org.eclipse.swt.graphics
Class GC

java.lang.Object
  org.eclipse.swt.graphics.Resource
      org.eclipse.swt.graphics.GC

public class GC

extends Resource

Class GC is provided to ease single-sourcing SWT and RWT code. Its text measurement methods directly delegate to the respective Graphics methods.

Styles:

LEFT_TO_RIGHT

Application code must explicitly invoke the GC.dispose() method to release the operating system resources managed by each instance when those instances are no longer required.

Constructor Summary

GC(Drawable drawable)
Constructs a new instance of this class which has been configured to draw on the specified drawable.

Method Summary

Color	getBackground() Returns the background color.
int	getCharWidth(char ch) Returns the width of the specified character in the font selected into the receiver.
Font	getFont() Returns the font currently being used by the receiver to draw and measure text.
FontMetrics	getFontMetrics() Returns a FontMetrics which contains information about the font currently being used by the receiver to draw and measure text.
Color	getForeground() Returns the receiver's foreground color.
void	setBackground(Color color) Sets the background color.
void	setFont(Font font) Sets the font which will be used by the receiver to draw and measure text to the argument.
void	setForeground(Color color) Sets the foreground color.
Point	stringExtent(String string) Returns the extent of the given string.
Point	textExtent(String string) Returns the extent of the given string.

Methods inherited from class org.eclipse.swt.graphics.Resource

dispose, getDevice, isDisposed

Methods inherited from class java.lang.Object

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

Constructor Detail

GC

public GC(Drawable drawable)

Constructs a new instance of this class which has been configured to draw on the specified drawable. Sets the foreground color, background color and font in the GC to match those in the drawable.

You must dispose the graphics context when it is no longer required.

Parameters:

drawable - the drawable to draw on

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the drawable is null
• ERROR_NULL_ARGUMENT - if there is no current device
• ERROR_INVALID_ARGUMENT - if the drawable is an image that is not a bitmap or an icon - if the drawable is an image or printer that is already selected into another graphics context

SWTError -

• ERROR_NO_HANDLES if a handle could not be obtained for GC creation
• ERROR_THREAD_INVALID_ACCESS if not called from the thread that created the drawable

Method Detail

setFont

public void setFont(Font font)

Sets the font which will be used by the receiver to draw and measure text to the argument. If the argument is null, then a default font appropriate for the platform will be used instead.

Parameters:

font - the new font for the receiver, or null to indicate a default font

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the font has been disposed

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getFont

public Font getFont()

Returns the font currently being used by the receiver to draw and measure text.

Returns:

the receiver's font

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getCharWidth

public int getCharWidth(char ch)

Returns the width of the specified character in the font selected into the receiver.

The width is defined as the space taken up by the actual character, not including the leading and tailing whitespace or overhang.

Parameters:

ch - the character to measure

Returns:

the width of the character

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

stringExtent

public Point stringExtent(String string)

Returns the extent of the given string. No tab expansion or carriage return processing will be performed.

The extent of a string is the width and height of the rectangular area it would cover if drawn in a particular font (in this case, the current font in the receiver).

Parameters:

string - the string to measure

Returns:

a point containing the extent of the string

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the string is null

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

textExtent

public Point textExtent(String string)

Returns the extent of the given string. Tab expansion and carriage return processing are performed.

The extent of a string is the width and height of the rectangular area it would cover if drawn in a particular font (in this case, the current font in the receiver).

Parameters:

string - the string to measure

Returns:

a point containing the extent of the string

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the string is null

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getFontMetrics

public FontMetrics getFontMetrics()

Returns a FontMetrics which contains information about the font currently being used by the receiver to draw and measure text.

Returns:

font metrics for the receiver's font

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setBackground

public void setBackground(Color color)

Sets the background color. The background color is used for fill operations and as the background color when text is drawn.

Parameters:

color - the new background color for the receiver

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the color is null
• ERROR_INVALID_ARGUMENT - if the color has been disposed

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getBackground

public Color getBackground()

Returns the background color.

Returns:

the receiver's background color

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setForeground

public void setForeground(Color color)

Sets the foreground color. The foreground color is used for drawing operations including when text is drawn.

Parameters:

color - the new foreground color for the receiver

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the color is null
• ERROR_INVALID_ARGUMENT - if the color has been disposed

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getForeground

public Color getForeground()

Returns the receiver's foreground color.

Returns:

the color used for drawing foreground things

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed