Find font metrics when font is initialized. Fill baseline table.

Separately track typographic ascent/descent and maximum ascent/descent.

(bzr r14430.1.7)

2 files changed, 222 insertions, 78 deletions

diff --git a/src/libnrtype/FontInstance.cpp b/src/libnrtype/FontInstance.cpp
index 5853d5217..4578efe8f 100644
--- a/src/libnrtype/FontInstance.cpp
+++ b/src/libnrtype/FontInstance.cpp
@@ -184,6 +184,20 @@ font_instance::font_instance(void) :
     theFace(0)
 {
     //printf("font instance born\n");
+    _ascent  = _ascent_max  = 0.8;
+    _descent = _descent_max = 0.2;
+    _xheight = 0.5;
+
+    // Default baseline values, alphabetic is reference
+    _baselines[ SP_CSS_BASELINE_AUTO             ] =  0.0;
+    _baselines[ SP_CSS_BASELINE_ALPHABETIC       ] =  0.0;
+    _baselines[ SP_CSS_BASELINE_IDEOGRAPHIC      ] = -_descent;
+    _baselines[ SP_CSS_BASELINE_HANGING          ] =  0.8 * _ascent;
+    _baselines[ SP_CSS_BASELINE_MATHEMATICAL     ] =  0.8 * _xheight;
+    _baselines[ SP_CSS_BASELINE_CENTRAL          ] =  0.5;
+    _baselines[ SP_CSS_BASELINE_MIDDLE           ] =  0.5 * _xheight;
+    _baselines[ SP_CSS_BASELINE_TEXT_BEFORE_EDGE ] = -_descent;
+    _baselines[ SP_CSS_BASELINE_TEXT_AFTER_EDGE  ] = _ascent;
 }
 
 font_instance::~font_instance(void)
@@ -260,6 +274,7 @@ void font_instance::InitTheFace()
         FT_Select_Charmap(theFace,ft_encoding_unicode) && FT_Select_Charmap(theFace,ft_encoding_symbol);
     }
 #endif
+    FindFontMetrics();
     }
 }
 
@@ -518,83 +533,16 @@ bool font_instance::FontMetrics(double &ascent,double &descent,double &xheight)
         return false;
     }
 
