[core] make forcing cache/network only more explicit

Previously, we used the existence of a `prior*` field in the Resource object as an indication for whether we should consult the cache or not. However, this is prone to error, since a failed cache lookup won't set any prior fields. Therefore, we manually set `priorExpires` to 0. This in turn triggered another bug where generated wrong expiration timestamps when the server response we got was expired (or expired between sending and receiving).

This commit changes the flags so that we can now explicitly request CacheOnly/NetworkOnly (or All) loading methods, rather than the implicit Optional/Required naming scheme.

2 files changed, 116 insertions, 116 deletions

diff --git a/test/algorithm/mock.hpp b/test/algorithm/mock.hpp
index d87f55343b..b8eb020105 100644
--- a/test/algorithm/mock.hpp
+++ b/test/algorithm/mock.hpp
@@ -26,7 +26,7 @@ struct MockBucket {};
 struct MockTileData {
     MockTileData(const mbgl::OverscaledTileID& tileID_) : tileID(tileID_) {}
 
-    bool hasTriedOptional() const {
+    bool hasTriedCache() const {
         return triedOptional;
     }
 
diff --git a/test/algorithm/update_renderables.test.cpp b/test/algorithm/update_renderables.test.cpp
index 2d37992579..7d6a0fcb13 100644
--- a/test/algorithm/update_renderables.test.cpp
+++ b/test/algorithm/update_renderables.test.cpp
@@ -45,7 +45,7 @@ std::ostream& operator<<(std::ostream& os, const CreateTileDataAction& action) {
 
 struct RetainTileDataAction {
     const OverscaledTileID tileID;
-    const Resource::Necessity necessity;
+    const TileNecessity necessity;
 
     bool operator==(const RetainTileDataAction& rhs) const {
         return tileID == rhs.tileID && necessity == rhs.necessity;
@@ -56,7 +56,7 @@ std::ostream& operator<<(std::ostream& os, const RetainTileDataAction& action) {
     return os << "RetainTileDataAction{ { " << int(action.tileID.overscaledZ) << ", " << int(action.tileID.wrap) << ", { "
               << int(action.tileID.canonical.z) << ", " << action.tileID.canonical.x << ", "
               << action.tileID.canonical.y << " } }, "
-              << (action.necessity == Resource::Necessity::Required ? "Required" : "Optional") << " }\n";
+              << (action.necessity == TileNecessity::Required ? "Required" : "Optional") << " }\n";
 }
 
 struct RenderTileAction {
@@ -102,7 +102,7 @@ auto createTileDataFn(ActionLog& log, T& dataTiles) {
 
 template <typename = int>
 auto retainTileDataFn(ActionLog& log) {
-    return [&](auto& tileData, Resource::Necessity necessity) {
+    return [&](auto& tileData, TileNecessity necessity) {
         log.emplace_back(RetainTileDataAction{ tileData.tileID, necessity });
     };
 }
@@ -132,7 +132,7 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // found ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render ideal tile
               }),
               log);
@@ -143,7 +143,7 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // found ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render ideal tile
               }),
               log);
@@ -156,7 +156,7 @@ TEST(UpdateRenderables, SingleTile) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, NotFound },    // missing ideal tile
                   CreateTileDataAction{ { 1, 0, { 1, 0, 1 } } },           // create ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 2 } }, NotFound },    // four child tiles
                   GetTileDataAction{ { 2, 0, { 2, 0, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 2 } }, NotFound },    // ...
@@ -164,7 +164,7 @@ TEST(UpdateRenderables, SingleTile) {
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // parent tile
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // found ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render found tile
               }),
               log);
@@ -176,17 +176,17 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // missing ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 2 } }, NotFound },    // four child tiles
                   GetTileDataAction{ { 2, 0, { 2, 0, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 2 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // parent tile
                   CreateTileDataAction{ { 0, 0, { 0, 0, 0 } } },           // load parent tile
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // found ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render found tile
               }),
               log);
@@ -199,11 +199,11 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // newly added tile
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 1 }, *tile_1_1_0_1 },       // render ideal tile
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render found tile
               }),
               log);
@@ -218,21 +218,21 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // found tile, not ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // four child tiles
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   // optional parent tile was already created before, but is not renderable
 
