Add basic rendering support for 'font-variation-settings'.

Requires Pango 1.41.1 and FreeType 2.8 (maybe 2.9).

1 files changed, 93 insertions, 2 deletions

diff --git a/src/libnrtype/FontInstance.cpp b/src/libnrtype/FontInstance.cpp
index 527c06ce9..cab8237ba 100644
--- a/src/libnrtype/FontInstance.cpp
+++ b/src/libnrtype/FontInstance.cpp
@@ -22,7 +22,12 @@
 #include FT_TRUETYPE_TAGS_H
 #include FT_TRUETYPE_TABLES_H
 #include FT_GLYPH_H
+#include FT_MULTIPLE_MASTERS_H
+
 #include <pango/pangoft2.h>
+
+#include <glibmm/regex.h>
+
 #include <2geom/pathvector.h>
 #include <2geom/path-sink.h>
 #include "libnrtype/font-glyph.h"
@@ -209,12 +214,98 @@ void font_instance::InitTheFace()
 
         theFace = pango_fc_font_lock_face(PANGO_FC_FONT(pFont));
         if ( theFace ) {
-            FT_Select_Charmap(theFace,ft_encoding_unicode) && FT_Select_Charmap(theFace,ft_encoding_symbol);
+            FT_Select_Charmap(theFace, ft_encoding_unicode);
+            FT_Select_Charmap(theFace, ft_encoding_symbol);
         }
 
 #endif
 
-        FindFontMetrics();
+#ifndef USE_PANGO_WIN32
+#if PANGO_VERSION_CHECK(1,41,1)
+#if FREETYPE_MAJOR == 2 && FREETYPE_MINOR >= 8  // 2.8 does not seem to work even though it has some support.
+
+        // 'font-variation-settings' support.
+        //    The font returned from pango_fc_font_lock_face does not include variation settings. We must set them.
+
+        // We need to:
+        //   Get a list of axes supported in the font with the range of allowed values.
+        //   Extract axes with values from Pango font description.
+        //   Fill an array indexed by FT axis with values from Pango.
+
+        char const *var = pango_font_description_get_variations( descr );
+        if (var) {
+
+            Glib::ustring variations(var);
+
+            FT_MM_Var* mmvar = NULL;
+            FT_Multi_Master mmtype;
+            if (FT_HAS_MULTIPLE_MASTERS( theFace )    &&    // Font has variables
+                FT_Get_MM_Var(theFace, &mmvar) == 0   &&    // We found the data
+                FT_Get_Multi_Master(theFace, &mmtype) !=0) {  // It's not an Adobe MM font
+
+                // std::cout << "  Multiple Masters: variables: " << mmvar->num_axis
+                //           << "  named styles: " << mmvar->num_namedstyles << std::endl;
+
+                // Get a list of axis and their default values from the font.
+                std::map<Glib::ustring, int> axis_map;
+                std::vector<int> axis_value;
+                for (FT_UInt axisIndex = 0; axisIndex < mmvar->num_axis; ++axisIndex) {
+
+                    const FT_Var_Axis& ftAxis = mmvar->axis[axisIndex];
+                    const FT_Tag axisTag = ftAxis.tag;
+
+                    Glib::ustring axis_name;
+                    axis_name += (char)(axisTag>>24 & 0xff);
+                    axis_name += (char)(axisTag>>16 & 0xff);
+                    axis_name += (char)(axisTag>> 8 & 0xff);
+                    axis_name += (char)(axisTag     & 0xff);
+
+                    axis_map.insert(std::pair<Glib::ustring, int>(axis_name, axisIndex));
+                    axis_value.push_back(static_cast<FT_Int32>(ftAxis.def/65536.0));
+                }
+
+                // Get the required values from Pango Font Description
+                // Need to check format of values from Pango, for the moment accept any format.
+                Glib::RefPtr<Glib::Regex> regex = Glib::Regex::create("(\\w{4})=([-+]?\\d*\\.?\\d+([eE][-+]?\\d+)?)");
+                Glib::MatchInfo matchInfo;
+
+                std::vector<Glib::ustring> tokens = Glib::Regex::split_simple(",", variations);
+                for (auto token: tokens) {
+
+                    regex->match(token, matchInfo);
+                    if (matchInfo.matches()) {
+                        float value = std::stod(matchInfo.fetch(2));  // Should clamp value
+
+                        auto it = axis_map.find(matchInfo.fetch(1));
+                        if (it != axis_map.end()) {
+                            axis_value[it->second] = value;
+                        }
+                    }
+                }
+
+                // Fill coordinate array
+                const FT_UInt num_axis = axis_map.size();
+                FT_Fixed w[num_axis];
+                for (FT_UInt axisIndex = 0; axisIndex < num_axis; ++axisIndex) {
+                    w[axisIndex] = axis_value[axisIndex] * 65536;
+                }
+
+                // Set design coordinates
+                FT_Error err;
+                err = FT_Set_Var_Design_Coordinates (theFace, 2, w);
+                if (err) {
+                    std::cout << "font_instance::InitTheFace(): Error in call to FT_Set_Var_Design_Coordinates(): " << err << std::endl;
+                }
+
+                // FT_Done_MM_Var(mmlib, mmvar);
+            }
+        }
+
+#endif // FreeType
+#endif // Pango
+#endif // !USE_PANGO_WIN32
+
+       FindFontMetrics();
     }
 }