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PDF writer: implement support for document internal links

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QPdfEngine already supported links to external URIs, but not internal
links for navigation in a document.

For internal links, PDF supports "named destinations" instead of
direct coordinates. That way, we avoid the need for a two-pass
implementation. Instead, we just store the name and position of all
anchors as we enounter them. At document finishing time, we export the
list of named destinations in a PDF "name tree" structure.

The PDF named destinations feature uses the same main catalog item
("Names") as the attached files feature. Hence, this commit must
slightly change the implementation of file attachment support also, so
that the structure supports both. Now, we always add a reference to a
Names object in the catalog when we start the document. When we
finish, we write that object, making it reference the attached
files-structure and/or the named destinations-structure, as needed.

Fixes: QTBUG-83458
Change-Id: I9c43e7b423062d3f21965ab8a0d81a53c4dd72cb
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
This commit is contained in:
Eirik Aavitsland 2022-10-28 10:56:00 +02:00
parent a9f94d078a
commit 5d95205bae
2 changed files with 107 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

133
src/gui/painting/qpdf.cpp
View File

@ -1505,8 +1505,9 @@ bool QPdfEngine::begin(QPaintDevice *pdev)
d->xrefPositions.clear();
d->pageRoot = 0;
d->embeddedfilesRoot = 0;
d->namesRoot = 0;
d->destsRoot = 0;
d->attachmentsRoot = 0;
d->catalog = 0;
d->info = 0;
d->graphicsState = 0;
@ -1543,6 +1544,7 @@ bool QPdfEngine::end()
d->outDevice = nullptr;
}
d->destCache.clear();
d->fileCache.clear();
setActive(false);
@ -1591,10 +1593,7 @@ void QPdfEnginePrivate::writeHeader()
catalog = addXrefEntry(-1);
pageRoot = requestObject();
if (!fileCache.isEmpty()) {
namesRoot = requestObject();
embeddedfilesRoot = requestObject();
}
namesRoot = requestObject();
// catalog
{
@ -1602,11 +1601,8 @@ void QPdfEnginePrivate::writeHeader()
QPdf::ByteStream s(&catalog);
s << "<<\n"
<< "/Type /Catalog\n"
<< "/Pages " << pageRoot << "0 R\n";
// Embedded files, if any
if (!fileCache.isEmpty())
s << "/Names " << embeddedfilesRoot << "0 R\n";
<< "/Pages " << pageRoot << "0 R\n"
<< "/Names " << namesRoot << "0 R\n";
if (pdfVersion == QPdfEngine::Version_A1b || !xmpDocumentMetadata.isEmpty())
s << "/Metadata " << metaDataObj << "0 R\n";
@ -1620,12 +1616,6 @@ void QPdfEnginePrivate::writeHeader()
write(catalog);
}
if (!fileCache.isEmpty()) {
addXrefEntry(embeddedfilesRoot);
xprintf("<</EmbeddedFiles %d 0 R>>\n"
"endobj\n", namesRoot);
}
// graphics state
graphicsState = addXrefEntry(-1);
xprintf("<<\n"
@ -1793,6 +1783,39 @@ void QPdfEnginePrivate::writePageRoot()
"endobj\n");
}
void QPdfEnginePrivate::writeDestsRoot()
{
if (destCache.isEmpty())
return;
QHash<QString, int> destObjects;
QByteArray xs, ys;
for (const DestInfo &destInfo : qAsConst(destCache)) {
int destObj = addXrefEntry(-1);
xs.setNum(static_cast<double>(destInfo.coords.x()), 'f');
ys.setNum(static_cast<double>(destInfo.coords.y()), 'f');
xprintf("[%d 0 R /XYZ %s %s 0]\n", destInfo.pageObj, xs.constData(), ys.constData());
xprintf("endobj\n");
destObjects.insert(destInfo.anchor, destObj);
}
// names
destsRoot = addXrefEntry(-1);
QStringList anchors = destObjects.keys();
anchors.sort();
xprintf("<<\n/Limits [");
printString(anchors.constFirst());
xprintf(" ");
printString(anchors.constLast());
xprintf("]\n/Names [\n");
for (const QString &anchor : qAsConst(anchors)) {
printString(anchor);
xprintf(" %d 0 R\n", destObjects[anchor]);
}
xprintf("]\n>>\n"
"endobj\n");
}
void QPdfEnginePrivate::writeAttachmentRoot()
{
if (fileCache.isEmpty())
@ -1832,7 +1855,7 @@ void QPdfEnginePrivate::writeAttachmentRoot()
}
// names
addXrefEntry(namesRoot);
attachmentsRoot = addXrefEntry(-1);
xprintf("<</Names[");
for (int i = 0; i < size; ++i) {
auto attachment = fileCache.at(i);
@ -1843,6 +1866,21 @@ void QPdfEnginePrivate::writeAttachmentRoot()
"endobj\n");
}
void QPdfEnginePrivate::writeNamesRoot()
{
