haiku/docs/user/interface/Control.dox

/*
 * Copyright 2011-2014 Haiku Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		John Scipione, jscipione@gmail.com
 *
 * Corresponds to:
 *		headers/os/interface/Control.h	 hrev47274
 *		src/kits/interface/Control.cpp	 hrev47274
 */


/*!
	\file Control.h
	\ingroup interface
	\ingroup libbe
	\brief BControl class definition and support enums.
*/


/*!
	\var B_CONTROL_ON

	Control on. Value equal to 1.
*/


/*!
	\var B_CONTROL_OFF

	Control off. Value equal to 0.
*/


/*!
	\class BControl
	\ingroup interface
	\ingroup libbe
	\brief BControl is the base class for user-event handling objects.

	Simple controls such as BCheckBox and BButton deviate only a bit from
	BControl, whereas more complicated controls such as BColorControl and
	BSlider re-implement much more functionality. Whether you are building
	a simple control or something more complicated you should inherit from
	BControl as it provides a common set of methods for intercepting
	received messages from mouse and keyboard events.

	Controls have state which they keep in their value. The value of a
	control, stored as an int32, is read and set by the virtual Value() and
	SetValue() methods. BControl defines \c B_CONTROL_ON and \c B_CONTROL_OFF
	values that you can use as a convenience if your control has a simple
	on/off state. If your BControl derived class stores a larger set of
	states then you should define your own integer values instead.
*/


/*!
	\fn BControl::BControl(BRect frame, const char* name, const char* label,
		BMessage* message, uint32 resizingMode, uint32 flags)
	\brief Construct a control in the \a frame with a \a name, \a label,
	       model \a message, \a resizingMode, and creation \a flags.

	The initial value of the control is set to 0 (\c B_CONTROL_OFF).
	The \a label and the \a message parameters can be set to \c NULL.

	\param frame The \a frame to draw the control in.
	\param name The \a name of the control.
	\param label The \a label displayed along with the control.
	\param message The \a message to send when the control is activated.
	\param resizingMode Defines the behavior of the control as the parent
	       view resizes, see BView for more details.
	\param flags Behavior \a flags for the control, see BView for details.
*/


/*!
	\fn BControl::BControl(const char* name, const char* label,
		BMessage* message, uint32 flags)
	\brief Construct a control with a \a name, \a label, model \a message,
	       and creation \a flags suitable for use with the Layout API.

	The initial value of the control is set to 0 (\c B_CONTROL_OFF).
	The \a label and the \a message parameters can be set to \c NULL.

	\note This method was not available in BeOS R5.

	\param name The \a name of the control.
	\param label The \a label displayed along with the control.
	\param message The \a message to send when the control is activated.
	\param flags Behavior \a flags for the control, see BView for details.
*/


/*!
	\fn BControl::~BControl()
	\brief Frees all memory used by the BControl object including the memory
	       used by the model message.
*/


/*!
	\fn BControl::BControl(BMessage* archive)
	\brief Creates a new BControl object from an \a archive message.

	This method is usually not called directly. If you want to build a
	control from a message you should call Instantiate() which can
	handle errors properly.

	If the \a archive deep, the BControl object will also unarchive each
	of its child views recursively.

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


/*!
	\fn BArchivable* BControl::Instantiate(BMessage* archive)
	\brief Creates a new object from an \a archive.

	If the message is a valid object then the instance created from the
	passed in \a archive will be returned. Otherwise this method will
	return \c NULL.

	\param archive The \a archive message.

	\returns An instance of the object if \a archive is valid or \c NULL.

	\sa BArchivable::Instantiate()
*/


/*!
	\fn status_t BControl::Archive(BMessage* archive, bool deep) const
	\brief Archives the control into \a archive.

	\param archive The target \a archive that the data will go into.
	\param deep Whether or not to recursively archive child views.

	\retval B_OK The archive operation was successful.
	\retval B_BAD_VALUE \c NULL \a archive message.
	\retval B_ERROR The archive operation failed.

	\sa BArchivable::Archive()
*/


/*!
	\fn void BControl::WindowActivated(bool active)
	\brief Hook method called when the attached window is activated or
	       deactivated.

	Redraws the focus ring around the menu field when the window is activated
	or deactivated if it is the window's current focus view.

	\param active \c true if the window becomes activated, \c false if the
	       window becomes deactivated.

	\sa BView::WindowActivated()
*/


/*!
	\fn void BControl::AttachedToWindow()
	\brief Hook method called when the control is attached to a window.

	This method overrides BView::AttachedToWindow() setting the low color
	and view color of the BControl so that it matches the view color of the
	control's parent view. It also makes the attached window the default
	target for Invoke() as long as another target has not already been set.

