textlayout.java

JAVA基本类源代码,大家可以学习学习!

    public float getDescent() {
        if (optInfo != null) {
            return optInfo.getLineMetrics().getDescent();
        }
        ensureCache();
        return lineMetrics.descent;
    }

    /**
     * Returns the leading of the <code>TextLayout</code>.
     * The leading is the suggested interline spacing for this 
     * <code>TextLayout</code>.
     * <p>
     * The leading is computed from the leading, descent, and baseline
     * of all glyphvectors in the <code>TextLayout</code>.  The algorithm 
     * is roughly as follows:
     * <blockquote><pre>
     * maxD = 0;
     * maxDL = 0;
     * for (GlyphVector g in all glyphvectors) {
     *    maxD = max(maxD, g.getDescent() + offsets[g.getBaseline()]);
     *    maxDL = max(maxDL, g.getDescent() + g.getLeading() +
     *                       offsets[g.getBaseline()]);
     * }
     * return maxDL - maxD;
     * </pre></blockquote>
     * @return the leading of this <code>TextLayout</code>.
     */
    public float getLeading() {
        if (optInfo != null) {
            return optInfo.getLineMetrics().getLeading();
        }
        ensureCache();
        return lineMetrics.leading;
    }

    /**
     * Returns the bounds of this <code>TextLayout</code>.
     * The bounds contains all of the pixels the <code>TextLayout</code>
     * can draw.  It might not coincide exactly with the ascent, descent, 
     * origin or advance of the <code>TextLayout</code>.
     * @return a {@link Rectangle2D} that is the bounds of this
     *        <code>TextLayout</code>.
     */
    public Rectangle2D getBounds() {
	if (optInfo != null) {
	    return optInfo.getVisualBounds();
	}

        ensureCache();

        if (boundsRect == null) {
            Rectangle2D lineBounds = textLine.getBounds();
            if (dx != 0 || dy != 0) {
                lineBounds.setRect(lineBounds.getX() - dx,
                                   lineBounds.getY() - dy,
                                   lineBounds.getWidth(),
                                   lineBounds.getHeight());
            }
            boundsRect = lineBounds;
        }

        Rectangle2D bounds = new Rectangle2D.Float();
        bounds.setRect(boundsRect);

        return bounds;
    }

    /**
     * Returns <code>true</code> if this <code>TextLayout</code> has 
     * a left-to-right base direction or <code>false</code> if it has
     * a right-to-left base direction.  The <code>TextLayout</code>
     * has a base direction of either left-to-right (LTR) or
     * right-to-left (RTL).  The base direction is independent of the 
     * actual direction of text on the line, which may be either LTR, 
     * RTL, or mixed. Left-to-right layouts by default should position 
     * flush left.  If the layout is on a tabbed line, the
     * tabs run left to right, so that logically successive layouts position
     * left to right.  The opposite is true for RTL layouts. By default they
     * should position flush left, and tabs run right-to-left.
     * @return <code>true</code> if the base direction of this 
     *         <code>TextLayout</code> is left-to-right; <code>false</code>
     *         otherwise.
     */
    public boolean isLeftToRight() {
        return (optInfo != null) || textLine.isDirectionLTR();
    }

    /**
     * Returns <code>true</code> if this <code>TextLayout</code> is vertical.
     * @return <code>true</code> if this <code>TextLayout</code> is vertical;
     *      <code>false</code> otherwise.
     */
    public boolean isVertical() {
        return isVerticalLine;
    }

    /**
     * Returns the number of characters represented by this 
     * <code>TextLayout</code>.
     * @return the number of characters in this <code>TextLayout</code>.
     */
    public int getCharacterCount() {
        return characterCount;
    }

