For text that will be edited, use a {@link DynamicLayout}, * which will be updated as the text changes. * For text that will not change, use a {@link StaticLayout}. */ public abstract class Layout { /** @hide */ @IntDef({BREAK_STRATEGY_SIMPLE, BREAK_STRATEGY_HIGH_QUALITY, BREAK_STRATEGY_BALANCED}) @Retention(RetentionPolicy.SOURCE) public @interface BreakStrategy {} /** * Value for break strategy indicating simple line breaking. Automatic hyphens are not added * (though soft hyphens are respected), and modifying text generally doesn't affect the layout * before it (which yields a more consistent user experience when editing), but layout may not * be the highest quality. */ public static final int BREAK_STRATEGY_SIMPLE = 0; /** * Value for break strategy indicating high quality line breaking, including automatic * hyphenation and doing whole-paragraph optimization of line breaks. */ public static final int BREAK_STRATEGY_HIGH_QUALITY = 1; /** * Value for break strategy indicating balanced line breaking. The breaks are chosen to * make all lines as close to the same length as possible, including automatic hyphenation. */ public static final int BREAK_STRATEGY_BALANCED = 2; /** @hide */ @IntDef({HYPHENATION_FREQUENCY_NORMAL, HYPHENATION_FREQUENCY_FULL, HYPHENATION_FREQUENCY_NONE}) @Retention(RetentionPolicy.SOURCE) public @interface HyphenationFrequency {} /** * Value for hyphenation frequency indicating no automatic hyphenation. Useful * for backward compatibility, and for cases where the automatic hyphenation algorithm results * in incorrect hyphenation. Mid-word breaks may still happen when a word is wider than the * layout and there is otherwise no valid break. Soft hyphens are ignored and will not be used * as suggestions for potential line breaks. */ public static final int HYPHENATION_FREQUENCY_NONE = 0; /** * Value for hyphenation frequency indicating a light amount of automatic hyphenation, which * is a conservative default. Useful for informal cases, such as short sentences or chat * messages. */ public static final int HYPHENATION_FREQUENCY_NORMAL = 1; /** * Value for hyphenation frequency indicating the full amount of automatic hyphenation, typical * in typography. Useful for running text and where it's important to put the maximum amount of * text in a screen with limited space. */ public static final int HYPHENATION_FREQUENCY_FULL = 2; private static final ParagraphStyle[] NO_PARA_SPANS = ArrayUtils.emptyArray(ParagraphStyle.class); /** @hide */ @IntDef({JUSTIFICATION_MODE_NONE, JUSTIFICATION_MODE_INTER_WORD}) @Retention(RetentionPolicy.SOURCE) public @interface JustificationMode {} /** * Value for justification mode indicating no justification. */ public static final int JUSTIFICATION_MODE_NONE = 0; /** * Value for justification mode indicating the text is justified by stretching word spacing. */ public static final int JUSTIFICATION_MODE_INTER_WORD = 1; /** * Return how wide a layout must be in order to display the specified text with one line per * paragraph. * *
As of O, Uses * {@link TextDirectionHeuristics#FIRSTSTRONG_LTR} as the default text direction heuristics. In * the earlier versions uses {@link TextDirectionHeuristics#LTR} as the default.
*/ public static float getDesiredWidth(CharSequence source, TextPaint paint) { return getDesiredWidth(source, 0, source.length(), paint); } /** * Return how wide a layout must be in order to display the specified text slice with one * line per paragraph. * *As of O, Uses * {@link TextDirectionHeuristics#FIRSTSTRONG_LTR} as the default text direction heuristics. In * the earlier versions uses {@link TextDirectionHeuristics#LTR} as the default.
*/ public static float getDesiredWidth(CharSequence source, int start, int end, TextPaint paint) { return getDesiredWidth(source, start, end, paint, TextDirectionHeuristics.FIRSTSTRONG_LTR); } /** * Return how wide a layout must be in order to display the * specified text slice with one line per paragraph. * * @hide */ public static float getDesiredWidth(CharSequence source, int start, int end, TextPaint paint, TextDirectionHeuristic textDir) { float need = 0; int next; for (int i = start; i <= end; i = next) { next = TextUtils.indexOf(source, '\n', i, end); if (next < 0) next = end; // note, omits trailing paragraph char float w = measurePara(paint, source, i, next, textDir); if (w > need) need = w; next++; } return need; } /** * Subclasses of Layout use this constructor to set the display text, * width, and other standard properties. * @param text the text to render * @param paint the default paint for the layout. Styles can override * various attributes of the paint. * @param width the wrapping width for the text. * @param align whether to left, right, or center the text. Styles can * override the alignment. * @param spacingMult factor by which to scale the font size to get the * default line spacing * @param spacingAdd amount to add to the default line spacing */ protected Layout(CharSequence text, TextPaint paint, int width, Alignment align, float spacingMult, float spacingAdd) { this(text, paint, width, align, TextDirectionHeuristics.FIRSTSTRONG_LTR, spacingMult, spacingAdd); } /** * Subclasses of Layout use this constructor to set the display text, * width, and other standard properties. * @param text the text to render * @param paint the default paint for the layout. Styles can override * various attributes of the paint. * @param width the wrapping width for the text. * @param align whether to left, right, or center the text. Styles can * override the alignment. * @param spacingMult factor by which to scale the font size to get the * default line spacing * @param spacingAdd amount to add to the default line spacing * * @hide */ protected Layout(CharSequence text, TextPaint paint, int width, Alignment align, TextDirectionHeuristic textDir, float spacingMult, float spacingAdd) { if (width < 0) throw new IllegalArgumentException("Layout: " + width + " < 0"); // Ensure paint doesn't have baselineShift set. // While normally we don't modify the paint the user passed in, // we were already doing this in Styled.drawUniformRun with both // baselineShift and bgColor. We probably should reevaluate bgColor. if (paint != null) { paint.bgColor = 0; paint.baselineShift = 0; } mText = text; mPaint = paint; mWidth = width; mAlignment = align; mSpacingMult = spacingMult; mSpacingAdd = spacingAdd; mSpannedText = text instanceof Spanned; mTextDir = textDir; } /** @hide */ protected void setJustificationMode(@JustificationMode int justificationMode) { mJustificationMode = justificationMode; } /** * Replace constructor properties of this Layout with new ones. Be careful. */ /* package */ void replaceWith(CharSequence text, TextPaint paint, int width, Alignment align, float spacingmult, float spacingadd) { if (width < 0) { throw new IllegalArgumentException("Layout: " + width + " < 0"); } mText = text; mPaint = paint; mWidth = width; mAlignment = align; mSpacingMult = spacingmult; mSpacingAdd = spacingadd; mSpannedText = text instanceof Spanned; } /** * Draw this Layout on the specified Canvas. */ public void draw(Canvas c) { draw(c, null, null, 0); } /** * Draw this Layout on the specified canvas, with the highlight path drawn * between the background and the text. * * @param canvas the canvas * @param highlight the path of the highlight or cursor; can be null * @param highlightPaint the paint for the highlight * @param cursorOffsetVertical the amount to temporarily translate the * canvas while rendering the highlight */ public void draw(Canvas canvas, Path highlight, Paint highlightPaint, int cursorOffsetVertical) { final long lineRange = getLineRangeForDraw(canvas); int firstLine = TextUtils.unpackRangeStartFromLong(lineRange); int lastLine = TextUtils.unpackRangeEndFromLong(lineRange); if (lastLine < 0) return; drawBackground(canvas, highlight, highlightPaint, cursorOffsetVertical, firstLine, lastLine); drawText(canvas, firstLine, lastLine); } private boolean isJustificationRequired(int lineNum) { if (mJustificationMode == JUSTIFICATION_MODE_NONE) return false; final int lineEnd = getLineEnd(lineNum); return lineEnd < mText.length() && mText.charAt(lineEnd - 1) != '\n'; } private float getJustifyWidth(int lineNum) { Alignment paraAlign = mAlignment; TabStops tabStops = null; boolean tabStopsIsInitialized = false; int left = 0; int right = mWidth; final int dir = getParagraphDirection(lineNum); ParagraphStyle[] spans = NO_PARA_SPANS; if (mSpannedText) { Spanned sp = (Spanned) mText; final int start = getLineStart(lineNum); final boolean isFirstParaLine = (start == 0 || mText.charAt(start - 1) == '\n'); if (isFirstParaLine) { final int spanEnd = sp.nextSpanTransition(start, mText.length(), ParagraphStyle.class); spans = getParagraphSpans(sp, start, spanEnd, ParagraphStyle.class); for (int n = spans.length - 1; n >= 0; n--) { if (spans[n] instanceof AlignmentSpan) { paraAlign = ((AlignmentSpan) spans[n]).getAlignment(); break; } } } final int length = spans.length; boolean useFirstLineMargin = isFirstParaLine; for (int n = 0; n < length; n++) { if (spans[n] instanceof LeadingMarginSpan2) { int count = ((LeadingMarginSpan2) spans[n]).getLeadingMarginLineCount(); int startLine = getLineForOffset(sp.getSpanStart(spans[n])); if (lineNum < startLine + count) { useFirstLineMargin = true; break; } } } for (int n = 0; n < length; n++) { if (spans[n] instanceof LeadingMarginSpan) { LeadingMarginSpan margin = (LeadingMarginSpan) spans[n]; if (dir == DIR_RIGHT_TO_LEFT) { right -= margin.getLeadingMargin(useFirstLineMargin); } else { left += margin.getLeadingMargin(useFirstLineMargin); } } } } if (getLineContainsTab(lineNum)) { tabStops = new TabStops(TAB_INCREMENT, spans); } final Alignment align; if (paraAlign == Alignment.ALIGN_LEFT) { align = (dir == DIR_LEFT_TO_RIGHT) ? Alignment.ALIGN_NORMAL : Alignment.ALIGN_OPPOSITE; } else if (paraAlign == Alignment.ALIGN_RIGHT) { align = (dir == DIR_LEFT_TO_RIGHT) ? Alignment.ALIGN_OPPOSITE : Alignment.ALIGN_NORMAL; } else { align = paraAlign; } final int indentWidth; if (align == Alignment.ALIGN_NORMAL) { if (dir == DIR_LEFT_TO_RIGHT) { indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_LEFT); } else { indentWidth = -getIndentAdjust(lineNum, Alignment.ALIGN_RIGHT); } } else if (align == Alignment.ALIGN_OPPOSITE) { if (dir == DIR_LEFT_TO_RIGHT) { indentWidth = -getIndentAdjust(lineNum, Alignment.ALIGN_RIGHT); } else { indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_LEFT); } } else { // Alignment.ALIGN_CENTER indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_CENTER); } return right - left - indentWidth; } /** * @hide */ public void drawText(Canvas canvas, int firstLine, int lastLine) { int previousLineBottom = getLineTop(firstLine); int previousLineEnd = getLineStart(firstLine); ParagraphStyle[] spans = NO_PARA_SPANS; int spanEnd = 0; final TextPaint paint = mPaint; CharSequence buf = mText; Alignment paraAlign = mAlignment; TabStops tabStops = null; boolean tabStopsIsInitialized = false; TextLine tl = TextLine.obtain(); // Draw the lines, one at a time. // The baseline is the top of the following line minus the current line's descent. for (int lineNum = firstLine; lineNum <= lastLine; lineNum++) { int start = previousLineEnd; previousLineEnd = getLineStart(lineNum + 1); final boolean justify = isJustificationRequired(lineNum); int end = getLineVisibleEnd(lineNum, start, previousLineEnd); int ltop = previousLineBottom; int lbottom = getLineTop(lineNum + 1); previousLineBottom = lbottom; int lbaseline = lbottom - getLineDescent(lineNum); int dir = getParagraphDirection(lineNum); int left = 0; int right = mWidth; if (mSpannedText) { Spanned sp = (Spanned) buf; int textLength = buf.length(); boolean isFirstParaLine = (start == 0 || buf.charAt(start - 1) == '\n'); // New batch of paragraph styles, collect into spans array. // Compute the alignment, last alignment style wins. // Reset tabStops, we'll rebuild if we encounter a line with // tabs. // We expect paragraph spans to be relatively infrequent, use // spanEnd so that we can check less frequently. Since // paragraph styles ought to apply to entire paragraphs, we can // just collect the ones present at the start of the paragraph. // If spanEnd is before the end of the paragraph, that's not // our problem. if (start >= spanEnd && (lineNum == firstLine || isFirstParaLine)) { spanEnd = sp.nextSpanTransition(start, textLength, ParagraphStyle.class); spans = getParagraphSpans(sp, start, spanEnd, ParagraphStyle.class); paraAlign = mAlignment; for (int n = spans.length - 1; n >= 0; n--) { if (spans[n] instanceof AlignmentSpan) { paraAlign = ((AlignmentSpan) spans[n]).getAlignment(); break; } } tabStopsIsInitialized = false; } // Draw all leading margin spans. Adjust left or right according // to the paragraph direction of the line. final int length = spans.length; boolean useFirstLineMargin = isFirstParaLine; for (int n = 0; n < length; n++) { if (spans[n] instanceof LeadingMarginSpan2) { int count = ((LeadingMarginSpan2) spans[n]).getLeadingMarginLineCount(); int startLine = getLineForOffset(sp.getSpanStart(spans[n])); // if there is more than one LeadingMarginSpan2, use // the count that is greatest if (lineNum < startLine + count) { useFirstLineMargin = true; break; } } } for (int n = 0; n < length; n++) { if (spans[n] instanceof LeadingMarginSpan) { LeadingMarginSpan margin = (LeadingMarginSpan) spans[n]; if (dir == DIR_RIGHT_TO_LEFT) { margin.drawLeadingMargin(canvas, paint, right, dir, ltop, lbaseline, lbottom, buf, start, end, isFirstParaLine, this); right -= margin.getLeadingMargin(useFirstLineMargin); } else { margin.drawLeadingMargin(canvas, paint, left, dir, ltop, lbaseline, lbottom, buf, start, end, isFirstParaLine, this); left += margin.getLeadingMargin(useFirstLineMargin); } } } } boolean hasTab = getLineContainsTab(lineNum); // Can't tell if we have tabs for sure, currently if (hasTab && !tabStopsIsInitialized) { if (tabStops == null) { tabStops = new TabStops(TAB_INCREMENT, spans); } else { tabStops.reset(TAB_INCREMENT, spans); } tabStopsIsInitialized = true; } // Determine whether the line aligns to normal, opposite, or center. Alignment align = paraAlign; if (align == Alignment.ALIGN_LEFT) { align = (dir == DIR_LEFT_TO_RIGHT) ? Alignment.ALIGN_NORMAL : Alignment.ALIGN_OPPOSITE; } else if (align == Alignment.ALIGN_RIGHT) { align = (dir == DIR_LEFT_TO_RIGHT) ? Alignment.ALIGN_OPPOSITE : Alignment.ALIGN_NORMAL; } int x; final int indentWidth; if (align == Alignment.ALIGN_NORMAL) { if (dir == DIR_LEFT_TO_RIGHT) { indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_LEFT); x = left + indentWidth; } else { indentWidth = -getIndentAdjust(lineNum, Alignment.ALIGN_RIGHT); x = right - indentWidth; } } else { int max = (int)getLineExtent(lineNum, tabStops, false); if (align == Alignment.ALIGN_OPPOSITE) { if (dir == DIR_LEFT_TO_RIGHT) { indentWidth = -getIndentAdjust(lineNum, Alignment.ALIGN_RIGHT); x = right - max - indentWidth; } else { indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_LEFT); x = left - max + indentWidth; } } else { // Alignment.ALIGN_CENTER indentWidth = getIndentAdjust(lineNum, Alignment.ALIGN_CENTER); max = max & ~1; x = ((right + left - max) >> 1) + indentWidth; } } paint.setHyphenEdit(getHyphen(lineNum)); Directions directions = getLineDirections(lineNum); if (directions == DIRS_ALL_LEFT_TO_RIGHT && !mSpannedText && !hasTab && !justify) { // XXX: assumes there's nothing additional to be done canvas.drawText(buf, start, end, x, lbaseline, paint); } else { tl.set(paint, buf, start, end, dir, directions, hasTab, tabStops); if (justify) { tl.justify(right - left - indentWidth); } tl.draw(canvas, x, ltop, lbaseline, lbottom); } paint.setHyphenEdit(0); } TextLine.recycle(tl); } /** * @hide */ public void drawBackground(Canvas canvas, Path highlight, Paint highlightPaint, int cursorOffsetVertical, int firstLine, int lastLine) { // First, draw LineBackgroundSpans. // LineBackgroundSpans know nothing about the alignment, margins, or // direction of the layout or line. XXX: Should they? // They are evaluated at each line. if (mSpannedText) { if (mLineBackgroundSpans == null) { mLineBackgroundSpans = new SpanSetNOTE: this is inadequate to support bidirectional text, and will change.
*/
public abstract Directions getLineDirections(int line);
/**
* Returns the (negative) number of extra pixels of ascent padding in the
* top line of the Layout.
*/
public abstract int getTopPadding();
/**
* Returns the number of extra pixels of descent padding in the
* bottom line of the Layout.
*/
public abstract int getBottomPadding();
/**
* Returns the hyphen edit for a line.
*
* @hide
*/
public int getHyphen(int line) {
return 0;
}
/**
* Returns the left indent for a line.
*
* @hide
*/
public int getIndentAdjust(int line, Alignment alignment) {
return 0;
}
/**
* Returns true if the character at offset and the preceding character
* are at different run levels (and thus there's a split caret).
* @param offset the offset
* @return true if at a level boundary
* @hide
*/
public boolean isLevelBoundary(int offset) {
int line = getLineForOffset(offset);
Directions dirs = getLineDirections(line);
if (dirs == DIRS_ALL_LEFT_TO_RIGHT || dirs == DIRS_ALL_RIGHT_TO_LEFT) {
return false;
}
int[] runs = dirs.mDirections;
int lineStart = getLineStart(line);
int lineEnd = getLineEnd(line);
if (offset == lineStart || offset == lineEnd) {
int paraLevel = getParagraphDirection(line) == 1 ? 0 : 1;
int runIndex = offset == lineStart ? 0 : runs.length - 2;
return ((runs[runIndex + 1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK) != paraLevel;
}
offset -= lineStart;
for (int i = 0; i < runs.length; i += 2) {
if (offset == runs[i]) {
return true;
}
}
return false;
}
/**
* Returns true if the character at offset is right to left (RTL).
* @param offset the offset
* @return true if the character is RTL, false if it is LTR
*/
public boolean isRtlCharAt(int offset) {
int line = getLineForOffset(offset);
Directions dirs = getLineDirections(line);
if (dirs == DIRS_ALL_LEFT_TO_RIGHT) {
return false;
}
if (dirs == DIRS_ALL_RIGHT_TO_LEFT) {
return true;
}
int[] runs = dirs.mDirections;
int lineStart = getLineStart(line);
for (int i = 0; i < runs.length; i += 2) {
int start = lineStart + runs[i];
int limit = start + (runs[i+1] & RUN_LENGTH_MASK);
if (offset >= start && offset < limit) {
int level = (runs[i+1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK;
return ((level & 1) != 0);
}
}
// Should happen only if the offset is "out of bounds"
return false;
}
/**
* Returns the range of the run that the character at offset belongs to.
