implement MBTiles offline fallback mode

tangrams · Oct 14, 2016 · 07e95b7 · 07e95b7
1 parent 18109cb
commit 07e95b7
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Showing 2 changed files with 37 additions and 10 deletions.
diff --git a/core/src/data/mbtilesDataSource.cpp b/core/src/data/mbtilesDataSource.cpp
@@ -126,6 +126,13 @@ MBTilesDataSource::~MBTilesDataSource() {
 
 bool MBTilesDataSource::loadTileData(std::shared_ptr<TileTask> _task, TileTaskCb _cb) {
 
+    if (m_offlineMode) {
+        // Try next source
+        _task->rawSource = next->level;
+
+        return loadNextSource(_task, _cb);
+    }
+
     if (_task->rawSource == this->level) {
 
         m_worker->enqueue([this, _task, _cb](){
@@ -137,7 +144,7 @@ bool MBTilesDataSource::loadTileData(std::shared_ptr<TileTask> _task, TileTaskCb
             getTileData(tileId, *task.rawTileData);
 
             if (task.hasData()) {
-                // LOGW("loaded tile: %s, %d", tileId.toString().c_str(), task.rawTileData->size());
+                LOGW("loaded tile: %s, %d", tileId.toString().c_str(), task.rawTileData->size());
 
                 _cb.func(_task);
 
@@ -166,20 +173,37 @@ bool MBTilesDataSource::loadNextSource(std::shared_ptr<TileTask> _task, TileTask
     // Intercept TileTaskCb to store result from next source.
     TileTaskCb cb{[this, _cb](std::shared_ptr<TileTask> _task) {
 
-        m_worker->enqueue([this, _task](){
+        if (_task->hasData()) {
 
-            auto& task = static_cast<DownloadTileTask&>(*_task);
-            TileID tileId = _task->tileId();
+            m_worker->enqueue([this, _task](){
 
-            //LOGW("store tile: %s, %d", tileId.toString().c_str(), task.hasData());
+                auto& task = static_cast<DownloadTileTask&>(*_task);
 
-            if (task.hasData()) {
-                storeTileData(tileId, *task.rawTileData);
-            }
-        });
+                LOGW("store tile: %s, %d", _task->tileId().toString().c_str(), task.hasData());
 
-        _cb.func(_task);
+                storeTileData(_task->tileId(), *task.rawTileData);
+            });
+            _cb.func(_task);
 
+        } else if (m_offlineMode) {
+            LOGW("try fallback tile: %s, %d", _task->tileId().toString().c_str());
+
+            m_worker->enqueue([this, _task, _cb](){
+
+                auto& task = static_cast<DownloadTileTask&>(*_task);
+                task.rawTileData = std::make_shared<std::vector<char>>();
+
+                getTileData(_task->tileId(), *task.rawTileData);
+
+                LOGW("loaded tile: %s, %d", _task->tileId().toString().c_str(), task.rawTileData->size());
+
+                _cb.func(_task);
+
+            });
+        } else {
+            LOGW("missing tile: %s, %d", _task->tileId().toString().c_str());
+            _cb.func(_task);
+        }
     }};
 
     return next->loadTileData(_task, cb);

diff --git a/core/src/data/mbtilesDataSource.h b/core/src/data/mbtilesDataSource.h
@@ -39,6 +39,9 @@ class MBTilesDataSource : public RawDataSource {
     std::unique_ptr<SQLite::Database> m_db;
     std::unique_ptr<MBTilesQueries> m_queries;
     std::unique_ptr<AsyncWorker> m_worker;
+
+    // Offline fallback: Try download (next source) first, then fall back to mbtiles
+    bool m_offlineMode = true;
 };
 
 }