haiku/docs/user/app/Clipboard.dox

/*
 * Copyright 2011 Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		Gabe Yoder, gyoder@stny.rr.com
 *		John Scipione, jscipione@gmail.com
 * 
 * Corresponds to:
 *		headers/os/app/Clipboard.h	 rev 42274
 *		src/kits/app/Clipboard.cpp	 rev 42274
 */


/*!
	\file Clipboard.h
	\ingroup app
	\ingroup libbe
	\brief Provides the BClipboard class.
*/


/*!
	\var be_clipboard
	\brief Global system clipboard object.
*/


/*!
	\class BClipboard
	\ingroup app
	\ingroup libbe
	\brief Used for short-term data storage between documents and
		applications via copy and paste operations.

	Clipboards are differentiated by their name. In order for two
	applications to share a clipboard they simply have to create a
	BClipboard object with the same name. However, it is rarely necessary
	to create your own clipboard, instead you can use the \c be_clipboard
	system clipboard object.

	\remark To access the system clipboard without a BApplication object,
	create a BClipboard object with the name "system". You should avoid
	creating a custom clipboard with the name "system" for your own use.

	To access the clipboard data call the Data() method. The BMessage object
	returned by the Data() method has the following properties:
		- The \c what value is unused.
		- The clipboard data is stored in a message field typed as
			\c B_MIME_TYPE.
		- The MIME type of the data is used as the name of the field that
			holds the data.
		- Each field in the data message contains the same data with a
			different format.

	To read and write to the clipboard you must first lock the BClipboard
	object. If you fail to lock the BClipboard object then the Data() method
	will return \c NULL instead of a pointer to a BMessage object.

	Below is an example of reading a string from the system clipboard.
\code
const char *string;
int32 stringLen;
if (be_clipboard->Lock()) {
	// Get the clipboard BMessage
	BMessage *clip = be_clipboard->Data();

	// Read the string from the clipboard data message
	clip->FindData("text/plain", B_MIME_TYPE, (const void **)&string,
		&stringLen);

	be_clipboard->Unlock();
} else
	fprintf(stderr, "could not lock clipboard.\n");
\endcode

	Below is an example of writing a string to the system clipboard.
\code
const char* string = "Some clipboard data";

if (be_clipboard->Lock()) {
	// Clear the clipboard data
	be_clipboard->Clear();

	// Get the clipboard data message
	BMessage *clip = be_clipboard->Data();

	// Write string data to the clipboard data message
	clip->AddData("text/plain", B_MIME_TYPE, string, strlen(string));

	// Commit the data to the clipboard
	status = be_clipboard->Commit();
	if (status != B_OK)
		fprintf(stderr, "could not commit data to clipboard.\n");

	be_clipboard->Unlock();
} else
	fprintf(stderr, "could not lock clipboard.\n");
\endcode
*/


/*!
	\fn BClipboard::BClipboard(const char *name, bool transient = false)
	\brief Create a BClipboard object with the given \a name.

	If the \a name parameter is \c NULL then the "system" BClipboard object
	is constructed instead.

	\param name The \a name of the clipboard.
	\param transient If \c true, lose data after a reboot (currently unused).
*/


/*!
	\fn BClipboard::~BClipboard()
	\brief Destroys the BClipboard object. The clipboard data is not destroyed.
*/


/*!
	\fn const char* BClipboard::Name() const
	\brief Returns the name of the BClipboard object.

	\returns The name of the clipboard.
*/


/*!
	\name Commit Count Methods
*/


//! @{


/*!
	\fn uint32 BClipboard::LocalCount() const
	\brief Returns the (locally cached) number of commits to the clipboard.

	The returned value is the number of successful Commit() invocations for
	the clipboard represented by this object, either invoked on this object
	or another (even from another application). This method returns a locally
	cached value, which might already be obsolete. For an up-to-date value
	use SystemCount().

	\return The number of commits to the clipboard.

	\sa SystemCount()
*/


/*!
	\fn uint32 BClipboard::SystemCount() const
	\brief Returns the number of commits to the clipboard.

