Related: tdf#54053 PDF export: add UNO API to customize the watermark rotation

The watermark direction is currently either 0 degrees for landscape
pages or 270 degrees for portrait pages.

The problem is many people expect 45 degrees rotation angle or some
custom angle in general, and we provide no way to control it.

Fix the problem by adding a new "WatermarkRotateAngle" PDF export filter
option to specify the rotation angle explicitly. Note that the watermark
text is still centered, and the text size is decreased to still fit the page
boundaries. To keep things simple, do this shrinking by going with a
size that matches the shorter dimension of the page, instead of some
more complex iterative approach.

Example cmdline usage:

soffice --convert-to pdf:writer_pdf_Export:'{"Watermark":{"type":"string","value":"draft"}, "WatermarkRotateAngle":{"type":"long","value":"450"}}' test.odt

Change-Id: I1fee14c333e68c92cf4c65ec100e04dcf024f907
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143229
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

filter/CppunitTest_filter_pdf.mk

@@ -20,6 +20,7 @@ $(eval $(call gb_CppunitTest_add_exception_objects,filter_pdf, \
 ))
 
 $(eval $(call gb_CppunitTest_use_libraries,filter_pdf, \
+    basegfx \
     comphelper \
     cppu \
     cppuhelper \

filter/qa/pdf.cxx

@@ -20,6 +20,7 @@
 #include <tools/stream.hxx>
 #include <unotools/streamwrap.hxx>
 #include <vcl/filter/PDFiumLibrary.hxx>
+#include <tools/helpers.hxx>
 
 using namespace ::com::sun::star;
 
@@ -276,6 +277,58 @@ CPPUNIT_TEST_FIXTURE(Test, testWatermarkFontName)
     // i.e. the font name was sans, could not specify an explicit name.
     CPPUNIT_ASSERT_EQUAL(aExpectedFontName, aFontName);
 }
+
+CPPUNIT_TEST_FIXTURE(Test, testWatermarkRotateAngle)
+{
+    // Given an empty Writer document:
+    std::shared_ptr<vcl::pdf::PDFium> pPDFium = vcl::pdf::PDFiumLibrary::get();
+    if (!pPDFium)
+        return;
+    mxComponent.set(loadFromDesktop("private:factory/swriter", "com.sun.star.text.TextDocument"));
+
+    // When exporting that as PDF with a rotated watermark:
+    uno::Reference<css::lang::XMultiServiceFactory> xFactory = getMultiServiceFactory();
+    uno::Reference<document::XFilter> xFilter(
+        xFactory->createInstance("com.sun.star.document.PDFFilter"), uno::UNO_QUERY);
+    uno::Reference<document::XExporter> xExporter(xFilter, uno::UNO_QUERY);
+    xExporter->setSourceDocument(mxComponent);
+    SvMemoryStream aStream;
+    uno::Reference<io::XOutputStream> xOutputStream(new utl::OStreamWrapper(aStream));
+    // 45.0 degrees, counter-clockwise.
+    sal_Int32 nExpectedRotateAngle = 45;
+    uno::Sequence<beans::PropertyValue> aFilterData{
+        comphelper::makePropertyValue("Watermark", OUString("X")),
+        comphelper::makePropertyValue("WatermarkRotateAngle", nExpectedRotateAngle * 10),
+    };
+    uno::Sequence<beans::PropertyValue> aDescriptor{
+        comphelper::makePropertyValue("FilterName", OUString("writer_pdf_Export")),
+        comphelper::makePropertyValue("FilterData", aFilterData),
+        comphelper::makePropertyValue("OutputStream", xOutputStream),
+    };
+    xFilter->filter(aDescriptor);
+
+    // Then make sure that the watermark rotation angle is correct:
+    std::unique_ptr<vcl::pdf::PDFiumDocument> pPdfDocument
+        = pPDFium->openDocument(aStream.GetData(), aStream.GetSize(), OString());
+    CPPUNIT_ASSERT(pPdfDocument);
+    std::unique_ptr<vcl::pdf::PDFiumPage> pPage = pPdfDocument->openPage(0);
+    CPPUNIT_ASSERT_EQUAL(1, pPage->getObjectCount());
+    std::unique_ptr<vcl::pdf::PDFiumPageObject> pPageObject = pPage->getObject(0);
+    CPPUNIT_ASSERT_EQUAL(1, pPageObject->getFormObjectCount());
+    std::unique_ptr<vcl::pdf::PDFiumPageObject> pFormObject = pPageObject->getFormObject(0);
+    basegfx::B2DHomMatrix aMatrix = pFormObject->getMatrix();
+    basegfx::B2DTuple aScale;
+    basegfx::B2DTuple aTranslate;
+    double fRotate{};
+    double fShearX{};
+    aMatrix.decompose(aScale, aTranslate, fRotate, fShearX);
+    sal_Int32 nActualRotateAngle = NormAngle360(basegfx::rad2deg<1>(fRotate));
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: 45
+    // - Actual  : 270
+    // i.e. the rotation angle was 270 for an A4 page, not the requested 45 degrees.
+    CPPUNIT_ASSERT_EQUAL(nExpectedRotateAngle, nActualRotateAngle);
+}
 }
 
