tdf#127471 correct EMF/WMF im/export for scaled font

If FontScaling is used, system-dependent data is held at
vcl::Font Width(). Already if not scaled, we have three
definitions: Width is zero, Width is equal to Height (unx)
or - on Windows - Width equals avgFontWidth.
If used it is W!=H where on unx Width equals Height multiplied
with the scale factor. On Windows, this is Width multiplied
with the only there existing avgFontWidth.
Unfortunately that is ex/imported (since ever) undetected
to EMF/WMF thus making EMF/WMF files containing FontScaling
system-dependent - on which system was LO running when
creating the file? The error can be seen when loading such
a EMF/WMF on the vice-versa system, the FontScale is very
ugly and wrong.
Since EMF/WMF *are* Windows-specific formats the Windows-like
definition is the correct one. This change makes all other
systems export that now, and adapt on import to their system-
specific definition (assuming coming from Windows).
As can be seen, the difficulty is that these adaptions are
necessary on non-Windows plattforms, but these do not have
that avgFontWidth available. Thus I made a deep-dive
investigation and multiple experiments to create a as
similar as possible value to apply the needed calculations.
For details and discussion refer to the bug description.

Change-Id: I983fb6d882e2e8fccf9c8460f01509201d8157f9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/111000
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/emfio/source/reader/mtftools.cxx b/emfio/source/reader/mtftools.cxx
index b05beeb2a9dc..6064ca937a16 100644
--- a/emfio/source/reader/mtftools.cxx
+++ b/emfio/source/reader/mtftools.cxx
@@ -277,8 +277,26 @@ namespace emfio
 
         // Convert height to positive
         aFontSize.setHeight( std::abs(aFontSize.Height()) );
-
         aFont.SetFontSize(aFontSize);
+
+        // tdf#127471 adapt nFontWidth from Windows-like notation to
+        // NormedFontScaling if used for text scaling
+#ifndef _WIN32
+        const bool bFontScaledHorizontally(aFontSize.Width() != 0 && aFontSize.Width() != aFontSize.Height());
+
+        if(bFontScaledHorizontally)
+        {
+            // tdf#127471 nFontWidth is the Windows FontScaling, need to convert to
+            // Non-Windowslike notation relative to FontHeight.
+            const tools::Long nAverageFontWidth(aFont.GetOrCalculateAverageFontWidth());
+
+            if(nAverageFontWidth > 0)
+            {
+                const double fScaleFactor(static_cast<double>(aFontSize.Height()) / static_cast<double>(nAverageFontWidth));
+                aFont.SetAverageFontWidth(static_cast<tools::Long>(static_cast<double>(aFontSize.Width()) * fScaleFactor));
+            }
+        }
+#endif
     };
 
     Color MtfTools::ReadColor()