	The returned value is the number of successful Commit() invocations for
	the clipboard represented by this object, either invoked on this object
	or another (even from another application). This method retrieves the
	value directly from the system service managing the clipboards, so it is
	more expensive, but more up-to-date than LocalCount(), which returns a
	locally cached value.

	\return The number of commits to the clipboard.

	\sa LocalCount()
*/


//! @}


/*!
	\name Monitoring Methods
*/


//! @{


/*!
	\fn status_t BClipboard::StartWatching(BMessenger target)
	\brief Start watching the BClipboard object for changes.

	When a change in the clipboard occurs, most like as the result of a cut
	or copy action, a \a B_CLIPBOARD_CHANGED message is sent to \a target.

	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a target is invalid.
	\retval B_ERROR An error occured.

	\sa StopWatching()
*/


/*!
	\fn status_t BClipboard::StopWatching(BMessenger target)
	\brief Stop watching the BClipboard object for changes.

	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a target is invalid.
	\retval B_ERROR An error occurred.

	\sa StartWatching()
*/


//! @}


/*!
	\name Locking Methods
*/


//! @{


/*!
	\fn bool BClipboard::Lock()
	\brief Locks the clipboard so that no other tread can read from it or
		write to it.

	You should call Lock() before reading or writing to the clipboard.

	\returns \c true if the clipboard was locked, \c false otherwise.

	\sa Unlock()
*/


/*!
	\fn void BClipboard::Unlock()
	\brief Unlocks the clipboard.

	\sa Lock()
*/


/*!
	\fn bool BClipboard::IsLocked() const
	\brief Returns whether or not the clipboard is locked.

	\returns \c true if the clipboard is locked, \c false if it is unlocked.
*/


//! @}


/*!
	\name Clipboard Data Transaction Methods
*/


//! @{


/*!
	\fn status_t BClipboard::Clear()
	\brief Clears out all data from the clipboard.

	You should call Clear() before adding new data to the BClipboard object.

	\retval B_OK Everything went find.
	\retval B_NOT_ALLOWED The clipboard is not locked.
	\retval B_NO_MEMORY Ran out of memory initializing the data message.
	\retval B_ERROR Another error occurred.
*/


/*!
	\fn status_t BClipboard::Commit()
	\brief Commits the clipboard data to the BClipboard object.

	\retval B_OK Everything went find.
	\retval B_NOT_ALLOWED The clipboard is not locked.
	\retval B_ERROR Another error occurred.
*/


/*!
	\fn status_t BClipboard::Commit(bool failIfChanged)
	\brief Commits the clipboard data to the BClipboard object with the
		option to fail if there is a change to the clipboard data.

	\param failIfChanged Whether or not to fail to commit the changes
		if there is a change in the clipboard data.

	\retval B_OK Everything went find.
	\retval B_NOT_ALLOWED The clipboard is not locked.
	\retval B_ERROR Another error occurred.
*/


/*!
	\fn status_t BClipboard::Revert()
	\brief Reverts the clipboard data.

	The method should be used in the case that you have made a change to the
	clipboard data message and then decide to revert the change instead of
	committing it.

	\retval B_OK Everything went find.
	\retval B_NOT_ALLOWED The clipboard is not locked.
	\retval B_NO_MEMORY Ran out of memory initializing the data message.
	\retval B_ERROR Another error occurred.
*/


//! @}


/*!
	\name Clipboard Data Message Methods
*/


//! @{


/*!
	\fn BMessenger BClipboard::DataSource() const
	\brief Gets a BMessenger object targeting the application that last
		modified the clipboard.

	The clipboard object does not need to be locked to call this method.

	\returns A BMessenger object that targets the application that last
		modified the clipboard.
*/


/*!
	\fn BMessage* BClipboard::Data() const
	\brief Gets a pointer to the BMessage object that holds the clipboard
		data.

	If the BClipboard object is not locked this method returns \c NULL.

	\returns A pointer to the BMessage object that holds the clipboard
		data or \c NULL if the clipboard is not locked.
*/


//! @}