	\sa BView::AttachedToWindow()
	\sa Invoke()
	\sa BInvoker::SetTarget()
*/


/*!
	\fn void BControl::DetachedFromWindow()
	\brief Hook method called when the object is detached from a window.

	The default implementation does nothing.

	\sa BView::DetachedFromWindow()
*/


/*!
	\fn void BControl::AllAttached()
	\brief Similar to AttachedToWindow() but this method is triggered after
	       all child views have already been attached to a window.

	The default implementation does nothing.

	\sa BView::AllAttached()
*/


/*!
	\fn void BControl::AllDetached()
	\brief Similar to AttachedToWindow() but this method is triggered after
	       all child views have already been detached from a window.

	The default implementation does nothing.

	\sa BView::AllDetached()
*/


/*!
	\fn void BControl::MakeFocus(bool focused)
	\brief Gives or removes focus from the control.

	BControl::MakeFocus() overrides BView::MakeFocus() to call Draw() when
	the focus changes. Derived classes generally don't have to re-implement
	MakeFocus().

	IsFocusChanging() returns \c true when Draw() is called from this method.

	\param focused \a true to set focus, \a false to remove it.

	\sa BView::MakeFocus()
	\sa IsFocusChanging()
*/


/*!
	\fn void BControl::KeyDown(const char *bytes, int32 numBytes)
	\brief Hook method called when a keyboard key is pressed.

	Overrides BView::KeyDown() to toggle the control value and then
	calls Invoke() for \c B_SPACE or \c B_ENTER. If this is not desired
	you should override this method in derived classes.

	The KeyDown() method is only called if the BControl is the focus view
	in the active window. If the window has a default button, \c B_ENTER
	will be passed to that object instead of the focus view.

	\param bytes The bytes of the key combination pressed.
	\param numBytes The number of bytes in \a bytes.

	\sa BView::KeyDown()
	\sa MakeFocus()
*/


/*!
	\fn void BControl::MessageReceived(BMessage* message)
	\brief Handle \a message received by the associated looper.

	\param message The \a message received by the associated looper.

	\see BView::MessageReceived()
*/


/*!
	\fn void BControl::MouseDown(BPoint where)
	\brief Hook method called when a mouse button is pressed.

	\param where The point on the screen where the mouse pointer is when
	       the mouse button is pressed in the view's coordinate system.

	\sa BView::MouseDown()
*/


/*!
	\fn void BControl::MouseUp(BPoint where)
	\brief Hook method called when a mouse button is released.

	\param where The point on the screen where the mouse pointer is located
	       when the mouse button is released in the view's coordinate system.

	\sa BView::MouseUp()
*/


/*!
	\fn void BControl::MouseMoved(BPoint where, uint32 code,
		const BMessage* dragMessage)
	\brief Hook method called when the mouse is moved.

	\param where The new location of the mouse in the control's coordinate system.
	\param code One of the following:
	- \c B_ENTERED_VIEW The cursor has just entered the control.
	- \c B_INSIDE_VIEW The cursor is inside the control.
	- \c B_EXITED_VIEW The cursor has left the control's bounds. This only gets
	     sent if the scope of the mouse events that the control can receive has
	     been expanded by BView::SetEventMask() or BView::SetMouseEventMask().
	- \c B_OUTSIDE_VIEW The cursor is outside the view. This only gets sent if the
	     scope of the mouse events that the control can receive has been expanded
	     by SetEventMask() or SetMouseEventMask().
	\param dragMessage If a drag-and-drop operation is taking place this is a
	       pointer to a BMessage that holds the drag information, otherwise the
	       pointer is \c NULL.

	\sa BView::MouseMoved()
*/


/*!
	\fn void BControl::SetLabel(const char *label)
	\brief Sets the \a label of the control.

	If the \a label changes the control is redrawn.

	\param label The \a label to set, can be \c NULL.
*/


/*!
	\fn const char* BControl::Label() const
	\brief Gets the label of the control.

	\return The control's label.
*/


/*!
	\fn void BControl::SetValue(int32 value)
	\brief Sets the value of the control.

	If the \a value changes the control is redrawn.

	\param value The \a value to set.

	\sa SetValueNoUpdate()
*/


/*!
	\fn void BControl::SetValueNoUpdate(int32 value)
	\brief Sets the value of the control without redrawing.

	\note This method was not available in BeOS R5.

	\param value The \a value to set.

	\sa SetValue()
*/


/*!
	\fn int32 BControl::Value() const
	\brief Gets the value of the control.

	\return The control's value.
*/


/*!
	\fn void BControl::SetEnabled(bool enabled)
	\brief Enables or disables the control.

	BControl objects are enabled by default. If the control changes enabled
	state then it is redrawn.

	Disabled controls generally won't allow the user to focus on them
	(The \c B_NAVIGABLE flag is turned off), and don't post any messages.

