If we don't do this, we can activate a request twice.
The issue here is that we use memory address as the 'key'. So if
we destroy a request, another request might take the same memory
address, or the same 'key'.
The entry at 'pendingRequests' survives the 'cancel()' and is
ultimatelly removed at 'activatePendingRequest()'. This is fine
unless a request is created using the same 'key' before we call
'activatePendingRequest()'.
The check if the request was canceled at 'activatePendingRequest()'
will be no longer valid, activating the request. At the same time
the request will be activated again by the task scheduled at the
constructor of the 'OnlineFileRequestImpl' class.
This results in a ~1% increase in database size, which is worth it for reducing complexity and making the tiles and resources tables more similar in structure.
* Under the hood, SQLite creates surrogate keys (ROWID) anyway. We may as well take advantage of this and use the surrogates for foreign keys as well, since they are simpler and more efficient than compound foreign keys.
* Create indexes for efficient eviction queries
When inserting an cached resource, or removing a region, remove least-recently used resources and tiles, not used by offline regions, until the used database size, as calculated by multiplying the number of in-use pages by the page size, is less than the maximum cache size minus 5 times the page size.
In addition, OfflineDatabase may be configured to ignore cache puts of individual resources larger than a certain size.
This policy is similar but not identical to the former SQLiteCache policy:
* It accounts for offline, by exempting resources required by offline regions from eviction.
* It must delete from two tables (resources and tiles), rather than one. Currently the strategy is naive: evict 50 rows at a time from each table.
* It makes maximumCacheSize and maximumCacheEntrySize completely independent. The SQLiteCache implementation evicted when `usedSize > maximumCacheSize - 2 * maximumCacheEntrySize`. This evicts when `usedSize > maximumCacheSize - 5 * pageSize`.
* It uses a non-unlimited default value for maximumCacheSize: 50 MB. We should have always had a limit in place; "a cache without an eviction policy is a resource leak".
This allows the FileSource interface itself to support revalidation. We could (and probably should) now rewrite HTTPContextBase implementations as FileSource implementations.
Should not be used at all, added for a corner case
on OSX network backend where the request is processed on
a worker thread managed by OSX and we need to wait for
that reply before destroying the thread that pushed the
request.
This reverts commit 6709bdcacd.
There was an issue with the script that removes '-lwebp' from WebP
linker flags, since we're statically linking. This is now fixed.
Map and Transform methods assume an origin at the top-left corner of the view, like iOS, Android, and GLFW but unlike OS X. Transform is responsible for flipping coordinates between the top-left origin of Map and the bottom-left origin of TransformState.
Fixes#3574.
If you use many different caches, expired weak_ptrs will pile up in the unordered_map, but that is an edge case, and you probably shouldn't do that anyway.
