package pl.djvuhtml5.client.ui;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import com.google.gwt.canvas.client.Canvas;
import com.google.gwt.canvas.dom.client.Context2d;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.Style;
import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.event.dom.client.ScrollEvent;
import com.google.gwt.event.dom.client.ScrollHandler;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.Label;
import com.lizardtech.djvu.DjVuInfo;
import com.lizardtech.djvu.text.DjVuText;
import com.lizardtech.djvu.text.DjVuText.Zone;
import pl.djvuhtml5.client.DjvuContext;
import pl.djvuhtml5.client.Djvu_html5;
public class TextLayer extends FlowPanel implements ScrollHandler {
private static final String PAGE_STYLE_VISIBLE = "visibleTextPage";
/**
* Extra space to the left so that user can scroll over the left edge and go to
* the previous page.
*/
private static final int EXTRA_PAGE_MARGIN = 500;
private class TextPage extends FlowPanel {
final List<TextLine> textLines = new ArrayList<>();
DjVuText text;
int width, height;
TextPage() {
setStyleName("textPage");
setPixelSize(1, 1);
}
void setSize(int width, int height) {
this.width = width;
this.height = height;
setPixelSize(width, height);
}
void resize(double zoom, boolean force) {
int w = (int) (width * zoom + 0.5);
int h = (int) (height * zoom + 0.5);
if (force || w != getOffsetWidth() || h != getOffsetHeight()) {
setPixelSize(w, h);
for (TextLine textLine : textLines)
textLine.resize(zoom);
}
}
String getText(Zone zone) {
return text.getString(zone.text_start, zone.text_start + zone.text_length);
}
}
private class TextLine extends FlowPanel {
final List<Token> tokens = new ArrayList<>();
TextLine(int minY, int maxY, int prevY, TextPage parent, List<Zone> lineTokens) {
Style style = getElement().getStyle();
double marginTop = round((prevY - maxY) * 100.0 / parent.width, PCT_ACCURACY);
if (parent.getWidgetCount() == 0) {
style.setPaddingTop(marginTop, Unit.PCT);
} else {
style.setMarginTop(marginTop, Unit.PCT);
}
style.setHeight(round((maxY - minY) * 100.0 / parent.height, PCT_ACCURACY), Unit.PCT);
Token lastToken = null;
int prevXmax = 0;
for (Zone zone : lineTokens) {
Token token = new Token(zone, prevXmax, parent);
if (token.text.isEmpty()) {
if (lastToken != null)
lastToken.setText(lastToken.getText() + token.getText());
continue;
}
add(token);
lastToken = token;
if (token.text.length() > 1 || lineTokens.size() == 1) {
tokens.add(token);
}
prevXmax = zone.xmax;
}
parent.textLines.add(this);
parent.add(this);
}
void resize(double zoom) {
double fontSize = 0;
for (Token token : tokens)
fontSize += token.getFontSize(zoom);
fontSize = round(fontSize / tokens.size(), FONT_ACCURACY);
getElement().getStyle().setFontSize(fontSize, Unit.PX);
for (Token token : tokens)
token.adjustSpacing(fontSize, zoom);
}
}
private class Token extends Label {
/** Token's text stripped of excessive whitespace, in contrast to {@link #getText()} */
final String text;
final double fullWidth;
Token(Zone zone, int prevXmax, TextPage page) {
super(Document.get().createSpanElement());
String text = page.getText(zone);
setText(text);
fullWidth = zone.xmax - zone.xmin;
this.text = text.trim().replaceAll("\\s+", "");
Style s = getElement().getStyle();
double marginLeft = (zone.xmin - prevXmax) * 100.0 / page.width;
s.setMarginLeft(round(marginLeft, PCT_ACCURACY), Unit.PCT);
double width = fullWidth * 100.0 / page.width;
s.setWidth(round(width, PCT_ACCURACY), Unit.PCT);
}
double getFontSize(double zoom) {
final double width = fullWidth * zoom;
double fontSize = previousFontSize;
double diff = Double.MAX_VALUE, prevDiff;
double ratio = 1;
int count = 0;
do {
fontSize *= ratio;
ratio = width / getWidth(fontSize);
prevDiff = diff;
diff = Math.abs(1 - ratio);
} while (count++ < 6 && diff > 0.05 && diff < prevDiff);
previousFontSize = fontSize;
return fontSize;
}
void adjustSpacing(double fontSize, double zoom) {
int textLength = text.length();
if (textLength < 2)
return;
double width = getWidth(fontSize);
double spacing = (fullWidth * zoom - width) / (textLength - 1);
getElement().getStyle().setProperty("letterSpacing", round(spacing, 0.1), Unit.PX);
}
private double getWidth(double fontSize) {
if (fontFamily == null)
fontFamily = getComputedFontFamily(getElement());
fontMeasure.setFont(fontSize + "px " + fontFamily);
return fontMeasure.measureText(text).getWidth();
}
