java/8 : javax/swing/text/PlainView.java

PlainView
https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.swing.text;

import java.util.Vector;
import java.util.Properties;
import java.awt.*;
import javax.swing.event.*;

Implements View interface for a simple multi-line text view
that has text in one font and color.  The view represents each
child element as a line of text.
Author:  Timothy Prinzing
See Also: View/**
 * Implements View interface for a simple multi-line text view
 * that has text in one font and color.  The view represents each
 * child element as a line of text.
 *
 * @author  Timothy Prinzing
 * @see     View
 */
public class PlainView extends View implements TabExpander {

    Constructs a new PlainView wrapped on an element.
Params: elem – the element/**
     * Constructs a new PlainView wrapped on an element.
     *
     * @param elem the element
     */
    public PlainView(Element elem) {
        super(elem);
    }

    Returns the tab size set for the document, defaulting to 8.
Returns: the tab size/**
     * Returns the tab size set for the document, defaulting to 8.
     *
     * @return the tab size
     */
    protected int getTabSize() {
        Integer i = (Integer) getDocument().getProperty(PlainDocument.tabSizeAttribute);
        int size = (i != null) ? i.intValue() : 8;
        return size;
    }

    Renders a line of text, suppressing whitespace at the end
and expanding any tabs.  This is implemented to make calls
to the methods drawUnselectedText and
drawSelectedText so that the way selected and
unselected text are rendered can be customized.
Params: lineIndex – the line to draw >= 0
g – the Graphics context
x – the starting X position >= 0
y – the starting Y position >= 0
See Also: drawUnselectedText
drawSelectedText/**
     * Renders a line of text, suppressing whitespace at the end
     * and expanding any tabs.  This is implemented to make calls
     * to the methods <code>drawUnselectedText</code> and
     * <code>drawSelectedText</code> so that the way selected and
     * unselected text are rendered can be customized.
     *
     * @param lineIndex the line to draw &gt;= 0
     * @param g the <code>Graphics</code> context
     * @param x the starting X position &gt;= 0
     * @param y the starting Y position &gt;= 0
     * @see #drawUnselectedText
     * @see #drawSelectedText
     */
    protected void drawLine(int lineIndex, Graphics g, int x, int y) {
        Element line = getElement().getElement(lineIndex);
        Element elem;

        try {
            if (line.isLeaf()) {
                drawElement(lineIndex, line, g, x, y);
            } else {
                // this line contains the composed text.
                int count = line.getElementCount();
                for(int i = 0; i < count; i++) {
                    elem = line.getElement(i);
                    x = drawElement(lineIndex, elem, g, x, y);
                }
            }
        } catch (BadLocationException e) {
            throw new StateInvariantError("Can't render line: " + lineIndex);
        }
    }

    private int drawElement(int lineIndex, Element elem, Graphics g, int x, int y) throws BadLocationException {
        int p0 = elem.getStartOffset();
        int p1 = elem.getEndOffset();
        p1 = Math.min(getDocument().getLength(), p1);

        if (lineIndex == 0) {
            x += firstLineOffset;
        }
        AttributeSet attr = elem.getAttributes();
        if (Utilities.isComposedTextAttributeDefined(attr)) {
            g.setColor(unselected);
            x = Utilities.drawComposedText(this, attr, g, x, y,
                                        p0-elem.getStartOffset(),
                                        p1-elem.getStartOffset());
        } else {
            if (sel0 == sel1 || selected == unselected) {
                // no selection, or it is invisible
                x = drawUnselectedText(g, x, y, p0, p1);
            } else if ((p0 >= sel0 && p0 <= sel1) && (p1 >= sel0 && p1 <= sel1)) {
                x = drawSelectedText(g, x, y, p0, p1);
            } else if (sel0 >= p0 && sel0 <= p1) {
                if (sel1 >= p0 && sel1 <= p1) {
                    x = drawUnselectedText(g, x, y, p0, sel0);
                    x = drawSelectedText(g, x, y, sel0, sel1);
                    x = drawUnselectedText(g, x, y, sel1, p1);
                } else {
                    x = drawUnselectedText(g, x, y, p0, sel0);
                    x = drawSelectedText(g, x, y, sel0, p1);
                }
            } else if (sel1 >= p0 && sel1 <= p1) {
                x = drawSelectedText(g, x, y, p0, sel1);
                x = drawUnselectedText(g, x, y, sel1, p1);
            } else {
                x = drawUnselectedText(g, x, y, p0, p1);
            }
        }

        return x;
    }

    Renders the given range in the model as normal unselected
text.  Uses the foreground or disabled color to render the text.
Params: g – the graphics context
x – the starting X coordinate >= 0
y – the starting Y coordinate >= 0
p0 – the beginning position in the model >= 0
p1 – the ending position in the model >= 0
Throws: BadLocationException – if the range is invalid
Returns: the X location of the end of the range >= 0/**
     * Renders the given range in the model as normal unselected
     * text.  Uses the foreground or disabled color to render the text.
     *
     * @param g the graphics context
     * @param x the starting X coordinate &gt;= 0
     * @param y the starting Y coordinate &gt;= 0
     * @param p0 the beginning position in the model &gt;= 0
     * @param p1 the ending position in the model &gt;= 0
     * @return the X location of the end of the range &gt;= 0
     * @exception BadLocationException if the range is invalid
     */
    protected int drawUnselectedText(Graphics g, int x, int y,
                                     int p0, int p1) throws BadLocationException {
        g.setColor(unselected);
        Document doc = getDocument();
        Segment s = SegmentCache.getSharedSegment();
        doc.getText(p0, p1 - p0, s);
        int ret = Utilities.drawTabbedText(this, s, x, y, g, this, p0);
        SegmentCache.releaseSharedSegment(s);
        return ret;
    }

    Renders the given range in the model as selected text.  This
is implemented to render the text in the color specified in
the hosting component.  It assumes the highlighter will render
the selected background.
Params: g – the graphics context
x – the starting X coordinate >= 0
y – the starting Y coordinate >= 0
p0 – the beginning position in the model >= 0
p1 – the ending position in the model >= 0
Throws: BadLocationException – if the range is invalid
Returns: the location of the end of the range/**
     * Renders the given range in the model as selected text.  This
     * is implemented to render the text in the color specified in
     * the hosting component.  It assumes the highlighter will render
     * the selected background.
     *
     * @param g the graphics context
     * @param x the starting X coordinate &gt;= 0
     * @param y the starting Y coordinate &gt;= 0
     * @param p0 the beginning position in the model &gt;= 0
     * @param p1 the ending position in the model &gt;= 0
     * @return the location of the end of the range
     * @exception BadLocationException if the range is invalid
     */
    protected int drawSelectedText(Graphics g, int x,
                                   int y, int p0, int p1) throws BadLocationException {
        g.setColor(selected);
        Document doc = getDocument();
        Segment s = SegmentCache.getSharedSegment();
        doc.getText(p0, p1 - p0, s);
        int ret = Utilities.drawTabbedText(this, s, x, y, g, this, p0);
        SegmentCache.releaseSharedSegment(s);
        return ret;
    }

    Gives access to a buffer that can be used to fetch
text from the associated document.
Returns: the buffer/**
     * Gives access to a buffer that can be used to fetch
     * text from the associated document.
     *
     * @return the buffer
     */
    protected final Segment getLineBuffer() {
        if (lineBuffer == null) {
            lineBuffer = new Segment();
        }
        return lineBuffer;
    }

    Checks to see if the font metrics and longest line
are up-to-date.
Since: 1.4/**
     * Checks to see if the font metrics and longest line
     * are up-to-date.
     *
     * @since 1.4
     */
    protected void updateMetrics() {
        Component host = getContainer();
        Font f = host.getFont();
        if (font != f) {
            // The font changed, we need to recalculate the
            // longest line.
            calculateLongestLine();
            tabSize = getTabSize() * metrics.charWidth('m');
        }
    }