	Disabled controls in derived classes should be drawn in subdued colors
	to visually indicate that they are disabled and should not respond to
	keyboard or mouse events.

	\param enabled If \c true enables the control, if \c false, disables it.
*/


/*!
	\fn bool BControl::IsEnabled() const
	\brief Gets whether or not the control is currently enabled.

	\return \c true if the control is enabled, \c false if it is disabled.
*/


/*!
	\fn void BControl::GetPreferredSize(float *_width, float *_height)
	\brief Fill out the preferred width and height of the control
		into the \a _width and \a _height parameters.

	Derived classes can override this method to set the preferred
	width and height of the control.

	\param[out] _width Pointer to a \c float to hold the width of the control.
	\param[out] _height Pointer to a \c float to hold the height of the control.

	\sa BView::GetPreferredSize()
*/


/*!
	\fn void BControl::ResizeToPreferred()
	\brief Resize the control to its preferred size.

	\sa BView::ResizeToPreferred()
*/


/*!
	\fn status_t BControl::Invoke(BMessage* message)
	\brief Sends a copy of the model \a message to the designated target.

	BControl::Invoke() overrides BInvoker::Invoke(). Derived classes
	should use this method in their MouseDown() and KeyDown() methods
	and should call IsEnabled() to check if the control is enabled
	before calling Invoke().

	The following fields added to the BMessage:
		- "when"	\c B_INT64_TYPE	system_time()
		- "source"	\c B_POINTER_TYPE	A pointer to the BControl object.

	\param message The \a message to send.

	\return \c B_OK if the control was invoked, otherwise an error
	        code is returned.

	\sa BInvoker::Invoke()
	\sa IsEnabled()
*/


/*!
	\fn BHandler* BControl::ResolveSpecifier(BMessage* message, int32 index,
		BMessage* specifier, int32 what, const char* property)
	\brief Determine the proper specifier for scripting messages.

	\sa BHandler::ResolveSpecifier()
*/


/*!
	\fn status_t BControl::GetSupportedSuites(BMessage* message)
	\brief Report the suites of messages this control understands.

	Adds the string "suite/vnd.Be-control" to the message.

	\param message Allows you to add the names of the suites the control
	       implements to the suites array.

	\return \c B_OK if all went well or an error code otherwise.

	\sa BHandler::GetSupportedSuites();
*/


/*!
	\fn status_t BControl::Perform(perform_code code, void* _data)
	\brief Perform some action. (Internal Method)

	The following perform codes are recognized:
		- \c PERFORM_CODE_MIN_SIZE
		- \c PERFORM_CODE_MAX_SIZE
		- \c PERFORM_CODE_PREFERRED_SIZE
		- \c PERFORM_CODE_LAYOUT_ALIGNMENT
		- \c PERFORM_CODE_HAS_HEIGHT_FOR_WIDTH
		- \c PERFORM_CODE_GET_HEIGHT_FOR_WIDTH
		- \c PERFORM_CODE_SET_LAYOUT
		- \c PERFORM_CODE_INVALIDATE_LAYOUT
		- \c PERFORM_CODE_DO_LAYOUT

	\param code The perform code.
	\param _data A pointer to store some data.

	\returns A status code.

	\sa BHandler::Perform()
*/


/*!
	\fn status_t BControl::SetIcon(const BBitmap* icon, uint32 flags)
	\brief This convenience method is used to set the bitmaps
	       for the standard states from a single bitmap.

	It also supports cropping the icon to its non-transparent area.
	The icon is meant as an addition to or replacement of the label.

	\note This method was not available in BeOS R5.

	\param icon The \a icon to set.
	\param flags Modify how the icon is set.
	- \c B_TRIM_ICON_BITMAP Crop the bitmap to the not fully transparent
	     area, may change the icon size.
	- \c B_TRIM_ICON_BITMAP_KEEP_ASPECT Like \c B_TRIM_BITMAP, but keeps
	     the aspect ratio.
	- \c B_CREATE_ACTIVE_ICON_BITMAP
	- \c B_CREATE_PARTIALLY_ACTIVE_ICON_BITMAP
	- \c B_CREATE_DISABLED_ICON_BITMAPS

	\return \c B_OK if the icon was set or an error code otherwise.
*/


/*!
	\fn status_t BControl::SetIconBitmap(const BBitmap* bitmap,
		uint32 which, uint32 flags)
	\brief Icon bitmaps for various states of the control (off, on,
	       partially on, each enabled or disabled, plus up to 125
	       custom states) can be set individually.

	\note This method was not available in BeOS R5.

	\param bitmap The \a bitmap icon to set.
	\param which The state to set the icon for.
	\param flags Modify how the icon is set.
		- \c B_KEEP_ICON_BITMAP Transfer ownership of the bitmap to the control.

	\return \c B_OK if the icon was set or an error code otherwise.
*/