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 1 }, *tile_1_1_0_1 },       // render ideal tile
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       // render ideal tile
               }),
               log);
@@ -244,15 +244,15 @@ TEST(UpdateRenderables, SingleTile) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // found tile, now ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 0 }, *tile_1_1_0_0 },       //
 
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 1 }, *tile_1_1_0_1 },       //
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, Found },       // ideal tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 1, 1 }, *tile_1_1_1_1 },       //
               }),
               log);
@@ -278,24 +278,24 @@ TEST(UpdateRenderables, UseParentTile) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, NotFound },    // missing ideal tile
                   CreateTileDataAction{ { 1, 0, { 1, 0, 1 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 2 } }, NotFound },    // child tile
                   GetTileDataAction{ { 2, 0, { 2, 0, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 2 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent found!
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       // render parent
                   GetTileDataAction{ { 1, 0, { 1, 1, 0 } }, NotFound },    // missing ideal tile
                   CreateTileDataAction{ { 1, 0, { 1, 1, 0 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 2, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 2, 0, { 2, 2, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 3, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 3, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, NotFound },    // missing tile
                   CreateTileDataAction{ { 1, 0, { 1, 1, 1 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 1 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 2, 2 } }, NotFound },    // child tile
                   GetTileDataAction{ { 2, 0, { 2, 2, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 3, 2 } }, NotFound },    // ...
@@ -321,7 +321,7 @@ TEST(UpdateRenderables, DontUseWrongParentTile) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // missing ideal tile
                   CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 3, 0, { 3, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 1, 0 } }, NotFound },    // ...
@@ -338,14 +338,14 @@ TEST(UpdateRenderables, DontUseWrongParentTile) {
                                  source.idealTiles, source.zoomRange, 2);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // non-ready ideal tile
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 3, 0, { 3, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // parent tile, missing
                   CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           // find optional parent
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // parent tile, missing
               }),
               log);
@@ -357,25 +357,25 @@ TEST(UpdateRenderables, DontUseWrongParentTile) {
                                  source.idealTiles, source.zoomRange, 2);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // non-ready ideal tile
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   // this tile was added by the previous invocation of updateRenderables
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 3, 0, { 3, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // parent tile not ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // missing parent tile
 
                   GetTileDataAction{ { 2, 0, { 2, 2, 0 } }, NotFound },    // missing ideal tile
                   CreateTileDataAction{ { 2, 0, { 2, 2, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 2, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 2, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 3, 4, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 3, 0, { 3, 4, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 5, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 5, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 1, 0 } }, Found },       // found parent tile
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 1, 1, 0 }, *tile_1_1_1_0 },       // render parent tile
               }),
               log);
@@ -402,13 +402,13 @@ TEST(UpdateRenderables, UseParentTileWhenChildNotReady) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // found, but not ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 2 } }, NotFound },    // child tile
                   GetTileDataAction{ { 2, 0, { 2, 0, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 2 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 3 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile, ready
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       // render parent tile
               }),
               log);
@@ -420,7 +420,7 @@ TEST(UpdateRenderables, UseParentTileWhenChildNotReady) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // found and ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 1 }, *tile_1_1_0_1 },       // render ideal tile
               }),
               log);
@@ -448,17 +448,17 @@ TEST(UpdateRenderables, UseOverlappingParentTile) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ideal tile not found
                   CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile found
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
 
