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.TH "map::slippy::cache" n 0.2 map "Mapping utilities"
.BS
.SH NAME
map::slippy::cache \- Management of a tile cache in the local filesystem
.SH SYNOPSIS
package require \fBTcl  8.4\fR
.sp
package require \fBTk  8.4\fR
.sp
package require \fBimg::png \fR
.sp
package require \fBmap::slippy \fR
.sp
package require \fBmap::slippy::cache  ?0.2?\fR
.sp
\fB::map::slippy::cache\fR \fIcacheName\fR \fIcachedir\fR \fIprovider\fR
.sp
\fIcacheName\fR \fBvalid\fR \fItile\fR ?\fImsgvar\fR?
.sp
\fIcacheName\fR \fBexists\fR \fItile\fR
.sp
\fIcacheName\fR \fBget\fR \fItile\fR \fIdonecmd\fR
.sp
.BE
.SH DESCRIPTION
This package provides a class for managing a cache of tiles for
slippy-based maps in the local filesystem.
.SH API
.TP
\fB::map::slippy::cache\fR \fIcacheName\fR \fIcachedir\fR \fIprovider\fR
Creates the cache \fIcacheName\fR and configures it with both the path
to the directory contaiing the locally cached tiles (\fIcachedir\fR),
and the command prefix from which it will pull tiles asked for and not
yet known to the cache itself (\fIprovider\fR).
.sp
The result of the command is \fIcacheName\fR.
.PP
.SS METHODS
.TP
\fIcacheName\fR \fBvalid\fR \fItile\fR ?\fImsgvar\fR?
This method checks the validity of a the given \fItile\fR identifier.
This is a convenience wrapper to \fB::map::slippy tile valid\fR and
has the same interface.
.TP
\fIcacheName\fR \fBexists\fR \fItile\fR
This methods tests whether the cache contains the specified \fItile\fR
or not. The result is a boolean value, \fBtrue\fR if the tile is
known, and \fBfalse\fR otherwise. The tile is identified by a list
containing three elements, zoom level, row, and column number, in this
order.
.TP
\fIcacheName\fR \fBget\fR \fItile\fR \fIdonecmd\fR
This is the main method of the cache, retrieving the image for the
specified \fItile\fR from the cache. The tile identifier is a list
containing three elements, the zoom level, row, and column number of
the tile, in this order.
.sp
The command refix \fIdonecmd\fR will be invoked when the cache
either knows the image for the tile or that no image will forthcoming.
It will be invoked with either 2 or 3 arguments, i.e.
.RS
.IP [1]
The string \fBset\fR, the \fItile\fR, and the image.
.IP [2]
The string \fBunset\fR, and the \fItile\fR.
.RE
These two possibilities are used to either signal the image for the
\fItile\fR, or that the \fItile\fR has no image defined for it.
.sp
When the cache has no information about the tile it will invoke the
\fIprovider\fR command prefix specified during its construction,
adding three arguments: The string \fBget\fR, the \fItile\fR, and a
callback into the cache. The latter will be invoked by the provider to
either transfer the image to the cache, or signal that the tile has no
image.
.sp
When multiple requests for the same tile are made only one request
will be issued to the provider.
.PP
.SH REFERENCES
.IP [1]
\fIhttp://wiki.openstreetmap.org/wiki/Main_Page\fR
.PP
.SH KEYWORDS
cache, filesystem, location, map, slippy, tile, zoom