When calling setPageSizeMM then the size needs to be passed as MM

This simplifies the code a bit and ensures that it is respecting what
the relevant function expects the size to be as.

Change-Id: Iec88fab84c27a33d6f1a9e9413ea6beb0a39c68d
Reviewed-by: John Layt <jlayt@kde.org>

src/printsupport/kernel/qprinter.cpp

@@ -127,6 +127,28 @@ Q_PRINTSUPPORT_EXPORT double qt_multiplierForUnit(QPrinter::Unit unit, int resol
     return 1.0;
 }
 
+/// return the QSize from the specified in unit as millimeters
+Q_PRINTSUPPORT_EXPORT QSizeF qt_SizeFromUnitToMillimeter(const QSizeF &size, QPrinter::Unit unit, double resolution)
+{
+    switch (unit) {
+    case QPrinter::Millimeter:
+        return size;
+    case QPrinter::Point:
+        return size * 0.352777778;
+    case QPrinter::Inch:
+        return size * 25.4;
+    case QPrinter::Pica:
+        return size * 4.23333333334;
+    case QPrinter::Didot:
+        return size * 0.377;
+    case QPrinter::Cicero:
+        return size * 4.511666667;
+    case QPrinter::DevicePixel:
+        return size * (0.352777778 * 72.0 / resolution);
+    }
+    return size;
+}
+
 // not static: it's needed in qpagesetupdialog_unix.cpp
 Q_PRINTSUPPORT_EXPORT QSizeF qt_printerPaperSize(QPrinter::Orientation orientation,
                            QPrinter::PaperSize paperSize,
@@ -983,9 +1005,7 @@ void QPrinter::setPaperSize(const QSizeF &paperSize, QPrinter::Unit unit)
     Q_D(QPrinter);
     if (d->paintEngine->type() != QPaintEngine::Pdf)
         ABORT_IF_ACTIVE("QPrinter::setPaperSize");
-    const qreal multiplier = qt_multiplierForUnit(unit, resolution());
-    QSizeF size(paperSize.width() * multiplier * 25.4/72., paperSize.height() * multiplier * 25.4/72.);
-    setPageSizeMM(size);
+    setPageSizeMM(qt_SizeFromUnitToMillimeter(paperSize, unit, resolution()));
 }
 
 /*!

tests/auto/printsupport/kernel/qprinter/tst_qprinter.cpp

@@ -590,6 +590,7 @@ void tst_QPrinter::setGetPaperSize()
     QSizeF size(500, 10);
     p.setPaperSize(size, QPrinter::Millimeter);
     QCOMPARE(p.paperSize(QPrinter::Millimeter), size);
+    QCOMPARE(p.pageSizeMM(), size);
     QSizeF ptSize = p.paperSize(QPrinter::Point);
     //qDebug() << ptSize;
     QVERIFY(qAbs(ptSize.width() - size.width() * (72/25.4)) < 1E-4);