 CPPUNIT_PLUGIN_IMPLEMENT();

filter/source/pdf/pdfexport.cxx

@@ -577,6 +577,14 @@ bool PDFExport::Export( const OUString& rFile, const Sequence< PropertyValue >&
                         moWatermarkFontHeight = nFontHeight;
                     }
                 }
+                else if (rProp.Name == "WatermarkRotateAngle")
+                {
+                    sal_Int32 nRotateAngle{};
+                    if (rProp.Value >>= nRotateAngle)
+                    {
+                        moWatermarkRotateAngle = Degree10(nRotateAngle);
+                    }
+                }
                 else if (rProp.Name == "WatermarkFontName")
                 {
                     OUString aFontName{};
@@ -1189,6 +1197,17 @@ void PDFExport::ImplWriteWatermark( vcl::PDFWriter& rWriter, const Size& rPageSi
         aFont.SetOrientation( 2700_deg10 );
     }
 
+    if (moWatermarkRotateAngle)
+    {
+        aFont.SetOrientation(*moWatermarkRotateAngle);
+        if (rPageSize.Width() < rPageSize.Height())
+        {
+            // Set text width based on the shorter side, so rotation can't push text outside the
+            // page boundaries.
+            nTextWidth = rPageSize.Width();
+        }
+    }
+
     // adjust font height for text to fit
     OutputDevice* pDev = rWriter.GetReferenceDevice();
     pDev->Push();
@@ -1242,6 +1261,25 @@ void PDFExport::ImplWriteWatermark( vcl::PDFWriter& rWriter, const Size& rPageSi
                             (rPageSize.Height()-w)/2 );
         aTextRect = tools::Rectangle( aTextPoint, Size( nTextHeight, w ) );
     }
+
+    if (moWatermarkRotateAngle)
+    {
+        // First set the text's starting point to the center of the page.
+        tools::Rectangle aPageRectangle(Point(0, 0), rPageSize);
+        aTextPoint = aPageRectangle.Center();
+        // Then adjust it so that the text remains centered, based on the rotation angle.
+        basegfx::B2DPolygon aTextPolygon
+            = basegfx::utils::createPolygonFromRect(basegfx::B2DRectangle(0, -nTextHeight, w, 0));
+        basegfx::B2DHomMatrix aMatrix;
+        aMatrix.rotate(-1 * toRadians(*moWatermarkRotateAngle));
+        aTextPolygon.transform(aMatrix);
+        basegfx::B2DPoint aPolygonCenter = aTextPolygon.getB2DRange().getCenter();
+        aTextPoint.AdjustX(-aPolygonCenter.getX());
+        aTextPoint.AdjustY(-aPolygonCenter.getY());
+
+        aTextRect = aPageRectangle;
+    }
+
     rWriter.SetClipRegion();
     rWriter.BeginTransparencyGroup();
     rWriter.DrawText( aTextPoint, msWatermark );

filter/source/pdf/pdfexport.hxx

@@ -76,6 +76,7 @@ private:
     Color               maWatermarkColor;
     std::optional<sal_Int32> moWatermarkFontHeight;
     OUString            maWatermarkFontName;
+    std::optional<Degree10> moWatermarkRotateAngle;
     OUString            msTiledWatermark;
 
     // these variable are here only to have a location in filter/pdf to set the default