org.eclipse.swt.graphics
Class Device

java.lang.Object
  org.eclipse.swt.graphics.Device

All Implemented Interfaces:

Drawable

Direct Known Subclasses:

Display

public abstract class Device

extends java.lang.Object

implements Drawable

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

Constructor Summary

Device()
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	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.
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(java.lang.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()
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 false prevents these messages from being printed.

Methods inherited from class java.lang.Object

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

Constructor Detail

Device

public Device()

Constructs a new instance of this class.

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

Since:

3.1

See Also:

init()

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

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

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(java.lang.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 - if true only scalable fonts are returned, otherwise only non-scalable fonts are 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 freed 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 freed 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()

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 false prevents these messages from being printed. If the argument is true then message printing is not blocked.

Parameters:

warnings - trueif warnings should be printed, and false otherwise

Throws:

SWTException -

• ERROR_DEVICE_DISPOSED - if the receiver has been disposed