* @param offset the offset
* @return The range of the run
* @hide
*/
public long getRunRange(int offset) {
int line = getLineForOffset(offset);
Directions dirs = getLineDirections(line);
if (dirs == DIRS_ALL_LEFT_TO_RIGHT || dirs == DIRS_ALL_RIGHT_TO_LEFT) {
return TextUtils.packRangeInLong(0, getLineEnd(line));
}
int[] runs = dirs.mDirections;
int lineStart = getLineStart(line);
for (int i = 0; i < runs.length; i += 2) {
int start = lineStart + runs[i];
int limit = start + (runs[i+1] & RUN_LENGTH_MASK);
if (offset >= start && offset < limit) {
return TextUtils.packRangeInLong(start, limit);
}
}
// Should happen only if the offset is "out of bounds"
return TextUtils.packRangeInLong(0, getLineEnd(line));
}
private boolean primaryIsTrailingPrevious(int offset) {
int line = getLineForOffset(offset);
int lineStart = getLineStart(line);
int lineEnd = getLineEnd(line);
int[] runs = getLineDirections(line).mDirections;
int levelAt = -1;
for (int i = 0; i < runs.length; i += 2) {
int start = lineStart + runs[i];
int limit = start + (runs[i+1] & RUN_LENGTH_MASK);
if (limit > lineEnd) {
limit = lineEnd;
}
if (offset >= start && offset < limit) {
if (offset > start) {
// Previous character is at same level, so don't use trailing.
return false;
}
levelAt = (runs[i+1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK;
break;
}
}
if (levelAt == -1) {
// Offset was limit of line.
levelAt = getParagraphDirection(line) == 1 ? 0 : 1;
}
// At level boundary, check previous level.
int levelBefore = -1;
if (offset == lineStart) {
levelBefore = getParagraphDirection(line) == 1 ? 0 : 1;
} else {
offset -= 1;
for (int i = 0; i < runs.length; i += 2) {
int start = lineStart + runs[i];
int limit = start + (runs[i+1] & RUN_LENGTH_MASK);
if (limit > lineEnd) {
limit = lineEnd;
}
if (offset >= start && offset < limit) {
levelBefore = (runs[i+1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK;
break;
}
}
}
return levelBefore < levelAt;
}
/**
* Get the primary horizontal position for the specified text offset.
* This is the location where a new character would be inserted in
* the paragraph's primary direction.
*/
public float getPrimaryHorizontal(int offset) {
return getPrimaryHorizontal(offset, false /* not clamped */);
}
/**
* Get the primary horizontal position for the specified text offset, but
* optionally clamp it so that it doesn't exceed the width of the layout.
* @hide
*/
public float getPrimaryHorizontal(int offset, boolean clamped) {
boolean trailing = primaryIsTrailingPrevious(offset);
return getHorizontal(offset, trailing, clamped);
}
/**
* Get the secondary horizontal position for the specified text offset.
* This is the location where a new character would be inserted in
* the direction other than the paragraph's primary direction.
*/
public float getSecondaryHorizontal(int offset) {
return getSecondaryHorizontal(offset, false /* not clamped */);
}
/**
* Get the secondary horizontal position for the specified text offset, but
* optionally clamp it so that it doesn't exceed the width of the layout.
* @hide
*/
public float getSecondaryHorizontal(int offset, boolean clamped) {
boolean trailing = primaryIsTrailingPrevious(offset);
return getHorizontal(offset, !trailing, clamped);
}
private float getHorizontal(int offset, boolean primary) {
return primary ? getPrimaryHorizontal(offset) : getSecondaryHorizontal(offset);
}
private float getHorizontal(int offset, boolean trailing, boolean clamped) {
int line = getLineForOffset(offset);
return getHorizontal(offset, trailing, line, clamped);
}
private float getHorizontal(int offset, boolean trailing, int line, boolean clamped) {
int start = getLineStart(line);
int end = getLineEnd(line);
int dir = getParagraphDirection(line);
boolean hasTab = getLineContainsTab(line);
Directions directions = getLineDirections(line);
TabStops tabStops = null;
if (hasTab && mText instanceof Spanned) {
// Just checking this line should be good enough, tabs should be
// consistent across all lines in a paragraph.
TabStopSpan[] tabs = getParagraphSpans((Spanned) mText, start, end, TabStopSpan.class);
if (tabs.length > 0) {
tabStops = new TabStops(TAB_INCREMENT, tabs); // XXX should reuse
}
}
TextLine tl = TextLine.obtain();
tl.set(mPaint, mText, start, end, dir, directions, hasTab, tabStops);
float wid = tl.measure(offset - start, trailing, null);
TextLine.recycle(tl);
if (clamped && wid > mWidth) {
wid = mWidth;
}
int left = getParagraphLeft(line);
int right = getParagraphRight(line);
return getLineStartPos(line, left, right) + wid;
}
/**
* Get the leftmost position that should be exposed for horizontal
* scrolling on the specified line.
*/
public float getLineLeft(int line) {
int dir = getParagraphDirection(line);
Alignment align = getParagraphAlignment(line);
if (align == Alignment.ALIGN_LEFT) {
return 0;
} else if (align == Alignment.ALIGN_NORMAL) {
if (dir == DIR_RIGHT_TO_LEFT)
return getParagraphRight(line) - getLineMax(line);
else
return 0;
} else if (align == Alignment.ALIGN_RIGHT) {
return mWidth - getLineMax(line);
} else if (align == Alignment.ALIGN_OPPOSITE) {
if (dir == DIR_RIGHT_TO_LEFT)
return 0;
else
return mWidth - getLineMax(line);
} else { /* align == Alignment.ALIGN_CENTER */
int left = getParagraphLeft(line);
int right = getParagraphRight(line);
int max = ((int) getLineMax(line)) & ~1;
return left + ((right - left) - max) / 2;
}
}
/**
* Get the rightmost position that should be exposed for horizontal
* scrolling on the specified line.
*/
public float getLineRight(int line) {
int dir = getParagraphDirection(line);
Alignment align = getParagraphAlignment(line);
if (align == Alignment.ALIGN_LEFT) {
return getParagraphLeft(line) + getLineMax(line);
} else if (align == Alignment.ALIGN_NORMAL) {
if (dir == DIR_RIGHT_TO_LEFT)
return mWidth;
else
return getParagraphLeft(line) + getLineMax(line);
} else if (align == Alignment.ALIGN_RIGHT) {
return mWidth;
} else if (align == Alignment.ALIGN_OPPOSITE) {
if (dir == DIR_RIGHT_TO_LEFT)
return getLineMax(line);
else
return mWidth;
} else { /* align == Alignment.ALIGN_CENTER */
int left = getParagraphLeft(line);
int right = getParagraphRight(line);
int max = ((int) getLineMax(line)) & ~1;
return right - ((right - left) - max) / 2;
}
}
/**
* Gets the unsigned horizontal extent of the specified line, including
* leading margin indent, but excluding trailing whitespace.
*/
public float getLineMax(int line) {
float margin = getParagraphLeadingMargin(line);
float signedExtent = getLineExtent(line, false);
return margin + (signedExtent >= 0 ? signedExtent : -signedExtent);
}
/**
* Gets the unsigned horizontal extent of the specified line, including
* leading margin indent and trailing whitespace.
*/
public float getLineWidth(int line) {
float margin = getParagraphLeadingMargin(line);
float signedExtent = getLineExtent(line, true);
return margin + (signedExtent >= 0 ? signedExtent : -signedExtent);
}
/**
* Like {@link #getLineExtent(int,TabStops,boolean)} but determines the
* tab stops instead of using the ones passed in.
* @param line the index of the line
* @param full whether to include trailing whitespace
* @return the extent of the line
*/
private float getLineExtent(int line, boolean full) {
int start = getLineStart(line);
int end = full ? getLineEnd(line) : getLineVisibleEnd(line);
boolean hasTabs = getLineContainsTab(line);
TabStops tabStops = null;
if (hasTabs && mText instanceof Spanned) {
// Just checking this line should be good enough, tabs should be
// consistent across all lines in a paragraph.
TabStopSpan[] tabs = getParagraphSpans((Spanned) mText, start, end, TabStopSpan.class);
if (tabs.length > 0) {
tabStops = new TabStops(TAB_INCREMENT, tabs); // XXX should reuse
}
}
Directions directions = getLineDirections(line);
// Returned directions can actually be null
if (directions == null) {
return 0f;
}
int dir = getParagraphDirection(line);
TextLine tl = TextLine.obtain();
mPaint.setHyphenEdit(getHyphen(line));
tl.set(mPaint, mText, start, end, dir, directions, hasTabs, tabStops);
if (isJustificationRequired(line)) {
tl.justify(getJustifyWidth(line));
}
float width = tl.metrics(null);
mPaint.setHyphenEdit(0);
TextLine.recycle(tl);
return width;
}
/**
* Returns the signed horizontal extent of the specified line, excluding
* leading margin. If full is false, excludes trailing whitespace.
* @param line the index of the line
* @param tabStops the tab stops, can be null if we know they're not used.
* @param full whether to include trailing whitespace
* @return the extent of the text on this line
*/
private float getLineExtent(int line, TabStops tabStops, boolean full) {
int start = getLineStart(line);
int end = full ? getLineEnd(line) : getLineVisibleEnd(line);
boolean hasTabs = getLineContainsTab(line);
Directions directions = getLineDirections(line);
int dir = getParagraphDirection(line);
TextLine tl = TextLine.obtain();
mPaint.setHyphenEdit(getHyphen(line));
tl.set(mPaint, mText, start, end, dir, directions, hasTabs, tabStops);
if (isJustificationRequired(line)) {
tl.justify(getJustifyWidth(line));
}
float width = tl.metrics(null);
mPaint.setHyphenEdit(0);
TextLine.recycle(tl);
return width;
}
/**
* Get the line number corresponding to the specified vertical position.
* If you ask for a position above 0, you get 0; if you ask for a position
* below the bottom of the text, you get the last line.
*/
// FIXME: It may be faster to do a linear search for layouts without many lines.
public int getLineForVertical(int vertical) {
int high = getLineCount(), low = -1, guess;
while (high - low > 1) {
guess = (high + low) / 2;
if (getLineTop(guess) > vertical)
high = guess;
else
low = guess;
}
if (low < 0)
return 0;
else
return low;
}
/**
* Get the line number on which the specified text offset appears.
* If you ask for a position before 0, you get 0; if you ask for a position
* beyond the end of the text, you get the last line.
*/
public int getLineForOffset(int offset) {
int high = getLineCount(), low = -1, guess;
while (high - low > 1) {
guess = (high + low) / 2;
if (getLineStart(guess) > offset)
high = guess;
else
low = guess;
}
if (low < 0) {
return 0;
} else {
return low;
}
}
/**
* Get the character offset on the specified line whose position is
* closest to the specified horizontal position.
*/
public int getOffsetForHorizontal(int line, float horiz) {
return getOffsetForHorizontal(line, horiz, true);
}
/**
* Get the character offset on the specified line whose position is
* closest to the specified horizontal position.
*
* @param line the line used to find the closest offset
* @param horiz the horizontal position used to find the closest offset
* @param primary whether to use the primary position or secondary position to find the offset
*
* @hide
*/
public int getOffsetForHorizontal(int line, float horiz, boolean primary) {
// TODO: use Paint.getOffsetForAdvance to avoid binary search
final int lineEndOffset = getLineEnd(line);
final int lineStartOffset = getLineStart(line);
Directions dirs = getLineDirections(line);
TextLine tl = TextLine.obtain();
// XXX: we don't care about tabs as we just use TextLine#getOffsetToLeftRightOf here.
tl.set(mPaint, mText, lineStartOffset, lineEndOffset, getParagraphDirection(line), dirs,
false, null);
final int max;
if (line == getLineCount() - 1) {
max = lineEndOffset;
} else {
max = tl.getOffsetToLeftRightOf(lineEndOffset - lineStartOffset,
!isRtlCharAt(lineEndOffset - 1)) + lineStartOffset;
}
int best = lineStartOffset;
float bestdist = Math.abs(getHorizontal(best, primary) - horiz);
for (int i = 0; i < dirs.mDirections.length; i += 2) {
int here = lineStartOffset + dirs.mDirections[i];
int there = here + (dirs.mDirections[i+1] & RUN_LENGTH_MASK);
boolean isRtl = (dirs.mDirections[i+1] & RUN_RTL_FLAG) != 0;
int swap = isRtl ? -1 : 1;
if (there > max)
there = max;
int high = there - 1 + 1, low = here + 1 - 1, guess;
while (high - low > 1) {
guess = (high + low) / 2;
int adguess = getOffsetAtStartOf(guess);
if (getHorizontal(adguess, primary) * swap >= horiz * swap) {
high = guess;
} else {
low = guess;
}
}
if (low < here + 1)
low = here + 1;
if (low < there) {
int aft = tl.getOffsetToLeftRightOf(low - lineStartOffset, isRtl) + lineStartOffset;
low = tl.getOffsetToLeftRightOf(aft - lineStartOffset, !isRtl) + lineStartOffset;
if (low >= here && low < there) {
float dist = Math.abs(getHorizontal(low, primary) - horiz);
if (aft < there) {
float other = Math.abs(getHorizontal(aft, primary) - horiz);
if (other < dist) {
dist = other;
low = aft;
}
}
if (dist < bestdist) {
bestdist = dist;
best = low;
}
}
}
float dist = Math.abs(getHorizontal(here, primary) - horiz);
if (dist < bestdist) {
bestdist = dist;
best = here;
}
}
float dist = Math.abs(getHorizontal(max, primary) - horiz);
if (dist <= bestdist) {
bestdist = dist;
best = max;
}
TextLine.recycle(tl);
return best;
}
/**
* Return the text offset after the last character on the specified line.
*/
public final int getLineEnd(int line) {
return getLineStart(line + 1);
}
/**
* Return the text offset after the last visible character (so whitespace
* is not counted) on the specified line.
*/
public int getLineVisibleEnd(int line) {
return getLineVisibleEnd(line, getLineStart(line), getLineStart(line+1));
}
private int getLineVisibleEnd(int line, int start, int end) {
CharSequence text = mText;
char ch;
if (line == getLineCount() - 1) {
return end;
}
for (; end > start; end--) {
ch = text.charAt(end - 1);
if (ch == '\n') {
return end - 1;
}
if (!TextLine.isLineEndSpace(ch)) {
break;
}
}
return end;
}
/**
* Return the vertical position of the bottom of the specified line.
*/
public final int getLineBottom(int line) {
return getLineTop(line + 1);
}
/**
* Return the vertical position of the baseline of the specified line.
*/
public final int getLineBaseline(int line) {
// getLineTop(line+1) == getLineTop(line)
return getLineTop(line+1) - getLineDescent(line);
}
/**
* Get the ascent of the text on the specified line.
* The return value is negative to match the Paint.ascent() convention.
*/
public final int getLineAscent(int line) {
// getLineTop(line+1) - getLineDescent(line) == getLineBaseLine(line)
return getLineTop(line) - (getLineTop(line+1) - getLineDescent(line));
}
public int getOffsetToLeftOf(int offset) {
return getOffsetToLeftRightOf(offset, true);
}
public int getOffsetToRightOf(int offset) {
return getOffsetToLeftRightOf(offset, false);
}
private int getOffsetToLeftRightOf(int caret, boolean toLeft) {
int line = getLineForOffset(caret);
int lineStart = getLineStart(line);
int lineEnd = getLineEnd(line);
int lineDir = getParagraphDirection(line);
boolean lineChanged = false;
boolean advance = toLeft == (lineDir == DIR_RIGHT_TO_LEFT);
// if walking off line, look at the line we're headed to
if (advance) {
if (caret == lineEnd) {
if (line < getLineCount() - 1) {
lineChanged = true;
++line;
} else {
return caret; // at very end, don't move
}
}
} else {
if (caret == lineStart) {
if (line > 0) {
lineChanged = true;
--line;
} else {
return caret; // at very start, don't move
}
}
}
if (lineChanged) {
lineStart = getLineStart(line);
lineEnd = getLineEnd(line);
int newDir = getParagraphDirection(line);
if (newDir != lineDir) {
// unusual case. we want to walk onto the line, but it runs
// in a different direction than this one, so we fake movement
// in the opposite direction.
toLeft = !toLeft;
lineDir = newDir;
}
}
Directions directions = getLineDirections(line);
TextLine tl = TextLine.obtain();
// XXX: we don't care about tabs
tl.set(mPaint, mText, lineStart, lineEnd, lineDir, directions, false, null);
caret = lineStart + tl.getOffsetToLeftRightOf(caret - lineStart, toLeft);
tl = TextLine.recycle(tl);
return caret;
}
private int getOffsetAtStartOf(int offset) {
// XXX this probably should skip local reorderings and
// zero-width characters, look at callers
if (offset == 0)
return 0;
CharSequence text = mText;
char c = text.charAt(offset);
if (c >= '\uDC00' && c <= '\uDFFF') {
char c1 = text.charAt(offset - 1);
if (c1 >= '\uD800' && c1 <= '\uDBFF')
offset -= 1;
}
if (mSpannedText) {
ReplacementSpan[] spans = ((Spanned) text).getSpans(offset, offset,
ReplacementSpan.class);
for (int i = 0; i < spans.length; i++) {
int start = ((Spanned) text).getSpanStart(spans[i]);
int end = ((Spanned) text).getSpanEnd(spans[i]);
if (start < offset && end > offset)
offset = start;
}
}
return offset;
}
/**
* Determine whether we should clamp cursor position. Currently it's
* only robust for left-aligned displays.
* @hide
*/
public boolean shouldClampCursor(int line) {
// Only clamp cursor position in left-aligned displays.
switch (getParagraphAlignment(line)) {
case ALIGN_LEFT:
return true;
case ALIGN_NORMAL:
return getParagraphDirection(line) > 0;
default:
return false;
}
}
/**
* Fills in the specified Path with a representation of a cursor
* at the specified offset. This will often be a vertical line
* but can be multiple discontinuous lines in text with multiple
* directionalities.
