5 files changed, 47 insertions, 11 deletions
diff --git a/src/gui/painting/qpagedpaintdevice.cpp b/src/gui/painting/qpagedpaintdevice.cpp
index 613a686848..72b2834470 100644
--- a/src/gui/painting/qpagedpaintdevice.cpp
+++ b/src/gui/painting/qpagedpaintdevice.cpp
@@ -290,7 +290,8 @@ QPagedPaintDevicePrivate *QPagedPaintDevice::dd()
 
     \value PdfVersion_A1b A PDF/A-1b compatible document is produced.
 
-    \since 5.10
+    \value PdfVersion_1_6 A PDF 1.6 compatible document is produced.
+           This value was added in Qt 5.12.
 */
 
 /*!
diff --git a/src/gui/painting/qpagedpaintdevice.h b/src/gui/painting/qpagedpaintdevice.h
index c8957edab8..1c37c17fa3 100644
--- a/src/gui/painting/qpagedpaintdevice.h
+++ b/src/gui/painting/qpagedpaintdevice.h
@@ -213,7 +213,7 @@ public:
         Envelope10 = Comm10E
     };
 
-    enum PdfVersion { PdfVersion_1_4, PdfVersion_A1b };
+    enum PdfVersion { PdfVersion_1_4, PdfVersion_A1b, PdfVersion_1_6 };
 
     // ### Qt6 Make these virtual
     bool setPageLayout(const QPageLayout &pageLayout);
diff --git a/src/gui/painting/qpdf.cpp b/src/gui/painting/qpdf.cpp
index 5220c24020..b410e9b900 100644
--- a/src/gui/painting/qpdf.cpp
+++ b/src/gui/painting/qpdf.cpp
@@ -1547,7 +1547,14 @@ void QPdfEnginePrivate::writeHeader()
 {
     addXrefEntry(0,false);
 
-    xprintf("%%PDF-1.4\n");
+    static const QHash<QPdfEngine::PdfVersion, const char *> mapping {
+        {QPdfEngine::Version_1_4, "1.4"},
+        {QPdfEngine::Version_A1b, "1.4"},
+        {QPdfEngine::Version_1_6, "1.6"}
+    };
+    const char *verStr = mapping.value(pdfVersion, "1.4");
+
+    xprintf("%%PDF-%s\n", verStr);
     xprintf("%%\303\242\303\243\n");
 
     writeInfo();
@@ -1880,6 +1887,19 @@ void QPdfEnginePrivate::embedFont(QFontSubset *font)
     }
 }
 
+qreal QPdfEnginePrivate::calcUserUnit() const
+{
+    // PDF standards < 1.6 support max 200x200in pages (no UserUnit)
+    if (pdfVersion < QPdfEngine::Version_1_6)
+        return 1.0;
+
+    const int maxLen = qMax(currentPage->pageSize.width(), currentPage->pageSize.height());
+    if (maxLen <= 14400)
+        return 1.0; // for pages up to 200x200in (14400x14400 units) use default scaling
+
+    // for larger pages, rescale units so we can have up to 381x381km
+    return qMin(maxLen / 14400.0, 75000.0);
+}
 
 void QPdfEnginePrivate::writeFonts()
 {
@@ -1902,6 +1922,8 @@ void QPdfEnginePrivate::writePage()
     uint resources = requestObject();
     uint annots = requestObject();
 
+    qreal userUnit = calcUserUnit();
+
     addXrefEntry(pages.constLast());
     xprintf("<<\n"
             "/Type /Page\n"
@@ -1909,12 +1931,16 @@ void QPdfEnginePrivate::writePage()
             "/Contents %d 0 R\n"
             "/Resources %d 0 R\n"
             "/Annots %d 0 R\n"
-            "/MediaBox [0 0 %d %d]\n"
-            ">>\n"
-            "endobj\n",
+            "/MediaBox [0 0 %f %f]\n",
             pageRoot, pageStream, resources, annots,
             // make sure we use the pagesize from when we started the page, since the user may have changed it
-            currentPage->pageSize.width(), currentPage->pageSize.height());
+            currentPage->pageSize.width() / userUnit, currentPage->pageSize.height() / userUnit);
+
+    if (pdfVersion >= QPdfEngine::Version_1_6)
+        xprintf("/UserUnit %f\n", userUnit);
+
+    xprintf(">>\n"
+            "endobj\n");
 
     addXrefEntry(resources);
     xprintf("<<\n"
@@ -2983,8 +3009,9 @@ void QPdfEnginePrivate::drawTextItem(const QPointF &p, const QTextItemInt &ti)
 
 QTransform QPdfEnginePrivate::pageMatrix() const
 {
-    qreal scale = 72./resolution;
-    QTransform tmp(scale, 0.0, 0.0, -scale, 0.0, m_pageLayout.fullRectPoints().height());
+    qreal userUnit = calcUserUnit();
+    qreal scale = 72. / userUnit / resolution;
+    QTransform tmp(scale, 0.0, 0.0, -scale, 0.0, m_pageLayout.fullRectPoints().height() / userUnit);
     if (m_pageLayout.mode() != QPageLayout::FullPageMode) {
         QRect r = m_pageLayout.paintRectPixels(resolution);
         tmp.translate(r.left(), r.top());
diff --git a/src/gui/painting/qpdf_p.h b/src/gui/painting/qpdf_p.h
index 5a909f2ede..e2526de67d 100644
--- a/src/gui/painting/qpdf_p.h
+++ b/src/gui/painting/qpdf_p.h
@@ -171,7 +171,8 @@ public:
     enum PdfVersion
     {
         Version_1_4,
-        Version_A1b
+        Version_A1b,
+        Version_1_6
     };
 
     QPdfEngine();
@@ -300,6 +301,7 @@ private:
     void writePageRoot();
     void writeFonts();
     void embedFont(QFontSubset *font);
+    qreal calcUserUnit() const;
 
     QVector<int> xrefPositions;
     QDataStream* stream;
diff --git a/src/gui/painting/qpdfwriter.cpp b/src/gui/painting/qpdfwriter.cpp
index e6c5cabd7f..6c85d65538 100644
--- a/src/gui/painting/qpdfwriter.cpp
+++ b/src/gui/painting/qpdfwriter.cpp
@@ -170,11 +170,17 @@ void QPdfWriter::setPdfVersion(PdfVersion version)
 {
     Q_D(QPdfWriter);
 
+    static const QHash<QPdfWriter::PdfVersion, QPdfEngine::PdfVersion> engineMapping {
+        {QPdfWriter::PdfVersion_1_4, QPdfEngine::Version_1_4},
+        {QPdfWriter::PdfVersion_A1b, QPdfEngine::Version_A1b},
+        {QPdfWriter::PdfVersion_1_6, QPdfEngine::Version_1_6}
+    };
+
     if (d->pdfVersion == version)
         return;
 
     d->pdfVersion = version;
-    d->engine->setPdfVersion(d->pdfVersion == QPdfWriter::PdfVersion_1_4 ? QPdfEngine::Version_1_4 : QPdfEngine::Version_A1b);
+    d->engine->setPdfVersion(engineMapping.value(version, QPdfEngine::Version_1_4));
 }
 
 /*!