com.jgoodies.forms.util

Class DefaultUnitConverter

java.lang.Object

com.jgoodies.common.bean.Bean

com.jgoodies.forms.util.AbstractUnitConverter

com.jgoodies.forms.util.DefaultUnitConverter

All Implemented Interfaces:

com.jgoodies.common.bean.ObservableBean, com.jgoodies.common.bean.ObservableBean2, UnitConverter, java.io.Serializable

public final class DefaultUnitConverter
extends AbstractUnitConverter

This is the default implementation of the UnitConverter interface. It converts horizontal and vertical dialog base units to pixels.

The horizontal base unit is equal to the average width, in pixels, of the characters in the system font; the vertical base unit is equal to the height, in pixels, of the font. Each horizontal base unit is equal to 4 horizontal dialog units; each vertical base unit is equal to 8 vertical dialog units.

The DefaultUnitConverter computes dialog base units using a default font and a test string for the average character width. You can configure the font and the test string via the bound Bean properties defaultDialogFont and averageCharacterWidthTestString. See also Microsoft's suggestion for a custom computation custom computation. More information how to use dialog units in screen design can be found in Microsoft's Design Specifications and Guidelines.

Since the Forms 1.1 this converter logs font information at the CONFIG level.

Version:

$Revision: 1.23 $

See Also:

UnitConverter, Size, Sizes, Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	DefaultUnitConverter.DialogBaseUnits Describes horizontal and vertical dialog base units.

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.String	averageCharWidthTestString Holds the string that is used to compute the average character width.
static java.lang.String	BALANCED_AVERAGE_CHARACTER_TEST_STRING
private java.awt.Font	cachedDefaultDialogFont Holds a cached default dialog font that is used as fallback, if no default dialog font has been set.
private DefaultUnitConverter.DialogBaseUnits	cachedDialogBaseUnits Holds the horizontal dialog base units that are valid for the FontMetrics stored in cachedFontMetrics.
private java.awt.FontMetrics	cachedFontMetrics Holds the FontMetrics used to compute the per-component dialog units.
private DefaultUnitConverter.DialogBaseUnits	cachedGlobalDialogBaseUnits Holds the lazily created cached global dialog base units that are used if a component is not (yet) available - for example in a Border.
private java.awt.Font	defaultDialogFont Holds a custom font that is used to compute the global dialog base units.
private static DefaultUnitConverter	instance Holds the sole instance that will be lazily instantiated.
private static java.util.logging.Logger	LOGGER
static java.lang.String	MODERN_AVERAGE_CHARACTER_TEST_STRING
static java.lang.String	OLD_AVERAGE_CHARACTER_TEST_STRING
static java.lang.String	PROPERTY_AVERAGE_CHARACTER_WIDTH_TEST_STRING
static java.lang.String	PROPERTY_DEFAULT_DIALOG_FONT

Fields inherited from class com.jgoodies.common.bean.Bean

changeSupport

Constructor Summary

Constructors

Modifier	Constructor and Description
private	DefaultUnitConverter() Constructs a DefaultUnitConverter and registers a listener that handles changes in the look&feel.

Method Summary

Modifier and Type	Method and Description
(package private) void	clearCache() Invalidates the caches.
private DefaultUnitConverter.DialogBaseUnits	computeDialogBaseUnits(java.awt.FontMetrics metrics) Computes and returns the horizontal dialog base units.
private DefaultUnitConverter.DialogBaseUnits	computeGlobalDialogBaseUnits() Computes the global dialog base units.
private static java.awt.Component	createDefaultGlobalComponent() Creates and returns a component that is used to lookup the default font metrics.
java.lang.String	getAverageCharacterWidthTestString() Returns the string used to compute the average character width.
private java.awt.Font	getCachedDefaultDialogFont() Lazily creates and returns a fallback for the dialog font that is used to compute the dialog base units.
java.awt.Font	getDefaultDialogFont() Returns the dialog font that is used to compute the dialog base units.
private DefaultUnitConverter.DialogBaseUnits	getDialogBaseUnits(java.awt.Component c) Looks up and returns the dialog base units for the given component.
protected double	getDialogBaseUnitsX(java.awt.Component component) Returns the cached or computed horizontal dialog base units.
protected double	getDialogBaseUnitsY(java.awt.Component component) Returns the cached or computed vertical dialog base units for the given component.
private DefaultUnitConverter.DialogBaseUnits	getGlobalDialogBaseUnits() Lazily computes and answer the global dialog base units.
static DefaultUnitConverter	getInstance() Lazily instantiates and returns the sole instance.
private static java.awt.Font	lookupDefaultDialogFont() Looks up and returns the font used by buttons.
void	setAverageCharacterWidthTestString(java.lang.String newTestString) Sets a string that will be used to compute the average character width.
void	setDefaultDialogFont(java.awt.Font newFont) Sets a dialog font that will be used to compute the dialog base units.