*/
public void getCursorPath(int point, Path dest,
CharSequence editingBuffer) {
dest.reset();
int line = getLineForOffset(point);
int top = getLineTop(line);
int bottom = getLineTop(line+1);
boolean clamped = shouldClampCursor(line);
float h1 = getPrimaryHorizontal(point, clamped) - 0.5f;
float h2 = isLevelBoundary(point) ? getSecondaryHorizontal(point, clamped) - 0.5f : h1;
int caps = TextKeyListener.getMetaState(editingBuffer, TextKeyListener.META_SHIFT_ON) |
TextKeyListener.getMetaState(editingBuffer, TextKeyListener.META_SELECTING);
int fn = TextKeyListener.getMetaState(editingBuffer, TextKeyListener.META_ALT_ON);
int dist = 0;
if (caps != 0 || fn != 0) {
dist = (bottom - top) >> 2;
if (fn != 0)
top += dist;
if (caps != 0)
bottom -= dist;
}
if (h1 < 0.5f)
h1 = 0.5f;
if (h2 < 0.5f)
h2 = 0.5f;
if (Float.compare(h1, h2) == 0) {
dest.moveTo(h1, top);
dest.lineTo(h1, bottom);
} else {
dest.moveTo(h1, top);
dest.lineTo(h1, (top + bottom) >> 1);
dest.moveTo(h2, (top + bottom) >> 1);
dest.lineTo(h2, bottom);
}
if (caps == 2) {
dest.moveTo(h2, bottom);
dest.lineTo(h2 - dist, bottom + dist);
dest.lineTo(h2, bottom);
dest.lineTo(h2 + dist, bottom + dist);
} else if (caps == 1) {
dest.moveTo(h2, bottom);
dest.lineTo(h2 - dist, bottom + dist);
dest.moveTo(h2 - dist, bottom + dist - 0.5f);
dest.lineTo(h2 + dist, bottom + dist - 0.5f);
dest.moveTo(h2 + dist, bottom + dist);
dest.lineTo(h2, bottom);
}
if (fn == 2) {
dest.moveTo(h1, top);
dest.lineTo(h1 - dist, top - dist);
dest.lineTo(h1, top);
dest.lineTo(h1 + dist, top - dist);
} else if (fn == 1) {
dest.moveTo(h1, top);
dest.lineTo(h1 - dist, top - dist);
dest.moveTo(h1 - dist, top - dist + 0.5f);
dest.lineTo(h1 + dist, top - dist + 0.5f);
dest.moveTo(h1 + dist, top - dist);
dest.lineTo(h1, top);
}
}
private void addSelection(int line, int start, int end,
int top, int bottom, Path dest) {
int linestart = getLineStart(line);
int lineend = getLineEnd(line);
Directions dirs = getLineDirections(line);
if (lineend > linestart && mText.charAt(lineend - 1) == '\n')
lineend--;
for (int i = 0; i < dirs.mDirections.length; i += 2) {
int here = linestart + dirs.mDirections[i];
int there = here + (dirs.mDirections[i+1] & RUN_LENGTH_MASK);
if (there > lineend)
there = lineend;
if (start <= there && end >= here) {
int st = Math.max(start, here);
int en = Math.min(end, there);
if (st != en) {
float h1 = getHorizontal(st, false, line, false /* not clamped */);
float h2 = getHorizontal(en, true, line, false /* not clamped */);
float left = Math.min(h1, h2);
float right = Math.max(h1, h2);
dest.addRect(left, top, right, bottom, Path.Direction.CW);
}
}
}
}
/**
* Fills in the specified Path with a representation of a highlight
* between the specified offsets. This will often be a rectangle
* or a potentially discontinuous set of rectangles. If the start
* and end are the same, the returned path is empty.
*/
public void getSelectionPath(int start, int end, Path dest) {
dest.reset();
if (start == end)
return;
if (end < start) {
int temp = end;
end = start;
start = temp;
}
int startline = getLineForOffset(start);
int endline = getLineForOffset(end);
int top = getLineTop(startline);
int bottom = getLineBottom(endline);
if (startline == endline) {
addSelection(startline, start, end, top, bottom, dest);
} else {
final float width = mWidth;
addSelection(startline, start, getLineEnd(startline),
top, getLineBottom(startline), dest);
if (getParagraphDirection(startline) == DIR_RIGHT_TO_LEFT)
dest.addRect(getLineLeft(startline), top,
0, getLineBottom(startline), Path.Direction.CW);
else
dest.addRect(getLineRight(startline), top,
width, getLineBottom(startline), Path.Direction.CW);
for (int i = startline + 1; i < endline; i++) {
top = getLineTop(i);
bottom = getLineBottom(i);
dest.addRect(0, top, width, bottom, Path.Direction.CW);
}
top = getLineTop(endline);
bottom = getLineBottom(endline);
addSelection(endline, getLineStart(endline), end,
top, bottom, dest);
if (getParagraphDirection(endline) == DIR_RIGHT_TO_LEFT)
dest.addRect(width, top, getLineRight(endline), bottom, Path.Direction.CW);
else
dest.addRect(0, top, getLineLeft(endline), bottom, Path.Direction.CW);
}
}
/**
* Get the alignment of the specified paragraph, taking into account
* markup attached to it.
*/
public final Alignment getParagraphAlignment(int line) {
Alignment align = mAlignment;
if (mSpannedText) {
Spanned sp = (Spanned) mText;
AlignmentSpan[] spans = getParagraphSpans(sp, getLineStart(line),
getLineEnd(line),
AlignmentSpan.class);
int spanLength = spans.length;
if (spanLength > 0) {
align = spans[spanLength-1].getAlignment();
}
}
return align;
}
/**
* Get the left edge of the specified paragraph, inset by left margins.
*/
public final int getParagraphLeft(int line) {
int left = 0;
int dir = getParagraphDirection(line);
if (dir == DIR_RIGHT_TO_LEFT || !mSpannedText) {
return left; // leading margin has no impact, or no styles
}
return getParagraphLeadingMargin(line);
}
/**
* Get the right edge of the specified paragraph, inset by right margins.
*/
public final int getParagraphRight(int line) {
int right = mWidth;
int dir = getParagraphDirection(line);
if (dir == DIR_LEFT_TO_RIGHT || !mSpannedText) {
return right; // leading margin has no impact, or no styles
}
return right - getParagraphLeadingMargin(line);
}
/**
* Returns the effective leading margin (unsigned) for this line,
* taking into account LeadingMarginSpan and LeadingMarginSpan2.