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, Found },       // ideal tile found
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 1 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 1, 0, 1 }, *tile_1_1_0_1 },       //
               }),
               log);
@@ -484,13 +484,13 @@ TEST(UpdateRenderables, UseChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // ideal tile, missing
                   CreateTileDataAction{ { 0, 0, { 0, 0, 0 } } },           //
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // child tile found
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 1, 0, 0 }, *tile_1_1_0_0 },       // render child tile
                   GetTileDataAction{ { 1, 0, { 1, 0, 1 } }, NotFound },    // child tile not found
                   GetTileDataAction{ { 1, 0, { 1, 1, 0 } }, Found },       // child tile found
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 1, 1, 0 }, *tile_1_1_1_0 },       // render child tile
                   GetTileDataAction{ { 1, 0, { 1, 1, 1 } }, NotFound },    // child tile not found
                   // no parent tile of 0 to consider
@@ -518,15 +518,15 @@ TEST(UpdateRenderables, PreferChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ideal tile, not found
                   CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // child tile, found
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    // child tile, not found
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile, found
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
               }),
               log);
@@ -541,17 +541,17 @@ TEST(UpdateRenderables, PreferChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found }, // ideal tile, not ready
                   // ideal tile was added in previous invocation, but is not yet ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // child tile, found
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, Resource::Necessity::Optional }, // ...
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, TileNecessity::Optional }, // ...
                   RenderTileAction{ { 2, 0, 1 }, *tile_2_2_0_1 },       //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    // child tile, not found
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile, found
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
               }),
               log);
@@ -564,19 +564,19 @@ TEST(UpdateRenderables, PreferChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found }, // ideal tile, not ready
                   // ideal tile was added in first invocation, but is not yet ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // child tile, found
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 1 }, *tile_2_2_0_1 },       //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 1, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 1, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 1, 0 }, *tile_2_2_1_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    // child tile, not found
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile, found
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
               }),
               log);
@@ -590,18 +590,18 @@ TEST(UpdateRenderables, PreferChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found }, // ideal tile, not ready
                   // ideal tile was added in first invocation, but is not yet ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // child tile, found
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 1 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 1 }, *tile_2_2_0_1 },       //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 1, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 1, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 1, 0 }, *tile_2_2_1_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, Found },       // ...
-                  RetainTileDataAction{ { 2, 0, { 2, 1, 1 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 1, 1 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 1, 1 }, *tile_2_2_1_1 },       //
               }),
               log);
@@ -628,15 +628,15 @@ TEST(UpdateRenderables, UseParentAndChildTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ideal tile, missing
                   CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // child tile
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
               }),
               log);
@@ -648,13 +648,13 @@ TEST(UpdateRenderables, UseParentAndChildTiles) {
                                  source.idealTiles, source.zoomRange, 1);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       // parent tile
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
               }),
               log);
@@ -679,7 +679,7 @@ TEST(UpdateRenderables, DontUseTilesLowerThanMinzoom) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ideal tile, missing
                   CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 3, 0, { 3, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 3, 0, { 3, 1, 0 } }, NotFound },    //
@@ -709,7 +709,7 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
         ActionLog({
             GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ideal tile, missing
             CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-            RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+            RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
             GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, NotFound },    // overzoomed tile, not children!
             GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    //
             GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    //
@@ -724,11 +724,11 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
     EXPECT_EQ(
         ActionLog({
             GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // ideal tile, missing
-            RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+            RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
             GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, NotFound },    // overzoomed tile, not children!
             GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    //
             CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           //
-            RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+            RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
             GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    //
         }),
         log);
@@ -742,10 +742,10 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, NotFound },    // ideal tile, missing
                   CreateTileDataAction{ { 3, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 4, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
               }),
               log);
@@ -758,7 +758,7 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
                                  source.idealTiles, source.zoomRange, 3);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_3_2_0_0 },       //
               }),
               log);
@@ -769,7 +769,7 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
                                  source.idealTiles, source.zoomRange, 2);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
               }),
               log);
@@ -785,9 +785,9 @@ TEST(UpdateRenderables, UseOverzoomedTileAfterMaxzoom) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    //
                   CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, Found },       // use overzoomed tile!
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_3_2_0_0 },       //
               }),
               log);
@@ -811,7 +811,7 @@ TEST(UpdateRenderables, AscendToNonOverzoomedTiles) {
                                  source.idealTiles, source.zoomRange, 3);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_3_2_0_0 },       //
               }),
               log);
@@ -827,10 +827,10 @@ TEST(UpdateRenderables, AscendToNonOverzoomedTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, NotFound },    //
                   CreateTileDataAction{ { 3, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 4, 0, { 2, 0, 0 } }, NotFound }, // prefer using a child first
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },    //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 2, 0, 0 }, *tile_2_2_0_0 },       //
               }),
               log);
@@ -845,11 +845,11 @@ TEST(UpdateRenderables, AscendToNonOverzoomedTiles) {
                                  source.idealTiles, source.zoomRange, 3);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 4, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 1, 0, 0 }, *tile_1_1_0_0 },       //
               }),
               log);
@@ -861,13 +861,13 @@ TEST(UpdateRenderables, AscendToNonOverzoomedTiles) {
                                  source.idealTiles, source.zoomRange, 3);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 3, 0, { 2, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 3, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 4, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    //
                   CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 1, 0, 0 }, *tile_1_1_0_0 },       //
               }),
               log);
@@ -889,7 +889,7 @@ TEST(UpdateRenderables, DoNotAscendMultipleTimesIfNotFound) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 8, 0, { 8, 0, 0 } }, NotFound },    // ideal tile
                   CreateTileDataAction{ { 8, 0, { 8, 0, 0 } } },           //
-                  RetainTileDataAction{ { 8, 0, { 8, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 8, 0, { 8, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 9, 0, { 9, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 9, 0, { 9, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 9, 0, { 9, 1, 0 } }, NotFound },    // ...
@@ -905,7 +905,7 @@ TEST(UpdateRenderables, DoNotAscendMultipleTimesIfNotFound) {
 