    // ---- View methods ----------------------------------------------------

    Determines the preferred span for this view along an
axis.
Params: axis – may be either View.X_AXIS or View.Y_AXIS
Throws: IllegalArgumentException – for an invalid axis
Returns:   the span the view would like to be rendered into >= 0.
          Typically the view is told to render into the span
          that is returned, although there is no guarantee.
          The parent may choose to resize or break the view./**
     * Determines the preferred span for this view along an
     * axis.
     *
     * @param axis may be either View.X_AXIS or View.Y_AXIS
     * @return   the span the view would like to be rendered into &gt;= 0.
     *           Typically the view is told to render into the span
     *           that is returned, although there is no guarantee.
     *           The parent may choose to resize or break the view.
     * @exception IllegalArgumentException for an invalid axis
     */
    public float getPreferredSpan(int axis) {
        updateMetrics();
        switch (axis) {
        case View.X_AXIS:
            return getLineWidth(longLine);
        case View.Y_AXIS:
            return getElement().getElementCount() * metrics.getHeight();
        default:
            throw new IllegalArgumentException("Invalid axis: " + axis);
        }
    }

    Renders using the given rendering surface and area on that surface.
The view may need to do layout and create child views to enable
itself to render into the given allocation.
Params: g – the rendering surface to use
a – the allocated region to render into
See Also: View.paint/**
     * Renders using the given rendering surface and area on that surface.
     * The view may need to do layout and create child views to enable
     * itself to render into the given allocation.
     *
     * @param g the rendering surface to use
     * @param a the allocated region to render into
     *
     * @see View#paint
     */
    public void paint(Graphics g, Shape a) {
        Shape originalA = a;
        a = adjustPaintRegion(a);
        Rectangle alloc = (Rectangle) a;
        tabBase = alloc.x;
        JTextComponent host = (JTextComponent) getContainer();
        Highlighter h = host.getHighlighter();
        g.setFont(host.getFont());
        sel0 = host.getSelectionStart();
        sel1 = host.getSelectionEnd();
        unselected = (host.isEnabled()) ?
            host.getForeground() : host.getDisabledTextColor();
        Caret c = host.getCaret();
        selected = c.isSelectionVisible() && h != null ?
                       host.getSelectedTextColor() : unselected;
        updateMetrics();

        // If the lines are clipped then we don't expend the effort to
        // try and paint them.  Since all of the lines are the same height
        // with this object, determination of what lines need to be repainted
        // is quick.
        Rectangle clip = g.getClipBounds();
        int fontHeight = metrics.getHeight();
        int heightBelow = (alloc.y + alloc.height) - (clip.y + clip.height);
        int heightAbove = clip.y - alloc.y;
        int linesBelow, linesAbove, linesTotal;

        if (fontHeight > 0) {
            linesBelow = Math.max(0, heightBelow / fontHeight);
            linesAbove = Math.max(0, heightAbove / fontHeight);
            linesTotal = alloc.height / fontHeight;
            if (alloc.height % fontHeight != 0) {
                linesTotal++;
            }
        } else {
            linesBelow = linesAbove = linesTotal = 0;
        }

        // update the visible lines
        Rectangle lineArea = lineToRect(a, linesAbove);
        int y = lineArea.y + metrics.getAscent();
        int x = lineArea.x;
        Element map = getElement();
        int lineCount = map.getElementCount();
        int endLine = Math.min(lineCount, linesTotal - linesBelow);
        lineCount--;
        LayeredHighlighter dh = (h instanceof LayeredHighlighter) ?
                           (LayeredHighlighter)h : null;
        for (int line = linesAbove; line < endLine; line++) {
            if (dh != null) {
                Element lineElement = map.getElement(line);
                if (line == lineCount) {
                    dh.paintLayeredHighlights(g, lineElement.getStartOffset(),
                                              lineElement.getEndOffset(),
                                              originalA, host, this);
                }
                else {
                    dh.paintLayeredHighlights(g, lineElement.getStartOffset(),
                                              lineElement.getEndOffset() - 1,
                                              originalA, host, this);
                }
            }
            drawLine(line, g, x, y);
            y += fontHeight;
            if (line == 0) {
                // This should never really happen, in so far as if
                // firstLineOffset is non 0, there should only be one
                // line of text.
                x -= firstLineOffset;
            }
        }
    }

    Should return a shape ideal for painting based on the passed in
Shape a. This is useful if painting in a different
region. The default implementation returns a.
/**
     * Should return a shape ideal for painting based on the passed in
     * Shape <code>a</code>. This is useful if painting in a different
     * region. The default implementation returns <code>a</code>.
     */
    Shape adjustPaintRegion(Shape a) {
        return a;
    }