* @param line the line index
* @return the leading margin of this line
*/
private int getParagraphLeadingMargin(int line) {
if (!mSpannedText) {
return 0;
}
Spanned spanned = (Spanned) mText;
int lineStart = getLineStart(line);
int lineEnd = getLineEnd(line);
int spanEnd = spanned.nextSpanTransition(lineStart, lineEnd,
LeadingMarginSpan.class);
LeadingMarginSpan[] spans = getParagraphSpans(spanned, lineStart, spanEnd,
LeadingMarginSpan.class);
if (spans.length == 0) {
return 0; // no leading margin span;
}
int margin = 0;
boolean isFirstParaLine = lineStart == 0 ||
spanned.charAt(lineStart - 1) == '\n';
boolean useFirstLineMargin = isFirstParaLine;
for (int i = 0; i < spans.length; i++) {
if (spans[i] instanceof LeadingMarginSpan2) {
int spStart = spanned.getSpanStart(spans[i]);
int spanLine = getLineForOffset(spStart);
int count = ((LeadingMarginSpan2) spans[i]).getLeadingMarginLineCount();
// if there is more than one LeadingMarginSpan2, use the count that is greatest
useFirstLineMargin |= line < spanLine + count;
}
}
for (int i = 0; i < spans.length; i++) {
LeadingMarginSpan span = spans[i];
margin += span.getLeadingMargin(useFirstLineMargin);
}
return margin;
}
/* package */
static float measurePara(TextPaint paint, CharSequence text, int start, int end,
TextDirectionHeuristic textDir) {
MeasuredText mt = MeasuredText.obtain();
TextLine tl = TextLine.obtain();
try {
mt.setPara(text, start, end, textDir, null);
Directions directions;
int dir;
if (mt.mEasy) {
directions = DIRS_ALL_LEFT_TO_RIGHT;
dir = Layout.DIR_LEFT_TO_RIGHT;
} else {
directions = AndroidBidi.directions(mt.mDir, mt.mLevels,
0, mt.mChars, 0, mt.mLen);
dir = mt.mDir;
}
char[] chars = mt.mChars;
int len = mt.mLen;
boolean hasTabs = false;
TabStops tabStops = null;
// leading margins should be taken into account when measuring a paragraph
int margin = 0;
if (text instanceof Spanned) {
Spanned spanned = (Spanned) text;
LeadingMarginSpan[] spans = getParagraphSpans(spanned, start, end,
LeadingMarginSpan.class);
for (LeadingMarginSpan lms : spans) {
margin += lms.getLeadingMargin(true);
}
}
for (int i = 0; i < len; ++i) {
if (chars[i] == '\t') {
hasTabs = true;
if (text instanceof Spanned) {
Spanned spanned = (Spanned) text;
int spanEnd = spanned.nextSpanTransition(start, end,
TabStopSpan.class);
TabStopSpan[] spans = getParagraphSpans(spanned, start, spanEnd,
TabStopSpan.class);
if (spans.length > 0) {
tabStops = new TabStops(TAB_INCREMENT, spans);
}
}
break;
}
}
tl.set(paint, text, start, end, dir, directions, hasTabs, tabStops);
return margin + Math.abs(tl.metrics(null));
} finally {
TextLine.recycle(tl);
MeasuredText.recycle(mt);
}
}
/**
* @hide
*/
/* package */ static class TabStops {
private int[] mStops;
private int mNumStops;
private int mIncrement;
TabStops(int increment, Object[] spans) {
reset(increment, spans);
}
void reset(int increment, Object[] spans) {
this.mIncrement = increment;
int ns = 0;
if (spans != null) {
int[] stops = this.mStops;
for (Object o : spans) {
if (o instanceof TabStopSpan) {
if (stops == null) {
stops = new int[10];
} else if (ns == stops.length) {
int[] nstops = new int[ns * 2];
for (int i = 0; i < ns; ++i) {
nstops[i] = stops[i];
}
stops = nstops;
}
stops[ns++] = ((TabStopSpan) o).getTabStop();
}
}
if (ns > 1) {
Arrays.sort(stops, 0, ns);
}
if (stops != this.mStops) {
this.mStops = stops;
}
}
this.mNumStops = ns;
}
float nextTab(float h) {
int ns = this.mNumStops;
if (ns > 0) {
int[] stops = this.mStops;
for (int i = 0; i < ns; ++i) {
int stop = stops[i];
if (stop > h) {
return stop;
}
}
}
return nextDefaultStop(h, mIncrement);
}
public static float nextDefaultStop(float h, int inc) {
return ((int) ((h + inc) / inc)) * inc;
}
}
/**
* Returns the position of the next tab stop after h on the line.
*
* @param text the text
* @param start start of the line
* @param end limit of the line
* @param h the current horizontal offset
* @param tabs the tabs, can be null. If it is null, any tabs in effect
* on the line will be used. If there are no tabs, a default offset
* will be used to compute the tab stop.
* @return the offset of the next tab stop.
*/
/* package */ static float nextTab(CharSequence text, int start, int end,
float h, Object[] tabs) {
float nh = Float.MAX_VALUE;
boolean alltabs = false;
if (text instanceof Spanned) {
if (tabs == null) {
tabs = getParagraphSpans((Spanned) text, start, end, TabStopSpan.class);
alltabs = true;
}
for (int i = 0; i < tabs.length; i++) {
if (!alltabs) {
if (!(tabs[i] instanceof TabStopSpan))
continue;
}
int where = ((TabStopSpan) tabs[i]).getTabStop();
if (where < nh && where > h)
nh = where;
}
if (nh != Float.MAX_VALUE)
return nh;
}
return ((int) ((h + TAB_INCREMENT) / TAB_INCREMENT)) * TAB_INCREMENT;
}
protected final boolean isSpanned() {
return mSpannedText;
}
/**
* Returns the same as text.getSpans(), except where
* start and end are the same and are not
* at the very beginning of the text, in which case an empty array
* is returned instead.
*
* This is needed because of the special case that getSpans()
* on an empty range returns the spans adjacent to that range, which is
* primarily for the sake of TextWatchers so they will get
* notifications when text goes from empty to non-empty. But it also
* has the unfortunate side effect that if the text ends with an empty
* paragraph, that paragraph accidentally picks up the styles of the
* preceding paragraph (even though those styles will not be picked up
* by new text that is inserted into the empty paragraph).
*
* The reason it just checks whether start and end
* is the same is that the only time a line can contain 0 characters
* is if it is the final paragraph of the Layout; otherwise any line will
* contain at least one printing or newline character. The reason for the
* additional check if start is greater than 0 is that
* if the empty paragraph is the entire content of the buffer, paragraph
* styles that are already applied to the buffer will apply to text that
* is inserted into it.
*/
/* package */static