    /*
     * carets and hit testing
     *
     * Positions on a text line are represented by instances of TextHitInfo.
     * Any TextHitInfo with characterOffset between 0 and characterCount-1,
     * inclusive, represents a valid position on the line.  Additionally,
     * [-1, trailing] and [characterCount, leading] are valid positions, and
     * represent positions at the logical start and end of the line,
     * respectively.
     *
     * The characterOffsets in TextHitInfo's used and returned by TextLayout
     * are relative to the beginning of the text layout, not necessarily to
     * the beginning of the text storage the client is using.
     *
     *
     * Every valid TextHitInfo has either one or two carets associated with it.
     * A caret is a visual location in the TextLayout indicating where text at
     * the TextHitInfo will be displayed on screen.  If a TextHitInfo
     * represents a location on a directional boundary, then there are two
     * possible visible positions for newly inserted text.  Consider the
     * following example, in which capital letters indicate right-to-left text,
     * and the overall line direction is left-to-right:
     *
     * Text Storage: [ a, b, C, D, E, f ]
     * Display:        a b E D C f
     *
     * The text hit info (1, t) represents the trailing side of 'b'.  If 'q',
     * a left-to-right character is inserted into the text storage at this
     * location, it will be displayed between the 'b' and the 'E':
     *
     * Text Storage: [ a, b, q, C, D, E, f ]
     * Display:        a b q E D C f
     *
     * However, if a 'W', which is right-to-left, is inserted into the storage
     * after 'b', the storage and display will be:
     *
     * Text Storage: [ a, b, W, C, D, E, f ]
     * Display:        a b E D C W f
     *
     * So, for the original text storage, two carets should be displayed for
     * location (1, t): one visually between 'b' and 'E' and one visually
     * between 'C' and 'f'.
     *
     *
     * When two carets are displayed for a TextHitInfo, one caret is the
     * 'strong' caret and the other is the 'weak' caret.  The strong caret
     * indicates where an inserted character will be displayed when that
     * character's direction is the same as the direction of the TextLayout.
     * The weak caret shows where an character inserted character will be
     * displayed when the character's direction is opposite that of the
     * TextLayout.
     *
     *
     * Clients should not be overly concerned with the details of correct
     * caret display. TextLayout.getCaretShapes(TextHitInfo) will return an
     * array of two paths representing where carets should be displayed.
     * The first path in the array is the strong caret; the second element,
     * if non-null, is the weak caret.  If the second element is null,
     * then there is no weak caret for the given TextHitInfo.
     *
     *
     * Since text can be visually reordered, logically consecutive
     * TextHitInfo's may not be visually consecutive.  One implication of this
     * is that a client cannot tell from inspecting a TextHitInfo whether the
     * hit represents the first (or last) caret in the layout.  Clients
     * can call getVisualOtherHit();  if the visual companion is
     * (-1, TRAILING) or (characterCount, LEADING), then the hit is at the
     * first (last) caret position in the layout.
     */

    private float[] getCaretInfo(int caret, 
                                 Rectangle2D bounds,
                                 float[] info) {

        float top1X, top2X;
        float bottom1X, bottom2X;

        if (caret == 0 || caret == characterCount) {

            float pos;
            int logIndex;
            if (caret == characterCount) {
                logIndex = textLine.visualToLogical(characterCount-1);
                pos = textLine.getCharLinePosition(logIndex)
                                        + textLine.getCharAdvance(logIndex);
            }
            else {
                logIndex = textLine.visualToLogical(caret);
                pos = textLine.getCharLinePosition(logIndex);
            }
            float angle = textLine.getCharAngle(logIndex);
            top1X = top2X = pos + angle*textLine.getCharAscent(logIndex);
            bottom1X = bottom2X = pos - angle*textLine.getCharDescent(logIndex);
        }
        else {

            {
                int logIndex = textLine.visualToLogical(caret-1);
                float angle1 = textLine.getCharAngle(logIndex);
                float pos1 = textLine.getCharLinePosition(logIndex)
                                    + textLine.getCharAdvance(logIndex);
                if (angle1 != 0) {
                    top1X = pos1 + angle1*textLine.getCharAscent(logIndex);
                    bottom1X = pos1 - angle1*textLine.getCharDescent(logIndex);
                }
                else {
                    top1X = bottom1X = pos1;
                }
            }
            {
                int logIndex = textLine.visualToLogical(caret);
                float angle2 = textLine.getCharAngle(logIndex);
                float pos2 = textLine.getCharLinePosition(logIndex);
                if (angle2 != 0) {
                    top2X = pos2 + angle2*textLine.getCharAscent(logIndex);
                    bottom2X = pos2 - angle2*textLine.getCharDescent(logIndex);
                }
                else {
                    top2X = bottom2X = pos2;
                }
            }
        }

