From bb1a209a6396dd5d41651092b354607b6852c0c8 Mon Sep 17 00:00:00 2001
From: "Thiago Marcos P. Santos" <tmpsantos@gmail.com>
Date: Wed, 12 Jul 2017 17:01:49 +0300
Subject: [Qt] Share the DefaultFileSource for all QMapboxGL instances

Fix issues of concurrent access to the sqlite cache.

Fixes #9108.
---
 platform/qt/src/qmapboxgl.cpp   | 20 +++++++++++++++++++-
 platform/qt/src/qmapboxgl_p.hpp |  2 +-
 2 files changed, 20 insertions(+), 2 deletions(-)

(limited to 'platform')

diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index eafc06c028..543a8bf2d6 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -70,6 +70,19 @@ namespace {
 
 QThreadStorage<std::shared_ptr<mbgl::util::RunLoop>> loop;
 
+std::shared_ptr<mbgl::DefaultFileSource> sharedDefaultFileSource(
+        const std::string& cachePath, const std::string& assetRoot, uint64_t maximumCacheSize) {
+    static std::weak_ptr<mbgl::DefaultFileSource> weak;
+    auto fs = weak.lock();
+
+    if (!fs) {
+        weak = fs = std::make_shared<mbgl::DefaultFileSource>(
+                cachePath, assetRoot, maximumCacheSize);
+    }
+
+    return fs;
+}
+
 // Conversion helper functions.
 
 mbgl::Size sanitizedSize(const QSize& size) {
@@ -106,6 +119,11 @@ std::unique_ptr<mbgl::style::Image> toStyleImage(const QString &id, const QImage
     QMapboxGLSettings is used to configure QMapboxGL at the moment of its creation.
     Once created, the QMapboxGLSettings of a QMapboxGL can no longer be changed.
 
+    Cache-related settings are shared between all QMapboxGL instances because different
+    maps will share the same cache database file. The first map to configure cache properties
+    such as size and path will force the configuration to all newly instantiated QMapboxGL
+    objects.
+
     \since 4.7
 */
 
@@ -1473,7 +1491,7 @@ QMapboxGLPrivate::QMapboxGLPrivate(QMapboxGL *q, const QMapboxGLSettings &settin
     : QObject(q)
     , size(size_)
     , q_ptr(q)
-    , fileSourceObj(std::make_unique<mbgl::DefaultFileSource>(
+    , fileSourceObj(sharedDefaultFileSource(
         settings.cacheDatabasePath().toStdString(),
         settings.assetPath().toStdString(),
         settings.cacheDatabaseMaximumSize()))
diff --git a/platform/qt/src/qmapboxgl_p.hpp b/platform/qt/src/qmapboxgl_p.hpp
index 49a7942cce..3c8a6cf09e 100644
--- a/platform/qt/src/qmapboxgl_p.hpp
+++ b/platform/qt/src/qmapboxgl_p.hpp
@@ -52,7 +52,7 @@ public:
 
     QMapboxGL *q_ptr { nullptr };
 
-    std::unique_ptr<mbgl::DefaultFileSource> fileSourceObj;
+    std::shared_ptr<mbgl::DefaultFileSource> fileSourceObj;
     std::shared_ptr<mbgl::ThreadPool> threadPool;
     std::unique_ptr<mbgl::Map> mapObj;
 
-- 
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