[core] do not render layers that are outside their zoom range

So far, we didn't properly disable layers that are outside the zoom range. This means that we rendered layers that should not have been rendered, albeit we didn't make any attempt to load tiles for those layers. However, when zooming in/out, existing tiles might already have been loaded in the source which continued to be rendered. In most cases they weren't actually visible because either the matrices weren't updated, or the clip IDs weren't set so that they would be "rendered" off-screen and clipped completely. In any case, we did way too much work.

4 files changed, 61 insertions, 0 deletions

diff --git a/test/fixtures/map/disabled_layers/first/expected.png b/test/fixtures/map/disabled_layers/first/expected.png
new file mode 100644
index 0000000000..388180c6d1
--- /dev/null
+++ b/test/fixtures/map/disabled_layers/first/expected.png
diff --git a/test/fixtures/map/disabled_layers/second/expected.png b/test/fixtures/map/disabled_layers/second/expected.png
new file mode 100644
index 0000000000..089ac0dde9
--- /dev/null
+++ b/test/fixtures/map/disabled_layers/second/expected.png
diff --git a/test/fixtures/map/disabled_layers/tile.png b/test/fixtures/map/disabled_layers/tile.png
new file mode 100644
index 0000000000..089ac0dde9
--- /dev/null
+++ b/test/fixtures/map/disabled_layers/tile.png
diff --git a/test/map/map.cpp b/test/map/map.cpp
index 6ecbc52e5f..0437296350 100644
--- a/test/map/map.cpp
+++ b/test/map/map.cpp
@@ -249,6 +249,67 @@ TEST(Map, RemoveLayer) {
     test::checkImage("test/fixtures/map/remove_layer", test::render(map));
 }
 
+TEST(Map, DisabledSources) {
+    MapTest test;
+
+    // Always load the same image tile for raster layers.
+    test.fileSource.response = [] (const Resource& res) -> optional<Response> {
+        if (res.url == "asset://tile.png") {
+            Response response;
+            response.data = std::make_shared<std::string>(
+                util::read_file("test/fixtures/map/disabled_layers/tile.png"));
+            return {std::move(response)};
+        }
+        return {};
+    };
+
+    Map map(test.view, test.fileSource, MapMode::Still);
+    map.setZoom(1);
+
+    // This stylesheet has two raster layers, one that starts at zoom 1, the other at zoom 0.
+    // We first render a map at zoom level 1, which should show both layers (both are "visible" due
+    // to an opacity of 0.5). Then, we are zooming back out to a zoom level of 0.5 and rerender.
+    // The "raster1" layer should not be visible anymore since it has minzoom 1, while "raster2"
+    // should still be there. Both layers have a distinct color through "raster-hue-rotate".
+    map.setStyleJSON(R"STYLE(
+{
+  "version": 8,
+  "name": "Test",
+  "sources": {
+    "raster": {
+      "type": "raster",
+      "tiles": [ "asset://tile.png" ],
+      "tileSize": 256
+    }
+  },
+  "layers": [{
+    "id": "background",
+    "type": "background",
+    "paint": {
+      "background-color": "white"
+    }
+  }, {
+    "id": "raster1",
+    "type": "raster",
+    "source": "raster",
+    "minzoom": 0
+  }, {
+    "id": "raster2",
+    "type": "raster",
+    "source": "raster",
+    "minzoom": 1,
+    "paint": {
+      "raster-hue-rotate": 180
+    }
+  }]
+}
+)STYLE");
+
+    test::checkImage("test/fixtures/map/disabled_layers/first", test::render(map));
+    map.setZoom(0.5);
+    test::checkImage("test/fixtures/map/disabled_layers/second", test::render(map));
+}
+
 TEST(Map, Classes) {
     MapTest test;