Clipboard allows applications to read and write data to and from
a shared clipboard.
The clipboard is implemented as a direct file store, as
defined in the File Store API. Data placed on the clipboard is in streams.
Every data type placed on the clipboard is identified by a UID. The store
has a stream dictionary to allow an application to retrieve the data by specifying
its UID.
The clipboard class, CClipboard, provides
operations to get the clipboard file store and stream dictionary. Applications
then read or write data using the standard store and stream interfaces. It
also provides special support for copying and pasting a TReal to
and from the clipboard.
To place data on the clipboard, construct
a CClipboard object and prepare it for the data to be written,
using the NewForWritingLC() static member function as illustrated
in the following code fragment:
CClipboard* cb = CClipboard::NewForWritingLC( fsSession );
The function requires a file server session.
The file associated
with the clipboard's store may or may not exist. If it already exists, any
existing content is discarded; if the file does not exist, it is created.
In either event, NewForWritingLC() results in an empty clipboard.
Once
the CClipboard object has been created, data is stored into
the clipboard 's store. Both the store (CStreamStore) and
the stream dictionary (CStreamDictionary), which the example
needs to access, are encapsulated by CClipboard. The class,
therefore, provides the Store() and StreamDictionary() member
functions to return suitable references.
- Creating the
data for the clipboard.
- Prepare a new
stream for writing using the CreateLC() member function of RStoreWriteStream.
The CClipboard's store is to contain the new stream and so cb->Store() is
passed as a parameter to CreateLC(). The item object is externalised.
The stream is committed. The resulting streamId and the UID,
which identifies the data type, i.e. stid and KExampleClipUid,
respectively, are placed in the stream dictionary using the stream dictionary's AssignL() member
function.
- Conclude by calling CClipboard's
CommitL() member function to store the dictionary store as the root
stream of the store and to commit all changes to the store.
Deleting the CClipboard object causes the file associated
with the clipboard's store to be closed, allowing other applications to access
it.
- Pasting the data
from clipboard
To attempt to retrieve data from the clipboard, construct a CClipboard object
and prepare it for reading using either NewForReadingL() or NewForReadingLC().
// Create clipboard object
TRAPD( ret,cb=CClipboard::NewForReadingL( fsSession ) );
CleanupStack::PushL( cb );
_LIT( KNoPaste,"Nothing to paste" );
if ( ret!=KErrNone )
{
doShow( KNoPaste,NULL );
User::Leave( ret );
}
// Get stream from store
TStreamId stid = ( cb->StreamDictionary() ).At( KExampleClipUid );
if ( stid == KNullStreamId )
{
doShow( KNoPaste,NULL );
User::Leave( 0 );
}
// Read stream
RStoreReadStream stream;
stream.OpenLC( cb->Store(),stid );
stream >> *item;
- Copying and pasting
real numbers
Use CopyToL( TReal ) to place a TReal on
the clipboard and use PasteFromL( TReal& ) to fetch a TReal from
the clipboard, if there is any data.
Applications that use these functions
to copy and paste TReal objects need not concern themselves
with the UID used to identify the corresponding stream in the clipboard store.
It
must be noted that applications which use CopyToL( TReal ),
must still call CClipboard's CommitL() member function before
deleting the CClipboard object.
Following is an example on how to create data for clipboard. In
this example, the data to be placed on the clipboard's store is a single object
item:
RStoreWriteStream stream;
TStreamId stid = stream.CreateLC( cb->Store() );
stream << *item;
stream.CommitL();
( cb->StreamDictionary() ).AssignL( KExampleClipUid,stid );
CleanupStack::PopAndDestroy(); // stream
cb->CommitL();
CleanupStack::PopAndDestroy(); // cb