private native String getComputedFontFamily(JavaScriptObject element) /*-{
return document.defaultView.getComputedStyle(element, null)["fontFamily"];
}-*/;
}
private static final double PCT_ACCURACY = 0.0001;
private static final double FONT_ACCURACY = 0.5;
private final Djvu_html5 app;
private final List<TextPage> pages = new ArrayList<>();
private final Context2d fontMeasure;
private String fontFamily;
private double previousFontSize = 20;
private int currentPage = 0;
public TextLayer(Djvu_html5 app) {
this.app = app;
setStyleName("textLayer");
getElement().setAttribute("tabindex", "-1");
addDomHandler(this, ScrollEvent.getType());
app.getDataStore().addInfoListener(this::pageInfoAvailable);
if (DjvuContext.getTextLayerEnabled())
app.getDataStore().addTextListener(this::textAvailable);
fontMeasure = Canvas.createIfSupported().getContext2d();
}
private void pageInfoAvailable(int pageNum) {
DjVuInfo pageInfo = app.getDataStore().getPageInfo(pageNum);
getPage(pageNum).setSize(pageInfo.width, pageInfo.height);
}
private void textAvailable(int pageNum) {
DjVuText text = app.getDataStore().getText(pageNum);
TextPage page = getPage(pageNum);
page.text = text;
if (text.length() > 0) {
List<Zone> tokens = new ArrayList<>();
text.page_zone.get_smallest(tokens);
createTextLines(page, tokens);
if (pageNum == currentPage)
app.getPageLayout().setPage(pageNum);
}
}
private void createTextLines(TextPage page, List<Zone> tokens) {
int prevY = page.height;
while (!tokens.isEmpty()) {
List<Zone> lineTokens = new ArrayList<>();
Zone lastToken = null;
int minY = Integer.MAX_VALUE, maxY = Integer.MIN_VALUE;
while (!tokens.isEmpty()) {
Zone token = tokens.get(0);
boolean hasMultipleChars = page.getText(token).trim().length() > 1;
if (lastToken != null) { //make sure it's the same line
if (token.xmin < lastToken.xmax)
break;
int commonPart = Math.min(maxY, token.ymax) - Math.max(minY, token.ymin);
int total = Math.max(maxY, token.ymax) - Math.min(minY, token.ymin);
if (hasMultipleChars) {
if (commonPart <= 0)
break;
} else {
if (commonPart * 2 <= total)
break;
}
}
tokens.remove(0);
lineTokens.add(token);
if (hasMultipleChars) {
lastToken = token;
minY = Math.min(minY, token.ymin);
maxY = Math.max(maxY, token.ymax);
}
}
if (lastToken != null) {
new TextLine(minY, maxY, prevY, page, lineTokens);
prevY = minY;
} else {
for (Zone lineToken : lineTokens) {
new TextLine(lineToken.ymin, lineToken.ymax, prevY, page, Arrays.asList(lineToken));
prevY = lineToken.ymin;
}
}
}
}
/**
* @param left position of page's left edge on the canvas
* @param top position of page's top edge on the canvas
*/
public void setViewPosition(int pageNum, int left, int top, double zoom) {
boolean pageChanged = currentPage != pageNum;
TextPage page = getPage(pageNum);
if (pageChanged) {
getPage(currentPage).removeStyleName(PAGE_STYLE_VISIBLE);
page.addStyleName(PAGE_STYLE_VISIBLE);
}
page.resize(zoom, pageChanged);
currentPage = pageNum;
Element layerElement = getElement();
Element pageElement = page.getElement();
pageElement.getStyle().setMarginLeft(Math.max(left, 0) + EXTRA_PAGE_MARGIN, Unit.PX);
int targetScrollLeft = Math.max(-left, 0) + EXTRA_PAGE_MARGIN;
if (layerElement.getScrollLeft() != targetScrollLeft)
layerElement.setScrollLeft(targetScrollLeft);
int targetScrollTop = pageElement.getOffsetTop() - top;
if (layerElement.getScrollTop() != targetScrollTop)
layerElement.setScrollTop(targetScrollTop);
}
@Override
public void onScroll(ScrollEvent event) {
int scrollTop = getElement().getScrollTop();
int page = currentPage;
Element pageElement = pages.get(page).getElement();
while (page > 0 && pageElement.getOffsetTop() > scrollTop) {
pageElement = pages.get(--page).getElement();
}
while (page + 1 < pages.size() && pageElement.getOffsetTop() + pageElement.getOffsetHeight() < scrollTop) {
pageElement = pages.get(++page).getElement();
}
int left = pageElement.getOffsetLeft() - getElement().getScrollLeft();
int top = pageElement.getOffsetTop() - scrollTop;
app.getPageLayout().externalScroll(page, left, top);
}
private TextPage getPage(int pageNum) {
while (pageNum >= pages.size()) {
TextPage page = new TextPage();
if (pages.size() == currentPage)
page.addStyleName(PAGE_STYLE_VISIBLE);
add(page);
pages.add(page);
}
return pages.get(pageNum);
}
private static double round(double value, double accuracy) {
return Math.round((value + accuracy / 2) / accuracy) * accuracy;
}
}
