org.eclipse.swt.graphics
Class Device

java.lang.Object
  |
  +--org.eclipse.swt.graphics.Device

All Implemented Interfaces:

Drawable

Direct Known Subclasses:

Display, Printer

public abstract class Device

extends Object

implements Drawable

This class is the abstract superclass of all device objects, such as the Display device and the Printer device. Devices can have a graphics context (GC) created for them, and they can be drawn on by sending messages to the associated GC.

Field Summary

protected static Device	CurrentDevice
static boolean	DEBUG
protected static Runnable	DeviceFinder
int	hPalette

Constructor Summary

Device(DeviceData data)
Constructs a new instance of this class.

Method Summary

protected void	checkDevice() Throws an SWTException if the receiver can not be accessed by the caller.
protected void	create(DeviceData data) Creates the device in the operating system.
protected void	destroy() Destroys the device in the operating system and releases the device's handle.
void	dispose() Disposes of the operating system resources associated with the receiver.
Rectangle	getBounds() Returns a rectangle describing the receiver's size and location.
Rectangle	getClientArea() Returns a rectangle which describes the area of the receiver which is capable of displaying data.
int	getDepth() Returns the bit depth of the screen, which is the number of bits it takes to represent the number of unique colors that the screen is currently capable of displaying.
DeviceData	getDeviceData() Returns a DeviceData based on the receiver.
Point	getDPI() Returns a point whose x coordinate is the horizontal dots per inch of the display, and whose y coordinate is the vertical dots per inch of the display.
FontData[]	getFontList(String faceName, boolean scalable) Returns FontData objects which describe the fonts that match the given arguments.
Color	getSystemColor(int id) Returns the matching standard color for the given constant, which should be one of the color constants specified in class SWT.
Font	getSystemFont() Returns a reasonable font for applications to use.
boolean	getWarnings() Returns true if the underlying window system prints out warning messages on the console, and setWarnings had previously been called with true.
protected void	init() Initializes any internal resources needed by the device.
abstract void	internal_dispose_GC(int hDC, GCData data) Invokes platform specific functionality to dispose a GC handle.
abstract int	internal_new_GC(GCData data) Invokes platform specific functionality to allocate a new GC handle.
boolean	isDisposed() Returns true if the device has been disposed, and false otherwise.
protected void	release() Releases any internal resources back to the operating system and clears all fields except the device handle.
void	setWarnings(boolean warnings) If the underlying window system supports printing warning messages to the console, setting warnings to true prevents these messages from being printed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEBUG

public static boolean DEBUG

hPalette

public int hPalette

CurrentDevice

protected static Device CurrentDevice

DeviceFinder

protected static Runnable DeviceFinder

Constructor Detail

Device

public Device(DeviceData data)

Constructs a new instance of this class.

You must dispose the device when it is no longer required.

Parameters:

data - the DeviceData which describes the receiver

See Also:

create(org.eclipse.swt.graphics.DeviceData), init(), DeviceData

Method Detail

checkDevice

protected void checkDevice()

Throws an SWTException if the receiver can not be accessed by the caller. This may include both checks on the state of the receiver and more generally on the entire execution context. This method should be called by device implementors to enforce the standard SWT invariants.

Currently, it is an error to invoke any method (other than isDisposed() and dispose()) on a device that has had its dispose() method called.

In future releases of SWT, there may be more or fewer error checks and exceptions may be thrown for different reasons.

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed

create

protected void create(DeviceData data)

Creates the device in the operating system. If the device does not have a handle, this method may do nothing depending on the device.

This method is called before init.

Subclasses are supposed to reimplement this method and not call the super implementation.

Parameters:

data - the DeviceData which describes the receiver

See Also:

init()

destroy

protected void destroy()

Destroys the device in the operating system and releases the device's handle. If the device does not have a handle, this method may do nothing depending on the device.

This method is called after release.

Subclasses are supposed to reimplement this method and not call the super implementation.

See Also:

dispose(), release()

dispose

public void dispose()

Disposes of the operating system resources associated with the receiver. After this method has been invoked, the receiver will answer true when sent the message isDisposed().

See Also:

release(), destroy(), checkDevice()

getBounds

public Rectangle getBounds()

Returns a rectangle describing the receiver's size and location.