Methods inherited from class com.jgoodies.forms.util.AbstractUnitConverter

centimeterAsPixel, centimeterAsPixel, computeAverageCharWidth, dialogUnitXAsPixel, dialogUnitXAsPixel, dialogUnitYAsPixel, dialogUnitYAsPixel, getDefaultScreenResolution, getScreenResolution, inchAsPixel, inchAsPixel, millimeterAsPixel, millimeterAsPixel, pointAsPixel, pointAsPixel

Methods inherited from class com.jgoodies.common.bean.Bean

addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, addVetoableChangeListener, createPropertyChangeSupport, fireIndexedPropertyChange, fireIndexedPropertyChange, fireIndexedPropertyChange, fireMultiplePropertiesChanged, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, getPropertyChangeListeners, getPropertyChangeListeners, getVetoableChangeListeners, getVetoableChangeListeners, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, removeVetoableChangeListener

Methods inherited from class java.lang.Object

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

Field Detail

PROPERTY_AVERAGE_CHARACTER_WIDTH_TEST_STRING

public static final java.lang.String PROPERTY_AVERAGE_CHARACTER_WIDTH_TEST_STRING

See Also:

Constant Field Values

PROPERTY_DEFAULT_DIALOG_FONT

public static final java.lang.String PROPERTY_DEFAULT_DIALOG_FONT

See Also:

Constant Field Values

OLD_AVERAGE_CHARACTER_TEST_STRING

public static final java.lang.String OLD_AVERAGE_CHARACTER_TEST_STRING

Since:

1.6

See Also:

Constant Field Values

MODERN_AVERAGE_CHARACTER_TEST_STRING

public static final java.lang.String MODERN_AVERAGE_CHARACTER_TEST_STRING

Since:

1.4

See Also:

Constant Field Values

BALANCED_AVERAGE_CHARACTER_TEST_STRING

public static final java.lang.String BALANCED_AVERAGE_CHARACTER_TEST_STRING

Since:

1.4

See Also:

Constant Field Values

LOGGER

private static final java.util.logging.Logger LOGGER

instance

private static DefaultUnitConverter instance

Holds the sole instance that will be lazily instantiated.

averageCharWidthTestString

private java.lang.String averageCharWidthTestString

Holds the string that is used to compute the average character width. Since 1.6 the default value is the balanced average character test string, where it was just "X" before.

defaultDialogFont

private java.awt.Font defaultDialogFont

Holds a custom font that is used to compute the global dialog base units. If not set, a fallback font is is lazily created in method #getCachedDefaultDialogFont, which in turn looks up a font in method #lookupDefaultDialogFont.

cachedGlobalDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits cachedGlobalDialogBaseUnits

Holds the lazily created cached global dialog base units that are used if a component is not (yet) available - for example in a Border.

cachedDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits cachedDialogBaseUnits

Holds the horizontal dialog base units that are valid for the FontMetrics stored in cachedFontMetrics.

cachedFontMetrics

private java.awt.FontMetrics cachedFontMetrics

Holds the FontMetrics used to compute the per-component dialog units. The latter are valid, if a FontMetrics equals this stored metrics.

cachedDefaultDialogFont

private java.awt.Font cachedDefaultDialogFont

Holds a cached default dialog font that is used as fallback, if no default dialog font has been set.

See Also:

getDefaultDialogFont(), setDefaultDialogFont(Font)

Constructor Detail

DefaultUnitConverter

private DefaultUnitConverter()

Constructs a DefaultUnitConverter and registers a listener that handles changes in the look&feel.

Method Detail

getInstance

public static DefaultUnitConverter getInstance()

Lazily instantiates and returns the sole instance.

Returns:

the lazily instantiated sole instance

getAverageCharacterWidthTestString

public java.lang.String getAverageCharacterWidthTestString()

Returns the string used to compute the average character width. By default it is initialized to BALANCED_AVERAGE_CHARACTER_TEST_STRING.

