haiku/docs/user/interface/Dragger.dox

/*
 * Copyright 2011 Haiku Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		John Scipione, jscipione@gmail.com
 *
 * Corresponds to:
 *		headers/os/interface/Dragger.h	 hrev45050
 *		src/kits/interface/Dragger.cpp	 hrev45050


/*!
	\file Dragger.h
	\ingroup interface
	\ingroup libbe
	\brief Provides the BDragger class.
*/


/*!
	\class BDragger
	\ingroup interface
	\ingroup libbe
	\brief A view that allows the user drag and drop a target view.

	The target view must be its immediate relative--a sibling, a parent, or
	single child. The target BView must be able to be archived.

	The dragger draws a handle on top of the target view, usually in the
	bottom left the corner that the user can grab. When the user drags the
	handle the target view appears to move with the handle.

	However the target view doesn't actually move, instead, the view is archived
	into a BMessage object and the BMessage object is dragged. When the BMessage
	is dropped, the target BView is reconstructed from the archive (along with
	the BDragger). The new object is a a replicant of the target view.

	An example of a dragger handle on the Clock app can be seen below.

	\image html BDragger_example.png

	This class is tied closely to BShelf. A BShelf object accepts dragged BViews,
	reconstructs them from their archives and adds them to the view hierarchy
	of another view.

	The Show Replicants/Hide Replicants menu item in Deskbar shows and hides the
	BDragger handles.
*/


/*!
	\fn BDragger::BDragger(BRect frame, BView* target, uint32 resizingMode,
		uint32 flags)
	\brief Creates a new BDragger and sets its target view.

	The target view must be its immediate relative--a sibling, a parent, or
	single child, however, the constructor does not establish this
	relationship for you.
	
	Once you construct the BDragger you must do one of of these:
	- Add the target as a child of the dragger.
	- Add the dragger as a child of the target.
	- Add the dragger as a sibling of the target.

	If you add the target as a child of the dragger it should be its only
	child.

	A BDragger draws in the right bottom corner of its frame rectangle. If the
	\a target view is a parent or a sibling of the dragger then the frame
	rectangle needs to be no larger than the handle. However, if the \a target
	is a child of the dragger then the dragger's frame rectangle must enclose
	the target's frame so that the dragger doesn't clip the \a target.

	\param frame The frame rectangle that the dragger is draw into.
	\param target The view to set the dragger to.
	\param resizingMode Sets the parameters by which the dragger can be
		resized. See BView for more information on resizing options.
	\param flags The flags mask sets what notifications the BDragger can
		receive. See BView for more information on \a flags.
*/


/*!
	\fn BDragger::BDragger(BMessage* data)
	\brief Constructs a BDragger object from message \a data.

	\param data The message \a data to restore from.
*/


/*!
	\fn BDragger::~BDragger()
	\brief Destroys the BDragger object and frees the memory it uses,
		primarily from the bitmap handle.
*/


/*!
	\fn static BArchivable* BDragger::Instantiate(BMessage* data)
	\brief Creates a new BDragger object from the BMessage constructor.

	\returns A newly created BDragger or \c NULL if the message doesn't
		contain an archived BDragger object.
*/


/*!
	\fn status_t BDragger::Archive(BMessage* data, bool deep) const
	\brief Archives the draggers's relationship to the target view.

	The \a deep parameter has no effect on the BDragger object but
	is passed on to BView::Archive().

	\returns A status code, typically \c B_OK or \c B_ERROR on error.

	\see BView::Archive()
*/


/*!
	\fn void BDragger::AttachedToWindow()
	\brief Puts the BDragger under the control of HideAllDraggers() and
		ShowAllDraggers().
*/


/*!
	\fn void BDragger::DetachedFromWindow()
	\brief Removes the BDragger from the control of HideAllDraggers()
		and ShowAllDraggers().
*/


/*!
	\fn void BDragger::Draw(BRect updateRect)
	\brief Draws the dragger handle.

	\param updateRect The rectangular area to draw the handle in.
*/


/*!
	\fn void BDragger::MouseDown(BPoint point)
	\brief Hook method that is called when a mouse button is pressed over the
		dragger.

	This results in the archiving of the target view and the dragger and
	initiates a drag-and-drop operation.

	\param point The point on the screen where to mouse pointer is when
		the mouse is clicked.
*/


/*!
	\fn void BDragger::MessageReceived(BMessage* msg)
	\brief Receives messages that control the visibility of the dragger handle.

	\param msg The message received

	\see BView::MessageReceived()
*/


/*!
	\fn static status_t BDragger::ShowAllDraggers()
	\brief Causes all BDragger objects to draw their handles.

	The Show Replicants menu item in Deskbar does its work through this
	method.

	\returns A status code, \c B_OK on success or an error code on failure.
*/


/*!
	\fn static status_t BDragger::HideAllDraggers()
	\brief Hides all BDragger objects so that they're not visible on screen.

	The Hide Replicants menu item in Deskbar does its work through this
	method.

	\returns A status code, \c B_OK on success or an error code on failure.
*/


/*!
	\fn static bool BDragger::AreDraggersDrawn()
	\brief Returns whether or not draggers are currently drawn.

	\returns \c true if draggers are drawn, \c false otherwise.
*/