addXrefEntry(namesRoot);
xprintf("<<\n");
if (attachmentsRoot)
xprintf("/EmbeddedFiles %d 0 R\n", attachmentsRoot);
if (destsRoot)
xprintf("/Dests %d 0 R\n", destsRoot);
xprintf(">>\n");
xprintf("endobj\n");
}
void QPdfEnginePrivate::embedFont(QFontSubset *font)
{
//qDebug() << "embedFont" << font->object_id;
@ -2099,7 +2137,9 @@ void QPdfEnginePrivate::writeTail()
writePage();
writeFonts();
writePageRoot();
writeDestsRoot();
writeAttachmentRoot();
writeNamesRoot();
addXrefEntry(xrefPositions.size(),false);
xprintf("xref\n"
@ -2951,7 +2991,9 @@ void QPdfEnginePrivate::drawTextItem(const QPointF &p, const QTextItemInt &ti)
{
Q_Q(QPdfEngine);
if (ti.charFormat.hasProperty(QTextFormat::AnchorHref)) {
const bool isLink = ti.charFormat.hasProperty(QTextFormat::AnchorHref);
const bool isAnchor = ti.charFormat.hasProperty(QTextFormat::AnchorName);
if (isLink || isAnchor) {
qreal size = ti.fontEngine->fontDef.pixelSize;
int synthesized = ti.fontEngine->synthesized();
qreal stretch = synthesized & QFontEngine::SynthesizedStretch ? ti.fontEngine->fontDef.stretch/100. : 1.;
@ -2971,32 +3013,47 @@ void QPdfEnginePrivate::drawTextItem(const QPointF &p, const QTextItemInt &ti)
trans.map(0, 0, &x1, &y1);
trans.map(ti.width.toReal()/size, (ti.ascent.toReal()-ti.descent.toReal())/size, &x2, &y2);
uint annot = addXrefEntry(-1);
QByteArray x1s, y1s, x2s, y2s;
x1s.setNum(static_cast<double>(x1), 'f');
y1s.setNum(static_cast<double>(y1), 'f');
x2s.setNum(static_cast<double>(x2), 'f');
y2s.setNum(static_cast<double>(y2), 'f');
QByteArray rectData = x1s + ' ' + y1s + ' ' + x2s + ' ' + y2s;
xprintf("<<\n/Type /Annot\n/Subtype /Link\n");
if (isLink) {
uint annot = addXrefEntry(-1);
QByteArray x1s, y1s, x2s, y2s;
x1s.setNum(static_cast<double>(x1), 'f');
y1s.setNum(static_cast<double>(y1), 'f');
x2s.setNum(static_cast<double>(x2), 'f');
y2s.setNum(static_cast<double>(y2), 'f');
QByteArray rectData = x1s + ' ' + y1s + ' ' + x2s + ' ' + y2s;
xprintf("<<\n/Type /Annot\n/Subtype /Link\n");
if (pdfVersion == QPdfEngine::Version_A1b)
xprintf("/F 4\n"); // enable print flag, disable all other
if (pdfVersion == QPdfEngine::Version_A1b)
xprintf("/F 4\n"); // enable print flag, disable all other
xprintf("/Rect [");
xprintf(rectData.constData());
xprintf("/Rect [");
xprintf(rectData.constData());
#ifdef Q_DEBUG_PDF_LINKS
xprintf("]\n/Border [16 16 1]\n/A <<\n");
xprintf("]\n/Border [16 16 1]\n");
#else
xprintf("]\n/Border [0 0 0]\n/A <<\n");
xprintf("]\n/Border [0 0 0]\n");
#endif
xprintf("/Type /Action\n/S /URI\n/URI (%s)\n",
ti.charFormat.anchorHref().toLatin1().constData());
xprintf(">>\n>>\n");
xprintf("endobj\n");
const QString link = ti.charFormat.anchorHref();
const bool isInternal = link.startsWith(QLatin1Char('#'));
if (!isInternal) {
xprintf("/A <<\n");
xprintf("/Type /Action\n/S /URI\n/URI (%s)\n", link.toLatin1().constData());
xprintf(">>\n");
} else {
xprintf("/Dest ");
printString(link.sliced(1));
xprintf("\n");
}
xprintf(">>\n");
xprintf("endobj\n");
if (!currentPage->annotations.contains(annot)) {
currentPage->annotations.append(annot);
if (!currentPage->annotations.contains(annot)) {
currentPage->annotations.append(annot);
}
} else {
const QString anchor = ti.charFormat.anchorNames().constFirst();
const uint curPage = pages.last();
destCache.append(DestInfo({ anchor, curPage, QPointF(x1, y2) }));
}
}

13
src/gui/painting/qpdf_p.h
View File

@ -271,7 +271,9 @@ private:
int writeXmpDcumentMetaData();
int writeOutputIntent();
void writePageRoot();
void writeDestsRoot();
void writeAttachmentRoot();
void writeNamesRoot();
void writeFonts();
void embedFont(QFontSubset *font);
qreal calcUserUnit() const;
@ -305,11 +307,20 @@ private:
QString mimeType;
};
struct DestInfo
{
QString anchor;
uint pageObj;
QPointF coords;
};
// various PDF objects
int pageRoot, embeddedfilesRoot, namesRoot, catalog, info, graphicsState, patternColorSpace;
int pageRoot, namesRoot, destsRoot, attachmentsRoot, catalog, info;
int graphicsState, patternColorSpace;
QList<uint> pages;
QHash<qint64, uint> imageCache;
QHash<QPair<uint, uint>, uint > alphaCache;
QList<DestInfo> destCache;
QList<AttachmentInfo> fileCache;
QByteArray xmpDocumentMetadata;
};