    Provides a mapping from the document model coordinate space
to the coordinate space of the view mapped to it.
Params: pos – the position to convert >= 0
a – the allocated region to render into
Throws: BadLocationException –  if the given position does not
  represent a valid location in the associated document
See Also: View.modelToView
Returns: the bounding box of the given position/**
     * Provides a mapping from the document model coordinate space
     * to the coordinate space of the view mapped to it.
     *
     * @param pos the position to convert &gt;= 0
     * @param a the allocated region to render into
     * @return the bounding box of the given position
     * @exception BadLocationException  if the given position does not
     *   represent a valid location in the associated document
     * @see View#modelToView
     */
    public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {
        // line coordinates
        Document doc = getDocument();
        Element map = getElement();
        int lineIndex = map.getElementIndex(pos);
        if (lineIndex < 0) {
            return lineToRect(a, 0);
        }
        Rectangle lineArea = lineToRect(a, lineIndex);

        // determine span from the start of the line
        tabBase = lineArea.x;
        Element line = map.getElement(lineIndex);
        int p0 = line.getStartOffset();
        Segment s = SegmentCache.getSharedSegment();
        doc.getText(p0, pos - p0, s);
        int xOffs = Utilities.getTabbedTextWidth(s, metrics, tabBase, this,p0);
        SegmentCache.releaseSharedSegment(s);

        // fill in the results and return
        lineArea.x += xOffs;
        lineArea.width = 1;
        lineArea.height = metrics.getHeight();
        return lineArea;
    }

    Provides a mapping from the view coordinate space to the logical
coordinate space of the model.
Params: fx – the X coordinate >= 0
fy – the Y coordinate >= 0
a – the allocated region to render into
See Also: View.viewToModel
Returns: the location within the model that best represents the
 given point in the view >= 0/**
     * Provides a mapping from the view coordinate space to the logical
     * coordinate space of the model.
     *
     * @param fx the X coordinate &gt;= 0
     * @param fy the Y coordinate &gt;= 0
     * @param a the allocated region to render into
     * @return the location within the model that best represents the
     *  given point in the view &gt;= 0
     * @see View#viewToModel
     */
    public int viewToModel(float fx, float fy, Shape a, Position.Bias[] bias) {
        // PENDING(prinz) properly calculate bias
        bias[0] = Position.Bias.Forward;

        Rectangle alloc = a.getBounds();
        Document doc = getDocument();
        int x = (int) fx;
        int y = (int) fy;
        if (y < alloc.y) {
            // above the area covered by this icon, so the the position
            // is assumed to be the start of the coverage for this view.
            return getStartOffset();
        } else if (y > alloc.y + alloc.height) {
            // below the area covered by this icon, so the the position
            // is assumed to be the end of the coverage for this view.
            return getEndOffset() - 1;
        } else {
            // positioned within the coverage of this view vertically,
            // so we figure out which line the point corresponds to.
            // if the line is greater than the number of lines contained, then
            // simply use the last line as it represents the last possible place
            // we can position to.
            Element map = doc.getDefaultRootElement();
            int fontHeight = metrics.getHeight();
            int lineIndex = (fontHeight > 0 ?
                                Math.abs((y - alloc.y) / fontHeight) :
                                map.getElementCount() - 1);
            if (lineIndex >= map.getElementCount()) {
                return getEndOffset() - 1;
            }
            Element line = map.getElement(lineIndex);
            int dx = 0;
            if (lineIndex == 0) {
                alloc.x += firstLineOffset;
                alloc.width -= firstLineOffset;
            }
            if (x < alloc.x) {
                // point is to the left of the line
                return line.getStartOffset();
            } else if (x > alloc.x + alloc.width) {
                // point is to the right of the line
                return line.getEndOffset() - 1;
            } else {
                // Determine the offset into the text
                try {
                    int p0 = line.getStartOffset();
                    int p1 = line.getEndOffset() - 1;
                    Segment s = SegmentCache.getSharedSegment();
                    doc.getText(p0, p1 - p0, s);
                    tabBase = alloc.x;
                    int offs = p0 + Utilities.getTabbedTextOffset(s, metrics,
                                                                  tabBase, x, this, p0);
                    SegmentCache.releaseSharedSegment(s);
                    return offs;
                } catch (BadLocationException e) {
                    // should not happen
                    return -1;
                }
            }
        }
    }

