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Eclipse Platform
Release 3.0

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org.eclipse.swt.graphics
Class TextLayout

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

public final class TextLayout

extends Object

TextLayout is a graphic object that represents styled text.

Instances of this class provide support for drawing, cursor navigation, hit testing, text wrapping, alignment, tab expansion line breaking, etc. These are aspects required for rendering internationalized text.

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

Since:

3.0

Constructor Summary

TextLayout(Device device)
Constructs a new instance of this class on the given device.

Method Summary

void	dispose() Disposes of the operating system resources associated with the text layout.
void	draw(GC gc, int x, int y) Draws the receiver's text using the specified GC at the specified point.
void	draw(GC gc, int x, int y, int selectionStart, int selectionEnd, Color selectionForeground, Color selectionBackground) Draws the receiver's text using the specified GC at the specified point.
int	getAlignment() Returns the receiver's horizontal text alignment, which will be one of SWT.LEFT, SWT.CENTER or SWT.RIGHT.
int	getAscent() Returns the ascent of the receiver.
Rectangle	getBounds() Returns the bounds of the receiver.
Rectangle	getBounds(int start, int end) Returns the bounds for the specified range of characters.
int	getDescent() Returns the descent of the receiver.
Font	getFont() Returns the default font currently being used by the receiver to draw and measure text.
int	getLevel(int offset) Returns the embedding level for the specified character offset.
Rectangle	getLineBounds(int lineIndex) Returns the bounds of the line for the specified line index.
int	getLineCount() Returns the receiver's line count.
int	getLineIndex(int offset) Returns the index of the line that contains the specified character offset.
FontMetrics	getLineMetrics(int lineIndex) Returns the font metrics for the specified line index.
int[]	getLineOffsets() Returns the line offsets.
Point	getLocation(int offset, boolean trailing) Returns the location for the specified character offset.
int	getNextOffset(int offset, int movement) Returns the next offset for the specified offset and movement type.
int	getOffset(int x, int y, int[] trailing) Returns the character offset for the specified point.
int	getOffset(Point point, int[] trailing) Returns the character offset for the specified point.
int	getOrientation() Returns the orientation of the receiver.
int	getPreviousOffset(int offset, int movement) Returns the previous offset for the specified offset and movement type.
int[]	getSegments() Returns the text segments offsets of the receiver.
int	getSpacing() Returns the line spacing of the receiver.
TextStyle	getStyle(int offset) Gets the style of the receiver at the specified character offset.
int[]	getTabs() Returns the tab list of the receiver.
String	getText() Gets the receiver's text, which will be an empty string if it has never been set.
int	getWidth() Returns the width of the receiver.
boolean	isDisposed() Returns true if the text layout has been disposed, and false otherwise.
void	setAlignment(int alignment) Sets the text alignment for the receiver.
void	setAscent(int ascent) Sets the ascent of the receiver.
void	setDescent(int descent) Sets the descent of the receiver.
void	setFont(Font font) Sets the default font which will be used by the receiver to draw and measure text.
void	setOrientation(int orientation) Sets the orientation of the receiver, which must be one of SWT.LEFT_TO_RIGHT or SWT.RIGHT_TO_LEFT.
void	setSegments(int[] segments) Sets the offsets of the receiver's text segments.
void	setSpacing(int spacing) Sets the line spacing of the receiver.
void	setStyle(TextStyle style, int start, int end) Sets the style of the receiver for the specified range.
void	setTabs(int[] tabs) Sets the receiver's tab list.
void	setText(String text) Sets the receiver's text.
void	setWidth(int width) Sets the line width of the receiver, which determines how text should be wrapped and aligned.

Methods inherited from class java.lang.Object

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

Constructor Detail

TextLayout

public TextLayout(Device device)

Constructs a new instance of this class on the given device.

You must dispose the text layout when it is no longer required.

Parameters:

device - the device on which to allocate the text layout

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if device is null and there is no current device

See Also:

dispose()

Method Detail

dispose

public void dispose()

Disposes of the operating system resources associated with the text layout. Applications must dispose of all allocated text layouts.

draw

public void draw(GC gc,
                 int x,
                 int y)

Draws the receiver's text using the specified GC at the specified point.

Parameters:

gc - the GC to draw

x - the x coordinate of the top left corner of the rectangular area where the text is to be drawn

y - the y coordinate of the top left corner of the rectangular area where the text is to be drawn

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

draw

public void draw(GC gc,
                 int x,
                 int y,
                 int selectionStart,
                 int selectionEnd,
                 Color selectionForeground,
                 Color selectionBackground)

Draws the receiver's text using the specified GC at the specified point.