-    // CSS2 recommends using the OS/2 values sTypoAscender and sTypoDescender
-    // for the ascender and descender values:
-    //   http://www.w3.org/TR/CSS2/visudet.html#sTypoAscender
-    // The typographic ascender and descender are taken from the
-    // otmMacAscent and otmMacDescent values:
-    //   http://microsoft.public.win32.programmer.gdi.narkive.com/LV6k4BDh/msdn-documentation-outlinetextmetrics-clarification
-    // The otmAscent and otmDescent values are the maxiumum ascent and maxiumum
-    // descent of all the glyphs in a font.
-
-#ifdef USE_PANGO_WIN32
-    OUTLINETEXTMETRIC otm;
-    if ( !GetOutlineTextMetrics(parent->hScreenDC,sizeof(otm),&otm) ) {
-        return false;
-    }
-
-    double scale=1.0/parent->fontSize;
-    ascent=fabs(otm.otmMacAscent*scale);
-    descent=fabs(otm.otmMacDescent*scale);
-    xheight=fabs(otm.otmXHeight*scale);
-    // May not be necessary... but if OS/2 table is missing or not version 2 or higher,
-    // xheight might be set to 0.
-    if( xheight = 0.0 ) xheight = ascent/2.0;
-    //otmSubscriptSize, otmSubscriptOffset, otmSuperscriptSize, otmSuperscriptOffset, 
-#else
-    if ( theFace->units_per_EM == 0 ) {
-        return false; // bitmap font
-    }
-    
-    TT_OS2*  os2 = (TT_OS2*)FT_Get_Sfnt_Table( theFace, FT_SFNT_OS2 );       
-    if( os2 ) {
-        ascent =fabs(((double)os2->sTypoAscender)/((double)theFace->units_per_EM));
-        descent=fabs(((double)os2->sTypoDescender)/((double)theFace->units_per_EM));
-    } else {
-        ascent =fabs(((double)theFace->ascender)/((double)theFace->units_per_EM));
-        descent=fabs(((double)theFace->descender)/((double)theFace->units_per_EM));
-    }
-
-    // We must find x-height ourselves! First try OS/2 table.
-    if( os2 && os2->version >= 0x0002 && os2->version != 0xffffu ) {
-        // Only os/2 version 2 and above have sxHeight, 0xffff marks "old Mac fonts" without table
-        xheight=fabs(((double)os2->sxHeight)/((double)theFace->units_per_EM));
-    } else {
-        // Measure 'x' height in font. Recommended option by XSL standard if no sxHeight.
-        FT_UInt index = FT_Get_Char_Index( theFace, 'x' );
-        if( index != 0 ) {
-            FT_Load_Glyph( theFace, index, FT_LOAD_NO_SCALE );
-            xheight = (fabs)(((double)theFace->glyph->metrics.height/(double)theFace->units_per_EM));
-        } else {
-            // No 'x' in font!
-            xheight = ascent/2.0;
-        }
-    }
-#endif
-
-    // CSS dictates em size is ascent + descent.... but this doesn't seem to be used in practice.
-    // The em size is what the font reports...
-    double em = ascent + descent;
-    if( em <= 0 ) {
-       return false; // Pathological
-    }
-    ascent /= em;
-    descent /= em;
-    xheight /= em;
-
-    // gchar* font_name = pango_font_description_to_string( descr );
-    // std::cout <<  "Font: " << (font_name ? font_name : ("Null")) << std::endl;
-    // g_free( font_name );
-    // std::cout << "  ascent: " << ascent << "  descent: " << descent
-    //           << "  x-height: " << xheight << "\n" << std::endl;
+    ascent = _ascent;
+    descent = _descent;
+    xheight = _xheight;
 
     return true;
 }
 
-bool font_instance::FontDecoration(
-    double &underline_position,     double &underline_thickness,
-    double &linethrough_position,   double &linethrough_thickness
-){
+bool font_instance::FontDecoration( double &underline_position,   double &underline_thickness,
+                                    double &linethrough_position, double &linethrough_thickness)
+{
     if ( pFont == NULL ) {
         return false;
     }
@@ -721,6 +669,179 @@ double font_instance::Advance(int glyph_id,bool vertical)
     return 0;
 }
 
+// Internal function to find baselines
+void font_instance::FindFontMetrics() {
+
+    // CSS2 recommends using the OS/2 values sTypoAscender and sTypoDescender for the Typographic
+    // ascender and descender values:
+    //   http://www.w3.org/TR/CSS2/visudet.html#sTypoAscender
+    // On Windows, the typographic ascender and descender are taken from the otmMacAscent and
+    // otmMacDescent values:
+    //   http://microsoft.public.win32.programmer.gdi.narkive.com/LV6k4BDh/msdn-documentation-outlinetextmetrics-clarification
+    // The otmAscent and otmDescent values are the maxiumum ascent and maxiumum descent of all the
+    // glyphs in a font.
+    if ( theFace ) {
+
+#ifdef USE_PANGO_WIN32
+        
+        if ( GetOutlineTextMetrics(parent->hScreenDC,sizeof(otm),&otm) ) {
+            double scale=1.0/parent->fontSize;
+            _ascent      = fabs(otm.otmMacAscent  * scale);
+            _descent     = fabs(otm.otmMacDescent * scale);
+            _xheight     = fabs(otm.otmXHeight    * scale);
+            _ascent_max  = fabs(otm.otmAscent     * scale);
+            _descent_max = fabs(otm.otmDescent    * scale);
+
+            // In CSS em size is ascent + descent... which should be 1. If not,
+            // adjust so it is.
+            double em = _ascent + _descent;
+            if( em > 0 ) {
+                _ascent /= em;
+                _descent /= em;
+            }
+
+            // May not be necessary but if OS/2 table missing or not version 2 or higher,
+            // xheight might be zero.
+            if( _xheight == 0.0 ) {
+                _xheight = 0.5;
+            }
+
+            // Baselines defined relative to  alphabetic.
+            _baselines[ SP_CSS_BASELINE_IDEOGRAPHIC      ] = -_descent;      // Recommendation
+            _baselines[ SP_CSS_BASELINE_HANGING          ] = 0.8 * _ascent;  // Guess
+            _baselines[ SP_CSS_BASELINE_MATHEMATICAL     ] = 0.8 * _xheight; // Guess
+            _baselines[ SP_CSS_BASELINE_CENTRAL          ] = 0.5;            // Definition
+            _baselines[ SP_CSS_BASELINE_MIDDLE           ] = 0.5 * _xheight; // Definition
+            _baselines[ SP_CSS_BASELINE_TEXT_BEFORE_EDGE ] = -_descent;      // Definition
+            _baselines[ SP_CSS_BASELINE_TEXT_AFTER_EDGE  ] = _ascent;        // Definition
+
+
+            MAT2 identity = {{0,1},{0,0},{0,0},{0,1}};
+            GLYPHMETRICS metrics;
+            int retval;
+
+            // Better math baseline:
+            // Try center of minus sign
+            retval =  GetGlyphOutline (parent->hScreenDC, 0x2212, GGO_NATIVE | GGO_UNHINTED, &metrics, 0, NULL, &identity);
+            // If no minus sign, try hyphen
+            if( retval <= 0 )
+                retval =  GetGlyphOutline (parent->hScreenDC, '-', GGO_NATIVE | GGO_UNHINTED, &metrics, 0, NULL, &identity);
+
+            if( retval > 0 ) {
+                double math = (metrics.gmptGlyphOrigin.y + 0.5 * metrics.gmBlackBoxY) * scale;
+                _baselines[ SP_CSS_BASELINE_MATHEMATICAL ] = math;
+            }
+
+            // Find hanging baseline... assume it is at top of 'म'.
+            retval =  GetGlyphOutline (parent->hScreenDC, 0x092E, GGO_NATIVE | GGO_UNHINTED, &metrics, 0, NULL, &identity);
+            if( retval > 0 ) {
+                double hanging = metrics.gmptGlyphOrigin.y * scale;
+                _baselines[ SP_CSS_BASELINE_MATHEMATICAL ] = hanging;
+            }
+        }
+
+#else
+
+        if ( theFace->units_per_EM != 0 ) {  // If zero then it's a bitmap font.
+
+            TT_OS2*  os2 = (TT_OS2*)FT_Get_Sfnt_Table( theFace, FT_SFNT_OS2 );       
+            if( os2 ) {
+                _ascent  = fabs(((double)os2->sTypoAscender) / ((double)theFace->units_per_EM));
+                _descent = fabs(((double)os2->sTypoDescender)/ ((double)theFace->units_per_EM));
+            } else {
+                _ascent  = fabs(((double)theFace->ascender)  / ((double)theFace->units_per_EM));
+                _descent = fabs(((double)theFace->descender) / ((double)theFace->units_per_EM));
+            }
+            _ascent_max  = fabs(((double)theFace->ascender)  / ((double)theFace->units_per_EM));
+            _descent_max = fabs(((double)theFace->descender) / ((double)theFace->units_per_EM));
+
+            // In CSS em size is ascent + descent... which should be 1. If not,
+            // adjust so it is.
+            double em = _ascent + _descent;
+            if( em > 0 ) {
+                _ascent /= em;
+                _descent /= em;
+            }
+
+            // x-height
+            if( os2 && os2->version >= 0x0002 && os2->version != 0xffffu ) {