    Gives notification that something was inserted into the document
in a location that this view is responsible for.
Params: changes – the change information from the associated document
a – the current allocation of the view
f – the factory to use to rebuild if the view has children
See Also: View.insertUpdate/**
     * Gives notification that something was inserted into the document
     * in a location that this view is responsible for.
     *
     * @param changes the change information from the associated document
     * @param a the current allocation of the view
     * @param f the factory to use to rebuild if the view has children
     * @see View#insertUpdate
     */
    public void insertUpdate(DocumentEvent changes, Shape a, ViewFactory f) {
        updateDamage(changes, a, f);
    }

    Gives notification that something was removed from the document
in a location that this view is responsible for.
Params: changes – the change information from the associated document
a – the current allocation of the view
f – the factory to use to rebuild if the view has children
See Also: View.removeUpdate/**
     * Gives notification that something was removed from the document
     * in a location that this view is responsible for.
     *
     * @param changes the change information from the associated document
     * @param a the current allocation of the view
     * @param f the factory to use to rebuild if the view has children
     * @see View#removeUpdate
     */
    public void removeUpdate(DocumentEvent changes, Shape a, ViewFactory f) {
        updateDamage(changes, a, f);
    }

    Gives notification from the document that attributes were changed
in a location that this view is responsible for.
Params: changes – the change information from the associated document
a – the current allocation of the view
f – the factory to use to rebuild if the view has children
See Also: View.changedUpdate/**
     * Gives notification from the document that attributes were changed
     * in a location that this view is responsible for.
     *
     * @param changes the change information from the associated document
     * @param a the current allocation of the view
     * @param f the factory to use to rebuild if the view has children
     * @see View#changedUpdate
     */
    public void changedUpdate(DocumentEvent changes, Shape a, ViewFactory f) {
        updateDamage(changes, a, f);
    }

    Sets the size of the view.  This should cause
layout of the view along the given axis, if it
has any layout duties.
Params: width – the width >= 0
height – the height >= 0/**
     * Sets the size of the view.  This should cause
     * layout of the view along the given axis, if it
     * has any layout duties.
     *
     * @param width the width &gt;= 0
     * @param height the height &gt;= 0
     */
    public void setSize(float width, float height) {
        super.setSize(width, height);
        updateMetrics();
    }

    // --- TabExpander methods ------------------------------------------

    Returns the next tab stop position after a given reference position.
This implementation does not support things like centering so it
ignores the tabOffset argument.
Params: x – the current position >= 0
tabOffset – the position within the text stream
  that the tab occurred at >= 0.
Returns: the tab stop, measured in points >= 0/**
     * Returns the next tab stop position after a given reference position.
     * This implementation does not support things like centering so it
     * ignores the tabOffset argument.
     *
     * @param x the current position &gt;= 0
     * @param tabOffset the position within the text stream
     *   that the tab occurred at &gt;= 0.
     * @return the tab stop, measured in points &gt;= 0
     */
    public float nextTabStop(float x, int tabOffset) {
        if (tabSize == 0) {
            return x;
        }
        int ntabs = (((int) x) - tabBase) / tabSize;
        return tabBase + ((ntabs + 1) * tabSize);
    }

    // --- local methods ------------------------------------------------

    Repaint the region of change covered by the given document
event.  Damages the line that begins the range to cover
the case when the insert/remove is only on one line.
If lines are added or removed, damages the whole
view.  The longest line is checked to see if it has
changed.
Since: 1.4/**
     * Repaint the region of change covered by the given document
     * event.  Damages the line that begins the range to cover
     * the case when the insert/remove is only on one line.
     * If lines are added or removed, damages the whole
     * view.  The longest line is checked to see if it has
     * changed.
     *
     * @since 1.4
     */
    protected void updateDamage(DocumentEvent changes, Shape a, ViewFactory f) {
        Component host = getContainer();
        updateMetrics();
        Element elem = getElement();
        DocumentEvent.ElementChange ec = changes.getChange(elem);

