Fix drawing of background for multipage QTextTable cells

Task-number: QTBUG-31330
Change-Id: I0103919ee2864b7cd8bed41e6d6fe4ac5b84142e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/gui/text/qtextdocumentlayout.cpp

@@ -1115,6 +1115,13 @@ void QTextDocumentLayoutPrivate::drawTableCell(const QRectF &cellRect, QPainter
     const QFixed leftPadding = td->leftPadding(fmt);
     const QFixed topPadding = td->topPadding(fmt);
 
+    qreal topMargin = (td->effectiveTopMargin + td->cellSpacing + td->border).toReal();
+    qreal bottomMargin = (td->effectiveBottomMargin + td->cellSpacing + td->border).toReal();
+
+    const int headerRowCount = qMin(table->format().headerRowCount(), table->rows() - 1);
+    if (r >= headerRowCount)
+        topMargin += td->headerHeight.toReal();
+
     if (td->border != 0) {
         const QBrush oldBrush = painter->brush();
         const QPen oldPen = painter->pen();
@@ -1142,13 +1149,6 @@ void QTextDocumentLayoutPrivate::drawTableCell(const QRectF &cellRect, QPainter
             break;
         }
 
-        qreal topMargin = (td->effectiveTopMargin + td->cellSpacing + td->border).toReal();
-        qreal bottomMargin = (td->effectiveBottomMargin + td->cellSpacing + td->border).toReal();
-
-        const int headerRowCount = qMin(table->format().headerRowCount(), table->rows() - 1);
-        if (r >= headerRowCount)
-            topMargin += td->headerHeight.toReal();
-
         drawBorder(painter, borderRect, topMargin, bottomMargin,
                    border, table->format().borderBrush(), cellBorder);
 
@@ -1159,7 +1159,30 @@ void QTextDocumentLayoutPrivate::drawTableCell(const QRectF &cellRect, QPainter
     const QBrush bg = cell.format().background();
     const QPointF brushOrigin = painter->brushOrigin();
     if (bg.style() != Qt::NoBrush) {
-        fillBackground(painter, cellRect, bg, cellRect.topLeft());
+        const qreal pageHeight = document->pageSize().height();
+        const int topPage = pageHeight > 0 ? static_cast<int>(cellRect.top() / pageHeight) : 0;
+        const int bottomPage = pageHeight > 0 ? static_cast<int>((cellRect.bottom()) / pageHeight) : 0;
+
+        if (topPage == bottomPage)
+            fillBackground(painter, cellRect, bg, cellRect.topLeft());
+        else {
+            for (int i = topPage; i <= bottomPage; ++i) {
+                QRectF clipped = cellRect.toRect();
+
+                if (topPage != bottomPage) {
+                    const qreal top = qMax(i * pageHeight + topMargin, cell_context.clip.top());
+                    const qreal bottom = qMin((i + 1) * pageHeight - bottomMargin, cell_context.clip.bottom());
+
+                    clipped.setTop(qMax(clipped.top(), top));
+                    clipped.setBottom(qMin(clipped.bottom(), bottom));
+
+                    if (clipped.bottom() <= clipped.top())
+                        continue;
+
+                    fillBackground(painter, clipped, bg, cellRect.topLeft());
+                }
+            }
+        }
 
         if (bg.style() > Qt::SolidPattern)
             painter->setBrushOrigin(cellRect.topLeft());

tests/auto/gui/text/qtexttable/tst_qtexttable.cpp

@@ -44,6 +44,11 @@
 #ifndef QT_NO_WIDGETS
 #include <qtextedit.h>
 #endif
+#ifndef QT_NO_PRINTER
+#include <QPagedPaintDevice>
+#include <QPainter>
+#include <QPaintEngine>
+#endif
 
 typedef QList<int> IntList;
 
@@ -96,6 +101,9 @@ private slots:
     void QTBUG11282_insertBeforeMergedEnding();
 #endif
     void QTBUG22011_insertBeforeRowSpan();
+#ifndef QT_NO_PRINTER
+    void QTBUG31330_renderBackground();
+#endif
 
 private:
     QTextTable *create2x2Table();
@@ -1024,5 +1032,112 @@ void tst_QTextTable::QTBUG22011_insertBeforeRowSpan()
     QCOMPARE(table->columns(), 6);
 }
 
+#ifndef QT_NO_PRINTER
+namespace {
+class QTBUG31330_PaintDevice : public QPagedPaintDevice
+{
+public:
+    class PaintEngine : public QPaintEngine
+    {
+    public:
+        QList<QRectF> rects;
+
+        PaintEngine()
+            : QPaintEngine(0)
+        {}
+        virtual Type type() const
+        {
+            return User;
+        }
+        virtual bool begin(QPaintDevice *)
+        {
+            return true;
+        }
+        virtual bool end()
+        {
+            return true;
+        }
+        virtual void updateState(const QPaintEngineState &)
+        {}
+        virtual void drawRects(const QRect *, int)
+        {}
+        virtual void drawRects(const QRectF *r, int)
+        {
+            if (painter()->brush() == QBrush(Qt::green))
+            {
+                rects.append(*r);
+            }
+        }
+        virtual void drawPixmap(const QRectF &, const QPixmap &, const QRectF &)
+        {}
+    };
+
+    int pages;
+    QPaintEngine* engine;
+
+    QTBUG31330_PaintDevice(QPaintEngine* engine)
+        : pages(1), engine(engine)
+    {
+        QPageLayout layout = pageLayout();
+        layout.setUnits(QPageLayout::Point);
+        setPageLayout(layout);
+    }
+    virtual int metric(PaintDeviceMetric metric) const
+    {
+        if (PdmDevicePixelRatio == metric)
+            return 1;
+        if (PdmDpiY == metric)
+            return 96;
+        if (PdmDpiX == metric)
+            return 96;
+        if (PdmHeight == metric)
+            return 1000;
+        if (PdmWidth == metric)
+            return 700;
+        return 900;
+    }
+    virtual QPaintEngine *paintEngine() const
+    {
+        return engine;
+    }
+    bool newPage()
+    {
+        ++pages;
+        return true;
+    }
+};
+}
+
+void tst_QTextTable::QTBUG31330_renderBackground()
+{
+    QTextDocument doc;
+    QTextCursor cursor(&doc);
+    QTextTable* table = cursor.insertTable(4, 2);
+
+    QTextTableCell cell = table->cellAt(3, 0);
+
+    QTextCharFormat cellFormat = cell.format();
+    cellFormat.setBackground(QBrush(Qt::green));
+    cell.setFormat(cellFormat);
+
+    QTextCursor tc = cell.firstCursorPosition();
+    for (int i = 0; i < 60; ++i) {
+        tc.insertBlock();
+    }
+    QTBUG31330_PaintDevice::PaintEngine engine;
+    QTBUG31330_PaintDevice paintDevice(&engine);
+    paintDevice.setPageSize(QPagedPaintDevice::A4);
+    doc.print(&paintDevice);
+
+    QVERIFY(paintDevice.pages >= 2);
+    QCOMPARE(engine.rects.count(), paintDevice.pages);
+    for (int i = 0; i < engine.rects.count(); ++i) {
+        QRectF rect = engine.rects[i];
+        QVERIFY(rect.top() > 0);
+        QVERIFY(rect.bottom() < 1000);
+    }
+}
+#endif
+
 QTEST_MAIN(tst_QTextTable)
 #include "tst_qtexttable.moc"