From 29b8b44b7767312095e9489a97ba9eea3f1797af Mon Sep 17 00:00:00 2001
From: "Thiago Marcos P. Santos" <thiago@mapbox.com>
Date: Fri, 29 May 2015 12:13:24 +0300
Subject: [PATCH] Fix race condition on error notification

We start loading the resources at the moment we set the style, but we
set the callback for error notification at renderStill(), which happen
afterwards.

If some error occurs in this short window, it was never being notified.
Now we save the last error and we check after we set the callback.
---
 src/mbgl/map/map_context.cpp | 5 +++++
 src/mbgl/style/style.cpp     | 1 +
 src/mbgl/style/style.hpp     | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/src/mbgl/map/map_context.cpp b/src/mbgl/map/map_context.cpp
index a834f5065..47a6b3e4b 100644
--- a/src/mbgl/map/map_context.cpp
+++ b/src/mbgl/map/map_context.cpp
@@ -176,6 +176,11 @@ void MapContext::renderStill(StillImageCallback fn) {
         throw util::Exception("Map is currently rendering an image");
     }
 
+    if (style->getLastError()) {
+        fn(style->getLastError(), nullptr);
+        return;
+    }
+
     callback = fn;
     triggerUpdate(Update::RenderStill);
 }
diff --git a/src/mbgl/style/style.cpp b/src/mbgl/style/style.cpp
index 8999af3c7..30798e08e 100644
--- a/src/mbgl/style/style.cpp
+++ b/src/mbgl/style/style.cpp
@@ -203,6 +203,7 @@ void Style::emitResourceLoadingFailed(std::exception_ptr error) {
 
     try {
         if (error) {
+            lastError = error;
             std::rethrow_exception(error);
         }
     } catch(const std::exception& e) {
diff --git a/src/mbgl/style/style.hpp b/src/mbgl/style/style.hpp
index c70f019c4..a22067cb1 100644
--- a/src/mbgl/style/style.hpp
+++ b/src/mbgl/style/style.hpp
@@ -59,6 +59,10 @@ public:
     void setDefaultTransitionDuration(Duration);
     bool hasTransitions() const;
 
+    std::exception_ptr getLastError() const {
+        return lastError;
+    }
+
     std::unique_ptr<GlyphStore> glyphStore;
     std::unique_ptr<GlyphAtlas> glyphAtlas;
     util::ptr<Sprite> sprite;
@@ -90,6 +94,8 @@ private:
 
     Observer* observer = nullptr;
 
+    std::exception_ptr lastError;
+
     std::string spriteURL;
     PropertyTransition defaultTransition;
     std::unique_ptr<uv::rwlock> mtx;