        Element[] added = (ec != null) ? ec.getChildrenAdded() : null;
        Element[] removed = (ec != null) ? ec.getChildrenRemoved() : null;
        if (((added != null) && (added.length > 0)) ||
            ((removed != null) && (removed.length > 0))) {
            // lines were added or removed...
            if (added != null) {
                int currWide = getLineWidth(longLine);
                for (int i = 0; i < added.length; i++) {
                    int w = getLineWidth(added[i]);
                    if (w > currWide) {
                        currWide = w;
                        longLine = added[i];
                    }
                }
            }
            if (removed != null) {
                for (int i = 0; i < removed.length; i++) {
                    if (removed[i] == longLine) {
                        calculateLongestLine();
                        break;
                    }
                }
            }
            preferenceChanged(null, true, true);
            host.repaint();
        } else {
            Element map = getElement();
            int line = map.getElementIndex(changes.getOffset());
            damageLineRange(line, line, a, host);
            if (changes.getType() == DocumentEvent.EventType.INSERT) {
                // check to see if the line is longer than current
                // longest line.
                int w = getLineWidth(longLine);
                Element e = map.getElement(line);
                if (e == longLine) {
                    preferenceChanged(null, true, false);
                } else if (getLineWidth(e) > w) {
                    longLine = e;
                    preferenceChanged(null, true, false);
                }
            } else if (changes.getType() == DocumentEvent.EventType.REMOVE) {
                if (map.getElement(line) == longLine) {
                    // removed from longest line... recalc
                    calculateLongestLine();
                    preferenceChanged(null, true, false);
                }
            }
        }
    }

    Repaint the given line range.
Params: host – the component hosting the view (used to call repaint)
a –  the region allocated for the view to render into
line0 – the starting line number to repaint.  This must
  be a valid line number in the model.
line1 – the ending line number to repaint.  This must
  be a valid line number in the model.
Since: 1.4/**
     * Repaint the given line range.
     *
     * @param host the component hosting the view (used to call repaint)
     * @param a  the region allocated for the view to render into
     * @param line0 the starting line number to repaint.  This must
     *   be a valid line number in the model.
     * @param line1 the ending line number to repaint.  This must
     *   be a valid line number in the model.
     * @since 1.4
     */
    protected void damageLineRange(int line0, int line1, Shape a, Component host) {
        if (a != null) {
            Rectangle area0 = lineToRect(a, line0);
            Rectangle area1 = lineToRect(a, line1);
            if ((area0 != null) && (area1 != null)) {
                Rectangle damage = area0.union(area1);
                host.repaint(damage.x, damage.y, damage.width, damage.height);
            } else {
                host.repaint();
            }
        }
    }

    Determine the rectangle that represents the given line.
Params: a –  the region allocated for the view to render into
line – the line number to find the region of.  This must
  be a valid line number in the model.
Since: 1.4/**
     * Determine the rectangle that represents the given line.
     *
     * @param a  the region allocated for the view to render into
     * @param line the line number to find the region of.  This must
     *   be a valid line number in the model.
     * @since 1.4
     */
    protected Rectangle lineToRect(Shape a, int line) {
        Rectangle r = null;
        updateMetrics();
        if (metrics != null) {
            Rectangle alloc = a.getBounds();
            if (line == 0) {
                alloc.x += firstLineOffset;
                alloc.width -= firstLineOffset;
            }
            r = new Rectangle(alloc.x, alloc.y + (line * metrics.getHeight()),
                              alloc.width, metrics.getHeight());
        }
        return r;
    }

    Iterate over the lines represented by the child elements
of the element this view represents, looking for the line
that is the longest.  The longLine variable is updated to
represent the longest line contained.  The font variable
is updated to indicate the font used to calculate the
longest line.
/**
     * Iterate over the lines represented by the child elements
     * of the element this view represents, looking for the line
     * that is the longest.  The <em>longLine</em> variable is updated to
     * represent the longest line contained.  The <em>font</em> variable
     * is updated to indicate the font used to calculate the
     * longest line.
     */
    private void calculateLongestLine() {
        Component c = getContainer();
        font = c.getFont();
        metrics = c.getFontMetrics(font);
        Document doc = getDocument();
        Element lines = getElement();
        int n = lines.getElementCount();
        int maxWidth = -1;
        for (int i = 0; i < n; i++) {
            Element line = lines.getElement(i);
            int w = getLineWidth(line);
            if (w > maxWidth) {
                maxWidth = w;
                longLine = line;
            }
        }
    }

