Module java.desktop
Package java.awt.font

Class TextMeasurer

java.lang.Object
java.awt.font.TextMeasurer
All Implemented Interfaces:
Cloneable
public final class TextMeasurer
extends Object
implements Cloneable
The TextMeasurer class provides the primitive operations needed for line break: measuring up to a given advance, determining the advance of a range of characters, and generating a TextLayout for a range of characters. It also provides methods for incremental editing of paragraphs.

A TextMeasurer object is constructed with an AttributedCharacterIterator representing a single paragraph of text. The value returned by the getBeginIndex method of AttributedCharacterIterator defines the absolute index of the first character. The value returned by the getEndIndex method of AttributedCharacterIterator defines the index past the last character. These values define the range of indexes to use in calls to the TextMeasurer. For example, calls to get the advance of a range of text or the line break of a range of text must use indexes between the beginning and end index values. Calls to insertChar and deleteChar reset the TextMeasurer to use the beginning index and end index of the AttributedCharacterIterator passed in those calls.

Most clients will use the more convenient LineBreakMeasurer, which implements the standard line break policy (placing as many words as will fit on each line).

Since:
1.3
See Also:
LineBreakMeasurer

  • Constructor Details

    • TextMeasurer

      public TextMeasurer​(AttributedCharacterIterator text, FontRenderContext frc)
      Constructs a TextMeasurer from the source text. The source text should be a single entire paragraph.
      Parameters:
      text - the source paragraph. Cannot be null.
      frc - the information about a graphics device which is needed to measure the text correctly. Cannot be null.

  • Method Details

    • getLineBreakIndex

      public int getLineBreakIndex​(int start, float maxAdvance)
      Returns the index of the first character which will not fit on on a line beginning at start and possible measuring up to maxAdvance in graphical width.
      Parameters:
      start - the character index at which to start measuring. start is an absolute index, not relative to the start of the paragraph
      maxAdvance - the graphical width in which the line must fit
      Returns:
      the index after the last character that will fit on a line beginning at start, which is not longer than maxAdvance in graphical width
      Throws:
      IllegalArgumentException - if start is less than the beginning of the paragraph.

    • getAdvanceBetween

      public float getAdvanceBetween​(int start, int limit)
      Returns the graphical width of a line beginning at start and including characters up to limit. start and limit are absolute indices, not relative to the start of the paragraph.
      Parameters:
      start - the character index at which to start measuring
      limit - the character index at which to stop measuring
      Returns:
      the graphical width of a line beginning at start and including characters up to limit
      Throws:
      IndexOutOfBoundsException - if limit is less than start
      IllegalArgumentException - if start or limit is not between the beginning of the paragraph and the end of the paragraph.

    • getLayout

      public TextLayout getLayout​(int start, int limit)
      Returns a TextLayout on the given character range.
      Parameters:
      start - the index of the first character
      limit - the index after the last character. Must be greater than start
      Returns:
      a TextLayout for the characters beginning at start up to (but not including) limit
      Throws:
      IndexOutOfBoundsException - if limit is less than start
      IllegalArgumentException - if start or limit is not between the beginning of the paragraph and the end of the paragraph.

    • insertChar

      public void insertChar​(AttributedCharacterIterator newParagraph, int insertPos)
      Updates the TextMeasurer after a single character has been inserted into the paragraph currently represented by this TextMeasurer. After this call, this TextMeasurer is equivalent to a new TextMeasurer created from the text; however, it will usually be more efficient to update an existing TextMeasurer than to create a new one from scratch.
      Parameters:
      newParagraph - the text of the paragraph after performing the insertion. Cannot be null.
      insertPos - the position in the text where the character was inserted. Must not be less than the start of newParagraph, and must be less than the end of newParagraph.
      Throws:
      IndexOutOfBoundsException - if insertPos is less than the start of newParagraph or greater than or equal to the end of newParagraph
      NullPointerException - if newParagraph is null

    • deleteChar

      public void deleteChar​(AttributedCharacterIterator newParagraph, int deletePos)
      Updates the TextMeasurer after a single character has been deleted from the paragraph currently represented by this TextMeasurer. After this call, this TextMeasurer is equivalent to a new TextMeasurer created from the text; however, it will usually be more efficient to update an existing TextMeasurer than to create a new one from scratch.
      Parameters:
      newParagraph - the text of the paragraph after performing the deletion. Cannot be null.
      deletePos - the position in the text where the character was removed. Must not be less than the start of newParagraph, and must not be greater than the end of newParagraph.
      Throws:
      IndexOutOfBoundsException - if deletePos is less than the start of newParagraph or greater than the end of newParagraph
      NullPointerException - if newParagraph is null