Related: tdf#145972 sw images: fix rounding error in relative size calculation

Open the bugdoc, see that the image is roughly half of the page width,
right click, properties, UI shows that the width of the image is 5% of
the width of the entire page. This only happens if tools -> options ->
writer -> general sets the UI units to points, the default cm case is
fine.

This went wrong with commit 9e8712ed6f9fb5dbd971e352a5709bd45fadc74f (sw
image dialog: fix fallback width/height for images with relative sizes,
2022-03-17), because the layout size started to matter more after that
commit. This lead to the nWidth !=
m_xWidthED->get_value(FieldUnit::TWIP) check in SwFramePage::Init() to
be true, because 11906 * 0.48 is 5714.88, so you got 5714 in the layout,
but got 5715 with rounding in SwFramePage::Reset() (which tries to calc
the page width based on the 48% and the fly width). And once we had that
mismatch, we went down the wrong path.

Fix the problem by using rtl::math::round() in SwFlyFrame::CalcRel(), so
the relative width twips value is 5715 everywhere: once we have
consisteny, the UI value is correct, too.

Note that the original bugdoc needs more fixing, this just fixes the
bugdoc where KeepRatio is false.

Change-Id: I1e8782c95a0cf9d97375c36d41134735c01f3e46
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167916
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Signed-off-by: Xisco Fauli <xiscofauli@libreoffice.org>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167926
(cherry picked from commit 3046bd0e30406d37813ce3eaa65f71f5ed10ab13)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167980
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>

4 files changed, 30 insertions, 4 deletions

diff --git a/sw/qa/core/layout/data/fly-rel-width-rounding.odt b/sw/qa/core/layout/data/fly-rel-width-rounding.odt
new file mode 100644
index 000000000000..b70b9e51a917
--- /dev/null
+++ b/sw/qa/core/layout/data/fly-rel-width-rounding.odt
diff --git a/sw/qa/core/layout/fly.cxx b/sw/qa/core/layout/fly.cxx
index 47cfb40fa6e7..81df20af3b35 100644
--- a/sw/qa/core/layout/fly.cxx
+++ b/sw/qa/core/layout/fly.cxx
@@ -86,6 +86,31 @@ CPPUNIT_TEST_FIXTURE(Test, testSplitFlyNegativeHeight)
         }
     }
 }
+
+CPPUNIT_TEST_FIXTURE(Test, testFlyRelWithRounding)
+{
+    // Given a document where page width is 21.001cm (11906 twips), and the image width is 48% of
+    // the page width:
+    createSwDoc("fly-rel-width-rounding.odt");
+
+    // When laying out that document:
+    SwDoc* pDoc = getSwDoc();
+    SwRootFrame* pLayout = pDoc->getIDocumentLayoutAccess().GetCurrentLayout();
+
+    // Then make sure that we calculate the width of the fly correctly:
+    auto pPage = pLayout->GetLower()->DynCastPageFrame();
+    CPPUNIT_ASSERT(pPage->GetSortedObjs());
+    SwSortedObjs& rPageObjs = *pPage->GetSortedObjs();
+    CPPUNIT_ASSERT_EQUAL(static_cast<size_t>(1), rPageObjs.size());
+    auto pFly = rPageObjs[0]->DynCastFlyFrame()->DynCastFlyAtContentFrame();
+    CPPUNIT_ASSERT(pFly);
+    tools::Long nFlyWidth = pFly->getFrameArea().Width();
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: 5715
+    // - Actual  : 5714
+    // i.e. 5714.88 was truncated, not rounded.
+    CPPUNIT_ASSERT_EQUAL(static_cast<tools::Long>(5715), nFlyWidth);
+}
 }
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/sw/source/core/layout/fly.cxx b/sw/source/core/layout/fly.cxx
index b454bd95917f..fd95ce192cf7 100644
--- a/sw/source/core/layout/fly.cxx
+++ b/sw/source/core/layout/fly.cxx
@@ -70,6 +70,7 @@
 #include <basegfx/matrix/b2dhommatrixtools.hxx>
 #include <osl/diagnose.h>
 #include <o3tl/string_view.hxx>
+#include <rtl/math.hxx>
 
 #include <wrtsh.hxx>
 #include <view.hxx>
@@ -2845,9 +2846,9 @@ Size SwFlyFrame::CalcRel( const SwFormatFrameSize &rSz ) const
         }
 
         if ( rSz.GetWidthPercent() && rSz.GetWidthPercent() != SwFormatFrameSize::SYNCED )
-            aRet.setWidth( nRelWidth * rSz.GetWidthPercent() / 100 );
+            aRet.setWidth(rtl::math::round(double(nRelWidth) * rSz.GetWidthPercent() / 100));
         if ( rSz.GetHeightPercent() && rSz.GetHeightPercent() != SwFormatFrameSize::SYNCED )
-            aRet.setHeight( nRelHeight * rSz.GetHeightPercent() / 100 );
+            aRet.setHeight(rtl::math::round(double(nRelHeight) * rSz.GetHeightPercent() / 100));
 
         if ( rSz.GetHeight() && rSz.GetWidthPercent() == SwFormatFrameSize::SYNCED )
         {
diff --git a/xmloff/qa/unit/text.cxx b/xmloff/qa/unit/text.cxx
index e6433b2b70f9..2da04387d707 100644
--- a/xmloff/qa/unit/text.cxx
+++ b/xmloff/qa/unit/text.cxx
@@ -505,11 +505,11 @@ CPPUNIT_TEST_FIXTURE(XmloffStyleTest, testRelativeWidth)
 
     xmlDocUniquePtr pXmlDoc = parseExport("content.xml");
     // Without the accompanying fix in place, this failed with:
-    // - Expected: 3.1492in (8cm)
+    // - Expected: 3.15in (8cm)
     // - Actual  : 0.0161in (0.04 cm)
     // i.e. the fallback width value wasn't the expected half of the body frame width, but a smaller
     // value.
-    assertXPath(pXmlDoc, "//draw:frame"_ostr, "width"_ostr, "3.1492in");
+    assertXPath(pXmlDoc, "//draw:frame"_ostr, "width"_ostr, "3.15in");
 }
 
 CPPUNIT_TEST_FIXTURE(XmloffStyleTest, testScaleWidthAndHeight)