Parameters:

gc - the GC to draw

x - the x coordinate of the top left corner of the rectangular area where the text is to be drawn

y - the y coordinate of the top left corner of the rectangular area where the text is to be drawn

selectionStart - the offset where the selections starts, or -1 indicating no selection

selectionEnd - the offset where the selections ends, or -1 indicating no selection

selectionForeground - selection foreground, or NULL to use the system default color

selectionBackground - selection background, or NULL to use the system default color

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getAlignment

public int getAlignment()

Returns the receiver's horizontal text alignment, which will be one of SWT.LEFT, SWT.CENTER or SWT.RIGHT.

Returns:

the alignment used to positioned text horizontally

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getAscent

public int getAscent()

Returns the ascent of the receiver.

Returns:

the ascent

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getDescent(), setDescent(int), setAscent(int), getLineMetrics(int)

getBounds

public Rectangle getBounds()

Returns the bounds of the receiver.

Returns:

the bounds of the receiver

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getBounds

public Rectangle getBounds(int start,
                           int end)

Returns the bounds for the specified range of characters. The bounds is the smallest rectangle that encompasses all characters in the range. The start and end offsets are inclusive and will be clamped if out of range.

Parameters:

start - the start offset

end - the end offset

Returns:

the bounds of the character range

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getDescent

public int getDescent()

Returns the descent of the receiver.

Returns:

the descent

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getAscent(), setAscent(int), setDescent(int), getLineMetrics(int)

getFont

public Font getFont()

Returns the default 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

getLevel

public int getLevel(int offset)

Returns the embedding level for the specified character offset. The embedding level is usually used to determine the directionality of a character in bidirectional text.

Parameters:

offset - the charecter offset

Returns:

the embedding level

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the character offset is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLineBounds

public Rectangle getLineBounds(int lineIndex)

Returns the bounds of the line for the specified line index.

Parameters:

lineIndex - the line index

Returns:

the line bounds

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the line index is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLineCount

public int getLineCount()

Returns the receiver's line count. This includes lines caused by wrapping.

Returns:

the line count

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLineIndex

public int getLineIndex(int offset)

Returns the index of the line that contains the specified character offset.

Parameters:

offset - the character offset

Returns:

the line index

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the character offset is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLineMetrics

public FontMetrics getLineMetrics(int lineIndex)

Returns the font metrics for the specified line index.

Parameters:

lineIndex - the line index

Returns:

the font metrics

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the line index is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLineOffsets

public int[] getLineOffsets()

Returns the line offsets. Each value in the array is the offset for the first character in a line except for the last value, which contains the length of the text.

Returns:

the line offsets

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getLocation

public Point getLocation(int offset,
                         boolean trailing)

Returns the location for the specified character offset. The trailing argument indicates whether the offset corresponds to the leading or trailing edge of the cluster.

Parameters:

offset - the character offset

trailing - the trailing flag

Returns:

the location of the character offset

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getOffset(Point, int[]), getOffset(int, int, int[])

getNextOffset

public int getNextOffset(int offset,
                         int movement)

Returns the next offset for the specified offset and movement type. The movement is one of SWT.MOVEMENT_CHAR, SWT.MOVEMENT_CLUSTER or SWT.MOVEMENT_WORD.

Parameters:

offset - the start offset

movement - the movement type

Returns:

the next offset

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the offset is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getPreviousOffset(int, int)

getOffset

public int getOffset(Point point,
                     int[] trailing)

Returns the character offset for the specified point. For a typical character, the trailing argument will be filled in to indicate whether the point is closer to the leading edge (0) or the trailing edge (1). When the point is over a cluster composed of multiple characters, the trailing argument will be filled with the position of the character in the cluster that is closest to the point.

Parameters:

point - the point

trailing - the trailing buffer

Returns:

the character offset

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the trailing length is less than 1

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getLocation(int, boolean)

getOffset

public int getOffset(int x,
                     int y,
                     int[] trailing)

Returns the character offset for the specified point. For a typical character, the trailing argument will be filled in to indicate whether the point is closer to the leading edge (0) or the trailing edge (1). When the point is over a cluster composed of multiple characters, the trailing argument will be filled with the position of the character in the cluster that is closest to the point.

