[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.

4 files changed, 39 insertions, 0 deletions

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"
+    }
+  }]
+}