        float topX = (top1X + top2X) / 2;
        float bottomX = (bottom1X + bottom2X) / 2;

        if (info == null) {
            info = new float[2];
        }

        if (isVerticalLine) {
            info[1] = (float) ((topX - bottomX) / bounds.getWidth());
            info[0] = (float) (topX + (info[1]*bounds.getX()));
        }
        else {
            info[1] = (float) ((topX - bottomX) / bounds.getHeight());
            info[0] = (float) (bottomX + (info[1]*bounds.getMaxY()));
        }

        return info;
    }

    /**
     * Returns information about the caret corresponding to <code>hit</code>.
     * The first element of the array is the intersection of the caret with
     * the baseline. The second element of the array is the inverse slope 
     * (run/rise) of the caret.
     * <p>
     * This method is meant for informational use.  To display carets, it
     * is better to use <code>getCaretShapes</code>.
     * @param hit a hit on a character in this <code>TextLayout</code>
     * @param bounds the bounds to which the caret info is constructed
     * @return a two-element array containing the position and slope of
     * the caret.
     * @see #getCaretShapes(int, Rectangle2D, TextLayout.CaretPolicy)
     * @see Font#getItalicAngle
     */
    public float[] getCaretInfo(TextHitInfo hit, Rectangle2D bounds) {
        ensureCache();
        checkTextHit(hit);

        return getCaretInfo(hitToCaret(hit), bounds, null);
    }

    /**
     * Returns information about the caret corresponding to <code>hit</code>.
     * This method is a convenience overload of <code>getCaretInfo</code> and
     * uses the natural bounds of this <code>TextLayout</code>.
     * @param hit a hit on a character in this <code>TextLayout</code>
     * @return the information about a caret corresponding to a hit.
     */
    public float[] getCaretInfo(TextHitInfo hit) {

        return getCaretInfo(hit, getNaturalBounds());
    }

    /**
     * Returns a caret index corresponding to <code>hit</code>.
     * Carets are numbered from left to right (top to bottom) starting from
     * zero. This always places carets next to the character hit, on the
     * indicated side of the character.
     * @param hit a hit on a character in this <code>TextLayout</code>
     * @return a caret index corresponding to the specified hit.
     */
    private int hitToCaret(TextHitInfo hit) {

        int hitIndex = hit.getCharIndex();

        if (hitIndex < 0) {
            return textLine.isDirectionLTR() ? 0 : characterCount;
        } else if (hitIndex >= characterCount) {
            return textLine.isDirectionLTR() ? characterCount : 0;
        }

        int visIndex = textLine.logicalToVisual(hitIndex);

        if (hit.isLeadingEdge() != textLine.isCharLTR(hitIndex)) {
            ++visIndex;
        }

        return visIndex;
    }

    /**
     * Given a caret index, return a hit whose caret is at the index.
     * The hit is NOT guaranteed to be strong!!!
     *
     * @param caret a caret index.
     * @return a hit on this layout whose strong caret is at the requested
     * index.
     */
    private TextHitInfo caretToHit(int caret) {

        if (caret == 0 || caret == characterCount) {

            if ((caret == characterCount) == textLine.isDirectionLTR()) {
                return TextHitInfo.leading(characterCount);
            }
            else {
                return TextHitInfo.trailing(-1);
            }
        }
        else {

            int charIndex = textLine.visualToLogical(caret);
            boolean leading = textLine.isCharLTR(charIndex);

            return leading? TextHitInfo.leading(charIndex)
                            : TextHitInfo.trailing(charIndex);
        }
    }

    private boolean caretIsValid(int caret) {

        if (caret == characterCount || caret == 0) {
            return true;
        }

        int offset = textLine.visualToLogical(caret);

        if (!textLine.isCharLTR(offset)) {
            offset = textLine.visualToLogical(caret-1);
            if (textLine.isCharLTR(offset)) {
                return true;
            }
        }

        // At this point, the leading edge of the character