Parameters:

x - the x coordinate of the point

y - the y coordinate of the point

trailing - the trailing buffer

Returns:

the character offset

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the trailing length is less than 1

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getLocation(int, boolean)

getOrientation

public int getOrientation()

Returns the orientation of the receiver.

Returns:

the orientation style

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getPreviousOffset

public int getPreviousOffset(int offset,
                             int movement)

Returns the previous offset for the specified offset and movement type. The movement is one of SWT.MOVEMENT_CHAR, SWT.MOVEMENT_CLUSTER or SWT.MOVEMENT_WORD.

Parameters:

offset - the start offset

movement - the movement type

Returns:

the previous offset

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the offset is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

getNextOffset(int, int)

getSegments

public int[] getSegments()

Returns the text segments offsets of the receiver.

Returns:

the text segments offsets

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getSpacing

public int getSpacing()

Returns the line spacing of the receiver.

Returns:

the line spacing

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getStyle

public TextStyle getStyle(int offset)

Gets the style of the receiver at the specified character offset.

Parameters:

offset - the text offset

Returns:

the style or null if not set

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the character offset is out of range

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getTabs

public int[] getTabs()

Returns the tab list of the receiver.

Returns:

the tab list

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getText

public String getText()

Gets the receiver's text, which will be an empty string if it has never been set.

Returns:

the receiver's text

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

getWidth

public int getWidth()

Returns the width of the receiver.

Returns:

the width

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

isDisposed

public boolean isDisposed()

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

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

Returns:

true when the text layout is disposed and false otherwise

setAlignment

public void setAlignment(int alignment)

Sets the text alignment for the receiver. The alignment controls how a line of text is positioned horizontally. The argument should be one of SWT.LEFT, SWT.RIGHT or SWT.CENTER.

The default alignment is SWT.LEFT. Note that the receiver's width must be set in order to use SWT.RIGHT or SWT.CENTER alignment.

Parameters:

alignment - the new alignment

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

setWidth(int)

setAscent

public void setAscent(int ascent)

Sets the ascent of the receiver. The ascent is distance in pixels from the baseline to the top of the line and it is applied to all lines. The default value is -1 which means that the ascent is calculated from the line fonts.

Parameters:

ascent - the new ascent

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the ascent is less than -1

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

setDescent(int), #getLineMetrics()

setDescent

public void setDescent(int descent)

Sets the descent of the receiver. The descent is distance in pixels from the baseline to the bottom of the line and it is applied to all lines. The default value is -1 which means that the descent is calculated from the line fonts.

Parameters:

descent - the new descent

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the descent is less than -1

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

setAscent(int), #getLineMetrics()

setFont

public void setFont(Font font)

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

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

setOrientation

public void setOrientation(int orientation)

Sets the orientation of the receiver, which must be one of SWT.LEFT_TO_RIGHT or SWT.RIGHT_TO_LEFT.

Parameters:

orientation - new orientation style

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setSegments

public void setSegments(int[] segments)

Sets the offsets of the receiver's text segments. Text segments are used to override the default behaviour of the bidirectional algorithm. Bidirectional reordering can happen within a text segment but not between two adjacent segments. Each text segment is determined by two consecutive offsets in the segments arrays. The first element of the array should always be zero and the last one should always be equals to length of the text.

Parameters:

segments - the text segments offset

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setSpacing

public void setSpacing(int spacing)

Sets the line spacing of the receiver. The line spacing is the space left between lines.

Parameters:

spacing - the new line spacing

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the spacing is negative

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setStyle

public void setStyle(TextStyle style,
                     int start,
                     int end)

Sets the style of the receiver for the specified range. Styles previously set for that range will be overwritten. The start and end offsets are inclusive and will be clamped if out of range.

Parameters:

style - the style

start - the start offset

end - the end offset

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setTabs

public void setTabs(int[] tabs)

Sets the receiver's tab list. Each value in the tab list specifies the space in pixels from the origin of the text layout to the respective tab stop. The last tab stop width is repeated continuously.

Parameters:

tabs - the new tab list

Throws:

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setText

public void setText(String text)

Sets the receiver's text.

Parameters:

text - the new text

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the text is null

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

setWidth

public void setWidth(int width)

Sets the line width of the receiver, which determines how text should be wrapped and aligned. The default value is -1 which means wrapping is disabled.

Parameters:

width - the new width

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the width is 0 or less than -1

SWTException -

• ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed

See Also:

setAlignment(int)