                   GetTileDataAction{ { 8, 0, { 8, 1, 0 } }, NotFound },    // ideal tile
                   CreateTileDataAction{ { 8, 0, { 8, 1, 0 } } },           //
-                  RetainTileDataAction{ { 8, 0, { 8, 1, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 8, 0, { 8, 1, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 9, 0, { 9, 2, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 9, 0, { 9, 2, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 9, 0, { 9, 3, 0 } }, NotFound },    // ...
@@ -923,7 +923,7 @@ TEST(UpdateRenderables, DoNotAscendMultipleTimesIfNotFound) {
                                  source.idealTiles, source.zoomRange, 8);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 8, 0, { 8, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 8, 0, { 8, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 8, 0, { 8, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 9, 0, { 9, 0, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 9, 0, { 9, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 9, 0, { 9, 1, 0 } }, NotFound },    // ...
@@ -932,11 +932,11 @@ TEST(UpdateRenderables, DoNotAscendMultipleTimesIfNotFound) {
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, Found },       // stops ascent
-                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 4, 0, 0 }, *tile_4_0_0_0 },       //
 
                   GetTileDataAction{ { 8, 0, { 8, 1, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 8, 0, { 8, 1, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 8, 0, { 8, 1, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 9, 0, { 9, 2, 0 } }, NotFound },    // child tile
                   GetTileDataAction{ { 9, 0, { 9, 2, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 9, 0, { 9, 3, 0 } }, NotFound },    // ...
@@ -963,13 +963,13 @@ TEST(UpdateRenderables, DontRetainUnusedNonIdealTiles) {
                                  source.idealTiles, source.zoomRange, 2);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 3, 0, { 3, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 3, 0, { 3, 1, 0 } }, NotFound },    //
                   GetTileDataAction{ { 3, 0, { 3, 1, 1 } }, NotFound },    //
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, Found },       // parent tile, not ready
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    //
               }),
               log);
@@ -996,7 +996,7 @@ TEST(UpdateRenderables, WrappedTiles) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 1, -1, { 1, 1, 0 } }, NotFound },    // ideal tile 1/-1/0 (wrapped to -1)
                   CreateTileDataAction{ { 1, -1, { 1, 1, 0 } } },           //
-                  RetainTileDataAction{ { 1, -1, { 1, 1, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, -1, { 1, 1, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, -1, { 2, 2, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, -1, { 2, 2, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, -1, { 2, 3, 0 } }, NotFound },    //
@@ -1005,18 +1005,18 @@ TEST(UpdateRenderables, WrappedTiles) {
 
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ideal tile 1/0/0
                   CreateTileDataAction{ { 1, 0, { 1, 0, 0 } } },           //
-                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 1, 1 } }, NotFound },    //
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, Found },       //
-                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 0, 0, { 0, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 0, 0, 0 }, *tile_0_0_0_0 },       //
 
                   GetTileDataAction{ { 1, 0, { 1, 1, 0 } }, NotFound },       // ideal tile 1/1/0, doesn't match 1/-/1/0
                   CreateTileDataAction{ { 1, 0, { 1, 1, 0 } } },
-                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 0, { 1, 1, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 0, { 2, 2, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 2, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, 0, { 2, 3, 0 } }, NotFound },    //
@@ -1025,7 +1025,7 @@ TEST(UpdateRenderables, WrappedTiles) {
 
