Introduce MinikinFont abstraction

This commit removes the direct dependency on FreeType and replaces it
with a MinikinFont abstraction, which is designed to support both
FreeType and Skia fonts (and possibly others in the future).

Also adds a "total advance" to the Layout, with an API for retrieving
it.

Change-Id: If20f92db9a43fd15b0fe9794b761ba00fb21338c

1 files changed, 70 insertions, 0 deletions

diff --git a/include/minikin/MinikinFont.h b/include/minikin/MinikinFont.h
new file mode 100644
index 0000000..2c265c3
--- /dev/null
+++ b/include/minikin/MinikinFont.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MINIKIN_FONT_H
+#define MINIKIN_FONT_H
+
+// An abstraction for platform fonts, allowing Minikin to be used with
+// multiple actual implementations of fonts.
+
+namespace android {
+
+class MinikinFont;
+
+// Possibly move into own .h file?
+struct MinikinPaint {
+    MinikinFont *font;
+    float size;
+    // todo: skew, stretch, hinting
+};
+
+class MinikinFontFreeType;
+
+class MinikinFont {
+public:
+    void Ref() { mRefcount_++; }
+    void Unref() { if (--mRefcount_ == 0) { delete this; } }
+
+    //MinikinFont();
+    virtual ~MinikinFont() = 0;
+
+    virtual bool GetGlyph(uint32_t codepoint, uint32_t *glyph) const = 0;
+
+    virtual float GetHorizontalAdvance(uint32_t glyph_id,
+        const MinikinPaint &paint) const = 0;
+
+    // If buf is NULL, just update size
+    virtual bool GetTable(uint32_t tag, uint8_t *buf, size_t *size) = 0;
+
+    virtual int32_t GetUniqueId() const = 0;
+
+    static uint32_t MakeTag(char c1, char c2, char c3, char c4) {
+        return ((uint32_t)c1 << 24) | ((uint32_t)c2 << 16) |
+            ((uint32_t)c3 << 8) | (uint32_t)c4;
+    }
+
+    // This is used to implement a downcast without RTTI
+    virtual MinikinFontFreeType* GetFreeType() {
+        return NULL;
+    }
+
+private:
+    int mRefcount_;
+};
+
+}  // namespace android
+
+#endif  // MINIKIN_FONT_H