support family name lists, both system and custom

* so you can now specify ctx.font = 'custom1, arial'; etc and the later
  fonts will be used for glyphs that aren't in the first ones
* i'm now calling them sys_desc and user_desc to distinguish the
  description that matches the font on the system vs the description the
  user passes to Canvas.registerFont
* cleaned up some style

lib/context2d.js

@@ -77,7 +77,9 @@ var parseFont = exports.parseFont = function(str){
   font.style = captures[2] || 'normal';
   font.size = parseFloat(captures[3]);
   font.unit = captures[4];
-  font.family = captures[5].replace(/["']/g, '').split(',')[0].trim();
+  font.family = captures[5].replace(/["']/g, '').split(',').map(function (family) {
+    return family.trim();
+  }).join(',');
 
   // TODO: dpi
   // TODO: remaining unit conversion

src/Canvas.cc

@@ -584,10 +584,10 @@ NAN_METHOD(Canvas::RegisterFont) {
 
   String::Utf8Value filePath(info[0]);
 
-  if (!register_font((unsigned char*) *filePath, &face.target_desc)) {
+  if (!register_font((unsigned char *) *filePath, &face.sys_desc)) {
     Nan::ThrowError("Could not load font to the system's font host");
   } else {
-    PangoFontDescription* d = pango_font_description_new();
+    PangoFontDescription *d = pango_font_description_new();
 
     if (!info[1]->IsObject()) {
       Nan::ThrowError(GENERIC_FACE_ERROR);
@@ -597,9 +597,9 @@ NAN_METHOD(Canvas::RegisterFont) {
       Local<String> weight_prop = Nan::New<String>("weight").ToLocalChecked();
       Local<String> style_prop = Nan::New<String>("style").ToLocalChecked();
 
-      const char* family;
-      const char* weight = "normal";
-      const char* style = "normal";
+      const char *family;
+      const char *weight = "normal";
+      const char *style = "normal";
 
       Local<Value> family_val = desc->Get(family_prop);
       if (family_val->IsString()) {
@@ -633,9 +633,9 @@ NAN_METHOD(Canvas::RegisterFont) {
       pango_font_description_set_style(d, Canvas::GetStyleFromCSSString(style));
       pango_font_description_set_family(d, family);
 
-      free((char*)family);
-      if (desc->HasOwnProperty(weight_prop)) free((char*)weight);
-      if (desc->HasOwnProperty(style_prop)) free((char*)style);
+      free((char *)family);
+      if (desc->HasOwnProperty(weight_prop)) free((char *)weight);
+      if (desc->HasOwnProperty(style_prop)) free((char *)style);
 
       face.user_desc = d;
       _font_face_list.push_back(face);
@@ -757,31 +757,48 @@ Canvas::GetWeightFromCSSString(const char *weight) {
 }
 
 /*
- * Tries to find a matching font given to registerFont
+ * Given a user description, return a description that will select the
+ * font either from the system or @font-face
  */
 
 PangoFontDescription *
-Canvas::FindCustomFace(PangoFontDescription *desc) {
-  PangoFontDescription* best_match = NULL;
-  PangoFontDescription* best_match_target = NULL;
-  std::vector<FontFace>::iterator it = _font_face_list.begin();
-
-  while (it != _font_face_list.end()) {
-    FontFace f = *it;
-
-    if (g_ascii_strcasecmp(pango_font_description_get_family(desc),
-      pango_font_description_get_family(f.user_desc)) == 0) {
-
-      if (best_match == NULL || pango_font_description_better_match(desc, best_match, f.user_desc)) {
-        best_match = f.user_desc;
-        best_match_target = f.target_desc;
+Canvas::ResolveFontDescription(const PangoFontDescription *desc) {
+  FontFace best;
+  PangoFontDescription *ret = NULL;
+
+  // One of the user-specified families could map to multiple SFNT family names
+  // if someone registered two different fonts under the same family name.
+  // https://drafts.csswg.org/css-fonts-3/#font-style-matching
+  char **families = g_strsplit(pango_font_description_get_family(desc), ",", -1);
+  GString *resolved_families = g_string_new("");
+
+  for (int i = 0; families[i]; ++i) {
+    GString *renamed_families = g_string_new("");
+    std::vector<FontFace>::iterator it = _font_face_list.begin();
+
+    for (; it != _font_face_list.end(); ++it) {
+      if (g_ascii_strcasecmp(families[i], pango_font_description_get_family(it->user_desc)) == 0) {
+        if (renamed_families->len) g_string_append(renamed_families, ",");
+        g_string_append(renamed_families, pango_font_description_get_family(it->sys_desc));
+
+        if (i == 0 && (best.user_desc == NULL || pango_font_description_better_match(desc, best.user_desc, it->user_desc))) {
+          best = *it;
+        }
       }
     }
 