                   GetTileDataAction{ { 1, 1, { 1, 0, 0 } }, NotFound },       // ideal tile 1/2/0 (wrapped to 1)
                   CreateTileDataAction{ { 1, 1, { 1, 0, 0 } } },
-                  RetainTileDataAction{ { 1, 1, { 1, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 1, 1, { 1, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 2, 1, { 2, 0, 0 } }, NotFound },    //
                   GetTileDataAction{ { 2, 1, { 2, 0, 1 } }, NotFound },    //
                   GetTileDataAction{ { 2, 1, { 2, 1, 0 } }, NotFound },    //
@@ -1050,7 +1050,7 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, NotFound },    // ideal tile, not found
                   CreateTileDataAction{ { 6, 0, { 6, 0, 0 } } },           //
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
@@ -1070,7 +1070,7 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
@@ -1091,14 +1091,14 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, NotFound },    // ascent
                   CreateTileDataAction{ { 5, 0, { 5, 0, 0 } } },           //
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ...
@@ -1113,13 +1113,13 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, Found },       // ascent
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ...
@@ -1135,16 +1135,16 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, Found },       // ascent
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, NotFound },    // ...
                   CreateTileDataAction{ { 4, 0, { 4, 0, 0 } } },           //
-                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ...
@@ -1159,18 +1159,18 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, Found },       // ascent
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound },    // ...
                   CreateTileDataAction{ { 3, 0, { 3, 0, 0 } } },           //
-                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // ...
@@ -1184,20 +1184,20 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, Found },       // ascent
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound },    // ...
                   CreateTileDataAction{ { 2, 0, { 2, 0, 0 } } },           //
-                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 2, 0, { 2, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 1, 0, { 1, 0, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 0, 0, { 0, 0, 0 } }, NotFound },    // ...
               }),
@@ -1211,17 +1211,17 @@ TEST(UpdateRenderables, RepeatedRenderWithMissingOptionals) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found },       // ideal tile, not ready
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 7, 0, 0 } }, NotFound },    // children
                   GetTileDataAction{ { 7, 0, { 7, 0, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 0 } }, NotFound },    // ...
                   GetTileDataAction{ { 7, 0, { 7, 1, 1 } }, NotFound },    // ...
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, Found },       // ascent
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 4, 0, { 4, 0, 0 } }, TileNecessity::Optional }, //
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, Found },       // ...
-                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, Resource::Necessity::Optional }, //
+                  RetainTileDataAction{ { 3, 0, { 3, 0, 0 } }, TileNecessity::Optional }, //
                   RenderTileAction{ { 3, 0, 0 }, *tile_3_3_0_0 },       //
               }),
               log);
@@ -1246,11 +1246,11 @@ TEST(UpdateRenderables, LoadRequiredIfIdealTileCantBeFound) {
                                  source.idealTiles, source.zoomRange, 6);
     EXPECT_EQ(ActionLog({
                   GetTileDataAction{ { 6, 0, { 6, 0, 0 } }, Found }, // ideal tile, not found
-                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, Resource::Necessity::Required }, //
+                  RetainTileDataAction{ { 6, 0, { 6, 0, 0 } }, TileNecessity::Required }, //
                   GetTileDataAction{ { 7, 0, { 6, 0, 0 } }, NotFound }, // overzoomed child
                   GetTileDataAction{ { 5, 0, { 5, 0, 0 } }, NotFound }, // ascent
                   CreateTileDataAction{ { 5, 0, { 5, 0, 0 } } },
-                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, Resource::Necessity::Required },
+                  RetainTileDataAction{ { 5, 0, { 5, 0, 0 } }, TileNecessity::Required },
                   GetTileDataAction{ { 4, 0, { 4, 0, 0 } }, NotFound }, // ...
                   GetTileDataAction{ { 3, 0, { 3, 0, 0 } }, NotFound }, // ...
                   GetTileDataAction{ { 2, 0, { 2, 0, 0 } }, NotFound }, // ...