+                // Only os/2 version 2 and above have sxHeight, 0xffff marks "old Mac fonts" without table
+                _xheight = fabs(((double)os2->sxHeight) / ((double)theFace->units_per_EM));
+            } else {
+                // Measure 'x' height in font. Recommended option by XSL standard if no sxHeight.
+                FT_UInt index = FT_Get_Char_Index( theFace, 'x' );
+                if( index != 0 ) {
+                    FT_Load_Glyph( theFace, index, FT_LOAD_NO_SCALE );
+                    _xheight = (fabs)(((double)theFace->glyph->metrics.height/(double)theFace->units_per_EM));
+                } else {
+                    // No 'x' in font!
+                    _xheight = 0.5;
+                }
+            }
+
+            // Baselines defined relative to  alphabetic.
+            _baselines[ SP_CSS_BASELINE_IDEOGRAPHIC      ] = -_descent;      // Recommendation
+            _baselines[ SP_CSS_BASELINE_HANGING          ] = 0.8 * _ascent;  // Guess
+            _baselines[ SP_CSS_BASELINE_MATHEMATICAL     ] = 0.8 * _xheight; // Guess
+            _baselines[ SP_CSS_BASELINE_CENTRAL          ] = 0.5;            // Definition
+            _baselines[ SP_CSS_BASELINE_MIDDLE           ] = 0.5 * _xheight; // Definition
+            _baselines[ SP_CSS_BASELINE_TEXT_BEFORE_EDGE ] = -_descent;      // Definition
+            _baselines[ SP_CSS_BASELINE_TEXT_AFTER_EDGE  ] = _ascent;        // Definition
+
+            // Better math baseline:
+            // Try center of minus sign
+            FT_UInt index = FT_Get_Char_Index( theFace, 0x2212 ); //'−'
+            // If no minus sign, try hyphen
+            if( index == 0 )
+                index = FT_Get_Char_Index( theFace, '-' );
+
+            if( index != 0 ) {
+                FT_Load_Glyph( theFace, index, FT_LOAD_NO_SCALE );
+                FT_Glyph aglyph;
+                FT_Get_Glyph( theFace->glyph, &aglyph );
+                FT_BBox acbox;
+                FT_Glyph_Get_CBox( aglyph, FT_GLYPH_BBOX_UNSCALED, &acbox );
+                double math = (acbox.yMin + acbox.yMax)/2.0/(double)theFace->units_per_EM;
+                _baselines[ SP_CSS_BASELINE_MATHEMATICAL ] = math;
+                std::cout << "Math baseline: - bbox: y_min: " << acbox.yMin
+                          << "  y_max: " << acbox.yMax
+                          << "  math: " << math << std::endl;
+            }
+
+            // Find hanging baseline... assume it is at top of 'म'.
+            index = FT_Get_Char_Index( theFace, 0x092E ); // 'म'
+            if( index != 0 ) {
+                FT_Load_Glyph( theFace, index, FT_LOAD_NO_SCALE );
+                FT_Glyph aglyph;
+                FT_Get_Glyph( theFace->glyph, &aglyph );
+                FT_BBox acbox;
+                FT_Glyph_Get_CBox( aglyph, FT_GLYPH_BBOX_UNSCALED, &acbox );
+                double hanging = (double)acbox.yMax/(double)theFace->units_per_EM;
+                _baselines[ SP_CSS_BASELINE_HANGING ] = hanging;
+                std::cout << "Hanging baseline:  प: " << hanging << std::endl;
+            }
+        }
+#endif
+        const gchar *family = pango_font_description_get_family(descr);
+        std::cout << "Font: " << (family?family:"null") << std::endl;
+        std::cout << "  ascent:      " << _ascent      << std::endl;
+        std::cout << "  descent:     " << _descent     << std::endl;
+        std::cout << "  x-height:    " << _xheight     << std::endl;
+        std::cout << "  max ascent:  " << _ascent_max  << std::endl;
+        std::cout << "  max descent: " << _descent_max << std::endl;
+        std::cout << " Baselines:" << std::endl;
+        std::cout << "  alphabetic:  " << _baselines[ SP_CSS_BASELINE_ALPHABETIC       ] << std::endl;
+        std::cout << "  ideographic: " << _baselines[ SP_CSS_BASELINE_IDEOGRAPHIC      ] << std::endl;
+        std::cout << "  hanging:     " << _baselines[ SP_CSS_BASELINE_HANGING          ] << std::endl;
+        std::cout << "  math:        " << _baselines[ SP_CSS_BASELINE_MATHEMATICAL     ] << std::endl;
+        std::cout << "  central:     " << _baselines[ SP_CSS_BASELINE_CENTRAL          ] << std::endl;
+        std::cout << "  middle:      " << _baselines[ SP_CSS_BASELINE_MIDDLE           ] << std::endl;
+        std::cout << "  text_before: " << _baselines[ SP_CSS_BASELINE_TEXT_BEFORE_EDGE ] << std::endl;
+        std::cout << "  text_after:  " << _baselines[ SP_CSS_BASELINE_TEXT_AFTER_EDGE  ] << std::endl;
+    }
+}
+
+
 /*
  Local Variables:
  mode:c++
diff --git a/src/libnrtype/font-instance.h b/src/libnrtype/font-instance.h
index 5a71e353b..2fac7c19b 100644
--- a/src/libnrtype/font-instance.h
+++ b/src/libnrtype/font-instance.h
@@ -57,19 +57,31 @@ public:
 