-    ++it;
+    if (resolved_families->len) g_string_append(resolved_families, ",");
+    g_string_append(resolved_families, renamed_families->len ? renamed_families->str : families[i]);
+    g_string_free(renamed_families, true);
   }
 
-  return best_match_target;
+  ret = pango_font_description_copy(best.sys_desc ? best.sys_desc : desc);
+  pango_font_description_set_family_static(ret, resolved_families->str);
+
+  g_strfreev(families);
+  g_string_free(resolved_families, false);
+
+  return ret;
 }
 
 /*

src/Canvas.h

@@ -40,14 +40,14 @@ typedef enum {
   CANVAS_TYPE_SVG
 } canvas_type_t;
 
-/**
+/*
  * FontFace describes a font file in terms of one PangoFontDescription that
  * will resolve to it and one that the user describes it as (like @font-face)
  */
 class FontFace {
   public:
-    PangoFontDescription *target_desc;
-    PangoFontDescription *user_desc;
+    PangoFontDescription *sys_desc = NULL;
+    PangoFontDescription *user_desc = NULL;
 };
 
 /*
@@ -89,7 +89,7 @@ class Canvas: public Nan::ObjectWrap {
 #endif
     static PangoWeight GetWeightFromCSSString(const char *weight);
     static PangoStyle GetStyleFromCSSString(const char *style);
-    static PangoFontDescription* FindCustomFace(PangoFontDescription *desc);
+    static PangoFontDescription *ResolveFontDescription(const PangoFontDescription *desc);
 
     inline bool isPDF(){ return CANVAS_TYPE_PDF == type; }
     inline bool isSVG(){ return CANVAS_TYPE_SVG == type; }

src/CanvasRenderingContext2d.cc

@@ -1840,17 +1840,14 @@ NAN_METHOD(Context2d::SetFont) {
 
   if (strlen(*family) > 0) pango_font_description_set_family(desc, *family);
 
-  PangoFontDescription *target_desc;
-  if ((target_desc = Canvas::FindCustomFace(desc))) {
-    pango_font_description_free(desc);
-    desc = pango_font_description_copy(target_desc);
-  }
+  PangoFontDescription *sys_desc = Canvas::ResolveFontDescription(desc);
+  pango_font_description_free(desc);
 
-  if (size > 0) pango_font_description_set_absolute_size(desc, size * PANGO_SCALE);
+  if (size > 0) pango_font_description_set_absolute_size(sys_desc, size * PANGO_SCALE);
 
-  context->state->fontDescription = desc;
+  context->state->fontDescription = sys_desc;
 
-  pango_layout_set_font_description(context->_layout, desc);
+  pango_layout_set_font_description(context->_layout, sys_desc);
 }
 
 /*

test/canvas.test.js

@@ -44,15 +44,15 @@ describe('Canvas', function () {
       , '20px monospace'
       , { size: 20, unit: 'px', family: 'monospace' }
       , '50px Arial, sans-serif'
-      , { size: 50, unit: 'px', family: 'Arial' }
+      , { size: 50, unit: 'px', family: 'Arial,sans-serif' }
       , 'bold italic 50px Arial, sans-serif'
-      , { style: 'italic', weight: 'bold', size: 50, unit: 'px', family: 'Arial' }
+      , { style: 'italic', weight: 'bold', size: 50, unit: 'px', family: 'Arial,sans-serif' }
       , '50px Helvetica ,  Arial, sans-serif'
-      , { size: 50, unit: 'px', family: 'Helvetica' }
+      , { size: 50, unit: 'px', family: 'Helvetica,Arial,sans-serif' }
       , '50px "Helvetica Neue", sans-serif'
-      , { size: 50, unit: 'px', family: 'Helvetica Neue' }
+      , { size: 50, unit: 'px', family: 'Helvetica Neue,sans-serif' }
       , '50px "Helvetica Neue", "foo bar baz" , sans-serif'
-      , { size: 50, unit: 'px', family: 'Helvetica Neue' }
+      , { size: 50, unit: 'px', family: 'Helvetica Neue,foo bar baz,sans-serif' }
       , "50px 'Helvetica Neue'"
       , { size: 50, unit: 'px', family: 'Helvetica Neue' }
       , 'italic 20px Arial'