From 4aba809e947fca4f043ded976f55178d28d9cf06 Mon Sep 17 00:00:00 2001
From: themancalledjakob <github@jrkb.land>
Date: Fri, 9 Sep 2022 09:05:02 +0200
Subject: [PATCH] Adding setVariationAxis for variable fonts (#158)

---
 ext/import-font.cpp | 51 +++++++++++++++++++++++++++++++++++++++++++++
 ext/import-font.h   | 15 +++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/ext/import-font.cpp b/ext/import-font.cpp
index 5995261..ff85df8 100644
--- a/ext/import-font.cpp
+++ b/ext/import-font.cpp
@@ -6,17 +6,22 @@
 #include <ft2build.h>
 #include FT_FREETYPE_H
 #include FT_OUTLINE_H
+#include FT_MULTIPLE_MASTERS_H
 
 namespace msdfgen {
 
 #define REQUIRE(cond) { if (!(cond)) return false; }
 #define F26DOT6_TO_DOUBLE(x) (1/64.*double(x))
+#define DOUBLE_TO_F16DOT16(x)  (FT_Fixed(x*65536.))
+#define F16DOT16_TO_DOUBLE(x)  (1/65536.*double(x))
 
 class FreetypeHandle {
     friend FreetypeHandle * initializeFreetype();
     friend void deinitializeFreetype(FreetypeHandle *library);
     friend FontHandle * loadFont(FreetypeHandle *library, const char *filename);
     friend FontHandle * loadFontData(FreetypeHandle *library, const byte *data, int length);
+    friend bool setVariationAxis(FontHandle *font, FreetypeHandle *library, const char *axisname, double coordinate);
+    friend bool getVariationAxes(std::vector<FontVariationAxis> &axes, FontHandle *font, FreetypeHandle *library);
 
     FT_Library library;
 
@@ -34,6 +39,8 @@ class FontHandle {
     friend bool loadGlyph(Shape &output, FontHandle *font, unicode_t unicode, double *advance);
     friend bool getKerning(double &output, FontHandle *font, GlyphIndex glyphIndex1, GlyphIndex glyphIndex2);
     friend bool getKerning(double &output, FontHandle *font, unicode_t unicode1, unicode_t unicode2);
+    friend bool setVariationAxis(FontHandle *font, FreetypeHandle *library, const char *axisname, double coordinate);
+    friend bool getVariationAxes(std::vector<FontVariationAxis> &axes, FontHandle *font, FreetypeHandle *library);
 
     FT_Face face;
     bool ownership;
@@ -215,4 +222,48 @@ bool getKerning(double &output, FontHandle *font, unicode_t unicode1, unicode_t
     return getKerning(output, font, GlyphIndex(FT_Get_Char_Index(font->face, unicode1)), GlyphIndex(FT_Get_Char_Index(font->face, unicode2)));
 }
 
+bool setVariationAxis(FontHandle *font, FreetypeHandle *library, const char *name, double coordinate) {
+    bool success = false;
+    if (font->face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
+        FT_MM_Var *amaster;
+        FT_Get_MM_Var(font->face, &amaster);
+
+        std::vector<FT_Fixed> coords;
+        coords.resize(amaster->num_axis);
+
+        FT_Get_Var_Design_Coordinates(font->face, coords.size(), coords.data());
+        for (FT_UInt i = 0; i < amaster->num_axis; i++) {
+            int strdiff = strcmp(name,amaster->axis[i].name);
+            if (strdiff == 0) {
+                coords[i] = DOUBLE_TO_F16DOT16(coordinate);
+                success = true;
+                break;
+            }
+        }
+        FT_Set_Var_Design_Coordinates(font->face, coords.size(), coords.data());
+        FT_Done_MM_Var(library->library, amaster);
+    }
+    return success;
+}
+
+bool getVariationAxes(std::vector<FontVariationAxis> &axes, FontHandle *font, FreetypeHandle *library) {
+    if (font->face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
+        FT_MM_Var *amaster;
+        FT_Get_MM_Var(font->face, &amaster);
+
+        for (FT_UInt i = 0; i < amaster->num_axis; i++) {
+            FontVariationAxis axis{
+                amaster->axis[i].name,
+                F16DOT16_TO_DOUBLE(amaster->axis[i].minimum),
+                F16DOT16_TO_DOUBLE(amaster->axis[i].def),
+                F16DOT16_TO_DOUBLE(amaster->axis[i].maximum)
+            };
+            axes.push_back(axis);
+        }
+        FT_Done_MM_Var(library->library, amaster);
+        return true;
+    }
+    return false;
+}
+
 }
diff --git a/ext/import-font.h b/ext/import-font.h
index 82859a6..9b7635b 100644
--- a/ext/import-font.h
+++ b/ext/import-font.h
@@ -35,6 +35,18 @@ struct FontMetrics {
     double underlineY, underlineThickness;
 };
 
+/// A structure to model a given axis for variation fonts.
+struct FontVariationAxis {
+    /// The name of the variation axis.
+    const char * name;
+    /// The axis's minimum design coordinate.
+    double minimum;
+    /// The axis's default design coordinate. FreeType computes meaningful default values for Adobe MM fonts.
+    double def;
+    /// The axis's maximum design coordinate.
+    double maximum;
+};
+
 /// Initializes the FreeType library.
 FreetypeHandle * initializeFreetype();
 /// Deinitializes the FreeType library.
@@ -62,5 +74,8 @@ bool loadGlyph(Shape &output, FontHandle *font, unicode_t unicode, double *advan
 /// Outputs the kerning distance adjustment between two specific glyphs.
 bool getKerning(double &output, FontHandle *font, GlyphIndex glyphIndex1, GlyphIndex glyphIndex2);
 bool getKerning(double &output, FontHandle *font, unicode_t unicode1, unicode_t unicode2);
+/// Sets variation axis of variable font.
+bool setVariationAxis(FontHandle *font, FreetypeHandle *library, const char *name, double coordinate);
+bool getVariationAxes(std::vector<FontVariationAxis> &axes, FontHandle *font, FreetypeHandle *library);
 
 }