    Calculate the width of the line represented by
the given element.  It is assumed that the font
and font metrics are up-to-date.
/**
     * Calculate the width of the line represented by
     * the given element.  It is assumed that the font
     * and font metrics are up-to-date.
     */
    private int getLineWidth(Element line) {
        if (line == null) {
            return 0;
        }
        int p0 = line.getStartOffset();
        int p1 = line.getEndOffset();
        int w;
        Segment s = SegmentCache.getSharedSegment();
        try {
            line.getDocument().getText(p0, p1 - p0, s);
            w = Utilities.getTabbedTextWidth(s, metrics, tabBase, this, p0);
        } catch (BadLocationException ble) {
            w = 0;
        }
        SegmentCache.releaseSharedSegment(s);
        return w;
    }

    // --- member variables -----------------------------------------------

    Font metrics for the current font.
/**
     * Font metrics for the current font.
     */
    protected FontMetrics metrics;

    The current longest line.  This is used to calculate
the preferred width of the view.  Since the calculation
is potentially expensive we try to avoid it by stashing
which line is currently the longest.
/**
     * The current longest line.  This is used to calculate
     * the preferred width of the view.  Since the calculation
     * is potentially expensive we try to avoid it by stashing
     * which line is currently the longest.
     */
    Element longLine;

    Font used to calculate the longest line... if this
changes we need to recalculate the longest line
/**
     * Font used to calculate the longest line... if this
     * changes we need to recalculate the longest line
     */
    Font font;

    Segment lineBuffer;
    int tabSize;
    int tabBase;

    int sel0;
    int sel1;
    Color unselected;
    Color selected;

    Offset of where to draw the first character on the first line.
This is a hack and temporary until we can better address the problem
of text measuring. This field is actually never set directly in
PlainView, but by FieldView.
/**
     * Offset of where to draw the first character on the first line.
     * This is a hack and temporary until we can better address the problem
     * of text measuring. This field is actually never set directly in
     * PlainView, but by FieldView.
     */
    int firstLineOffset;

}
Params:	lineIndex – the line to draw >= 0 g – the `Graphics` context x – the starting X position >= 0 y – the starting Y position >= 0
See Also:	drawUnselectedText drawSelectedText
Params:	g – the graphics context x – the starting X coordinate >= 0 y – the starting Y coordinate >= 0 p0 – the beginning position in the model >= 0 p1 – the ending position in the model >= 0
Throws:	BadLocationException – if the range is invalid
Returns:	the X location of the end of the range >= 0
Params:	axis – may be either View.X_AXIS or View.Y_AXIS
Throws:	IllegalArgumentException – for an invalid axis
Returns:	the span the view would like to be rendered into >= 0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
Params:	g – the rendering surface to use a – the allocated region to render into
See Also:	View.paint
Params:	pos – the position to convert >= 0 a – the allocated region to render into
Throws:	BadLocationException – if the given position does not represent a valid location in the associated document
See Also:	View.modelToView
Returns:	the bounding box of the given position
Params:	fx – the X coordinate >= 0 fy – the Y coordinate >= 0 a – the allocated region to render into
See Also:	View.viewToModel
Returns:	the location within the model that best represents the given point in the view >= 0
Params:	changes – the change information from the associated document a – the current allocation of the view f – the factory to use to rebuild if the view has children
See Also:	View.insertUpdate
Params:	x – the current position >= 0 tabOffset – the position within the text stream that the tab occurred at >= 0.
Returns:	the tab stop, measured in points >= 0
Params:	host – the component hosting the view (used to call repaint) a – the region allocated for the view to render into line0 – the starting line number to repaint. This must be a valid line number in the model. line1 – the ending line number to repaint. This must be a valid line number in the model.
Since:	1.4
Params:	a – the region allocated for the view to render into line – the line number to find the region of. This must be a valid line number in the model.
Since:	1.4
/

java/ 8/ javax/swing/text/PlainView.java
