = "http://127.0.0.1:3000";
+
+}
+
+auto display = std::make_shared<mbgl::HeadlessDisplay>();
+
+TEST_F(Storage, CacheStaleStyle) {
+    HeadlessView view(display, 1);
+
+    auto cache = SQLiteCache::getShared(":memory:");
+
+    // Rig the cache with an expired stylesheet.
+    const std::string stylePath = "stale/style.json";
+    const Resource styleResource{ Resource::Kind::Style, prefix + "/" + stylePath };
+    cache->put(styleResource, expiredItem(stylePath));
+
+    DefaultFileSource fileSource(":memory:", ".");
+
+    Map map(view, fileSource, MapMode::Still);
+    map.setStyleURL(styleResource.url);
+
+    checkRendering(map, "stale_style", 1000ms);
+}
diff --git a/test/storage/server.js b/test/storage/server.js
index 5d547b1506..0024330037 100755
--- a/test/storage/server.js
+++ b/test/storage/server.js
@@ -32,6 +32,9 @@ app.get('/test', function (req, res) {
     res.send('Hello World!');
 });
 
+app.get('/stale/*', function() {
+    // Never respond.
+});
 
 var cacheCounter = 0;
 app.get('/cache', function(req, res) {
diff --git a/test/test.gypi b/test/test.gypi
index 607dd2b76c..8b13db4c6b 100644
--- a/test/test.gypi
+++ b/test/test.gypi
@@ -72,6 +72,7 @@
         'storage/cache_revalidate.cpp',
         'storage/cache_shared.cpp',
         'storage/cache_size.cpp',
+        'storage/cache_stale.cpp',
         'storage/database.cpp',
         'storage/asset_file_source.cpp',
         'storage/headers.cpp',