Returns:

the bounding rectangle

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

getDeviceData

public DeviceData getDeviceData()

Returns a DeviceData based on the receiver. Modifications made to this DeviceData will not affect the receiver.

Returns:

a DeviceData containing the device's data and attributes

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

See Also:

DeviceData

getClientArea

public Rectangle getClientArea()

Returns a rectangle which describes the area of the receiver which is capable of displaying data.

Returns:

the client area

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

See Also:

getBounds()

getDepth

public int getDepth()

Returns the bit depth of the screen, which is the number of bits it takes to represent the number of unique colors that the screen is currently capable of displaying. This number will typically be one of 1, 8, 15, 16, 24 or 32.

Returns:

the depth of the screen

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

getDPI

public Point getDPI()

Returns a point whose x coordinate is the horizontal dots per inch of the display, and whose y coordinate is the vertical dots per inch of the display.

Returns:

the horizontal and vertical DPI

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

getFontList

public FontData[] getFontList(String faceName,
                              boolean scalable)

Returns FontData objects which describe the fonts that match the given arguments. If the faceName is null, all fonts will be returned.

Parameters:

faceName - the name of the font to look for, or null

scalable - true if scalable fonts should be returned.

Returns:

the matching font data

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

getSystemColor

public Color getSystemColor(int id)

Returns the matching standard color for the given constant, which should be one of the color constants specified in class SWT. Any value other than one of the SWT color constants which is passed in will result in the color black. This color should not be free'd because it was allocated by the system, not the application.

Parameters:

id - the color constant

Returns:

the matching color

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

See Also:

SWT

getSystemFont

public Font getSystemFont()

Returns a reasonable font for applications to use. On some platforms, this will match the "default font" or "system font" if such can be found. This font should not be free'd because it was allocated by the system, not the application.

Typically, applications which want the default look should simply not set the font on the widgets they create. Widgets are always created with the correct default font for the class of user-interface component they represent.

Returns:

a font

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

getWarnings

public boolean getWarnings()

Returns true if the underlying window system prints out warning messages on the console, and setWarnings had previously been called with true.

Returns:

trueif warnings are being handled, and false otherwise

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed

init

protected void init()

Initializes any internal resources needed by the device.

This method is called after create.

If subclasses reimplement this method, they must call the super implementation.

See Also:

create(org.eclipse.swt.graphics.DeviceData)

internal_new_GC

public abstract int internal_new_GC(GCData data)

Invokes platform specific functionality to allocate a new GC handle.

IMPORTANT: This method is not part of the public API for Device. It is marked public only so that it can be shared within the packages provided by SWT. It is not available on all platforms, and should never be called from application code.

Specified by:

internal_new_GC in interface Drawable

Parameters:

data - the platform specific GC data

Returns:

the platform specific GC handle

internal_dispose_GC

public abstract void internal_dispose_GC(int hDC,
                                         GCData data)

Invokes platform specific functionality to dispose a GC handle.

IMPORTANT: This method is not part of the public API for Device. It is marked public only so that it can be shared within the packages provided by SWT. It is not available on all platforms, and should never be called from application code.

Specified by:

internal_dispose_GC in interface Drawable

Parameters:

data - the platform specific GC data

hDC - the platform specific GC handle

isDisposed

public boolean isDisposed()

Returns true if the device has been disposed, and false otherwise.

This method gets the dispose state for the device. When a device has been disposed, it is an error to invoke any other method using the device.

Returns:

true when the device is disposed and false otherwise

release

protected void release()

Releases any internal resources back to the operating system and clears all fields except the device handle.

When a device is destroyed, resources that were acquired on behalf of the programmer need to be returned to the operating system. For example, if the device allocated a font to be used as the system font, this font would be freed in release. Also,to assist the garbage collector and minimize the amount of memory that is not reclaimed when the programmer keeps a reference to a disposed device, all fields except the handle are zero'd. The handle is needed by destroy.

This method is called before destroy.

If subclasses reimplement this method, they must call the super implementation.

See Also:

dispose(), destroy()

setWarnings

public void setWarnings(boolean warnings)

If the underlying window system supports printing warning messages to the console, setting warnings to true prevents these messages from being printed. If the argument is false message printing is not blocked.

Parameters:

warnings - trueif warnings should be handled, and false otherwise

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed