org.jdesktop.layout
Class Baseline

java.lang.Object
  org.jdesktop.layout.Baseline

public class Baseline
extends Object

Convenience class that can be used to determine the baseline of a particular component. The static method getBaseline uses the following algorithm to determine the baseline:

1. If the component has a getBaseline(JComponent,int,int) method, invoke it.
2. If there is a UIManager property of the name Baseline.instance, forward the call to that Baseline.
3. Otherwise use the built in support.

In addition to determining the baseline, this class also allows for determining how the baseline changes as the size of the component changes. The method getBaselineResizeBehavior can be used for this. This will return one of BRB_OTHER, BRB_CONSTANT_ASCENT, BRB_CONSTANT_DESCENT or BRB_CENTER_OFFSET. The following algorithm is used in determining the baseline resize behavior.

1. If the Component defines the method getBaselineResizeBehaviorInt, the return value from that method is used.
2. If running on 1.6, the Component method getBaselineResizeBehavior is invoked and the return value converted to one of the constants defined by this class.
3. If the component is one of the known Swing components,the baseline resize behavior is calculated and returned.
4. Otherwise, BRB_OTHER is returned.

This class is primarily useful for JREs prior to 1.6. In 1.6 API for this was added directly to Component. When run on 1.6 or newer, this class calls into the appropriate Component methods.

Version:

$Revision: 1.13 $

Field Summary

static int	BRB_CENTER_OFFSET Baseline resize behavior constant.
static int	BRB_CONSTANT_ASCENT Baseline resize behavior constant.
static int	BRB_CONSTANT_DESCENT Baseline resize behavior constant.
static int	BRB_OTHER Baseline resize behavior constant.

Constructor Summary

protected

Baseline() Creates an instance of Baseline.

Method Summary

static int	getBaseline(JComponent component) Returns the baseline for the specified component, or -1 if the baseline can not be determined.
static int	getBaseline(JComponent component, int width, int height) Returns the baseline for the specified component, or a value less than 0 if the baseline can not be determined.
static int	getBaselineResizeBehavior(JComponent c) Returns a constant indicating how the baseline varies with the size of the component.
int	getComponentBaseline(JComponent component, int width, int height) Returns the baseline for the specified component, or -1 if the baseline can not be determined.

Methods inherited from class java.lang.Object

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

Field Detail

BRB_CONSTANT_ASCENT

public static final int BRB_CONSTANT_ASCENT

Baseline resize behavior constant. Indicates as the size of the component changes the baseline remains a fixed distance from the top of the component.

See Also:

Constant Field Values

BRB_CONSTANT_DESCENT

public static final int BRB_CONSTANT_DESCENT

Baseline resize behavior constant. Indicates as the size of the component changes the baseline remains a fixed distance from the bottom of the component.

See Also:

Constant Field Values

BRB_CENTER_OFFSET

public static final int BRB_CENTER_OFFSET

Baseline resize behavior constant. Indicates as the size of the component changes the baseline remains a fixed distance from the center of the component.

See Also:

Constant Field Values

BRB_OTHER

public static final int BRB_OTHER

Baseline resize behavior constant. Indicates as the size of the component changes the baseline can not be determined using one of the other constants.

See Also:

Constant Field Values

Constructor Detail

Baseline

protected Baseline()

Creates an instance of Baseline. You typically don't create a Baseline. The constructor is provided by look and feels that wish to provide baseline support.

A custom look and feel that wants to provide Baseline support should put the instance in the defaults returned from getDefaults. If you want to override the baseline suport for a look and feel place the instance in the defaults returned from UIManager.getLookAndFeelDefaults(). Tthis will ensure that if the look and feel changes the appropriate baseline can be used.

Method Detail

getBaselineResizeBehavior

public static int getBaselineResizeBehavior(JComponent c)

Returns a constant indicating how the baseline varies with the size of the component.

Parameters:

c - the JComponent to get the baseline resize behavior for

Returns:

one of BRB_CONSTANT_ASCENT, BRB_CONSTANT_DESCENT, BRB_CENTER_OFFSET or BRB_OTHER

getBaseline

public static int getBaseline(JComponent component)

Returns the baseline for the specified component, or -1 if the baseline can not be determined. The baseline is measured from the top of the component. This method returns the baseline based on the preferred size.

Parameters:

component - JComponent to calculate baseline for

Returns:

baseline for the specified component

getBaseline

public static int getBaseline(JComponent component,
                              int width,
                              int height)

Returns the baseline for the specified component, or a value less than 0 if the baseline can not be determined. The baseline is measured from the top of the component.

Parameters:

component - JComponent to calculate baseline for

width - Width of the component to determine baseline for.

height - Height of the component to determine baseline for.

Returns:

baseline for the specified component

getComponentBaseline

public int getComponentBaseline(JComponent component,
                                int width,
                                int height)

Returns the baseline for the specified component, or -1 if the baseline can not be determined. The baseline is measured from the top of the component.

Parameters:

component - JComponent to calculate baseline for

width - Width of the component to determine baseline for.

height - Height of the component to determine baseline for.

Returns:

baseline for the specified component