This API will let the client force a network status. If set
to Offline, we won't make network requests.
When set make to Online, it will trigger the pending requests
and try to fetch tiles from the network.
GeoJSONTile and AnnotationTile don't need to reimplement getExtent() if
they use the same default value. This also helps point and shape
annotations to avoid using raw values.
If the server keeps sending replies considered from the client in the
past (there is no way to tell if the server or client clock is wrong),
the client will try to interpolate a valid expiration time based
on the delta of the expiration intervals sent by the server.
If the intervals are always the same, exponential backoff kicks in
until we get a different expiration time from what we already have.
When looking for child tiles that cover a parent tile, we're computing the lower bound of the child tile in the set of tiles. Three things can happen:
- all remaining tiles are sorted before the child tile we're looking for. in that case, there can not be a child tile.
- the lower bound is the child tile; in this case, we want to continue checking the other children of the parent tile.
- the lower bound isn't the child tile we're looking for, but there are still tiles sorted after the tile we were looking for. these could be four children of the child tile we're looking for, so we're recursively descending.
what the current algorithm didn't take into account so far is that tiles with a higher w number (i.e. tiles that are outside the "main" tile pyramid of 0/0/0) were always sorted *after* the current w number. this meant that we thought there were still remaining children to be checked, so continued our recursive descent until eventually the number overflowed and we aborted our search. unfortunately, on Android this recursive descent and accompanying overflow caused a crash.
this patch fixes this by making sure that before we're continuing to descent, we're sure that the w numbers match: all tiles with a different (= higher) w number essentially mean the same as "all remaining tiles are sorted before the child tile we're looking for" for the purpose of finding covering children
This eliminates the reliance on ThreadContext to provide GLObjectStore, and statically enforces that GL cleanup functions happen only when GLObjectStore::performCleanup is called.
With the elimination of the Map thread, this becomes important because there may be multiple GLObjectStore's per-thread, and Map will need to ensure that the correct context is active when calling GLObjectStore::performCleanup.
Texture pool now allocates a block of 64 textures per time. Each block
contains a TextureObject which handles GL object lifetime. Blocks can be
added or removed according to the following rules:
1. If pool is empty, created a new block upon first call (lazy load);
2. Iterate blocks to find an available texture ID:
- If found, remove that from the list of available IDs for that block
and return its ID.
- Othewise, allocate a new block and grab an available ID from that.
3. When releasing a texture ID, check if the associated block is free.
If no IDs are currently in use, then abandon its TextureObject and
remove the block from the pool.
