public final Class TextLayout

It provides the following capabilities:

• implicit bidirectional analysis and reordering,
• cursor positioning and movement, including split cursors for mixed directional text,
• highlighting, including both logical and visual highlighting for mixed directional text,
• multiple baselines (roman, hanging, and centered),
• hit testing,
• justification,
• default font substitution,
• metric information such as ascent, descent, and advance, and
• rendering

A TextLayout object can be rendered using its draw method.

TextLayout can be constructed either directly or through the use of a LineBreakMeasurer. When constructed directly, the source text represents a single paragraph. LineBreakMeasurer allows styled text to be broken into lines that fit within a particular width. See the LineBreakMeasurer documentation for more information.

TextLayout construction logically proceeds as follows:

• paragraph attributes are extracted and examined,
• text is analyzed for bidirectional reordering, and reordering information is computed if needed,
• text is segmented into style runs
• fonts are chosen for style runs, first by using a font if the attribute TextAttribute#FONT is present, otherwise by computing a default font using the attributes that have been defined
• if text is on multiple baselines, the runs or subruns are further broken into subruns sharing a common baseline,
• glyphvectors are generated for each run using the chosen font,
• final bidirectional reordering is performed on the glyphvectors

All graphical information returned from a TextLayout object's methods is relative to the origin of the TextLayout, which is the intersection of the TextLayout object's baseline with its left edge. Also, coordinates passed into a TextLayout object's methods are assumed to be relative to the TextLayout object's origin. Clients usually need to translate between a TextLayout object's coordinate system and the coordinate system in another object (such as a Graphics object).

TextLayout objects are constructed from styled text, but they do not retain a reference to their source text. Thus, changes in the text previously used to generate a TextLayout do not affect the TextLayout.

Three methods on a TextLayout object (getNextRightHit, getNextLeftHit, and hitTestChar) return instances of TextHitInfo. The offsets contained in these TextHitInfo objects are relative to the start of the TextLayout, not to the text used to create the TextLayout. Similarly, TextLayout methods that accept TextHitInfo instances as parameters expect the TextHitInfo object's offsets to be relative to the TextLayout, not to any underlying text storage model.

Examples:

Constructing and drawing a TextLayout and its bounding rectangle:

  Graphics2D g = ...;
  Point2D loc = ...;
  Font font = Font.getFont("Helvetica-bold-italic");
  FontRenderContext frc = g.getFontRenderContext();
  TextLayout layout = new TextLayout("This is a string", font, frc);
  layout.draw(g, (float)loc.getX(), (float)loc.getY());

  Rectangle2D bounds = layout.getBounds();
  bounds.setRect(bounds.getX()+loc.getX(),
                 bounds.getY()+loc.getY(),
                 bounds.getWidth(),
                 bounds.getHeight());
  g.draw(bounds);

Hit-testing a TextLayout (determining which character is at a particular graphical location):

  Point2D click = ...;
  TextHitInfo hit = layout.hitTestChar(
                        (float) (click.getX() - loc.getX()),
                        (float) (click.getY() - loc.getY()));

Responding to a right-arrow key press:

  int insertionIndex = ...;
  TextHitInfo next = layout.getNextRightHit(insertionIndex);
  if (next != null) {
      // translate graphics to origin of layout on screen
      g.translate(loc.getX(), loc.getY());
      Shape[] carets = layout.getCaretShapes(next.getInsertionIndex());
      g.draw(carets[0]);
      if (carets[1] != null) {
          g.draw(carets[1]);
      }
  }

Drawing a selection range corresponding to a substring in the source text. The selected area may not be visually contiguous:

  // selStart, selLimit should be relative to the layout,
  // not to the source text

  int selStart = ..., selLimit = ...;
  Color selectionColor = ...;
  Shape selection = layout.getLogicalHighlightShape(selStart, selLimit);
  // selection may consist of disjoint areas
  // graphics is assumed to be translated to origin of layout
  g.setColor(selectionColor);
  g.fill(selection);

Drawing a visually contiguous selection range. The selection range may correspond to more than one substring in the source text. The ranges of the corresponding source text substrings can be obtained with getLogicalRangesForVisualSelection():

  TextHitInfo selStart = ..., selLimit = ...;
  Shape selection = layout.getVisualHighlightShape(selStart, selLimit);
  g.setColor(selectionColor);
  g.fill(selection);
  int[] ranges = getLogicalRangesForVisualSelection(selStart, selLimit);
  // ranges[0], ranges[1] is the first selection range,
  // ranges[2], ranges[3] is the second selection range, etc.