Add OpenTypeCapsSupport class

third_party/WebKit/Source/platform/fonts/opentype/OpenTypeCapsSupportMPL.cpp

+/* ***** BEGIN LICENSE BLOCK *****
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include "platform/fonts/opentype/OpenTypeCapsSupport.h"
+
+#include <hb-ot.h>
+
+namespace blink  {
+
+bool OpenTypeCapsSupport::supportsOpenTypeFeature(
+    hb_script_t script,
+    uint32_t tag) const
+{
+
+    hb_face_t* face = m_harfBuzzFace->face();
+    ASSERT(face);
+
+    ASSERT((tag == HB_TAG('s', 'm', 'c', 'p')
+        || tag == HB_TAG('c', '2', 's', 'c')
+        || tag == HB_TAG('p', 'c', 'a', 'p')
+        || tag == HB_TAG('c', '2', 'p', 'c')
+        || tag == HB_TAG('s', 'u', 'p', 's')
+        || tag == HB_TAG('s', 'u', 'b', 's')
+        || tag == HB_TAG('t', 'i', 't', 'l')
+        || tag == HB_TAG('u', 'n', 'i', 'c')
+        || tag == HB_TAG('v', 'e', 'r', 't')));
+
+    bool result = false;
+
+    if (!hb_ot_layout_has_substitution(face))
+        return false;
+
+    // Get the OpenType tag(s) that match this script code
+    const size_t kMaxScriptTags = 4;
+    hb_tag_t scriptTags[kMaxScriptTags] = {
+        HB_TAG_NONE,
+        HB_TAG_NONE,
+        HB_TAG_NONE,
+        HB_TAG_NONE
+    };
+    hb_ot_tags_from_script(static_cast<hb_script_t>(script),
+        &scriptTags[0],
+        &scriptTags[1]);
+
+    // Replace the first remaining NONE with DEFAULT
+    for (size_t i = 0; i < kMaxScriptTags; ++i) {
+        if (scriptTags[i] == HB_TAG_NONE) {
+            scriptTags[i] = HB_OT_TAG_DEFAULT_SCRIPT;
+            break;
+        }
+    }
+
+    // Now check for 'smcp' under the first of those scripts that is present
+    const hb_tag_t kGSUB = HB_TAG('G', 'S', 'U', 'B');
+    for (size_t j = 0; j < kMaxScriptTags; ++j) {
+        if (scriptTags[j] == HB_TAG_NONE)
+            break;
+
+        unsigned scriptIndex;
+        if (hb_ot_layout_table_find_script(face,

[behdad, 2016/04/13 05:32:50]

Using hb_ot_layout_table_choose_script instead of hb_ot_layout_table_find_script
simplifies the logic a bit, if you are up to updating for that.

+            kGSUB,
+            scriptTags[j],
+            &scriptIndex)) {
+            if (hb_ot_layout_language_find_feature(face, kGSUB,
+                scriptIndex,
+                HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX,
+                tag, nullptr)) {
+                result = true;
+            }
+            break;
+        }
+    }
+    return result;
+}
+
+} // namespace blink