[core] use stale sprite data

This is a naïve implementation that essentially merges updated data into existing data. It will *not* remove icons from the stale sprite if they aren't present in the fresh sprite (we aren't tracking the source of a sprite, and the user could have changed it as well). Similarly, it will not update icons that have changed in dimension. This is a rare edge case and probably not worth implementing.

1 files changed, 16 insertions, 14 deletions

diff --git a/src/mbgl/sprite/sprite_store.cpp b/src/mbgl/sprite/sprite_store.cpp
index 0c3a7d3ba0..8f99ea7626 100644
--- a/src/mbgl/sprite/sprite_store.cpp
+++ b/src/mbgl/sprite/sprite_store.cpp
@@ -40,15 +40,17 @@ void SpriteStore::setURL(const std::string& url) {
     FileSource* fs = util::ThreadContext::getFileSource();
     loader->jsonRequest = fs->request({ Resource::Kind::SpriteJSON, jsonURL },
                                       [this, jsonURL](Response res) {
-        if (res.stale) {
-            // Only handle fresh responses.
+        if (res.error) {
+            observer->onSpriteError(std::make_exception_ptr(std::runtime_error(res.error->message)));
+        }
+
+        if (res.notModified) {
+            // We got the same data back as last time. Abort early.
             return;
         }
-        loader->jsonRequest = nullptr;
 
-        if (res.error) {
-            observer->onSpriteError(std::make_exception_ptr(std::runtime_error(res.error->message)));
-        } else {
+        if (!loader->json || *loader->json != *res.data) {
+            // Only trigger a sprite loaded event we got new data.
             loader->json = res.data;
             emitSpriteLoadedIfComplete();
         }
@@ -57,15 +59,16 @@ void SpriteStore::setURL(const std::string& url) {
     loader->spriteRequest =
         fs->request({ Resource::Kind::SpriteImage, spriteURL },
                     [this, spriteURL](Response res) {
-            if (res.stale) {
-                // Only handle fresh responses.
+            if (res.error) {
+                observer->onSpriteError(std::make_exception_ptr(std::runtime_error(res.error->message)));
+            }
+
+            if (res.notModified) {
+                // We got the same data back as last time. Abort early.
                 return;
             }
-            loader->spriteRequest = nullptr;
 
-            if (res.error) {
-                observer->onSpriteError(std::make_exception_ptr(std::runtime_error(res.error->message)));
-            } else {
+            if (!loader->image || *loader->image != *res.data) {
                 loader->image = res.data;
                 emitSpriteLoadedIfComplete();
             }
@@ -79,8 +82,7 @@ void SpriteStore::emitSpriteLoadedIfComplete() {
         return;
     }
 
-    auto local = std::move(loader);
-    auto result = parseSprite(*local->image, *local->json);
+    auto result = parseSprite(*loader->image, *loader->json);
     if (result.is<Sprites>()) {
         loaded = true;
         setSprites(result.get<Sprites>());