     // nota: all coordinates returned by these functions are on a [0..1] scale; you need to multiply
     // by the fontsize to get the real sizes
+
+    // Return 2geom pathvector for glyph. Deallocated when font instance dies.
     Geom::PathVector*    PathVector(int glyph_id);
-                         // returns the 2geom-type pathvector for this glyph. no refcounting needed, it's deallocated when the font_instance dies
+
+    // Horizontal advance if 'vertical' is false, vertical advance if true.
     double               Advance(int glyph_id, bool vertical);
-    // nominal advance of the font.
+
+    double               GetTypoAscent()  { return _ascent; }
+    double               GetTypoDescent() { return _descent; }
+    double               GetXHeight()     { return _xheight; }
+    double               GetMaxAscent()   { return _ascent_max; }
+    double               GetMaxDescent()  { return _descent_max; }
+    const double*        GetBaselines()   { return _baselines; }
+
     bool                 FontMetrics(double &ascent, double &descent, double &leading);
-    bool                 FontDecoration(double &underline_position,     double &underline_thickness,
-                         double &linethrough_position,   double &linethrough_thickness);
+    bool                 FontDecoration(double &underline_position, double &underline_thickness,
+                                        double &linethrough_position, double &linethrough_thickness);
     bool                 FontSlope(double &run, double &rise);
                                 // for generating slanted cursors for oblique fonts
-    Geom::OptRect             BBox(int glyph_id);
+    Geom::OptRect        BBox(int glyph_id);
 
 private:
     void                 FreeTheFace();
+    // Find ascent, descent, x-height, and baselines.
+    void                 FindFontMetrics();
 
     // Temp: make public
 public:
@@ -81,6 +93,17 @@ public:
                 // as long as pFont is valid, theFace is too
 #endif
 
+private:
+
+    // Font metrics in em-box units
+    double  _ascent;       // Typographic ascent.
+    double  _descent;      // Typographic descent.
+    double  _xheight;      // x-height of font.
+    double  _ascent_max;   // Maxiumum ascent of all glyphs in font.
+    double  _descent_max;  // Maxiumum descent of all glyphs in font.
+
+    // Baselines
+    double _baselines[SP_CSS_BASELINE_SIZE];
 };