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, 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:

  • Field Details

    • PROPERTY_AVERAGE_CHARACTER_WIDTH_TEST_STRING

      public static final String PROPERTY_AVERAGE_CHARACTER_WIDTH_TEST_STRING
      See Also:

    • PROPERTY_DEFAULT_DIALOG_FONT

      public static final String PROPERTY_DEFAULT_DIALOG_FONT
      See Also:

    • OLD_AVERAGE_CHARACTER_TEST_STRING

      public static final String OLD_AVERAGE_CHARACTER_TEST_STRING
      Since:
      1.6
      See Also:

    • MODERN_AVERAGE_CHARACTER_TEST_STRING

      public static final String MODERN_AVERAGE_CHARACTER_TEST_STRING
      Since:
      1.4
      See Also:

    • BALANCED_AVERAGE_CHARACTER_TEST_STRING

      public static final String BALANCED_AVERAGE_CHARACTER_TEST_STRING
      Since:
      1.4
      See Also:

    • LOGGER

      private static final Logger LOGGER

    • instance

      private static DefaultUnitConverter instance
      Holds the sole instance that will be lazily instantiated.

    • averageCharWidthTestString

      private 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 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 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 Font cachedDefaultDialogFont
      Holds a cached default dialog font that is used as fallback, if no default dialog font has been set.
      See Also:

  • Constructor Details

    • DefaultUnitConverter

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

  • Method Details

    • getInstance

      public static DefaultUnitConverter getInstance()
      Lazily instantiates and returns the sole instance.
      Returns:
      the lazily instantiated sole instance

    • getAverageCharacterWidthTestString

      public 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(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:
      NullPointerException - if newTestString is null
      IllegalArgumentException - if newTestString is empty or whitespace

    • getDefaultDialogFont

      public 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(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(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(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(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(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 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 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 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.