tdf#81144 Chinese full-width punctuation does not align properly

Ideographic fullstop and comma in most Chinese fonts are centered,
while those in Japanese fonts align closer to the left. Original
compression algorithm trimed right side of the punctuation, making
fullwidth fullstop or comma in Chinese font visually unbalanced.
In worst case, it crowds together with the followed compressed
punctuation.

This patch fix the situation in the folowing way
1) make compression less stronger.
2) Trim space according to glyph bearing to font height ratio.
3) fix a memory access violation issue

Change-Id: Icff215064e6c442fd36eac8e01b01fb6acb27594
Reviewed-on: https://gerrit.libreoffice.org/19517
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>

4 files changed, 27 insertions, 1 deletions

diff --git a/vcl/inc/impfont.hxx b/vcl/inc/impfont.hxx
index 25aa15afb75e..fd9fb347516c 100644
--- a/vcl/inc/impfont.hxx
+++ b/vcl/inc/impfont.hxx
@@ -103,7 +103,7 @@ private:
     sal_uInt16          mnMiscFlags;   // Misc Flags
     sal_uInt32          mnRefCount;    // Reference Counter
 
-    enum { DEVICE_FLAG=1, SCALABLE_FLAG=2, LATIN_FLAG=4, CJK_FLAG=8, CTL_FLAG=16 };
+    enum { DEVICE_FLAG=1, SCALABLE_FLAG=2, LATIN_FLAG=4, CJK_FLAG=8, CTL_FLAG=16, FULLSTOP_CENTERED_FLAG=32 };
 
 public:
                         ImplFontMetric();
@@ -116,6 +116,7 @@ public:
     long                GetExtLeading() const   { return mnExtLeading; }
     long                GetLineHeight() const   { return mnLineHeight; }
     long                GetSlant() const        { return mnSlant; }
+    bool                IsFullstopCentered() const { return  ((mnMiscFlags & FULLSTOP_CENTERED_FLAG ) != 0); }
 
     bool                IsScalable() const      { return ((mnMiscFlags & SCALABLE_FLAG) != 0); }
 
diff --git a/vcl/inc/outfont.hxx b/vcl/inc/outfont.hxx
index c4c30fbc81bd..0becf0ad55e5 100644
--- a/vcl/inc/outfont.hxx
+++ b/vcl/inc/outfont.hxx
@@ -183,6 +183,7 @@ public: // TODO: hide members behind accessor methods
     bool                mbDevice;                   // Flag for Device Fonts
     bool                mbScalableFont;
     bool                mbKernableFont;
+    bool                mbFullstopCentered;
 
     // font metrics that are usually derived from the measurements
     long                mnUnderlineSize;            // Lineheight of Underline
diff --git a/vcl/source/gdi/metric.cxx b/vcl/source/gdi/metric.cxx
index 5ed467ef912e..05630c63f895 100644
--- a/vcl/source/gdi/metric.cxx
+++ b/vcl/source/gdi/metric.cxx
@@ -151,6 +151,11 @@ long FontMetric::GetSlant() const
     return mpImplMetric->GetSlant();
 }
 
+bool FontMetric::IsFullstopCentered() const
+{
+    return mpImplMetric->IsFullstopCentered();
+}
+
 FontMetric& FontMetric::operator =( const FontMetric& rMetric )
 {
     vcl::FontInfo::operator=( rMetric );
diff --git a/vcl/source/outdev/font.cxx b/vcl/source/outdev/font.cxx
index fd7b818ac871..6d641648eb03 100644
--- a/vcl/source/outdev/font.cxx
+++ b/vcl/source/outdev/font.cxx
@@ -216,6 +216,8 @@ FontMetric OutputDevice::GetFontMetric() const
             aMetric.mpImplMetric->mnMiscFlags |= ImplFontMetric::DEVICE_FLAG;
     if( pMetric->mbScalableFont )
             aMetric.mpImplMetric->mnMiscFlags |= ImplFontMetric::SCALABLE_FLAG;
+    if ( pMetric->mbFullstopCentered)
+            aMetric.mpImplMetric->mnMiscFlags |= ImplFontMetric::FULLSTOP_CENTERED_FLAG;
     aMetric.mpImplMetric->mnAscent      = ImplDevicePixelToLogicHeight( pMetric->mnAscent+mnEmphasisAscent );
     aMetric.mpImplMetric->mnDescent     = ImplDevicePixelToLogicHeight( pMetric->mnDescent+mnEmphasisDescent );
     aMetric.mpImplMetric->mnIntLeading  = ImplDevicePixelToLogicHeight( pMetric->mnIntLeading+mnEmphasisAscent );
@@ -1744,6 +1746,7 @@ ImplFontMetricData::ImplFontMetricData( const FontSelectPattern& rFontSelData )
     , mnMinKashida( 0 )
     , meFamilyType(FAMILY_DONTKNOW)
     , mbScalableFont(false)
+    , mbFullstopCentered(false)
     , mnUnderlineSize( 0 )
     , mnUnderlineOffset( 0 )
     , mnBUnderlineSize( 0 )
@@ -1788,6 +1791,7 @@ ImplFontMetricData::ImplFontMetricData( const FontSelectPattern& rFontSelData )
     }
 }
 
+
 void ImplFontMetricData::ImplInitTextLineSize( const OutputDevice* pDev )
 {
     long nDescent = mnDescent;
@@ -1870,6 +1874,21 @@ void ImplFontMetricData::ImplInitTextLineSize( const OutputDevice* pDev )
     mnDStrikeoutSize       = n2LineHeight;
     mnDStrikeoutOffset1    = nStrikeoutOffset - n2LineDY2 - n2LineHeight;
     mnDStrikeoutOffset2    = mnDStrikeoutOffset1 + n2LineDY + n2LineHeight;
+
+    const vcl::Font& rFont ( pDev->GetFont() );
+    bool bCentered = true;
+    if (MsLangId::isCJK(rFont.GetLanguage()))
+    {
+        const OUString sFullstop( sal_Unicode( 0x3001 ) ); // Fullwidth fullstop
+        Rectangle aRect;
+        pDev->GetTextBoundRect( aRect, sFullstop );
+        const sal_uInt16 nH = rFont.GetSize().Height();
+        const sal_uInt16 nB = aRect.Left();
+        // Use 18.75% as a threshold to define a centered fullwidth fullstop.
+        // In general, nB/nH < 5% for most Japanese fonts.
+        bCentered = (nB > (((nH >> 1)+nH)>>3)) ? true : false;
+    }
+    mbFullstopCentered = bCentered ;
 }
 
 void ImplFontMetricData::ImplInitAboveTextLineSize()