Font variations.

src/ports/SkFontConfigParser_android.cpp

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkFontConfigParser_android.h"
 #include "SkFontMgr_android.h"
 #include "SkStream.h"
@@ skipping 145 matching lines @@
         const char* value = attributes[i+1];
         size_t nameLen = strlen(name);
         if (MEMEQ("weight", name, nameLen)) {
             if (!parse_non_negative_integer(value, &file->fWeight)) {
                 SkDebugf("---- Font weight %s (INVALID)", value);
             }
         } else if (MEMEQ("index", name, nameLen)) {
             if (!parse_non_negative_integer(value, &file->fIndex)) {
                 SkDebugf("---- Font index %s (INVALID)", value);
             }
+        } else if (MEMEQ("axis", name, nameLen)) {

[bungeman-skia, 2015/04/01 20:38:28]

Need support for multiple axes. By index, id (four char tag), or name? Note that
this already currently assumes the user knows the font here. As a result index
is easy and nice.

Axis space. Normalized or design? Prefer design.

Need to be able to specify in something other than 'SkFixed' in base 10.

Possibilities for 400 weight, slightly greater than normal width, no slant:

axis="400 1.2 0"

axis="wght:400 wdth:1.2 slnt:0" (also 'opsz' is standard)

axis="weight:400 width:1.2 slant:0" (also 'optical-size')

axis-wght="400" axis-wdth="1.2" axis-slnt="0"

axis-weight="400" axis-width="1.2" axis-slant="0"

'weight' is easier to read, but 'wght' maps directly to the underlying data in
the font, meaning that it is easy to use non-standard variation ids (since no
translation is needed). Using positional indexes here isn't very clear at all,
but is very simple to implement and extend, 'wght' means we have to do string
matching at some point. In theory though, we could do this string matching up
front based on the font scan. However, it's not clear how to specify all four
byte codes like this. In css this would look something like

font-axis-settings: 'wght' 800, 'wdth' 1.2, 'slnt' 0;

with the grammar:

<axis-tag-value>#
axis-tag-value: <string> <number>

on the other hand, I don't want to write too many parsers here.

+            if (!parse_non_negative_integer(value, &file->fAxes.push_back())) {
+                SkDebugf("---- Font axis %s (INVALID)", value);
+            }
         }
     }
     XML_SetCharacterDataHandler(self->fParser, font_file_name_handler);
 }
 
 static FontFamily* find_family(FamilyData* self, const SkString& familyName) {
     for (int i = 0; i < self->fFamilies.count(); i++) {
         FontFamily* candidate = self->fFamilies[i];
         for (int j = 0; j < candidate->fNames.count(); j++) {
             if (candidate->fNames[j] == familyName) {
@@ skipping 451 matching lines @@
     const char* tag = fTag.c_str();
 
     // strip off the rightmost "-.*"
     const char* parentTagEnd = strrchr(tag, '-');
     if (parentTagEnd == NULL) {
         return SkLanguage();
     }
     size_t parentTagLen = parentTagEnd - tag;
     return SkLanguage(tag, parentTagLen);
 }