Returns:

the test string used to compute the average character width

setAverageCharacterWidthTestString

public void setAverageCharacterWidthTestString(java.lang.String newTestString)

Sets a string that will be used to compute the average character width. By default it is initialized to BALANCED_AVERAGE_CHARACTER_TEST_STRING. You can provide other test strings, for example:

• "Xximeee"
• "ABCEDEFHIJKLMNOPQRSTUVWXYZ"
• "abcdefghijklmnopqrstuvwxyz"

Parameters:

newTestString - the test string to be used

Throws:

java.lang.NullPointerException - if newTestString is null

java.lang.IllegalArgumentException - if newTestString is empty or whitespace

getDefaultDialogFont

public java.awt.Font getDefaultDialogFont()

Returns the dialog font that is used to compute the dialog base units. If a default dialog font has been set using setDefaultDialogFont(Font), this font will be returned. Otherwise a cached fallback will be lazily created.

Returns:

the font used to compute the dialog base units

setDefaultDialogFont

public void setDefaultDialogFont(java.awt.Font newFont)

Sets a dialog font that will be used to compute the dialog base units.

Parameters:

newFont - the default dialog font to be set

getDialogBaseUnitsX

protected double getDialogBaseUnitsX(java.awt.Component component)

Returns the cached or computed horizontal dialog base units.

Specified by:

getDialogBaseUnitsX in class AbstractUnitConverter

Parameters:

component - a Component that provides the font and graphics

Returns:

the horizontal dialog base units

getDialogBaseUnitsY

protected double getDialogBaseUnitsY(java.awt.Component component)

Returns the cached or computed vertical dialog base units for the given component.

Specified by:

getDialogBaseUnitsY in class AbstractUnitConverter

Parameters:

component - a Component that provides the font and graphics

Returns:

the vertical dialog base units

getGlobalDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits getGlobalDialogBaseUnits()

Lazily computes and answer the global dialog base units. Should be re-computed if the l&f, platform, or screen changes.

Returns:

a cached DialogBaseUnits object used globally if no container is available

getDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits getDialogBaseUnits(java.awt.Component c)

Looks up and returns the dialog base units for the given component. In case the component is null the global dialog base units are answered.

Before we compute the dialog base units we check whether they have been computed and cached before - for the same component FontMetrics.

Parameters:

c - the component that provides the graphics object

Returns:

the DialogBaseUnits object for the given component

computeDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits computeDialogBaseUnits(java.awt.FontMetrics metrics)

Computes and returns the horizontal dialog base units. Honors the font, font size and resolution.

Implementation Note: 14dluY map to 22 pixel for 8pt Tahoma on 96 dpi. I could not yet manage to compute the Microsoft compliant font height. Therefore this method adds a correction value that seems to work well with the vast majority of desktops.

TODO: Revise the computation of vertical base units as soon as there are more information about the original computation in Microsoft environments.

Parameters:

metrics - the FontMetrics used to measure the dialog font

Returns:

the horizontal and vertical dialog base units

computeGlobalDialogBaseUnits

private DefaultUnitConverter.DialogBaseUnits computeGlobalDialogBaseUnits()

Computes the global dialog base units. The current implementation assumes a fixed 8pt font and on 96 or 120 dpi. A better implementation should ask for the main dialog font and should honor the current screen resolution.

Should be re-computed if the l&f, platform, or screen changes.

Returns:

a DialogBaseUnits object used globally if no container is available

getCachedDefaultDialogFont

private java.awt.Font getCachedDefaultDialogFont()

Lazily creates and returns a fallback for the dialog font that is used to compute the dialog base units. This fallback font is cached and will be reset if the L&F changes.

Returns:

the cached fallback font used to compute the dialog base units

lookupDefaultDialogFont

private static java.awt.Font lookupDefaultDialogFont()

Looks up and returns the font used by buttons. First, tries to request the button font from the UIManager; if this fails a JButton is created and asked for its font.

Returns:

the font used for a standard button

createDefaultGlobalComponent

private static java.awt.Component createDefaultGlobalComponent()

Creates and returns a component that is used to lookup the default font metrics. The current implementation creates a JPanel. Since this panel has no parent, it has no toolkit assigned. And so, requesting the font metrics will end up using the default toolkit and its deprecated method ToolKit#getFontMetrics().

TODO: Consider publishing this method and providing a setter, so that an API user can set a realized component that has a toolkit assigned.

Returns:

a component used to compute the default font metrics

clearCache

void clearCache()

Invalidates the caches. Resets the global dialog base units, clears the Map from FontMetrics to dialog base units, and resets the fallback for the default dialog font. This is invoked after a change of the look&feel.